diff --git a/pkgs/development/compilers/llvm/15/bintools/default.nix b/pkgs/development/compilers/llvm/15/bintools/default.nix
new file mode 100644
index 0000000000000..303faf7bbb61b
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/bintools/default.nix
@@ -0,0 +1,40 @@
+{ runCommand, stdenv, llvm, lld, version }:
+
+let
+  prefix =
+    if stdenv.hostPlatform != stdenv.targetPlatform
+    then "${stdenv.targetPlatform.config}-"
+    else "";
+in runCommand "llvm-binutils-${version}" {
+  preferLocalBuild = true;
+  passthru = {
+    isLLVM = true;
+  };
+} ''
+   mkdir -p $out/bin
+   for prog in ${lld}/bin/*; do
+     ln -s $prog $out/bin/${prefix}$(basename $prog)
+   done
+   for prog in ${llvm}/bin/*; do
+     ln -sf $prog $out/bin/${prefix}$(basename $prog)
+   done
+
+   ln -s ${llvm}/bin/llvm-ar $out/bin/${prefix}ar
+   ln -s ${llvm}/bin/llvm-ar $out/bin/${prefix}dlltool
+   ln -s ${llvm}/bin/llvm-ar $out/bin/${prefix}ranlib
+   ln -s ${llvm}/bin/llvm-cxxfilt $out/bin/${prefix}c++filt
+   ln -s ${llvm}/bin/llvm-debuginfod $out/bin/${prefix}debuginfod
+   ln -s ${llvm}/bin/llvm-debuginfod-find $out/bin/${prefix}debuginfod-find
+   ln -s ${llvm}/bin/llvm-dwp $out/bin/${prefix}dwp
+   ln -s ${llvm}/bin/llvm-nm $out/bin/${prefix}nm
+   ln -s ${llvm}/bin/llvm-objcopy $out/bin/${prefix}objcopy
+   ln -s ${llvm}/bin/llvm-objcopy $out/bin/${prefix}strip
+   ln -s ${llvm}/bin/llvm-objdump $out/bin/${prefix}objdump
+   ln -s ${llvm}/bin/llvm-rc $out/bin/${prefix}windres
+   ln -s ${llvm}/bin/llvm-readobj $out/bin/${prefix}readelf
+   ln -s ${llvm}/bin/llvm-size $out/bin/${prefix}size
+   ln -s ${llvm}/bin/llvm-strings $out/bin/${prefix}strings
+   ln -s ${llvm}/bin/llvm-symbolizer $out/bin/${prefix}addr2line
+
+   ln -s ${lld}/bin/lld $out/bin/${prefix}ld
+''
diff --git a/pkgs/development/compilers/llvm/15/clang/default.nix b/pkgs/development/compilers/llvm/15/clang/default.nix
new file mode 100644
index 0000000000000..b0671150a7bd9
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/clang/default.nix
@@ -0,0 +1,129 @@
+{ lib, stdenv, llvm_meta
+, monorepoSrc, runCommand
+, substituteAll, cmake, ninja, libxml2, libllvm, version, python3
+, buildLlvmTools
+, fixDarwinDylibNames
+, enableManpages ? false
+}:
+
+let
+  self = stdenv.mkDerivation (rec {
+    pname = "clang";
+    inherit version;
+
+    src = runCommand "${pname}-src-${version}" {} ''
+      mkdir -p "$out"
+      cp -r ${monorepoSrc}/cmake "$out"
+      cp -r ${monorepoSrc}/${pname} "$out"
+      cp -r ${monorepoSrc}/clang-tools-extra "$out"
+    '';
+
+    sourceRoot = "${src.name}/${pname}";
+
+    nativeBuildInputs = [ cmake ninja python3 ]
+      ++ lib.optional enableManpages python3.pkgs.sphinx
+      ++ lib.optional stdenv.hostPlatform.isDarwin fixDarwinDylibNames;
+
+    buildInputs = [ libxml2 libllvm ];
+
+    cmakeFlags = [
+      "-DCLANG_INSTALL_PACKAGE_DIR=${placeholder "dev"}/lib/cmake/clang"
+      "-DCLANGD_BUILD_XPC=OFF"
+      "-DLLVM_ENABLE_RTTI=ON"
+    ] ++ lib.optionals enableManpages [
+      "-DCLANG_INCLUDE_DOCS=ON"
+      "-DLLVM_ENABLE_SPHINX=ON"
+      "-DSPHINX_OUTPUT_MAN=ON"
+      "-DSPHINX_OUTPUT_HTML=OFF"
+      "-DSPHINX_WARNINGS_AS_ERRORS=OFF"
+    ] ++ lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
+      "-DLLVM_TABLEGEN_EXE=${buildLlvmTools.llvm}/bin/llvm-tblgen"
+      "-DCLANG_TABLEGEN=${buildLlvmTools.libclang.dev}/bin/clang-tblgen"
+    ];
+
+    patches = [
+      ./purity.patch
+      # https://reviews.llvm.org/D51899
+      ./gnu-install-dirs.patch
+      (substituteAll {
+        src = ../../clang-11-12-LLVMgold-path.patch;
+        libllvmLibdir = "${libllvm.lib}/lib";
+      })
+    ];
+
+    postPatch = ''
+      (cd tools && ln -s ../../clang-tools-extra extra)
+
+      sed -i -e 's/DriverArgs.hasArg(options::OPT_nostdlibinc)/true/' \
+             -e 's/Args.hasArg(options::OPT_nostdlibinc)/true/' \
+             lib/Driver/ToolChains/*.cpp
+    '' + lib.optionalString stdenv.hostPlatform.isMusl ''
+      sed -i -e 's/lgcc_s/lgcc_eh/' lib/Driver/ToolChains/*.cpp
+    '';
+
+    outputs = [ "out" "lib" "dev" "python" ];
+
+    postInstall = ''
+      ln -sv $out/bin/clang $out/bin/cpp
+
+      # Move libclang to 'lib' output
+      moveToOutput "lib/libclang.*" "$lib"
+      moveToOutput "lib/libclang-cpp.*" "$lib"
+      substituteInPlace $dev/lib/cmake/clang/ClangTargets-release.cmake \
+          --replace "\''${_IMPORT_PREFIX}/lib/libclang." "$lib/lib/libclang." \
+          --replace "\''${_IMPORT_PREFIX}/lib/libclang-cpp." "$lib/lib/libclang-cpp."
+
+      mkdir -p $python/bin $python/share/clang/
+      mv $out/bin/{git-clang-format,scan-view} $python/bin
+      if [ -e $out/bin/set-xcode-analyzer ]; then
+        mv $out/bin/set-xcode-analyzer $python/bin
+      fi
+      mv $out/share/clang/*.py $python/share/clang
+      rm $out/bin/c-index-test
+      patchShebangs $python/bin
+
+      mkdir -p $dev/bin
+      cp bin/clang-tblgen $dev/bin
+    '';
+
+    passthru = {
+      isClang = true;
+      inherit libllvm;
+    };
+
+    meta = llvm_meta // {
+      homepage = "https://clang.llvm.org/";
+      description = "A C language family frontend for LLVM";
+      longDescription = ''
+        The Clang project provides a language front-end and tooling
+        infrastructure for languages in the C language family (C, C++, Objective
+        C/C++, OpenCL, CUDA, and RenderScript) for the LLVM project.
+        It aims to deliver amazingly fast compiles, extremely useful error and
+        warning messages and to provide a platform for building great source
+        level tools. The Clang Static Analyzer and clang-tidy are tools that
+        automatically find bugs in your code, and are great examples of the sort
+        of tools that can be built using the Clang frontend as a library to
+        parse C/C++ code.
+      '';
+      mainProgram = "clang";
+    };
+  } // lib.optionalAttrs enableManpages {
+    pname = "clang-manpages";
+
+    ninjaFlags = [ "docs-clang-man" ];
+
+    installPhase = ''
+      mkdir -p $out/share/man/man1
+      # Manually install clang manpage
+      cp docs/man/*.1 $out/share/man/man1/
+    '';
+
+    outputs = [ "out" ];
+
+    doCheck = false;
+
+    meta = llvm_meta // {
+      description = "man page for Clang ${version}";
+    };
+  });
+in self
diff --git a/pkgs/development/compilers/llvm/15/clang/gnu-install-dirs.patch b/pkgs/development/compilers/llvm/15/clang/gnu-install-dirs.patch
new file mode 100644
index 0000000000000..f767c56836d5c
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/clang/gnu-install-dirs.patch
@@ -0,0 +1,105 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index c27beec313d7..480f13e73c9f 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -78,15 +78,17 @@ if(CLANG_BUILT_STANDALONE)
+   if (NOT LLVM_CONFIG_FOUND)
+     # Pull values from LLVMConfig.cmake.  We can drop this once the llvm-config
+     # path is removed.
+-    set(MAIN_INCLUDE_DIR "${LLVM_INCLUDE_DIR}")
++    set(INCLUDE_DIRS ${LLVM_INCLUDE_DIRS})
+     set(LLVM_OBJ_DIR "${LLVM_BINARY_DIR}")
+     # N.B. this is just a default value, the CACHE PATHs below can be overriden.
+     set(MAIN_SRC_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../llvm")
+     set(TOOLS_BINARY_DIR "${LLVM_TOOLS_BINARY_DIR}")
+     set(LIBRARY_DIR "${LLVM_LIBRARY_DIR}")
++  else()
++    set(INCLUDE_DIRS "${LLVM_BINARY_DIR}/include" "${MAIN_INCLUDE_DIR}")
+   endif()
+ 
+-  set(LLVM_MAIN_INCLUDE_DIR "${MAIN_INCLUDE_DIR}" CACHE PATH "Path to llvm/include")
++  set(LLVM_INCLUDE_DIRS ${INCLUDE_DIRS} CACHE PATH "Path to llvm/include and any other header dirs needed")
+   set(LLVM_BINARY_DIR "${LLVM_OBJ_ROOT}" CACHE PATH "Path to LLVM build tree")
+   set(LLVM_MAIN_SRC_DIR "${MAIN_SRC_DIR}" CACHE PATH "Path to LLVM source tree")
+   set(LLVM_TOOLS_BINARY_DIR "${TOOLS_BINARY_DIR}" CACHE PATH "Path to llvm/bin")
+@@ -128,7 +130,7 @@ if(CLANG_BUILT_STANDALONE)
+     set(LLVM_INCLUDE_TESTS ON)
+   endif()
+ 
+-  include_directories("${LLVM_BINARY_DIR}/include" "${LLVM_MAIN_INCLUDE_DIR}")
++  include_directories(${LLVM_INCLUDE_DIRS})
+   link_directories("${LLVM_LIBRARY_DIR}")
+ 
+   set( CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin )
+diff --git a/cmake/modules/AddClang.cmake b/cmake/modules/AddClang.cmake
+index 21ac332e4f5f..b16c314bd1e2 100644
+--- a/cmake/modules/AddClang.cmake
++++ b/cmake/modules/AddClang.cmake
+@@ -119,8 +119,8 @@ macro(add_clang_library name)
+         install(TARGETS ${lib}
+           COMPONENT ${lib}
+           ${export_to_clangtargets}
+-          LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX}
+-          ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX}
++          LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}"
++          ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}"
+           RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}")
+ 
+         if (NOT LLVM_ENABLE_IDE)
+diff --git a/lib/Headers/CMakeLists.txt b/lib/Headers/CMakeLists.txt
+index 6e2060991b92..b9bc930d26b8 100644
+--- a/lib/Headers/CMakeLists.txt
++++ b/lib/Headers/CMakeLists.txt
+@@ -420,7 +420,7 @@ add_header_target("openmp-resource-headers" ${openmp_wrapper_files})
+ add_header_target("windows-resource-headers" ${windows_only_files})
+ add_header_target("utility-resource-headers" ${utility_files})
+ 
+-set(header_install_dir lib${LLVM_LIBDIR_SUFFIX}/clang/${CLANG_VERSION}/include)
++set(header_install_dir ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}/clang/${CLANG_VERSION}/include)
+ 
+ #############################################################
+ # Install rules for the catch-all clang-resource-headers target
+diff --git a/tools/libclang/CMakeLists.txt b/tools/libclang/CMakeLists.txt
+index 8d95d0900e8c..ebc70ff7526d 100644
+--- a/tools/libclang/CMakeLists.txt
++++ b/tools/libclang/CMakeLists.txt
+@@ -180,7 +180,7 @@ foreach(PythonVersion ${CLANG_PYTHON_BINDINGS_VERSIONS})
+           COMPONENT
+             libclang-python-bindings
+           DESTINATION
+-            "lib${LLVM_LIBDIR_SUFFIX}/python${PythonVersion}/site-packages")
++            "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}/python${PythonVersion}/site-packages")
+ endforeach()
+ if(NOT LLVM_ENABLE_IDE)
+   add_custom_target(libclang-python-bindings)
+diff --git a/tools/scan-build-py/CMakeLists.txt b/tools/scan-build-py/CMakeLists.txt
+index 061dc7ef4dd9..adc54b2edc32 100644
+--- a/tools/scan-build-py/CMakeLists.txt
++++ b/tools/scan-build-py/CMakeLists.txt
+@@ -88,7 +88,7 @@ foreach(lib ${LibScanbuild})
+                      DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/lib/libscanbuild/${lib})
+   list(APPEND Depends ${CMAKE_BINARY_DIR}/lib/libscanbuild/${lib})
+   install(PROGRAMS lib/libscanbuild/${lib}
+-          DESTINATION lib/libscanbuild
++          DESTINATION "${CMAKE_INSTALL_LIBDIR}/libscanbuild"
+           COMPONENT scan-build-py)
+ endforeach()
+ 
+@@ -106,7 +106,7 @@ foreach(resource ${LibScanbuildResources})
+                      DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/lib/libscanbuild/resources/${resource})
+   list(APPEND Depends ${CMAKE_BINARY_DIR}/lib/libscanbuild/resources/${resource})
+   install(PROGRAMS lib/libscanbuild/resources/${resource}
+-          DESTINATION lib/libscanbuild/resources
++          DESTINATION "${CMAKE_INSTALL_LIBDIR}/libscanbuild/resources"
+           COMPONENT scan-build-py)
+ endforeach()
+ 
+@@ -122,7 +122,7 @@ foreach(lib ${LibEar})
+                      DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/lib/libear/${lib})
+   list(APPEND Depends ${CMAKE_BINARY_DIR}/lib/libear/${lib})
+   install(PROGRAMS lib/libear/${lib}
+-          DESTINATION lib/libear
++          DESTINATION "${CMAKE_INSTALL_LIBDIR}/libear"
+           COMPONENT scan-build-py)
+ endforeach()
+ 
diff --git a/pkgs/development/compilers/llvm/15/clang/purity.patch b/pkgs/development/compilers/llvm/15/clang/purity.patch
new file mode 100644
index 0000000000000..1c94f293eb934
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/clang/purity.patch
@@ -0,0 +1,29 @@
+From 4add81bba40dcec62c4ea4481be8e35ac53e89d8 Mon Sep 17 00:00:00 2001
+From: Will Dietz <w@wdtz.org>
+Date: Thu, 18 May 2017 11:56:12 -0500
+Subject: [PATCH] "purity" patch for 5.0
+
+---
+ lib/Driver/ToolChains/Gnu.cpp | 7 -------
+ 1 file changed, 7 deletions(-)
+
+diff --git a/lib/Driver/ToolChains/Gnu.cpp b/lib/Driver/ToolChains/Gnu.cpp
+index fe3c0191bb..c6a482bece 100644
+--- a/lib/Driver/ToolChains/Gnu.cpp
++++ b/lib/Driver/ToolChains/Gnu.cpp
+@@ -487,13 +487,7 @@ void tools::gnutools::Linker::ConstructJob(Compilation &C, const JobAction &JA,
+   } else {
+     if (Args.hasArg(options::OPT_rdynamic))
+       CmdArgs.push_back("-export-dynamic");
+
+-    if (!Args.hasArg(options::OPT_shared) && !IsStaticPIE &&
+-        !Args.hasArg(options::OPT_r)) {
+-      CmdArgs.push_back("-dynamic-linker");
+-      CmdArgs.push_back(Args.MakeArgString(Twine(D.DyldPrefix) +
+-                                           ToolChain.getDynamicLinker(Args)));
+-    }
+   }
+ 
+   CmdArgs.push_back("-o");
+-- 
+2.11.0
diff --git a/pkgs/development/compilers/llvm/15/compiler-rt/X86-support-extension.patch b/pkgs/development/compilers/llvm/15/compiler-rt/X86-support-extension.patch
new file mode 100644
index 0000000000000..07013e5a68259
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/compiler-rt/X86-support-extension.patch
@@ -0,0 +1,21 @@
+diff --git a/lib/builtins/CMakeLists.txt b/lib/builtins/CMakeLists.txt
+index 3a66dd9c3fb..7efc85d9f9f 100644
+--- a/lib/builtins/CMakeLists.txt
++++ b/lib/builtins/CMakeLists.txt
+@@ -348,4 +348,8 @@ if (NOT MSVC)
+ 
++  set(i486_SOURCES ${i386_SOURCES})
++  set(i586_SOURCES ${i386_SOURCES})
++  set(i686_SOURCES ${i386_SOURCES})
++
+   if (WIN32)
+     set(i386_SOURCES
+       ${i386_SOURCES}
+@@ -723,6 +723,7 @@ else ()
+   endif()
+ 
+   foreach (arch ${BUILTIN_SUPPORTED_ARCH})
++      message("arch: ${arch}")
+     if (CAN_TARGET_${arch})
+       # For ARM archs, exclude any VFP builtins if VFP is not supported
+       if (${arch} MATCHES "^(arm|armhf|armv7|armv7s|armv7k|armv7m|armv7em)$")
diff --git a/pkgs/development/compilers/llvm/15/compiler-rt/armv7l.patch b/pkgs/development/compilers/llvm/15/compiler-rt/armv7l.patch
new file mode 100644
index 0000000000000..ca1c2332abd9f
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/compiler-rt/armv7l.patch
@@ -0,0 +1,32 @@
+diff -ur a/cmake/builtin-config-ix.cmake b/cmake/builtin-config-ix.cmake
+--- a/cmake/builtin-config-ix.cmake @llvm 15.0.6
++++ b/cmake/builtin-config-ix.cmake
+@@ -46,7 +46,7 @@
+ 
+ set(ARM64 aarch64)
+-set(ARM32 arm armhf armv6m armv7m armv7em armv7 armv7s armv7k armv8m.main armv8.1m.main)
++set(ARM32 arm armhf armv6m armv7m armv7em armv7 armv7s armv7k armv7l armv8m.main armv8.1m.main)
+ set(AVR avr)
+ set(HEXAGON hexagon)
+ set(X86 i386)
+ set(X86_64 x86_64)
+diff -ur a/lib/builtins/CMakeLists.txt b/lib/builtins/CMakeLists.txt
+--- a/lib/builtins/CMakeLists.txt @llvm 15.0.6
++++ b/lib/builtins/CMakeLists.txt
+@@ -565,6 +565,7 @@
+ set(armv7_SOURCES ${arm_SOURCES})
+ set(armv7s_SOURCES ${arm_SOURCES})
+ set(armv7k_SOURCES ${arm_SOURCES})
++set(armv7l_SOURCES ${arm_SOURCES})
+ set(arm64_SOURCES ${aarch64_SOURCES})
+ 
+ # macho_embedded archs
+@@ -734,7 +735,7 @@
+   foreach (arch ${BUILTIN_SUPPORTED_ARCH})
+     if (CAN_TARGET_${arch})
+       # For ARM archs, exclude any VFP builtins if VFP is not supported
+-      if (${arch} MATCHES "^(arm|armhf|armv7|armv7s|armv7k|armv7m|armv7em|armv8m.main|armv8.1m.main)$")
++      if (${arch} MATCHES "^(arm|armhf|armv7|armv7s|armv7k|armv7l|armv7m|armv7em|armv8m.main|armv8.1m.main)$")
+         string(REPLACE ";" " " _TARGET_${arch}_CFLAGS "${TARGET_${arch}_CFLAGS}")
+         check_compile_definition(__VFP_FP__ "${CMAKE_C_FLAGS} ${_TARGET_${arch}_CFLAGS}" COMPILER_RT_HAS_${arch}_VFP)
+         if(NOT COMPILER_RT_HAS_${arch}_VFP)
diff --git a/pkgs/development/compilers/llvm/15/compiler-rt/darwin-targetconditionals.patch b/pkgs/development/compilers/llvm/15/compiler-rt/darwin-targetconditionals.patch
new file mode 100644
index 0000000000000..425dc2af01e7c
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/compiler-rt/darwin-targetconditionals.patch
@@ -0,0 +1,71 @@
+diff --git a/lib/sanitizer_common/sanitizer_mac.cpp b/lib/sanitizer_common/sanitizer_mac.cpp
+--- a/lib/sanitizer_common/sanitizer_mac.cpp
++++ b/lib/sanitizer_common/sanitizer_mac.cpp
+@@ -613,9 +613,15 @@ HandleSignalMode GetHandleSignalMode(int signum) {
+ // Offset example:
+ // XNU 17 -- macOS 10.13 -- iOS 11 -- tvOS 11 -- watchOS 4
+ constexpr u16 GetOSMajorKernelOffset() {
+-  if (TARGET_OS_OSX) return 4;
+-  if (TARGET_OS_IOS || TARGET_OS_TV) return 6;
+-  if (TARGET_OS_WATCH) return 13;
++#if TARGET_OS_OSX
++  return 4;
++#endif
++#if TARGET_OS_IOS || TARGET_OS_TV
++  return 6;
++#endif
++#if TARGET_OS_WATCH
++  return 13;
++#endif
+ }
+ 
+ using VersStr = char[64];
+@@ -627,13 +633,13 @@ static uptr ApproximateOSVersionViaKernelVersion(VersStr vers) {
+   u16 os_major = kernel_major - offset;
+ 
+   const char *format = "%d.0";
+-  if (TARGET_OS_OSX) {
+-    if (os_major >= 16) {  // macOS 11+
+-      os_major -= 5;
+-    } else {  // macOS 10.15 and below
+-      format = "10.%d";
+-    }
++#if TARGET_OS_OSX
++  if (os_major >= 16) {  // macOS 11+
++    os_major -= 5;
++  } else {  // macOS 10.15 and below
++    format = "10.%d";
+   }
++#endif
+   return internal_snprintf(vers, sizeof(VersStr), format, os_major);
+ }
+ 
+@@ -681,15 +687,14 @@ void ParseVersion(const char *vers, u16 *major, u16 *minor) {
+ // Aligned versions example:
+ // macOS 10.15 -- iOS 13 -- tvOS 13 -- watchOS 6
+ static void MapToMacos(u16 *major, u16 *minor) {
+-  if (TARGET_OS_OSX)
+-    return;
+-
+-  if (TARGET_OS_IOS || TARGET_OS_TV)
++#if !TARGET_OS_OSX
++#if TARGET_OS_IOS || TARGET_OS_TV
+     *major += 2;
+-  else if (TARGET_OS_WATCH)
++#elif TARGET_OS_WATCH
+     *major += 9;
+-  else
++#else
+     UNREACHABLE("unsupported platform");
++#endif
+ 
+   if (*major >= 16) {  // macOS 11+
+     *major -= 5;
+@@ -697,6 +702,7 @@ static void MapToMacos(u16 *major, u16 *minor) {
+     *minor = *major;
+     *major = 10;
+   }
++#endif
+ }
+ 
+ static MacosVersion GetMacosAlignedVersionInternal() {
diff --git a/pkgs/development/compilers/llvm/15/compiler-rt/default.nix b/pkgs/development/compilers/llvm/15/compiler-rt/default.nix
new file mode 100644
index 0000000000000..722a5bd90cbd6
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/compiler-rt/default.nix
@@ -0,0 +1,156 @@
+{ lib, stdenv, llvm_meta, version
+, monorepoSrc, runCommand
+, cmake, ninja, python3, xcbuild, libllvm, libcxxabi, libxcrypt
+, doFakeLibgcc ? stdenv.hostPlatform.isFreeBSD
+}:
+
+let
+
+  useLLVM = stdenv.hostPlatform.useLLVM or false;
+  bareMetal = stdenv.hostPlatform.parsed.kernel.name == "none";
+  haveLibc = stdenv.cc.libc != null;
+  inherit (stdenv.hostPlatform) isMusl isGnu;
+
+  baseName = "compiler-rt";
+
+  src = runCommand "${baseName}-src-${version}" {} ''
+    mkdir -p "$out"
+    cp -r ${monorepoSrc}/cmake "$out"
+    cp -r ${monorepoSrc}/${baseName} "$out"
+  '';
+in
+
+stdenv.mkDerivation {
+  pname = baseName + lib.optionalString (haveLibc) "-libc";
+  inherit version;
+
+  inherit src;
+  sourceRoot = "${src.name}/${baseName}";
+
+  nativeBuildInputs = [ cmake ninja python3 libllvm.dev ]
+    ++ lib.optional stdenv.isDarwin xcbuild.xcrun;
+  buildInputs = lib.optional stdenv.hostPlatform.isDarwin libcxxabi;
+
+  NIX_CFLAGS_COMPILE = [
+    "-DSCUDO_DEFAULT_OPTIONS=DeleteSizeMismatch=0:DeallocationTypeMismatch=0"
+  ];
+
+  cmakeFlags = [
+    "-DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON"
+    "-DCMAKE_C_COMPILER_TARGET=${stdenv.hostPlatform.config}"
+    "-DCMAKE_ASM_COMPILER_TARGET=${stdenv.hostPlatform.config}"
+  ] ++ lib.optionals (haveLibc && stdenv.hostPlatform.libc == "glibc") [
+    "-DSANITIZER_COMMON_CFLAGS=-I${libxcrypt}/include"
+  ] ++ lib.optionals (useLLVM || bareMetal || isMusl) [
+    "-DCOMPILER_RT_BUILD_SANITIZERS=OFF"
+    "-DCOMPILER_RT_BUILD_XRAY=OFF"
+    "-DCOMPILER_RT_BUILD_LIBFUZZER=OFF"
+    "-DCOMPILER_RT_BUILD_PROFILE=OFF"
+    "-DCOMPILER_RT_BUILD_MEMPROF=OFF"
+    "-DCOMPILER_RT_BUILD_ORC=OFF" # may be possible to build with musl if necessary
+  ] ++ lib.optionals (useLLVM || bareMetal) [
+     "-DCOMPILER_RT_BUILD_PROFILE=OFF"
+  ] ++ lib.optionals ((useLLVM && !haveLibc) || bareMetal) [
+    "-DCMAKE_C_COMPILER_WORKS=ON"
+    "-DCMAKE_CXX_COMPILER_WORKS=ON"
+    "-DCOMPILER_RT_BAREMETAL_BUILD=ON"
+    "-DCMAKE_SIZEOF_VOID_P=${toString (stdenv.hostPlatform.parsed.cpu.bits / 8)}"
+  ] ++ lib.optionals (useLLVM && !haveLibc) [
+    "-DCMAKE_C_FLAGS=-nodefaultlibs"
+  ] ++ lib.optionals (useLLVM) [
+    "-DCOMPILER_RT_BUILD_BUILTINS=ON"
+    #https://stackoverflow.com/questions/53633705/cmake-the-c-compiler-is-not-able-to-compile-a-simple-test-program
+    "-DCMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY"
+  ] ++ lib.optionals (bareMetal) [
+    "-DCOMPILER_RT_OS_DIR=baremetal"
+  ] ++ lib.optionals (stdenv.hostPlatform.isDarwin) [
+    "-DDARWIN_macosx_OVERRIDE_SDK_VERSION=ON"
+    "-DDARWIN_osx_ARCHS=${stdenv.hostPlatform.darwinArch}"
+    "-DDARWIN_osx_BUILTIN_ARCHS=${stdenv.hostPlatform.darwinArch}"
+
+    # `COMPILER_RT_DEFAULT_TARGET_ONLY` does not apply to Darwin:
+    # https://github.com/llvm/llvm-project/blob/27ef42bec80b6c010b7b3729ed0528619521a690/compiler-rt/cmake/base-config-ix.cmake#L153
+    "-DCOMPILER_RT_ENABLE_IOS=OFF"
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  patches = [
+    ./X86-support-extension.patch # Add support for i486 i586 i686 by reusing i386 config
+    ./gnu-install-dirs.patch
+    # ld-wrapper dislikes `-rpath-link //nix/store`, so we normalize away the
+    # extra `/`.
+    ./normalize-var.patch
+    # Prevent a compilation error on darwin
+    ./darwin-targetconditionals.patch
+    # See: https://github.com/NixOS/nixpkgs/pull/186575
+    ../../common/compiler-rt/darwin-plistbuddy-workaround.patch
+    # See: https://github.com/NixOS/nixpkgs/pull/194634#discussion_r999829893
+    ./armv7l.patch
+  ]
+    # The `compiler-rt` build inspects `ld` to figure out whether it needs to
+    # explicitly call `codesign`:
+    # https://github.com/llvm/llvm-project/blob/27ef42bec80b6c010b7b3729ed0528619521a690/compiler-rt/cmake/Modules/AddCompilerRT.cmake#L409-L422
+    #
+    # In our case, despite (currently) having an `ld` version than 609, we don't
+    # need an explicit codesigning step because `postLinkSignHook` handles this
+    # for us.
+    #
+    # Unfortunately there isn't an easy way to override
+    # `NEED_EXPLICIT_ADHOC_CODESIGN`.
+    #
+    # Adding `codesign` as a build input also doesn't currently work because, as
+    # of this writing, `codesign` in nixpkgs doesn't support the `--sign` alias
+    # which the `compiler-rt` build uses. See here for context:
+    # https://github.com/NixOS/nixpkgs/pull/194634#issuecomment-1272116014
+    #
+    # So, for now, we patch `compiler-rt` to skip the explicit codesigning step.
+    ++ lib.optional stdenv.hostPlatform.isDarwin ./skip-explicit-codesign.patch;
+
+  # TSAN requires XPC on Darwin, which we have no public/free source files for. We can depend on the Apple frameworks
+  # to get it, but they're unfree. Since LLVM is rather central to the stdenv, we patch out TSAN support so that Hydra
+  # can build this. If we didn't do it, basically the entire nixpkgs on Darwin would have an unfree dependency and we'd
+  # get no binary cache for the entire platform. If you really find yourself wanting the TSAN, make this controllable by
+  # a flag and turn the flag off during the stdenv build.
+  postPatch = lib.optionalString (!stdenv.isDarwin) ''
+    substituteInPlace cmake/builtin-config-ix.cmake \
+      --replace 'set(X86 i386)' 'set(X86 i386 i486 i586 i686)'
+  '' + lib.optionalString stdenv.isDarwin ''
+    substituteInPlace cmake/builtin-config-ix.cmake \
+      --replace 'set(ARM64 arm64 arm64e)' 'set(ARM64)'
+    substituteInPlace cmake/config-ix.cmake \
+      --replace 'set(COMPILER_RT_HAS_TSAN TRUE)' 'set(COMPILER_RT_HAS_TSAN FALSE)'
+  '' + lib.optionalString (useLLVM) ''
+    substituteInPlace lib/builtins/int_util.c \
+      --replace "#include <stdlib.h>" ""
+    substituteInPlace lib/builtins/clear_cache.c \
+      --replace "#include <assert.h>" ""
+    substituteInPlace lib/builtins/cpu_model.c \
+      --replace "#include <assert.h>" ""
+  '';
+
+  # Hack around weird upsream RPATH bug
+  postInstall = lib.optionalString (stdenv.hostPlatform.isDarwin || stdenv.hostPlatform.isWasm) ''
+    ln -s "$out/lib"/*/* "$out/lib"
+  '' + lib.optionalString (useLLVM) ''
+    ln -s $out/lib/*/clang_rt.crtbegin-*.o $out/lib/crtbegin.o
+    ln -s $out/lib/*/clang_rt.crtend-*.o $out/lib/crtend.o
+    ln -s $out/lib/*/clang_rt.crtbegin_shared-*.o $out/lib/crtbeginS.o
+    ln -s $out/lib/*/clang_rt.crtend_shared-*.o $out/lib/crtendS.o
+  '' + lib.optionalString doFakeLibgcc ''
+     ln -s $out/lib/freebsd/libclang_rt.builtins-*.a $out/lib/libgcc.a
+  '';
+
+  meta = llvm_meta // {
+    homepage = "https://compiler-rt.llvm.org/";
+    description = "Compiler runtime libraries";
+    longDescription = ''
+      The compiler-rt project provides highly tuned implementations of the
+      low-level code generator support routines like "__fixunsdfdi" and other
+      calls generated when a target doesn't have a short sequence of native
+      instructions to implement a core IR operation. It also provides
+      implementations of run-time libraries for dynamic testing tools such as
+      AddressSanitizer, ThreadSanitizer, MemorySanitizer, and DataFlowSanitizer.
+    '';
+  };
+}
diff --git a/pkgs/development/compilers/llvm/15/compiler-rt/gnu-install-dirs.patch b/pkgs/development/compilers/llvm/15/compiler-rt/gnu-install-dirs.patch
new file mode 100644
index 0000000000000..f3b1f63a7d713
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/compiler-rt/gnu-install-dirs.patch
@@ -0,0 +1,20 @@
+diff --git a/cmake/base-config-ix.cmake b/cmake/base-config-ix.cmake
+index 8a6219568b3f..30ee68a47ccf 100644
+--- a/cmake/base-config-ix.cmake
++++ b/cmake/base-config-ix.cmake
+@@ -100,13 +100,13 @@ endif()
+ if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
+   set(COMPILER_RT_OUTPUT_LIBRARY_DIR
+     ${COMPILER_RT_OUTPUT_DIR}/lib)
+-  extend_path(default_install_path "${COMPILER_RT_INSTALL_PATH}" lib)
++  extend_path(default_install_path "${COMPILER_RT_INSTALL_PATH}" "${CMAKE_INSTALL_LIBDIR}")
+   set(COMPILER_RT_INSTALL_LIBRARY_DIR "${default_install_path}" CACHE PATH
+     "Path where built compiler-rt libraries should be installed.")
+ else(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
+   set(COMPILER_RT_OUTPUT_LIBRARY_DIR
+     ${COMPILER_RT_OUTPUT_DIR}/lib/${COMPILER_RT_OS_DIR})
+-  extend_path(default_install_path "${COMPILER_RT_INSTALL_PATH}" "lib/${COMPILER_RT_OS_DIR}")
++  extend_path(default_install_path "${COMPILER_RT_INSTALL_PATH}" "${CMAKE_INSTALL_LIBDIR}/${COMPILER_RT_OS_DIR}")
+   set(COMPILER_RT_INSTALL_LIBRARY_DIR "${default_install_path}" CACHE PATH
+     "Path where built compiler-rt libraries should be installed.")
+ endif()
diff --git a/pkgs/development/compilers/llvm/15/compiler-rt/normalize-var.patch b/pkgs/development/compilers/llvm/15/compiler-rt/normalize-var.patch
new file mode 100644
index 0000000000000..135cf625ef78f
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/compiler-rt/normalize-var.patch
@@ -0,0 +1,16 @@
+diff --git a/compiler-rt/cmake/Modules/CompilerRTUtils.cmake b/compiler-rt/cmake/Modules/CompilerRTUtils.cmake
+index f1f46fb9599c..6f19e69507ba 100644
+--- a/cmake/Modules/CompilerRTUtils.cmake
++++ b/cmake/Modules/CompilerRTUtils.cmake
+@@ -302,8 +302,9 @@ macro(load_llvm_config)
+     # Get some LLVM variables from LLVMConfig.
+     include("${LLVM_CMAKE_PATH}/LLVMConfig.cmake")
+ 
+-    set(LLVM_LIBRARY_OUTPUT_INTDIR
+-      ${LLVM_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib${LLVM_LIBDIR_SUFFIX})
++    get_filename_component(LLVM_LIBRARY_OUTPUT_INTDIR
++      ${LLVM_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib${LLVM_LIBDIR_SUFFIX}
++      REALPATH)
+   endif()
+ endmacro()
+ 
diff --git a/pkgs/development/compilers/llvm/15/compiler-rt/skip-explicit-codesign.patch b/pkgs/development/compilers/llvm/15/compiler-rt/skip-explicit-codesign.patch
new file mode 100644
index 0000000000000..894a74e74d464
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/compiler-rt/skip-explicit-codesign.patch
@@ -0,0 +1,12 @@
+diff --git a/cmake/Modules/AddCompilerRT.cmake b/cmake/Modules/AddCompilerRT.cmake
+--- a/cmake/Modules/AddCompilerRT.cmake
++++ b/cmake/Modules/AddCompilerRT.cmake
+@@ -406,7 +406,7 @@ function(add_compiler_rt_runtime name type)
+         if (HAD_ERROR)
+           message(FATAL_ERROR "${CMAKE_LINKER} failed with status ${HAD_ERROR}")
+         endif()
+-        set(NEED_EXPLICIT_ADHOC_CODESIGN 1)
++        set(NEED_EXPLICIT_ADHOC_CODESIGN 0) # `postLinkSignHook` handles this for us
+         if ("${LD_V_OUTPUT}" MATCHES ".*ld64-([0-9.]+).*")
+           string(REGEX REPLACE ".*ld64-([0-9.]+).*" "\\1" HOST_LINK_VERSION ${LD_V_OUTPUT})
+           if (HOST_LINK_VERSION VERSION_GREATER_EQUAL 609)
diff --git a/pkgs/development/compilers/llvm/15/default.nix b/pkgs/development/compilers/llvm/15/default.nix
new file mode 100644
index 0000000000000..db98f2854a093
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/default.nix
@@ -0,0 +1,354 @@
+{ lowPrio, newScope, pkgs, lib, stdenv, stdenvNoCC, cmake, ninja
+, gccForLibs, preLibcCrossHeaders
+, libxml2, python3, fetchFromGitHub, overrideCC, wrapCCWith, wrapBintoolsWith
+, buildLlvmTools # tools, but from the previous stage, for cross
+, targetLlvmLibraries # libraries, but from the next stage, for cross
+, targetLlvm
+# This is the default binutils, but with *this* version of LLD rather
+# than the default LLVM verion's, if LLD is the choice. We use these for
+# the `useLLVM` bootstrapping below.
+, bootBintoolsNoLibc ?
+    if stdenv.targetPlatform.linker == "lld"
+    then null
+    else pkgs.bintoolsNoLibc
+, bootBintools ?
+    if stdenv.targetPlatform.linker == "lld"
+    then null
+    else pkgs.bintools
+, darwin
+# LLVM release information; specify one of these but not both:
+, gitRelease ? null
+  # i.e.:
+  # {
+  #   version = /* i.e. "15.0.0" */;
+  #   rev = /* commit SHA */;
+  #   rev-version = /* human readable version; i.e. "unstable-2022-26-07" */;
+  #   sha256 = /* checksum for this release, can omit if specifying your own `monorepoSrc` */;
+  # }
+, officialRelease ? { version = "15.0.7"; sha256 = "sha256-wjuZQyXQ/jsmvy6y1aksCcEDXGBjuhpgngF3XQJ/T4s="; }
+  # i.e.:
+  # {
+  #   version = /* i.e. "15.0.0" */;
+  #   candidate = /* optional; if specified, should be: "rcN" */
+  #   sha256 = /* checksum for this release, can omit if specifying your own `monorepoSrc` */;
+  # }
+# By default, we'll try to fetch a release from `github:llvm/llvm-project`
+# corresponding to the `gitRelease` or `officialRelease` specified.
+#
+# You can provide your own LLVM source by specifying this arg but then it's up
+# to you to make sure that the LLVM repo given matches the release configuration
+# specified.
+, monorepoSrc ? null
+}:
+
+assert let
+  int = a: if a then 1 else 0;
+  xor = a: b: ((builtins.bitXor (int a) (int b)) == 1);
+in
+  lib.assertMsg
+    (xor
+      (gitRelease != null)
+      (officialRelease != null))
+    ("must specify `gitRelease` or `officialRelease`" +
+      (lib.optionalString (gitRelease != null) " — not both"));
+let
+  monorepoSrc' = monorepoSrc;
+in let
+  releaseInfo = if gitRelease != null then rec {
+    original = gitRelease;
+    release_version = original.version;
+    version = gitRelease.rev-version;
+  } else rec {
+    original = officialRelease;
+    release_version = original.version;
+    version = if original ? candidate then
+      "${release_version}-${original.candidate}"
+    else
+      release_version;
+  };
+
+  monorepoSrc = if monorepoSrc' != null then
+    monorepoSrc'
+  else let
+    sha256 = releaseInfo.original.sha256;
+    rev = if gitRelease != null then
+      gitRelease.rev
+    else
+      "llvmorg-${releaseInfo.version}";
+  in fetchFromGitHub {
+    owner = "llvm";
+    repo = "llvm-project";
+    inherit rev sha256;
+  };
+
+  inherit (releaseInfo) release_version version;
+
+  llvm_meta = {
+    license     = with lib.licenses; [ ncsa llvm-exception ];
+    maintainers = lib.teams.llvm.members;
+    platforms   = lib.platforms.all;
+  };
+
+  tools = lib.makeExtensible (tools: let
+    callPackage = newScope (tools // { inherit stdenv cmake ninja libxml2 python3 release_version version monorepoSrc buildLlvmTools; });
+    mkExtraBuildCommands0 = cc: ''
+      rsrc="$out/resource-root"
+      mkdir "$rsrc"
+      ln -s "${cc.lib}/lib/clang/${release_version}/include" "$rsrc"
+      echo "-resource-dir=$rsrc" >> $out/nix-support/cc-cflags
+    '';
+    mkExtraBuildCommands = cc: mkExtraBuildCommands0 cc + ''
+      ln -s "${targetLlvmLibraries.compiler-rt.out}/lib" "$rsrc/lib"
+      ln -s "${targetLlvmLibraries.compiler-rt.out}/share" "$rsrc/share"
+    '';
+
+  bintoolsNoLibc' =
+    if bootBintoolsNoLibc == null
+    then tools.bintoolsNoLibc
+    else bootBintoolsNoLibc;
+  bintools' =
+    if bootBintools == null
+    then tools.bintools
+    else bootBintools;
+
+  in {
+
+    libllvm = callPackage ./llvm {
+      inherit llvm_meta;
+    };
+
+    # `llvm` historically had the binaries.  When choosing an output explicitly,
+    # we need to reintroduce `outputSpecified` to get the expected behavior e.g. of lib.get*
+    llvm = tools.libllvm.out // { outputSpecified = false; };
+
+    libclang = callPackage ./clang {
+      inherit llvm_meta;
+    };
+
+    clang-unwrapped = tools.libclang.out // { outputSpecified = false; };
+
+    llvm-manpages = lowPrio (tools.libllvm.override {
+      enableManpages = true;
+      python3 = pkgs.python3;  # don't use python-boot
+    });
+
+    clang-manpages = lowPrio (tools.libclang.override {
+      enableManpages = true;
+      python3 = pkgs.python3;  # don't use python-boot
+    });
+
+    lldb-manpages = lowPrio (tools.lldb.override {
+      enableManpages = true;
+      python3 = pkgs.python3;  # don't use python-boot
+    });
+
+    # pick clang appropriate for package set we are targeting
+    clang =
+      /**/ if stdenv.targetPlatform.useLLVM or false then tools.clangUseLLVM
+      else if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU then tools.libstdcxxClang
+      else tools.libcxxClang;
+
+    libstdcxxClang = wrapCCWith rec {
+      cc = tools.clang-unwrapped;
+      # libstdcxx is taken from gcc in an ad-hoc way in cc-wrapper.
+      libcxx = null;
+      extraPackages = [
+        targetLlvmLibraries.compiler-rt
+      ];
+      extraBuildCommands = mkExtraBuildCommands cc;
+    };
+
+    libcxxClang = wrapCCWith rec {
+      cc = tools.clang-unwrapped;
+      libcxx = targetLlvmLibraries.libcxx;
+      extraPackages = [
+        libcxx.cxxabi
+        targetLlvmLibraries.compiler-rt
+      ];
+      extraBuildCommands = mkExtraBuildCommands cc;
+    };
+
+    lld = callPackage ./lld {
+      inherit llvm_meta;
+    };
+
+    lldb = callPackage ./lldb {
+      inherit llvm_meta;
+      inherit (darwin) libobjc bootstrap_cmds;
+      inherit (darwin.apple_sdk.libs) xpc;
+      inherit (darwin.apple_sdk.frameworks) Foundation Carbon Cocoa;
+    };
+
+    # Below, is the LLVM bootstrapping logic. It handles building a
+    # fully LLVM toolchain from scratch. No GCC toolchain should be
+    # pulled in. As a consequence, it is very quick to build different
+    # targets provided by LLVM and we can also build for what GCC
+    # doesn’t support like LLVM. Probably we should move to some other
+    # file.
+
+    bintools-unwrapped = callPackage ./bintools {};
+
+    bintoolsNoLibc = wrapBintoolsWith {
+      bintools = tools.bintools-unwrapped;
+      libc = preLibcCrossHeaders;
+    };
+
+    bintools = wrapBintoolsWith {
+      bintools = tools.bintools-unwrapped;
+    };
+
+    clangUseLLVM = wrapCCWith rec {
+      cc = tools.clang-unwrapped;
+      libcxx = targetLlvmLibraries.libcxx;
+      bintools = bintools';
+      extraPackages = [
+        libcxx.cxxabi
+        targetLlvmLibraries.compiler-rt
+      ] ++ lib.optionals (!stdenv.targetPlatform.isWasm) [
+        targetLlvmLibraries.libunwind
+      ];
+      extraBuildCommands = mkExtraBuildCommands cc;
+      nixSupport.cc-cflags =
+        [ "-rtlib=compiler-rt"
+          "-Wno-unused-command-line-argument"
+          "-B${targetLlvmLibraries.compiler-rt}/lib"
+        ]
+        ++ lib.optional (!stdenv.targetPlatform.isWasm) "--unwindlib=libunwind"
+        ++ lib.optional
+          (!stdenv.targetPlatform.isWasm && stdenv.targetPlatform.useLLVM or false)
+          "-lunwind"
+        ++ lib.optional stdenv.targetPlatform.isWasm "-fno-exceptions";
+    };
+
+    clangNoLibcxx = wrapCCWith rec {
+      cc = tools.clang-unwrapped;
+      libcxx = null;
+      bintools = bintools';
+      extraPackages = [
+        targetLlvmLibraries.compiler-rt
+      ];
+      extraBuildCommands = mkExtraBuildCommands cc;
+      nixSupport.cc-cflags = [
+        "-rtlib=compiler-rt"
+        "-B${targetLlvmLibraries.compiler-rt}/lib"
+        "-nostdlib++"
+      ];
+    };
+
+    clangNoLibc = wrapCCWith rec {
+      cc = tools.clang-unwrapped;
+      libcxx = null;
+      bintools = bintoolsNoLibc';
+      extraPackages = [
+        targetLlvmLibraries.compiler-rt
+      ];
+      extraBuildCommands = mkExtraBuildCommands cc;
+      nixSupport.cc-cflags = [
+        "-rtlib=compiler-rt"
+        "-B${targetLlvmLibraries.compiler-rt}/lib"
+      ];
+    };
+
+    clangNoCompilerRt = wrapCCWith rec {
+      cc = tools.clang-unwrapped;
+      libcxx = null;
+      bintools = bintoolsNoLibc';
+      extraPackages = [ ];
+      extraBuildCommands = mkExtraBuildCommands0 cc;
+      nixSupport.cc-cflags = [ "-nostartfiles" ];
+    };
+
+    clangNoCompilerRtWithLibc = wrapCCWith rec {
+      cc = tools.clang-unwrapped;
+      libcxx = null;
+      bintools = bintools';
+      extraPackages = [ ];
+      extraBuildCommands = mkExtraBuildCommands0 cc;
+    };
+
+  });
+
+  libraries = lib.makeExtensible (libraries: let
+    callPackage = newScope (libraries // buildLlvmTools // { inherit stdenv cmake ninja libxml2 python3 release_version version monorepoSrc; });
+  in {
+
+    compiler-rt-libc = callPackage ./compiler-rt {
+      inherit llvm_meta;
+      stdenv = if stdenv.hostPlatform.useLLVM or false
+               then overrideCC stdenv buildLlvmTools.clangNoCompilerRtWithLibc
+               else stdenv;
+    };
+
+    compiler-rt-no-libc = callPackage ./compiler-rt {
+      inherit llvm_meta;
+      stdenv = if stdenv.hostPlatform.useLLVM or false
+               then overrideCC stdenv buildLlvmTools.clangNoCompilerRt
+               else stdenv;
+    };
+
+    # N.B. condition is safe because without useLLVM both are the same.
+    compiler-rt = if stdenv.hostPlatform.isAndroid
+      then libraries.compiler-rt-libc
+      else libraries.compiler-rt-no-libc;
+
+    stdenv = overrideCC stdenv buildLlvmTools.clang;
+
+    libcxxStdenv = overrideCC stdenv buildLlvmTools.libcxxClang;
+
+    libcxxabi = let
+      # CMake will "require" a compiler capable of compiling C++ programs
+      # cxx-header's build does not actually use one so it doesn't really matter
+      # what stdenv we use here, as long as CMake is happy.
+      cxx-headers = callPackage ./libcxx {
+        inherit llvm_meta;
+        # Note that if we use the regular stdenv here we'll get cycle errors
+        # when attempting to use this compiler in the stdenv.
+        #
+        # The final stdenv pulls `cxx-headers` from the package set where
+        # hostPlatform *is* the target platform which means that `stdenv` at
+        # that point attempts to use this toolchain.
+        #
+        # So, we use `stdenv_` (the stdenv containing `clang` from this package
+        # set, defined below) to sidestep this issue.
+        #
+        # Because we only use `cxx-headers` in `libcxxabi` (which depends on the
+        # clang stdenv _anyways_), this is okay.
+        stdenv = stdenv_;
+        headersOnly = true;
+      };
+
+      # `libcxxabi` *doesn't* need a compiler with a working C++ stdlib but it
+      # *does* need a relatively modern C++ compiler (see:
+      # https://releases.llvm.org/15.0.0/projects/libcxx/docs/index.html#platform-and-compiler-support).
+      #
+      # So, we use the clang from this LLVM package set, like libc++
+      # "boostrapping builds" do:
+      # https://releases.llvm.org/15.0.0/projects/libcxx/docs/BuildingLibcxx.html#bootstrapping-build
+      #
+      # We cannot use `clangNoLibcxx` because that contains `compiler-rt` which,
+      # on macOS, depends on `libcxxabi`, thus forming a cycle.
+      stdenv_ = overrideCC stdenv buildLlvmTools.clangNoCompilerRtWithLibc;
+    in callPackage ./libcxxabi {
+      stdenv = stdenv_;
+      inherit llvm_meta cxx-headers;
+    };
+
+    # Like `libcxxabi` above, `libcxx` requires a fairly modern C++ compiler,
+    # so: we use the clang from this LLVM package set instead of the regular
+    # stdenv's compiler.
+    libcxx = callPackage ./libcxx {
+      inherit llvm_meta;
+      stdenv = overrideCC stdenv buildLlvmTools.clangNoLibcxx;
+    };
+
+    libunwind = callPackage ./libunwind {
+      inherit llvm_meta;
+      stdenv = overrideCC stdenv buildLlvmTools.clangNoLibcxx;
+    };
+
+    openmp = callPackage ./openmp {
+      inherit llvm_meta targetLlvm;
+    };
+  });
+
+in { inherit tools libraries release_version; } // libraries // tools
diff --git a/pkgs/development/compilers/llvm/15/libcxx/default.nix b/pkgs/development/compilers/llvm/15/libcxx/default.nix
new file mode 100644
index 0000000000000..7762df29386ef
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/libcxx/default.nix
@@ -0,0 +1,107 @@
+{ lib, stdenv, llvm_meta
+, monorepoSrc, runCommand
+, cmake, ninja, python3, fixDarwinDylibNames, version
+, cxxabi ? if stdenv.hostPlatform.isFreeBSD then libcxxrt else libcxxabi
+, libcxxabi, libcxxrt
+, enableShared ? !stdenv.hostPlatform.isStatic
+
+# If headersOnly is true, the resulting package would only include the headers.
+# Use this to break the circular dependency between libcxx and libcxxabi.
+#
+# Some context:
+# https://reviews.llvm.org/rG1687f2bbe2e2aaa092f942d4a97d41fad43eedfb
+, headersOnly ? false
+}:
+
+let
+  basename = "libcxx";
+in
+
+assert stdenv.isDarwin -> cxxabi.libName == "c++abi";
+
+stdenv.mkDerivation rec {
+  pname = basename + lib.optionalString headersOnly "-headers";
+  inherit version;
+
+  src = runCommand "${pname}-src-${version}" {} ''
+    mkdir -p "$out"
+    cp -r ${monorepoSrc}/cmake "$out"
+    cp -r ${monorepoSrc}/${basename} "$out"
+    mkdir -p "$out/libcxxabi"
+    cp -r ${monorepoSrc}/libcxxabi/include "$out/libcxxabi"
+    mkdir -p "$out/llvm"
+    cp -r ${monorepoSrc}/llvm/cmake "$out/llvm"
+    cp -r ${monorepoSrc}/llvm/utils "$out/llvm"
+    cp -r ${monorepoSrc}/third-party "$out"
+    cp -r ${monorepoSrc}/runtimes "$out"
+  '';
+
+  sourceRoot = "${src.name}/runtimes";
+
+  outputs = [ "out" ] ++ lib.optional (!headersOnly) "dev";
+
+  prePatch = ''
+    cd ../${basename}
+    chmod -R u+w .
+  '';
+
+  patches = [
+    ./gnu-install-dirs.patch
+  ] ++ lib.optionals stdenv.hostPlatform.isMusl [
+    ../../libcxx-0001-musl-hacks.patch
+  ];
+
+  postPatch = ''
+    cd ../runtimes
+  '';
+
+  preConfigure = lib.optionalString stdenv.hostPlatform.isMusl ''
+    patchShebangs utils/cat_files.py
+  '';
+
+  nativeBuildInputs = [ cmake ninja python3 ]
+    ++ lib.optional stdenv.isDarwin fixDarwinDylibNames;
+
+  buildInputs = lib.optionals (!headersOnly) [ cxxabi ];
+
+  cmakeFlags = let
+    # See: https://libcxx.llvm.org/BuildingLibcxx.html#cmdoption-arg-libcxx-cxx-abi-string
+    libcxx_cxx_abi_opt = {
+      "c++abi" = "system-libcxxabi";
+      "cxxrt" = "libcxxrt";
+    }.${cxxabi.libName} or (throw "unknown cxxabi: ${cxxabi.libName} (${cxxabi.pname})");
+  in [
+    "-DLLVM_ENABLE_RUNTIMES=libcxx"
+    "-DLIBCXX_CXX_ABI=${if headersOnly then "none" else libcxx_cxx_abi_opt}"
+  ] ++ lib.optional (!headersOnly && cxxabi.libName == "c++abi") "-DLIBCXX_CXX_ABI_INCLUDE_PATHS=${cxxabi.dev}/include/c++/v1"
+    ++ lib.optional (stdenv.hostPlatform.isMusl || stdenv.hostPlatform.isWasi) "-DLIBCXX_HAS_MUSL_LIBC=1"
+    ++ lib.optional (stdenv.hostPlatform.useLLVM or false) "-DLIBCXX_USE_COMPILER_RT=ON"
+    ++ lib.optionals stdenv.hostPlatform.isWasm [
+      "-DLIBCXX_ENABLE_THREADS=OFF"
+      "-DLIBCXX_ENABLE_FILESYSTEM=OFF"
+      "-DLIBCXX_ENABLE_EXCEPTIONS=OFF"
+    ] ++ lib.optional (!enableShared) "-DLIBCXX_ENABLE_SHARED=OFF"
+    # If we're only building the headers we don't actually *need* a functioning
+    # C/C++ compiler:
+    ++ lib.optionals (headersOnly) [
+      "-DCMAKE_C_COMPILER_WORKS=ON"
+      "-DCMAKE_CXX_COMPILER_WORKS=ON"
+    ];
+
+  ninjaFlags = lib.optional headersOnly "generate-cxx-headers";
+  installTargets = lib.optional headersOnly "install-cxx-headers";
+
+  passthru = {
+    isLLVM = true;
+    inherit cxxabi;
+  };
+
+  meta = llvm_meta // {
+    homepage = "https://libcxx.llvm.org/";
+    description = "C++ standard library";
+    longDescription = ''
+      libc++ is an implementation of the C++ standard library, targeting C++11,
+      C++14 and above.
+    '';
+  };
+}
diff --git a/pkgs/development/compilers/llvm/15/libcxx/gnu-install-dirs.patch b/pkgs/development/compilers/llvm/15/libcxx/gnu-install-dirs.patch
new file mode 100644
index 0000000000000..daee5bdd0ed33
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/libcxx/gnu-install-dirs.patch
@@ -0,0 +1,22 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index 74eff2002fc9..c935d10878bb 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -419,7 +419,7 @@ if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
+   set(LIBCXX_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/${LLVM_DEFAULT_TARGET_TRIPLE})
+   set(LIBCXX_GENERATED_INCLUDE_DIR "${LLVM_BINARY_DIR}/include/c++/v1")
+   set(LIBCXX_GENERATED_INCLUDE_TARGET_DIR "${LLVM_BINARY_DIR}/include/${LLVM_DEFAULT_TARGET_TRIPLE}/c++/v1")
+-  set(LIBCXX_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX}/${LLVM_DEFAULT_TARGET_TRIPLE} CACHE PATH
++  set(LIBCXX_INSTALL_LIBRARY_DIR ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}/${LLVM_DEFAULT_TARGET_TRIPLE} CACHE PATH
+       "Path where built libc++ libraries should be installed.")
+   set(LIBCXX_INSTALL_INCLUDE_TARGET_DIR "${CMAKE_INSTALL_INCLUDEDIR}/${LLVM_DEFAULT_TARGET_TRIPLE}/c++/v1" CACHE PATH
+       "Path where target-specific libc++ headers should be installed.")
+@@ -436,7 +436,7 @@ else()
+     set(LIBCXX_GENERATED_INCLUDE_DIR "${CMAKE_BINARY_DIR}/include/c++/v1")
+   endif()
+   set(LIBCXX_GENERATED_INCLUDE_TARGET_DIR "${LIBCXX_GENERATED_INCLUDE_DIR}")
+-  set(LIBCXX_INSTALL_LIBRARY_DIR lib${LIBCXX_LIBDIR_SUFFIX} CACHE PATH
++  set(LIBCXX_INSTALL_LIBRARY_DIR ${CMAKE_INSTALL_LIBDIR}${LIBCXX_LIBDIR_SUFFIX} CACHE PATH
+       "Path where built libc++ libraries should be installed.")
+   set(LIBCXX_INSTALL_INCLUDE_TARGET_DIR "${LIBCXX_INSTALL_INCLUDE_DIR}" CACHE PATH
+       "Path where target-specific libc++ headers should be installed.")
diff --git a/pkgs/development/compilers/llvm/15/libcxxabi/default.nix b/pkgs/development/compilers/llvm/15/libcxxabi/default.nix
new file mode 100644
index 0000000000000..fd99f4553c0cc
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/libcxxabi/default.nix
@@ -0,0 +1,105 @@
+{ lib, stdenv, llvm_meta, cmake, ninja, python3
+, monorepoSrc, runCommand, fetchpatch
+, cxx-headers, libunwind, version
+, enableShared ? !stdenv.hostPlatform.isStatic
+}:
+
+stdenv.mkDerivation rec {
+  pname = "libcxxabi";
+  inherit version;
+
+  src = runCommand "${pname}-src-${version}" {} ''
+    mkdir -p "$out"
+    cp -r ${monorepoSrc}/cmake "$out"
+    cp -r ${monorepoSrc}/${pname} "$out"
+    mkdir -p "$out/libcxx/src"
+    cp -r ${monorepoSrc}/libcxx/cmake "$out/libcxx"
+    cp -r ${monorepoSrc}/libcxx/include "$out/libcxx"
+    cp -r ${monorepoSrc}/libcxx/src/include "$out/libcxx/src"
+    mkdir -p "$out/llvm"
+    cp -r ${monorepoSrc}/llvm/cmake "$out/llvm"
+    cp -r ${monorepoSrc}/llvm/utils "$out/llvm"
+    cp -r ${monorepoSrc}/runtimes "$out"
+  '';
+
+  sourceRoot = "${src.name}/runtimes";
+
+  outputs = [ "out" "dev" ];
+
+  postUnpack = lib.optionalString stdenv.isDarwin ''
+    export TRIPLE=x86_64-apple-darwin
+  '' + lib.optionalString stdenv.hostPlatform.isWasm ''
+    patch -p1 -d llvm -i ${./wasm.patch}
+  '';
+
+  prePatch = ''
+    cd ../${pname}
+    chmod -R u+w .
+  '';
+
+  patches = [
+    ./gnu-install-dirs.patch
+
+    # https://reviews.llvm.org/D132298, Allow building libcxxabi alone
+    (fetchpatch {
+      url = "https://github.com/llvm/llvm-project/commit/e6a0800532bb409f6d1c62f3698bdd6994a877dc.patch";
+      sha256 = "1xyjd56m4pfwq8p3xh6i8lhkk9kq15jaml7qbhxdf87z4jjkk63a";
+      stripLen = 1;
+    })
+  ];
+
+  postPatch = ''
+    cd ../runtimes
+  '';
+
+  nativeBuildInputs = [ cmake ninja python3 ];
+  buildInputs = lib.optional (!stdenv.isDarwin && !stdenv.hostPlatform.isWasm) libunwind;
+
+  cmakeFlags = [
+    "-DLLVM_ENABLE_RUNTIMES=libcxxabi"
+    "-DLIBCXXABI_LIBCXX_INCLUDES=${cxx-headers}/include/c++/v1"
+
+    # `libcxxabi`'s build does not need a toolchain with a c++ stdlib attached
+    # (we specify the headers it should use explicitly above).
+    #
+    # CMake however checks for this anyways; this flag tells it not to. See:
+    # https://github.com/llvm/llvm-project/blob/4bd3f3759259548e159aeba5c76efb9a0864e6fa/llvm/runtimes/CMakeLists.txt#L243
+    "-DCMAKE_CXX_COMPILER_WORKS=ON"
+  ] ++ lib.optionals (stdenv.hostPlatform.useLLVM or false) [
+    "-DLLVM_ENABLE_LIBCXX=ON"
+    "-DLIBCXXABI_USE_LLVM_UNWINDER=ON"
+  ] ++ lib.optionals stdenv.hostPlatform.isWasm [
+    "-DLIBCXXABI_ENABLE_THREADS=OFF"
+    "-DLIBCXXABI_ENABLE_EXCEPTIONS=OFF"
+  ] ++ lib.optionals (!enableShared) [
+    "-DLIBCXXABI_ENABLE_SHARED=OFF"
+  ];
+
+  preInstall = lib.optionalString stdenv.isDarwin ''
+    for file in lib/*.dylib; do
+      # this should be done in CMake, but having trouble figuring out
+      # the magic combination of necessary CMake variables
+      # if you fancy a try, take a look at
+      # https://gitlab.kitware.com/cmake/community/-/wikis/doc/cmake/RPATH-handling
+      install_name_tool -id $out/$file $file
+    done
+  '';
+
+  postInstall = ''
+    mkdir -p "$dev/include"
+    install -m 644 ../../${pname}/include/${if stdenv.isDarwin then "*" else "cxxabi.h"} "$dev/include"
+  '';
+
+  passthru = {
+    libName = "c++abi";
+  };
+
+  meta = llvm_meta // {
+    homepage = "https://libcxxabi.llvm.org/";
+    description = "Provides C++ standard library support";
+    longDescription = ''
+      libc++abi is a new implementation of low level support for a standard C++ library.
+    '';
+    maintainers = llvm_meta.maintainers ++ [ lib.maintainers.vlstill ];
+  };
+}
diff --git a/pkgs/development/compilers/llvm/15/libcxxabi/gnu-install-dirs.patch b/pkgs/development/compilers/llvm/15/libcxxabi/gnu-install-dirs.patch
new file mode 100644
index 0000000000000..fa587612aaf63
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/libcxxabi/gnu-install-dirs.patch
@@ -0,0 +1,22 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index b8326d08d23a..a1e36f713161 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -187,7 +187,7 @@ set(LIBCXXABI_INSTALL_RUNTIME_DIR "${CMAKE_INSTALL_BINDIR}" CACHE PATH
+ if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
+   set(LIBCXXABI_HEADER_DIR ${LLVM_BINARY_DIR})
+   set(LIBCXXABI_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/${LLVM_DEFAULT_TARGET_TRIPLE})
+-  set(LIBCXXABI_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX}/${LLVM_DEFAULT_TARGET_TRIPLE} CACHE PATH
++  set(LIBCXXABI_INSTALL_LIBRARY_DIR ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}/${LLVM_DEFAULT_TARGET_TRIPLE} CACHE PATH
+       "Path where built libc++abi libraries should be installed.")
+   if(LIBCXX_LIBDIR_SUBDIR)
+     string(APPEND LIBCXXABI_LIBRARY_DIR /${LIBCXXABI_LIBDIR_SUBDIR})
+@@ -201,7 +201,7 @@ else()
+     set(LIBCXXABI_HEADER_DIR ${CMAKE_BINARY_DIR})
+     set(LIBCXXABI_LIBRARY_DIR ${CMAKE_BINARY_DIR}/lib${LIBCXXABI_LIBDIR_SUFFIX})
+   endif()
+-  set(LIBCXXABI_INSTALL_LIBRARY_DIR lib${LIBCXXABI_LIBDIR_SUFFIX} CACHE PATH
++  set(LIBCXXABI_INSTALL_LIBRARY_DIR ${CMAKE_INSTALL_LIBDIR}${LIBCXXABI_LIBDIR_SUFFIX} CACHE PATH
+       "Path where built libc++abi libraries should be installed.")
+ endif()
+ 
diff --git a/pkgs/development/compilers/llvm/15/libcxxabi/wasm.patch b/pkgs/development/compilers/llvm/15/libcxxabi/wasm.patch
new file mode 100644
index 0000000000000..4ebfe46aa813d
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/libcxxabi/wasm.patch
@@ -0,0 +1,16 @@
+diff --git a/cmake/modules/HandleLLVMOptions.cmake b/cmake/modules/HandleLLVMOptions.cmake
+index 15497d405e0..33f7f18193a 100644
+--- a/cmake/modules/HandleLLVMOptions.cmake
++++ b/cmake/modules/HandleLLVMOptions.cmake
+@@ -127,7 +127,10 @@ else(WIN32)
+       set(LLVM_HAVE_LINK_VERSION_SCRIPT 1)
+     endif()
+   else(FUCHSIA OR UNIX)
+-    MESSAGE(SEND_ERROR "Unable to determine platform")
++    if(${CMAKE_SYSTEM_NAME} MATCHES "Wasi")
++    else()
++      MESSAGE(SEND_ERROR "Unable to determine platform")
++    endif()
+   endif(FUCHSIA OR UNIX)
+ endif(WIN32)
+ 
diff --git a/pkgs/development/compilers/llvm/15/libunwind/default.nix b/pkgs/development/compilers/llvm/15/libunwind/default.nix
new file mode 100644
index 0000000000000..dd14e2acaf869
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/libunwind/default.nix
@@ -0,0 +1,62 @@
+{ lib, stdenv, llvm_meta, version
+, monorepoSrc, runCommand
+, cmake
+, ninja
+, python3
+, enableShared ? !stdenv.hostPlatform.isStatic
+}:
+
+stdenv.mkDerivation rec {
+  pname = "libunwind";
+  inherit version;
+
+  # I am not so comfortable giving libc++ and friends the whole monorepo as
+  # requested, so I filter it to what is needed.
+  src = runCommand "${pname}-src-${version}" {} ''
+    mkdir -p "$out"
+    cp -r ${monorepoSrc}/cmake "$out"
+    cp -r ${monorepoSrc}/${pname} "$out"
+    mkdir -p "$out/libcxx"
+    cp -r ${monorepoSrc}/libcxx/cmake "$out/libcxx"
+    cp -r ${monorepoSrc}/libcxx/utils "$out/libcxx"
+    mkdir -p "$out/llvm"
+    cp -r ${monorepoSrc}/llvm/cmake "$out/llvm"
+    cp -r ${monorepoSrc}/llvm/utils "$out/llvm"
+    cp -r ${monorepoSrc}/runtimes "$out"
+  '';
+
+  sourceRoot = "${src.name}/runtimes";
+
+  prePatch = ''
+    cd ../${pname}
+    chmod -R u+w .
+  '';
+
+  patches = [
+    ./gnu-install-dirs.patch
+  ];
+
+  postPatch = ''
+    cd ../runtimes
+  '';
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [ cmake ninja python3 ];
+
+  cmakeFlags = [
+    "-DLLVM_ENABLE_RUNTIMES=libunwind"
+  ] ++ lib.optional (!enableShared) "-DLIBUNWIND_ENABLE_SHARED=OFF";
+
+  meta = llvm_meta // {
+    # Details: https://github.com/llvm/llvm-project/blob/main/libunwind/docs/index.rst
+    homepage = "https://clang.llvm.org/docs/Toolchain.html#unwind-library";
+    description = "LLVM's unwinder library";
+    longDescription = ''
+      The unwind library provides a family of _Unwind_* functions implementing
+      the language-neutral stack unwinding portion of the Itanium C++ ABI (Level
+      I). It is a dependency of the C++ ABI library, and sometimes is a
+      dependency of other runtimes.
+    '';
+  };
+}
diff --git a/pkgs/development/compilers/llvm/15/libunwind/gnu-install-dirs.patch b/pkgs/development/compilers/llvm/15/libunwind/gnu-install-dirs.patch
new file mode 100644
index 0000000000000..edfb2a8760bd6
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/libunwind/gnu-install-dirs.patch
@@ -0,0 +1,22 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index 5a06805f05f1..86a50329e6a8 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -117,7 +117,7 @@ set(LIBUNWIND_INSTALL_RUNTIME_DIR "${CMAKE_INSTALL_BINDIR}" CACHE PATH
+ 
+ if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
+   set(LIBUNWIND_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/${LLVM_DEFAULT_TARGET_TRIPLE})
+-  set(LIBUNWIND_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX}/${LLVM_DEFAULT_TARGET_TRIPLE} CACHE PATH
++  set(LIBUNWIND_INSTALL_LIBRARY_DIR ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}/${LLVM_DEFAULT_TARGET_TRIPLE} CACHE PATH
+       "Path where built libunwind libraries should be installed.")
+   if(LIBCXX_LIBDIR_SUBDIR)
+     string(APPEND LIBUNWIND_LIBRARY_DIR /${LIBUNWIND_LIBDIR_SUBDIR})
+@@ -129,7 +129,7 @@ else()
+   else()
+     set(LIBUNWIND_LIBRARY_DIR ${CMAKE_BINARY_DIR}/lib${LIBUNWIND_LIBDIR_SUFFIX})
+   endif()
+-  set(LIBUNWIND_INSTALL_LIBRARY_DIR lib${LIBUNWIND_LIBDIR_SUFFIX} CACHE PATH
++  set(LIBUNWIND_INSTALL_LIBRARY_DIR ${CMAKE_INSTALL_LIBDIR}${LIBUNWIND_LIBDIR_SUFFIX} CACHE PATH
+       "Path where built libunwind libraries should be installed.")
+ endif()
+ 
diff --git a/pkgs/development/compilers/llvm/15/lld/default.nix b/pkgs/development/compilers/llvm/15/lld/default.nix
new file mode 100644
index 0000000000000..e8bca769de5fa
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/lld/default.nix
@@ -0,0 +1,55 @@
+{ lib, stdenv, llvm_meta
+, buildLlvmTools
+, monorepoSrc, runCommand
+, cmake
+, ninja
+, libxml2
+, libllvm
+, version
+}:
+
+stdenv.mkDerivation rec {
+  pname = "lld";
+  inherit version;
+
+  # Blank llvm dir just so relative path works
+  src = runCommand "${pname}-src-${version}" {} ''
+    mkdir -p "$out"
+    cp -r ${monorepoSrc}/cmake "$out"
+    cp -r ${monorepoSrc}/${pname} "$out"
+    mkdir -p "$out/libunwind"
+    cp -r ${monorepoSrc}/libunwind/include "$out/libunwind"
+    mkdir -p "$out/llvm"
+  '';
+
+  sourceRoot = "${src.name}/${pname}";
+
+  patches = [
+    ./gnu-install-dirs.patch
+  ];
+
+  nativeBuildInputs = [ cmake ninja ];
+  buildInputs = [ libllvm libxml2 ];
+
+  cmakeFlags = [
+    "-DLLD_INSTALL_PACKAGE_DIR=${placeholder "dev"}/lib/cmake/lld"
+  ] ++ lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
+    "-DLLVM_TABLEGEN_EXE=${buildLlvmTools.llvm}/bin/llvm-tblgen"
+  ];
+  LDFLAGS = lib.optionalString stdenv.hostPlatform.isMusl "-Wl,-z,stack-size=2097152";
+
+  outputs = [ "out" "lib" "dev" ];
+
+  meta = llvm_meta // {
+    homepage = "https://lld.llvm.org/";
+    description = "The LLVM linker (unwrapped)";
+    longDescription = ''
+      LLD is a linker from the LLVM project that is a drop-in replacement for
+      system linkers and runs much faster than them. It also provides features
+      that are useful for toolchain developers.
+      The linker supports ELF (Unix), PE/COFF (Windows), Mach-O (macOS), and
+      WebAssembly in descending order of completeness. Internally, LLD consists
+      of several different linkers.
+    '';
+  };
+}
diff --git a/pkgs/development/compilers/llvm/15/lld/gnu-install-dirs.patch b/pkgs/development/compilers/llvm/15/lld/gnu-install-dirs.patch
new file mode 100644
index 0000000000000..ea62b2ad50c75
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/lld/gnu-install-dirs.patch
@@ -0,0 +1,46 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index dcc649629a4b..58dca54642e4 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -70,13 +70,15 @@ if(LLD_BUILT_STANDALONE)
+   if (NOT LLVM_CONFIG_FOUND)
+     # Pull values from LLVMConfig.cmake.  We can drop this once the llvm-config
+     # path is removed.
+-    set(MAIN_INCLUDE_DIR "${LLVM_INCLUDE_DIR}")
++    set(INCLUDE_DIRS ${LLVM_INCLUDE_DIRS})
+     set(LLVM_OBJ_DIR "${LLVM_BINARY_DIR}")
+     # N.B. this is just a default value, the CACHE PATHs below can be overridden.
+     set(MAIN_SRC_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../llvm")
++  else()
++    set(INCLUDE_DIRS "${LLVM_BINARY_DIR}/include" "${MAIN_INCLUDE_DIR}")
+   endif()
+ 
+-  set(LLVM_MAIN_INCLUDE_DIR "${MAIN_INCLUDE_DIR}" CACHE PATH "Path to llvm/include")
++  set(LLVM_INCLUDE_DIRS ${INCLUDE_DIRS} CACHE PATH "Path to llvm/include and any other header dirs needed")
+   set(LLVM_BINARY_DIR "${LLVM_OBJ_ROOT}" CACHE PATH "Path to LLVM build tree")
+   set(LLVM_MAIN_SRC_DIR "${MAIN_SRC_DIR}" CACHE PATH "Path to LLVM source tree")
+ 
+@@ -95,7 +97,7 @@ if(LLD_BUILT_STANDALONE)
+ 
+   set(PACKAGE_VERSION "${LLVM_PACKAGE_VERSION}")
+ 
+-  include_directories("${LLVM_BINARY_DIR}/include" ${LLVM_INCLUDE_DIRS})
++  include_directories(${LLVM_INCLUDE_DIRS})
+   link_directories(${LLVM_LIBRARY_DIRS})
+ 
+   if(LLVM_INCLUDE_TESTS)
+diff --git a/cmake/modules/AddLLD.cmake b/cmake/modules/AddLLD.cmake
+index d3924f7243d4..42a7cd62281c 100644
+--- a/cmake/modules/AddLLD.cmake
++++ b/cmake/modules/AddLLD.cmake
+@@ -18,8 +18,8 @@ macro(add_lld_library name)
+     install(TARGETS ${name}
+       COMPONENT ${name}
+       ${export_to_lldtargets}
+-      LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX}
+-      ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX}
++      LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}"
++      ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}"
+       RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}")
+ 
+     if (${ARG_SHARED} AND NOT CMAKE_CONFIGURATION_TYPES)
diff --git a/pkgs/development/compilers/llvm/15/lldb/cpu_subtype_arm64e_replacement.patch b/pkgs/development/compilers/llvm/15/lldb/cpu_subtype_arm64e_replacement.patch
new file mode 100644
index 0000000000000..20d35c9f3ea91
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/lldb/cpu_subtype_arm64e_replacement.patch
@@ -0,0 +1,12 @@
+diff --git a/source/Host/macosx/objcxx/HostInfoMacOSX.mm b/source/Host/macosx/objcxx/HostInfoMacOSX.mm
+--- a/source/Host/macosx/objcxx/HostInfoMacOSX.mm
++++ b/source/Host/macosx/objcxx/HostInfoMacOSX.mm
+@@ -233,7 +233,7 @@ void HostInfoMacOSX::ComputeHostArchitectureSupport(ArchSpec &arch_32,
+     len = sizeof(is_64_bit_capable);
+     ::sysctlbyname("hw.cpu64bit_capable", &is_64_bit_capable, &len, NULL, 0);
+ 
+-    if (cputype == CPU_TYPE_ARM64 && cpusubtype == CPU_SUBTYPE_ARM64E) {
++    if (cputype == CPU_TYPE_ARM64 && cpusubtype == ((cpu_subtype_t) 2)) { // CPU_SUBTYPE_ARM64E is not available in the macOS 10.12 headers
+       // The arm64e architecture is a preview. Pretend the host architecture
+       // is arm64.
+       cpusubtype = CPU_SUBTYPE_ARM64_ALL;
diff --git a/pkgs/development/compilers/llvm/15/lldb/default.nix b/pkgs/development/compilers/llvm/15/lldb/default.nix
new file mode 100644
index 0000000000000..4b50b79cf613b
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/lldb/default.nix
@@ -0,0 +1,186 @@
+{ lib, stdenv, llvm_meta
+, runCommand
+, monorepoSrc
+, cmake
+, ninja
+, zlib
+, ncurses
+, swig
+, which
+, libedit
+, libxml2
+, libllvm
+, libclang
+, python3
+, version
+, libobjc
+, xpc
+, Foundation
+, bootstrap_cmds
+, Carbon
+, Cocoa
+, lit
+, makeWrapper
+, darwin
+, enableManpages ? false
+, lua5_3
+}:
+
+# TODO: we build the python bindings but don't expose them as a python package
+# TODO: expose the vscode extension?
+
+stdenv.mkDerivation (rec {
+  pname = "lldb";
+  inherit version;
+
+  src = runCommand "${pname}-src-${version}" {} ''
+    mkdir -p "$out"
+    cp -r ${monorepoSrc}/cmake "$out"
+    cp -r ${monorepoSrc}/${pname} "$out"
+  '';
+
+  sourceRoot = "${src.name}/${pname}";
+
+  patches = [
+    ./procfs.patch
+    (runCommand "resource-dir.patch" {
+      clangLibDir = "${libclang.lib}/lib";
+    } ''
+      substitute '${./resource-dir.patch}' "$out" --subst-var clangLibDir
+    '')
+    ./gnu-install-dirs.patch
+  ]
+  # This is a stopgap solution if/until the macOS SDK used for x86_64 is
+  # updated.
+  #
+  # The older 10.12 SDK used on x86_64 as of this writing has a `mach/machine.h`
+  # header that does not define `CPU_SUBTYPE_ARM64E` so we replace the one use
+  # of this preprocessor symbol in `lldb` with its expansion.
+  #
+  # See here for some context:
+  # https://github.com/NixOS/nixpkgs/pull/194634#issuecomment-1272129132
+  ++ lib.optional (
+    stdenv.targetPlatform.isDarwin
+      && !stdenv.targetPlatform.isAarch64
+      && (lib.versionOlder darwin.apple_sdk.sdk.version "11.0")
+  ) ./cpu_subtype_arm64e_replacement.patch;
+
+  outputs = [ "out" "lib" "dev" ];
+
+  nativeBuildInputs = [
+    cmake ninja python3 which swig lit makeWrapper lua5_3
+  ] ++ lib.optionals enableManpages [
+    python3.pkgs.sphinx python3.pkgs.recommonmark
+  ];
+
+  buildInputs = [
+    ncurses
+    zlib
+    libedit
+    libxml2
+    libllvm
+  ] ++ lib.optionals stdenv.isDarwin [
+    libobjc
+    xpc
+    Foundation
+    bootstrap_cmds
+    Carbon
+    Cocoa
+  ]
+  # The older libSystem used on x86_64 macOS is missing the
+  # `<bsm/audit_session.h>` header which `lldb` uses.
+  #
+  # We copy this header over from macOS 10.12 SDK.
+  #
+  # See here for context:
+  # https://github.com/NixOS/nixpkgs/pull/194634#issuecomment-1272129132
+  ++ lib.optional (
+      stdenv.targetPlatform.isDarwin
+        && !stdenv.targetPlatform.isAarch64
+    ) (
+      runCommand "bsm-audit-session-header" { } ''
+        install -Dm444 \
+          "${lib.getDev darwin.apple_sdk.sdk}/include/bsm/audit_session.h" \
+          "$out/include/bsm/audit_session.h"
+      ''
+    );
+
+  hardeningDisable = [ "format" ];
+
+  cmakeFlags = [
+    "-DLLDB_INCLUDE_TESTS=${if doCheck then "YES" else "NO"}"
+    "-DLLVM_ENABLE_RTTI=OFF"
+    "-DClang_DIR=${libclang.dev}/lib/cmake"
+    "-DLLVM_EXTERNAL_LIT=${lit}/bin/lit"
+  ] ++ lib.optionals stdenv.isDarwin [
+    "-DLLDB_USE_SYSTEM_DEBUGSERVER=ON"
+  ] ++ lib.optionals (!stdenv.isDarwin) [
+    "-DLLDB_CODESIGN_IDENTITY=" # codesigning makes nondeterministic
+  ] ++ lib.optionals enableManpages [
+    "-DLLVM_ENABLE_SPHINX=ON"
+    "-DSPHINX_OUTPUT_MAN=ON"
+    "-DSPHINX_OUTPUT_HTML=OFF"
+
+    # docs reference `automodapi` but it's not added to the extensions list when
+    # only building the manpages:
+    # https://github.com/llvm/llvm-project/blob/af6ec9200b09039573d85e349496c4f5b17c3d7f/lldb/docs/conf.py#L54
+    #
+    # so, we just ignore the resulting errors
+    "-DSPHINX_WARNINGS_AS_ERRORS=OFF"
+  ] ++ lib.optionals doCheck [
+    "-DLLDB_TEST_C_COMPILER=${stdenv.cc}/bin/${stdenv.cc.targetPrefix}cc"
+    "-DLLDB_TEST_CXX_COMPILER=${stdenv.cc}/bin/${stdenv.cc.targetPrefix}c++"
+  ];
+
+  doCheck = false;
+
+  installCheckPhase = ''
+    if [ ! -e "$lib/${python3.sitePackages}/lldb/_lldb.so" ] ; then
+        return 1;
+    fi
+  '';
+
+  postInstall = ''
+    wrapProgram $out/bin/lldb --prefix PYTHONPATH : $lib/${python3.sitePackages}/
+
+    # Editor support
+    # vscode:
+    install -D ../tools/lldb-vscode/package.json $out/share/vscode/extensions/llvm-org.lldb-vscode-0.1.0/package.json
+    mkdir -p $out/share/vscode/extensions/llvm-org.lldb-vscode-0.1.0/bin
+    ln -s $out/bin/lldb-vscode $out/share/vscode/extensions/llvm-org.lldb-vscode-0.1.0/bin
+  '';
+
+  meta = llvm_meta // {
+    homepage = "https://lldb.llvm.org/";
+    description = "A next-generation high-performance debugger";
+    longDescription = ''
+      LLDB is a next generation, high-performance debugger. It is built as a set
+      of reusable components which highly leverage existing libraries in the
+      larger LLVM Project, such as the Clang expression parser and LLVM
+      disassembler.
+    '';
+  };
+} // lib.optionalAttrs enableManpages {
+  pname = "lldb-manpages";
+
+  ninjaFlags = [ "docs-lldb-man" ];
+
+  propagatedBuildInputs = [];
+
+  # manually install lldb man page
+  installPhase = ''
+    mkdir -p $out/share/man/man1
+    install docs/man/lldb.1 -t $out/share/man/man1/
+  '';
+
+  postPatch = null;
+  postInstall = null;
+
+  outputs = [ "out" ];
+
+  doCheck = false;
+
+  meta = llvm_meta // {
+    description = "man pages for LLDB ${version}";
+  };
+})
diff --git a/pkgs/development/compilers/llvm/15/lldb/gnu-install-dirs.patch b/pkgs/development/compilers/llvm/15/lldb/gnu-install-dirs.patch
new file mode 100644
index 0000000000000..4388f5c7f593f
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/lldb/gnu-install-dirs.patch
@@ -0,0 +1,23 @@
+diff --git a/cmake/modules/AddLLDB.cmake b/cmake/modules/AddLLDB.cmake
+index 3291a7c808e1..b27d27ce6a87 100644
+--- a/cmake/modules/AddLLDB.cmake
++++ b/cmake/modules/AddLLDB.cmake
+@@ -109,7 +109,7 @@ function(add_lldb_library name)
+   endif()
+ 
+   if(PARAM_SHARED)
+-    set(install_dest lib${LLVM_LIBDIR_SUFFIX})
++    set(install_dest ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX})
+     if(PARAM_INSTALL_PREFIX)
+       set(install_dest ${PARAM_INSTALL_PREFIX})
+     endif()
+diff --git a/tools/intel-features/CMakeLists.txt b/tools/intel-features/CMakeLists.txt
+index 7d48491ec89a..c04543585588 100644
+--- a/tools/intel-features/CMakeLists.txt
++++ b/tools/intel-features/CMakeLists.txt
+@@ -30,4 +30,4 @@ add_lldb_library(lldbIntelFeatures SHARED
+   )
+ 
+ install(TARGETS lldbIntelFeatures
+-  LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX})
++  LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX})
diff --git a/pkgs/development/compilers/llvm/15/lldb/procfs.patch b/pkgs/development/compilers/llvm/15/lldb/procfs.patch
new file mode 100644
index 0000000000000..7b200e86505ca
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/lldb/procfs.patch
@@ -0,0 +1,46 @@
+--- a/source/Plugins/Process/Linux/Procfs.h
++++ b/source/Plugins/Process/Linux/Procfs.h
+@@ -10,6 +10,13 @@
+ // sys/procfs.h on Android/Linux for all supported architectures.
+ 
+ #include <sys/ptrace.h>
++#include <asm/ptrace.h>
++
++// on i686 preprocessor symbols with these register names are defined as
++// numeric constants; these symbols clash with identifier names used in
++// `llvm/Support/VirtualFileSystem.h` and `llvm/ADT/SmallVector.h`
++#undef FS
++#undef CS
+ 
+ #include "lldb/lldb-types.h"
+ 
+@@ -17,23 +24,13 @@
+ 
+ #include <vector>
+ 
+-#ifdef __ANDROID__
+-#if defined(__arm64__) || defined(__aarch64__)
+-typedef unsigned long elf_greg_t;
+-typedef elf_greg_t
+-    elf_gregset_t[(sizeof(struct user_pt_regs) / sizeof(elf_greg_t))];
+-typedef struct user_fpsimd_state elf_fpregset_t;
+-#ifndef NT_FPREGSET
+-#define NT_FPREGSET NT_PRFPREG
+-#endif // NT_FPREGSET
+-#elif defined(__mips__)
+-#ifndef NT_FPREGSET
+-#define NT_FPREGSET NT_PRFPREG
+-#endif // NT_FPREGSET
+-#endif
+-#else // __ANDROID__
++#if !defined(__GLIBC__) && defined(__powerpc__)
++#define pt_regs musl_pt_regs
++#include <sys/procfs.h>
++#undef pt_regs
++#else
+ #include <sys/procfs.h>
+-#endif // __ANDROID__
++#endif
+ 
+ namespace lldb_private {
+ namespace process_linux {
diff --git a/pkgs/development/compilers/llvm/15/lldb/resource-dir.patch b/pkgs/development/compilers/llvm/15/lldb/resource-dir.patch
new file mode 100644
index 0000000000000..e0db80afeb9f7
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/lldb/resource-dir.patch
@@ -0,0 +1,13 @@
+diff --git a/lldb/cmake/modules/LLDBConfig.cmake b/lldb/cmake/modules/LLDBConfig.cmake
+index 37364341ff8b..7f74c1a3e257 100644
+--- a/cmake/modules/LLDBConfig.cmake
++++ b/cmake/modules/LLDBConfig.cmake
+@@ -257,7 +257,7 @@ if (NOT TARGET clang-resource-headers)
+   # Iterate over the possible places where the external resource directory
+   # could be and pick the first that exists.
+   foreach(CANDIDATE "${Clang_DIR}/../.." "${LLVM_DIR}" "${LLVM_LIBRARY_DIRS}"
+-                    "${LLVM_BUILD_LIBRARY_DIR}"
++                    "${LLVM_BUILD_LIBRARY_DIR}" "@clangLibDir@"
+                     "${LLVM_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}")
+     # Build the resource directory path by appending 'clang/<version number>'.
+     set(CANDIDATE_RESOURCE_DIR "${CANDIDATE}/clang/${LLDB_CLANG_RESOURCE_DIR_NAME}")
diff --git a/pkgs/development/compilers/llvm/15/llvm/default.nix b/pkgs/development/compilers/llvm/15/llvm/default.nix
new file mode 100644
index 0000000000000..e0b79a9acfefc
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/llvm/default.nix
@@ -0,0 +1,429 @@
+{ lib, stdenv, llvm_meta
+, pkgsBuildBuild
+, monorepoSrc
+, runCommand
+, fetchpatch
+, cmake
+, darwin
+, ninja
+, python3
+, python3Packages
+, libffi
+, libbfd
+, libpfm
+, libxml2
+, ncurses
+, version
+, release_version
+, zlib
+, which
+, sysctl
+, buildLlvmTools
+, debugVersion ? false
+, doCheck ? (!stdenv.isx86_32 /* TODO: why */) && (!stdenv.hostPlatform.isMusl)
+  && (stdenv.hostPlatform == stdenv.buildPlatform)
+, enableManpages ? false
+, enableSharedLibraries ? !stdenv.hostPlatform.isStatic
+, enablePFM ? stdenv.isLinux /* PFM only supports Linux */
+  # broken for Ampere eMAG 8180 (c2.large.arm on Packet) #56245
+  # broken for the armv7l builder
+  && !stdenv.hostPlatform.isAarch
+, enablePolly ? true
+} @args:
+
+let
+  inherit (lib) optional optionals optionalString;
+
+  # Used when creating a version-suffixed symlink of libLLVM.dylib
+  shortVersion = with lib;
+    concatStringsSep "." (take 1 (splitString "." release_version));
+
+  # Ordinarily we would just the `doCheck` and `checkDeps` functionality
+  # `mkDerivation` gives us to manage our test dependencies (instead of breaking
+  # out `doCheck` as a package level attribute).
+  #
+  # Unfortunately `lit` does not forward `$PYTHONPATH` to children processes, in
+  # particular the children it uses to do feature detection.
+  #
+  # This means that python deps we add to `checkDeps` (which the python
+  # interpreter is made aware of via `$PYTHONPATH` – populated by the python
+  # setup hook) are not picked up by `lit` which causes it to skip tests.
+  #
+  # Adding `python3.withPackages (ps: [ ... ])` to `checkDeps` also doesn't work
+  # because this package is shadowed in `$PATH` by the regular `python3`
+  # package.
+  #
+  # So, we "manually" assemble one python derivation for the package to depend
+  # on, taking into account whether checks are enabled or not:
+  python = if doCheck then
+    # Note that we _explicitly_ ask for a python interpreter for our host
+    # platform here; the splicing that would ordinarily take care of this for
+    # us does not seem to work once we use `withPackages`.
+    let
+      checkDeps = ps: with ps; [ psutil ];
+    in pkgsBuildBuild.targetPackages.python3.withPackages checkDeps
+  else python3;
+
+in stdenv.mkDerivation (rec {
+  pname = "llvm";
+  inherit version;
+
+  src = runCommand "${pname}-src-${version}" {} (''
+    mkdir -p "$out"
+    cp -r ${monorepoSrc}/cmake "$out"
+    cp -r ${monorepoSrc}/${pname} "$out"
+    cp -r ${monorepoSrc}/third-party "$out"
+  '' + lib.optionalString enablePolly ''
+    chmod u+w "$out/${pname}/tools"
+    cp -r ${monorepoSrc}/polly "$out/${pname}/tools"
+  '');
+
+  sourceRoot = "${src.name}/${pname}";
+
+  outputs = [ "out" "lib" "dev" "python" ];
+
+  nativeBuildInputs = [ cmake ninja python ]
+    ++ optionals enableManpages [
+      # Note: we intentionally use `python3Packages` instead of `python3.pkgs`;
+      # splicing does *not* work with the latter. (TODO: fix)
+      python3Packages.sphinx python3Packages.recommonmark
+    ];
+
+  buildInputs = [ libxml2 libffi ]
+    ++ optional enablePFM libpfm; # exegesis
+
+  propagatedBuildInputs = [ ncurses zlib ];
+
+  nativeCheckInputs = [
+    which
+  ] ++ lib.optional stdenv.isDarwin sysctl;
+
+  patches = [
+    ./gnu-install-dirs.patch
+
+    # Running the tests involves invoking binaries (like `opt`) that depend on
+    # the LLVM dylibs and reference them by absolute install path (i.e. their
+    # nix store path).
+    #
+    # Because we have not yet run the install phase (we're running these tests
+    # as part of `checkPhase` instead of `installCheckPhase`) these absolute
+    # paths do not exist yet; to work around this we point the loader (`ld` on
+    # unix, `dyld` on macOS) at the `lib` directory which will later become this
+    # package's `lib` output.
+    #
+    # Previously we would just set `LD_LIBRARY_PATH` to include the build `lib`
+    # dir but:
+    #   - this doesn't generalize well to other platforms; `lit` doesn't forward
+    #     `DYLD_LIBRARY_PATH` (macOS):
+    #     + https://github.com/llvm/llvm-project/blob/0d89963df354ee309c15f67dc47c8ab3cb5d0fb2/llvm/utils/lit/lit/TestingConfig.py#L26
+    #   - even if `lit` forwarded this env var, we actually cannot set
+    #     `DYLD_LIBRARY_PATH` in the child processes `lit` launches because
+    #     `DYLD_LIBRARY_PATH` (and `DYLD_FALLBACK_LIBRARY_PATH`) is cleared for
+    #     "protected processes" (i.e. the python interpreter that runs `lit`):
+    #     https://stackoverflow.com/a/35570229
+    #   - other LLVM subprojects deal with this issue by having their `lit`
+    #     configuration set these env vars for us; it makes sense to do the same
+    #     for LLVM:
+    #     + https://github.com/llvm/llvm-project/blob/4c106cfdf7cf7eec861ad3983a3dd9a9e8f3a8ae/clang-tools-extra/test/Unit/lit.cfg.py#L22-L31
+    #
+    # !!! TODO: look into upstreaming this patch
+    ./llvm-lit-cfg-add-libs-to-dylib-path.patch
+
+    # `lit` has a mode where it executes run lines as a shell script which is
+    # constructs; this is problematic for macOS because it means that there's
+    # another process in between `lit` and the binaries being tested. As noted
+    # above, this means that `DYLD_LIBRARY_PATH` is cleared which means that our
+    # tests fail with dyld errors.
+    #
+    # To get around this we patch `lit` to reintroduce `DYLD_LIBRARY_PATH`, when
+    # present in the test configuration.
+    #
+    # It's not clear to me why this isn't an issue for LLVM developers running
+    # on macOS (nothing about this _seems_ nix specific)..
+    ./lit-shell-script-runner-set-dyld-library-path.patch
+  ] ++ lib.optionals enablePolly [
+    ./gnu-install-dirs-polly.patch
+
+    # Just like the `llvm-lit-cfg` patch, but for `polly`.
+    ./polly-lit-cfg-add-libs-to-dylib-path.patch
+  ];
+
+  postPatch = optionalString stdenv.isDarwin ''
+    substituteInPlace cmake/modules/AddLLVM.cmake \
+      --replace 'set(_install_name_dir INSTALL_NAME_DIR "@rpath")' "set(_install_name_dir)" \
+      --replace 'set(_install_rpath "@loader_path/../''${CMAKE_INSTALL_LIBDIR}''${LLVM_LIBDIR_SUFFIX}" ''${extra_libdir})' ""
+
+    # As of LLVM 15, marked as XFAIL on arm64 macOS but lit doesn't seem to pick
+    # this up: https://github.com/llvm/llvm-project/blob/c344d97a125b18f8fed0a64aace73c49a870e079/llvm/test/MC/ELF/cfi-version.ll#L7
+    rm test/MC/ELF/cfi-version.ll
+
+    # This test tries to call `sw_vers` by absolute path (`/usr/bin/sw_vers`)
+    # and thus fails under the sandbox:
+    substituteInPlace unittests/Support/Host.cpp \
+      --replace '/usr/bin/sw_vers' "${(builtins.toString darwin.DarwinTools) + "/bin/sw_vers" }"
+  '' + optionalString (stdenv.isDarwin && stdenv.hostPlatform.isx86) ''
+    # This test tries to call the intrinsics `@llvm.roundeven.f32` and
+    # `@llvm.roundeven.f64` which seem to (incorrectly?) lower to `roundevenf`
+    # and `roundeven` on x86_64 macOS.
+    #
+    # However these functions are glibc specific so the test fails:
+    #   - https://www.gnu.org/software/gnulib/manual/html_node/roundevenf.html
+    #   - https://www.gnu.org/software/gnulib/manual/html_node/roundeven.html
+    #
+    # TODO(@rrbutani): this seems to run fine on `aarch64-darwin`, why does it
+    # pass there?
+    substituteInPlace test/ExecutionEngine/Interpreter/intrinsics.ll \
+      --replace "%roundeven32 = call float @llvm.roundeven.f32(float 0.000000e+00)" "" \
+      --replace "%roundeven64 = call double @llvm.roundeven.f64(double 0.000000e+00)" ""
+
+    # This test fails on darwin x86_64 because `sw_vers` reports a different
+    # macOS version than what LLVM finds by reading
+    # `/System/Library/CoreServices/SystemVersion.plist` (which is passed into
+    # the sandbox on macOS).
+    #
+    # The `sw_vers` provided by nixpkgs reports the macOS version associated
+    # with the `CoreFoundation` framework with which it was built. Because
+    # nixpkgs pins the SDK for `aarch64-darwin` and `x86_64-darwin` what
+    # `sw_vers` reports is not guaranteed to match the macOS version of the host
+    # that's building this derivation.
+    #
+    # Astute readers will note that we only _patch_ this test on aarch64-darwin
+    # (to use the nixpkgs provided `sw_vers`) instead of disabling it outright.
+    # So why does this test pass on aarch64?
+    #
+    # Well, it seems that `sw_vers` on aarch64 actually links against the _host_
+    # CoreFoundation framework instead of the nixpkgs provided one.
+    #
+    # Not entirely sure what the right fix is here. I'm assuming aarch64
+    # `sw_vers` doesn't intentionally link against the host `CoreFoundation`
+    # (still digging into how this ends up happening, will follow up) but that
+    # aside I think the more pertinent question is: should we be patching LLVM's
+    # macOS version detection logic to use `sw_vers` instead of reading host
+    # paths? This *is* a way in which details about builder machines can creep
+    # into the artifacts that are produced, affecting reproducibility, but it's
+    # not clear to me when/where/for what this even gets used in LLVM.
+    #
+    # TODO(@rrbutani): fix/follow-up
+    substituteInPlace unittests/Support/Host.cpp \
+      --replace "getMacOSHostVersion" "DISABLED_getMacOSHostVersion"
+
+    # This test fails with a `dysmutil` crash; have not yet dug into what's
+    # going on here (TODO(@rrbutani)).
+    rm test/tools/dsymutil/ARM/obfuscated.test
+  '' + ''
+    # FileSystem permissions tests fail with various special bits
+    substituteInPlace unittests/Support/CMakeLists.txt \
+      --replace "Path.cpp" ""
+    rm unittests/Support/Path.cpp
+    substituteInPlace unittests/IR/CMakeLists.txt \
+      --replace "PassBuilderCallbacksTest.cpp" ""
+    rm unittests/IR/PassBuilderCallbacksTest.cpp
+    rm test/tools/llvm-objcopy/ELF/mirror-permissions-unix.test
+  '' + optionalString stdenv.hostPlatform.isMusl ''
+    patch -p1 -i ${../../TLI-musl.patch}
+    substituteInPlace unittests/Support/CMakeLists.txt \
+      --replace "add_subdirectory(DynamicLibrary)" ""
+    rm unittests/Support/DynamicLibrary/DynamicLibraryTest.cpp
+    # valgrind unhappy with musl or glibc, but fails w/musl only
+    rm test/CodeGen/AArch64/wineh4.mir
+  '' + optionalString stdenv.hostPlatform.isAarch32 ''
+    # skip failing X86 test cases on 32-bit ARM
+    rm test/DebugInfo/X86/convert-debugloc.ll
+    rm test/DebugInfo/X86/convert-inlined.ll
+    rm test/DebugInfo/X86/convert-linked.ll
+    rm test/tools/dsymutil/X86/op-convert.test
+    rm test/tools/gold/X86/split-dwarf.ll
+    rm test/tools/llvm-dwarfdump/X86/prettyprint_types.s
+    rm test/tools/llvm-dwarfdump/X86/simplified-template-names.s
+
+    # !!! Note: these tests are removed in LLVM 16.
+    #
+    # See here for context: https://github.com/NixOS/nixpkgs/pull/194634#discussion_r999790443
+    rm test/CodeGen/RISCV/rv32zbp.ll
+    rm test/CodeGen/RISCV/rv64zbp.ll
+  '' + optionalString (stdenv.hostPlatform.system == "armv6l-linux") ''
+    # Seems to require certain floating point hardware (NEON?)
+    rm test/ExecutionEngine/frem.ll
+  '' + ''
+    patchShebangs test/BugPoint/compile-custom.ll.py
+  '';
+
+  preConfigure = ''
+    # Workaround for configure flags that need to have spaces
+    cmakeFlagsArray+=(
+      -DLLVM_LIT_ARGS="-svj''${NIX_BUILD_CORES} --no-progress-bar"
+    )
+  '';
+
+  # Defensive check: some paths (that we make symlinks to) depend on the release
+  # version, for example:
+  #  - https://github.com/llvm/llvm-project/blob/406bde9a15136254f2b10d9ef3a42033b3cb1b16/clang/lib/Headers/CMakeLists.txt#L185
+  #
+  # So we want to sure that the version in the source matches the release
+  # version we were given.
+  #
+  # We do this check here, in the LLVM build, because it happens early.
+  postConfigure = let
+    v = lib.versions;
+    major = v.major release_version;
+    minor = v.minor release_version;
+    patch = v.patch release_version;
+  in ''
+    # $1: part, $2: expected
+    check_version() {
+      part="''${1^^}"
+      part="$(cat include/llvm/Config/llvm-config.h  | grep "#define LLVM_VERSION_''${part} " | cut -d' ' -f3)"
+
+      if [[ "$part" != "$2" ]]; then
+        echo >&2 \
+          "mismatch in the $1 version! we have version ${release_version}" \
+          "and expected the $1 version to be '$2'; the source has '$part' instead"
+        exit 3
+      fi
+    }
+
+    check_version major ${major}
+    check_version minor ${minor}
+    check_version patch ${patch}
+  '';
+
+  # E.g. mesa.drivers use the build-id as a cache key (see #93946):
+  LDFLAGS = optionalString (enableSharedLibraries && !stdenv.isDarwin) "-Wl,--build-id=sha1";
+
+  cmakeFlags = with stdenv; let
+    # These flags influence llvm-config's BuildVariables.inc in addition to the
+    # general build. We need to make sure these are also passed via
+    # CROSS_TOOLCHAIN_FLAGS_NATIVE when cross-compiling or llvm-config-native
+    # will return different results from the cross llvm-config.
+    #
+    # Some flags don't need to be repassed because LLVM already does so (like
+    # CMAKE_BUILD_TYPE), others are irrelevant to the result.
+    flagsForLlvmConfig = [
+      "-DLLVM_INSTALL_PACKAGE_DIR=${placeholder "dev"}/lib/cmake/llvm"
+      "-DLLVM_ENABLE_RTTI=ON"
+    ] ++ optionals enableSharedLibraries [
+      "-DLLVM_LINK_LLVM_DYLIB=ON"
+    ];
+  in flagsForLlvmConfig ++ [
+    "-DCMAKE_BUILD_TYPE=${if debugVersion then "Debug" else "Release"}"
+    "-DLLVM_INSTALL_UTILS=ON"  # Needed by rustc
+    "-DLLVM_BUILD_TESTS=${if doCheck then "ON" else "OFF"}"
+    "-DLLVM_ENABLE_FFI=ON"
+    "-DLLVM_HOST_TRIPLE=${stdenv.hostPlatform.config}"
+    "-DLLVM_DEFAULT_TARGET_TRIPLE=${stdenv.hostPlatform.config}"
+    "-DLLVM_ENABLE_DUMP=ON"
+  ] ++ optionals stdenv.hostPlatform.isStatic [
+    # Disables building of shared libs, -fPIC is still injected by cc-wrapper
+    "-DLLVM_ENABLE_PIC=OFF"
+    "-DLLVM_BUILD_STATIC=ON"
+    "-DLLVM_LINK_LLVM_DYLIB=off"
+    # libxml2 needs to be disabled because the LLVM build system ignores its .la
+    # file and doesn't link zlib as well.
+    # https://github.com/ClangBuiltLinux/tc-build/issues/150#issuecomment-845418812
+    "-DLLVM_ENABLE_LIBXML2=OFF"
+  ] ++ optionals enableManpages [
+    "-DLLVM_BUILD_DOCS=ON"
+    "-DLLVM_ENABLE_SPHINX=ON"
+    "-DSPHINX_OUTPUT_MAN=ON"
+    "-DSPHINX_OUTPUT_HTML=OFF"
+    "-DSPHINX_WARNINGS_AS_ERRORS=OFF"
+  ] ++ optionals (!isDarwin) [
+    "-DLLVM_BINUTILS_INCDIR=${libbfd.dev}/include"
+  ] ++ optionals isDarwin [
+    "-DLLVM_ENABLE_LIBCXX=ON"
+    "-DCAN_TARGET_i386=false"
+  ] ++ optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
+    "-DCMAKE_CROSSCOMPILING=True"
+    "-DLLVM_TABLEGEN=${buildLlvmTools.llvm}/bin/llvm-tblgen"
+    (
+      let
+        nativeCC = pkgsBuildBuild.targetPackages.stdenv.cc;
+        nativeBintools = nativeCC.bintools.bintools;
+        nativeToolchainFlags = [
+          "-DCMAKE_C_COMPILER=${nativeCC}/bin/${nativeCC.targetPrefix}cc"
+          "-DCMAKE_CXX_COMPILER=${nativeCC}/bin/${nativeCC.targetPrefix}c++"
+          "-DCMAKE_AR=${nativeBintools}/bin/${nativeBintools.targetPrefix}ar"
+          "-DCMAKE_STRIP=${nativeBintools}/bin/${nativeBintools.targetPrefix}strip"
+          "-DCMAKE_RANLIB=${nativeBintools}/bin/${nativeBintools.targetPrefix}ranlib"
+        ];
+        # We need to repass the custom GNUInstallDirs values, otherwise CMake
+        # will choose them for us, leading to wrong results in llvm-config-native
+        nativeInstallFlags = [
+          "-DCMAKE_INSTALL_PREFIX=${placeholder "out"}"
+          "-DCMAKE_INSTALL_BINDIR=${placeholder "out"}/bin"
+          "-DCMAKE_INSTALL_INCLUDEDIR=${placeholder "dev"}/include"
+          "-DCMAKE_INSTALL_LIBDIR=${placeholder "lib"}/lib"
+          "-DCMAKE_INSTALL_LIBEXECDIR=${placeholder "lib"}/libexec"
+        ];
+      in "-DCROSS_TOOLCHAIN_FLAGS_NATIVE:list="
+      + lib.concatStringsSep ";" (lib.concatLists [
+        flagsForLlvmConfig
+        nativeToolchainFlags
+        nativeInstallFlags
+      ])
+    )
+  ];
+
+  postInstall = ''
+    mkdir -p $python/share
+    mv $out/share/opt-viewer $python/share/opt-viewer
+    moveToOutput "bin/llvm-config*" "$dev"
+    substituteInPlace "$dev/lib/cmake/llvm/LLVMExports-${if debugVersion then "debug" else "release"}.cmake" \
+      --replace "\''${_IMPORT_PREFIX}/lib/lib" "$lib/lib/lib" \
+      --replace "$out/bin/llvm-config" "$dev/bin/llvm-config"
+    substituteInPlace "$dev/lib/cmake/llvm/LLVMConfig.cmake" \
+      --replace 'set(LLVM_BINARY_DIR "''${LLVM_INSTALL_PREFIX}")' 'set(LLVM_BINARY_DIR "'"$lib"'")'
+  ''
+  + optionalString (stdenv.isDarwin && enableSharedLibraries) ''
+    ln -s $lib/lib/libLLVM.dylib $lib/lib/libLLVM-${shortVersion}.dylib
+    ln -s $lib/lib/libLLVM.dylib $lib/lib/libLLVM-${release_version}.dylib
+  ''
+  + optionalString (stdenv.buildPlatform != stdenv.hostPlatform) ''
+    cp NATIVE/bin/llvm-config $dev/bin/llvm-config-native
+  '';
+
+  inherit doCheck;
+
+  checkTarget = "check-all";
+
+  # For the update script:
+  passthru.monorepoSrc = monorepoSrc;
+
+  requiredSystemFeatures = [ "big-parallel" ];
+  meta = llvm_meta // {
+    homepage = "https://llvm.org/";
+    description = "A collection of modular and reusable compiler and toolchain technologies";
+    longDescription = ''
+      The LLVM Project is a collection of modular and reusable compiler and
+      toolchain technologies. Despite its name, LLVM has little to do with
+      traditional virtual machines. The name "LLVM" itself is not an acronym; it
+      is the full name of the project.
+      LLVM began as a research project at the University of Illinois, with the
+      goal of providing a modern, SSA-based compilation strategy capable of
+      supporting both static and dynamic compilation of arbitrary programming
+      languages. Since then, LLVM has grown to be an umbrella project consisting
+      of a number of subprojects, many of which are being used in production by
+      a wide variety of commercial and open source projects as well as being
+      widely used in academic research. Code in the LLVM project is licensed
+      under the "Apache 2.0 License with LLVM exceptions".
+    '';
+  };
+} // lib.optionalAttrs enableManpages {
+  pname = "llvm-manpages";
+
+  propagatedBuildInputs = [];
+
+  ninjaFlags = [ "docs-llvm-man" ];
+  installTargets = [ "install-docs-llvm-man" ];
+
+  postPatch = null;
+  postInstall = null;
+
+  outputs = [ "out" ];
+
+  doCheck = false;
+
+  meta = llvm_meta // {
+    description = "man pages for LLVM ${version}";
+  };
+})
diff --git a/pkgs/development/compilers/llvm/15/llvm/gnu-install-dirs-polly.patch b/pkgs/development/compilers/llvm/15/llvm/gnu-install-dirs-polly.patch
new file mode 100644
index 0000000000000..b01363e98aa00
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/llvm/gnu-install-dirs-polly.patch
@@ -0,0 +1,19 @@
+This is the one remaining Polly install dirs related change that hasn't made it
+into upstream yet; previously this patch file also included:
+https://reviews.llvm.org/D117541
+
+diff --git a/tools/polly/cmake/polly_macros.cmake b/tools/polly/cmake/polly_macros.cmake
+index 518a09b45a42..bd9d6f5542ad 100644
+--- a/tools/polly/cmake/polly_macros.cmake
++++ b/tools/polly/cmake/polly_macros.cmake
+@@ -44,8 +44,8 @@ macro(add_polly_library name)
+   if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY OR ${name} STREQUAL "LLVMPolly")
+     install(TARGETS ${name}
+       EXPORT LLVMExports
+-      LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX}
+-      ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX})
++	  LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}
++      ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX})
+   endif()
+   set_property(GLOBAL APPEND PROPERTY LLVM_EXPORTS ${name})
+ endmacro(add_polly_library)
diff --git a/pkgs/development/compilers/llvm/15/llvm/gnu-install-dirs.patch b/pkgs/development/compilers/llvm/15/llvm/gnu-install-dirs.patch
new file mode 100644
index 0000000000000..0ef317af8cc75
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/llvm/gnu-install-dirs.patch
@@ -0,0 +1,138 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index 45399dc0537e..5d946e9e6583 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -942,7 +942,7 @@ if (NOT TENSORFLOW_AOT_PATH STREQUAL "")
+   add_subdirectory(${TENSORFLOW_AOT_PATH}/xla_aot_runtime_src
+     ${CMAKE_ARCHIVE_OUTPUT_DIRECTORY}/tf_runtime)
+   install(TARGETS tf_xla_runtime EXPORT LLVMExports
+-    ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX} COMPONENT tf_xla_runtime)
++    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX} COMPONENT tf_xla_runtime)
+   set_property(GLOBAL APPEND PROPERTY LLVM_EXPORTS tf_xla_runtime)
+   # Once we add more modules, we should handle this more automatically.
+   if (DEFINED LLVM_OVERRIDE_MODEL_HEADER_INLINERSIZEMODEL)
+diff --git a/cmake/modules/AddLLVM.cmake b/cmake/modules/AddLLVM.cmake
+index 057431208322..56f0dcb258da 100644
+--- a/cmake/modules/AddLLVM.cmake
++++ b/cmake/modules/AddLLVM.cmake
+@@ -844,8 +844,8 @@ macro(add_llvm_library name)
+       get_target_export_arg(${name} LLVM export_to_llvmexports ${umbrella})
+       install(TARGETS ${name}
+               ${export_to_llvmexports}
+-              LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX} COMPONENT ${name}
+-              ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX} COMPONENT ${name}
++              LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}" COMPONENT ${name}
++              ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}" COMPONENT ${name}
+               RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}" COMPONENT ${name})
+ 
+       if (NOT LLVM_ENABLE_IDE)
+@@ -2007,7 +2007,7 @@ function(llvm_install_library_symlink name dest type)
+   set(full_name ${CMAKE_${type}_LIBRARY_PREFIX}${name}${CMAKE_${type}_LIBRARY_SUFFIX})
+   set(full_dest ${CMAKE_${type}_LIBRARY_PREFIX}${dest}${CMAKE_${type}_LIBRARY_SUFFIX})
+ 
+-  set(output_dir lib${LLVM_LIBDIR_SUFFIX})
++  set(output_dir ${CMAKE_INSTALL_FULL_LIBDIR}${LLVM_LIBDIR_SUFFIX})
+   if(WIN32 AND "${type}" STREQUAL "SHARED")
+     set(output_dir "${CMAKE_INSTALL_BINDIR}")
+   endif()
+@@ -2271,15 +2271,15 @@ function(llvm_setup_rpath name)
+ 
+   if (APPLE)
+     set(_install_name_dir INSTALL_NAME_DIR "@rpath")
+-    set(_install_rpath "@loader_path/../lib${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
++    set(_install_rpath "@loader_path/../${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
+   elseif(${CMAKE_SYSTEM_NAME} MATCHES "AIX" AND BUILD_SHARED_LIBS)
+     # $ORIGIN is not interpreted at link time by aix ld.
+     # Since BUILD_SHARED_LIBS is only recommended for use by developers,
+     # hardcode the rpath to build/install lib dir first in this mode.
+     # FIXME: update this when there is better solution.
+-    set(_install_rpath "${LLVM_LIBRARY_OUTPUT_INTDIR}" "${CMAKE_INSTALL_PREFIX}/lib${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
++    set(_install_rpath "${LLVM_LIBRARY_OUTPUT_INTDIR}" "${CMAKE_INSTALL_FULL_LIBDIR}${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
+   elseif(UNIX)
+-    set(_install_rpath "\$ORIGIN/../lib${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
++    set(_install_rpath "\$ORIGIN/../${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
+     if(${CMAKE_SYSTEM_NAME} MATCHES "(FreeBSD|DragonFly)")
+       set_property(TARGET ${name} APPEND_STRING PROPERTY
+                    LINK_FLAGS " -Wl,-z,origin ")
+diff --git a/cmake/modules/AddOCaml.cmake b/cmake/modules/AddOCaml.cmake
+index 891c9e6d618c..8d963f3b0069 100644
+--- a/cmake/modules/AddOCaml.cmake
++++ b/cmake/modules/AddOCaml.cmake
+@@ -147,9 +147,9 @@ function(add_ocaml_library name)
+   endforeach()
+ 
+   if( APPLE )
+-    set(ocaml_rpath "@executable_path/../../../lib${LLVM_LIBDIR_SUFFIX}")
++    set(ocaml_rpath "@executable_path/../../../${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}")
+   elseif( UNIX )
+-    set(ocaml_rpath "\\$ORIGIN/../../../lib${LLVM_LIBDIR_SUFFIX}")
++    set(ocaml_rpath "\\$ORIGIN/../../../${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}")
+   endif()
+   list(APPEND ocaml_flags "-ldopt" "-Wl,-rpath,${ocaml_rpath}")
+ 
+diff --git a/cmake/modules/CMakeLists.txt b/cmake/modules/CMakeLists.txt
+index d4b0ab959148..26ed981fd09f 100644
+--- a/cmake/modules/CMakeLists.txt
++++ b/cmake/modules/CMakeLists.txt
+@@ -128,7 +128,7 @@ set(LLVM_CONFIG_INCLUDE_DIRS
+   )
+ list(REMOVE_DUPLICATES LLVM_CONFIG_INCLUDE_DIRS)
+ 
+-extend_path(LLVM_CONFIG_LIBRARY_DIR "\${LLVM_INSTALL_PREFIX}" "lib\${LLVM_LIBDIR_SUFFIX}")
++extend_path(LLVM_CONFIG_LIBRARY_DIR "\${LLVM_INSTALL_PREFIX}" "${CMAKE_INSTALL_LIBDIR}\${LLVM_LIBDIR_SUFFIX}")
+ set(LLVM_CONFIG_LIBRARY_DIRS
+   "${LLVM_CONFIG_LIBRARY_DIR}"
+   # FIXME: Should there be other entries here?
+diff --git a/docs/CMake.rst b/docs/CMake.rst
+index 879b7b231d4c..9c31d14e8950 100644
+--- a/docs/CMake.rst
++++ b/docs/CMake.rst
+@@ -250,7 +250,7 @@ description is in `LLVM-related variables`_ below.
+ **LLVM_LIBDIR_SUFFIX**:STRING
+   Extra suffix to append to the directory where libraries are to be
+   installed. On a 64-bit architecture, one could use ``-DLLVM_LIBDIR_SUFFIX=64``
+-  to install libraries to ``/usr/lib64``.
++  to install libraries to ``/usr/lib64``. See also ``CMAKE_INSTALL_LIBDIR``.
+ 
+ **LLVM_PARALLEL_{COMPILE,LINK}_JOBS**:STRING
+   Building the llvm toolchain can use a lot of resources, particularly
+@@ -284,6 +284,10 @@ manual, or execute ``cmake --help-variable VARIABLE_NAME``.
+   The path to install executables, relative to the *CMAKE_INSTALL_PREFIX*.
+   Defaults to "bin".
+ 
++**CMAKE_INSTALL_LIBDIR**:PATH
++  The path to install libraries, relative to the *CMAKE_INSTALL_PREFIX*.
++  Defaults to "lib".
++
+ **CMAKE_INSTALL_INCLUDEDIR**:PATH
+   The path to install header files, relative to the *CMAKE_INSTALL_PREFIX*.
+   Defaults to "include".
+diff --git a/tools/llvm-config/BuildVariables.inc.in b/tools/llvm-config/BuildVariables.inc.in
+index 370005cd8d7d..7e790bc52111 100644
+--- a/tools/llvm-config/BuildVariables.inc.in
++++ b/tools/llvm-config/BuildVariables.inc.in
+@@ -23,6 +23,7 @@
+ #define LLVM_CXXFLAGS "@LLVM_CXXFLAGS@"
+ #define LLVM_BUILDMODE "@LLVM_BUILDMODE@"
+ #define LLVM_LIBDIR_SUFFIX "@LLVM_LIBDIR_SUFFIX@"
++#define LLVM_INSTALL_LIBDIR "@CMAKE_INSTALL_LIBDIR@"
+ #define LLVM_INSTALL_INCLUDEDIR "@CMAKE_INSTALL_INCLUDEDIR@"
+ #define LLVM_INSTALL_PACKAGE_DIR "@LLVM_INSTALL_PACKAGE_DIR@"
+ #define LLVM_TARGETS_BUILT "@LLVM_TARGETS_BUILT@"
+diff --git a/tools/llvm-config/llvm-config.cpp b/tools/llvm-config/llvm-config.cpp
+index 2c6c55f89d38..f6d2068a0827 100644
+--- a/tools/llvm-config/llvm-config.cpp
++++ b/tools/llvm-config/llvm-config.cpp
+@@ -369,7 +369,11 @@ int main(int argc, char **argv) {
+       sys::fs::make_absolute(ActivePrefix, Path);
+       ActiveBinDir = std::string(Path.str());
+     }
+-    ActiveLibDir = ActivePrefix + "/lib" + LLVM_LIBDIR_SUFFIX;
++    {
++      SmallString<256> Path(LLVM_INSTALL_LIBDIR LLVM_LIBDIR_SUFFIX);
++      sys::fs::make_absolute(ActivePrefix, Path);
++      ActiveLibDir = std::string(Path.str());
++    }
+     {
+       SmallString<256> Path(LLVM_INSTALL_PACKAGE_DIR);
+       sys::fs::make_absolute(ActivePrefix, Path);
diff --git a/pkgs/development/compilers/llvm/15/llvm/lit-shell-script-runner-set-dyld-library-path.patch b/pkgs/development/compilers/llvm/15/llvm/lit-shell-script-runner-set-dyld-library-path.patch
new file mode 100644
index 0000000000000..32f1d13a9dc23
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/llvm/lit-shell-script-runner-set-dyld-library-path.patch
@@ -0,0 +1,26 @@
+diff --git a/utils/lit/lit/TestRunner.py b/utils/lit/lit/TestRunner.py
+index 0242e0b75af3..d732011306f7 100644
+--- a/utils/lit/lit/TestRunner.py
++++ b/utils/lit/lit/TestRunner.py
+@@ -1029,6 +1029,12 @@ def executeScript(test, litConfig, tmpBase, commands, cwd):
+             f.write('@echo off\n')
+         f.write('\n@if %ERRORLEVEL% NEQ 0 EXIT\n'.join(commands))
+     else:
++        # This env var is *purged* when invoking subprocesses so we have to
++        # manually set it from within the bash script in order for the commands
++        # in run lines to see this var:
++        if "DYLD_LIBRARY_PATH" in test.config.environment:
++            f.write(f'export DYLD_LIBRARY_PATH="{test.config.environment["DYLD_LIBRARY_PATH"]}"\n')
++
+         for i, ln in enumerate(commands):
+             match = re.match(kPdbgRegex, ln)
+             if match:
+@@ -1363,7 +1369,7 @@ def applySubstitutions(script, substitutions, conditions={},
+         return processed
+ 
+     process = processLine if recursion_limit is None else processLineToFixedPoint
+-    
++
+     return [unescapePercents(process(ln)) for ln in script]
+ 
+ 
diff --git a/pkgs/development/compilers/llvm/15/llvm/llvm-lit-cfg-add-libs-to-dylib-path.patch b/pkgs/development/compilers/llvm/15/llvm/llvm-lit-cfg-add-libs-to-dylib-path.patch
new file mode 100644
index 0000000000000..d824516c0a16c
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/llvm/llvm-lit-cfg-add-libs-to-dylib-path.patch
@@ -0,0 +1,79 @@
+diff --git a/test/Unit/lit.cfg.py b/test/Unit/lit.cfg.py
+index 81e8dc04acea..479ff95681e2 100644
+--- a/test/Unit/lit.cfg.py
++++ b/test/Unit/lit.cfg.py
+@@ -3,6 +3,7 @@
+ # Configuration file for the 'lit' test runner.
+ 
+ import os
++import platform
+ import subprocess
+ 
+ import lit.formats
+@@ -55,3 +56,26 @@ if sys.platform in ['win32', 'cygwin'] and os.path.isdir(config.shlibdir):
+ # Win32 may use %SYSTEMDRIVE% during file system shell operations, so propogate.
+ if sys.platform == 'win32' and 'SYSTEMDRIVE' in os.environ:
+     config.environment['SYSTEMDRIVE'] = os.environ['SYSTEMDRIVE']
++
++# Add the LLVM dynamic libs to the platform-specific loader search path env var:
++#
++# TODO: this is copied from `clang`'s `lit.cfg.py`; should unify..
++def find_shlibpath_var():
++    if platform.system() in ['Linux', 'FreeBSD', 'NetBSD', 'OpenBSD', 'SunOS']:
++        yield 'LD_LIBRARY_PATH'
++    elif platform.system() == 'Darwin':
++        yield 'DYLD_LIBRARY_PATH'
++    elif platform.system() == 'Windows':
++        yield 'PATH'
++    elif platform.system() == 'AIX':
++        yield 'LIBPATH'
++
++for shlibpath_var in find_shlibpath_var():
++    shlibpath = os.path.pathsep.join(
++        (config.shlibdir,
++         config.environment.get(shlibpath_var, '')))
++    config.environment[shlibpath_var] = shlibpath
++    break
++else:
++    lit_config.warning("unable to inject shared library path on '{}'"
++                       .format(platform.system()))
+diff --git a/test/lit.cfg.py b/test/lit.cfg.py
+index 75a38b4c5dad..856fc75c9d74 100644
+--- a/test/lit.cfg.py
++++ b/test/lit.cfg.py
+@@ -42,6 +42,26 @@ llvm_config.with_environment('PATH', config.llvm_tools_dir, append_path=True)
+ llvm_config.with_system_environment(
+     ['HOME', 'INCLUDE', 'LIB', 'TMP', 'TEMP'])
+ 
++# Add the LLVM dynamic libs to the platform-specific loader search path env var:
++#
++# TODO: this is copied from `clang`'s `lit.cfg.py`; should unify..
++def find_shlibpath_var():
++    if platform.system() in ['Linux', 'FreeBSD', 'NetBSD', 'OpenBSD', 'SunOS']:
++        yield 'LD_LIBRARY_PATH'
++    elif platform.system() == 'Darwin':
++        yield 'DYLD_LIBRARY_PATH'
++    elif platform.system() == 'Windows':
++        yield 'PATH'
++    elif platform.system() == 'AIX':
++        yield 'LIBPATH'
++
++for shlibpath_var in find_shlibpath_var():
++    shlibpath = config.llvm_shlib_dir
++    llvm_config.with_environment(shlibpath_var, shlibpath, append_path = True)
++    break
++else:
++    lit_config.warning("unable to inject shared library path on '{}'"
++                       .format(platform.system()))
+ 
+ # Set up OCAMLPATH to include newly built OCaml libraries.
+ top_ocaml_lib = os.path.join(config.llvm_lib_dir, 'ocaml')
+@@ -318,7 +338,7 @@ def have_cxx_shared_library():
+ 
+     try:
+         readobj_cmd = subprocess.Popen(
+-            [readobj_exe, '--needed-libs', readobj_exe], stdout=subprocess.PIPE)
++            [readobj_exe, '--needed-libs', readobj_exe], stdout=subprocess.PIPE, env=config.environment)
+     except OSError:
+         print('could not exec llvm-readobj')
+         return False
diff --git a/pkgs/development/compilers/llvm/15/llvm/polly-lit-cfg-add-libs-to-dylib-path.patch b/pkgs/development/compilers/llvm/15/llvm/polly-lit-cfg-add-libs-to-dylib-path.patch
new file mode 100644
index 0000000000000..1354ad267314a
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/llvm/polly-lit-cfg-add-libs-to-dylib-path.patch
@@ -0,0 +1,24 @@
+diff --git a/tools/polly/test/lit.cfg b/tools/polly/test/lit.cfg
+index 41e3a589c61e..09f3b17498b0 100644
+--- a/tools/polly/test/lit.cfg
++++ b/tools/polly/test/lit.cfg
+@@ -36,9 +36,17 @@ base_paths = [config.llvm_tools_dir, config.environment['PATH']]
+ path = os.path.pathsep.join(base_paths + config.extra_paths)
+ config.environment['PATH'] = path
+ 
++# (Copied from polly/test/Unit/lit.cfg)
++if platform.system() == 'Darwin':
++    shlibpath_var = 'DYLD_LIBRARY_PATH'
++elif platform.system() == 'Windows':
++    shlibpath_var = 'PATH'
++else:
++    shlibpath_var = 'LD_LIBRARY_PATH'
++
+ path = os.path.pathsep.join((config.llvm_libs_dir,
+-                              config.environment.get('LD_LIBRARY_PATH','')))
+-config.environment['LD_LIBRARY_PATH'] = path
++                              config.environment.get(shlibpath_var,'')))
++config.environment[shlibpath_var] = path
+ 
+ llvm_config.use_default_substitutions()
+ 
diff --git a/pkgs/development/compilers/llvm/15/openmp/default.nix b/pkgs/development/compilers/llvm/15/openmp/default.nix
new file mode 100644
index 0000000000000..8047cb1122dee
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/openmp/default.nix
@@ -0,0 +1,71 @@
+{ lib
+, stdenv
+, llvm_meta
+, monorepoSrc
+, runCommand
+, cmake
+, ninja
+, llvm
+, targetLlvm
+, lit
+, clang-unwrapped
+, perl
+, pkg-config
+, xcbuild
+, version
+}:
+
+stdenv.mkDerivation rec {
+  pname = "openmp";
+  inherit version;
+
+  src = runCommand "${pname}-src-${version}" {} ''
+    mkdir -p "$out"
+    cp -r ${monorepoSrc}/cmake "$out"
+    cp -r ${monorepoSrc}/${pname} "$out"
+  '';
+
+  sourceRoot = "${src.name}/${pname}";
+
+  patches = [
+    ./fix-find-tool.patch
+    ./gnu-install-dirs.patch
+    ./run-lit-directly.patch
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [ cmake ninja perl pkg-config lit ];
+  buildInputs = [
+    (if stdenv.buildPlatform == stdenv.hostPlatform then llvm else targetLlvm)
+  ];
+
+  nativeCheckInputs = lib.optional stdenv.hostPlatform.isDarwin xcbuild.xcrun;
+
+  # Unsup:Pass:XFail:Fail
+  # 26:267:16:8
+  doCheck = false;
+  checkTarget = "check-openmp";
+
+  preCheck = ''
+    patchShebangs ../tools/archer/tests/deflake.bash
+  '';
+
+  cmakeFlags = [
+    "-DCLANG_TOOL=${clang-unwrapped}/bin/clang"
+    "-DOPT_TOOL=${llvm}/bin/opt"
+    "-DLINK_TOOL=${llvm}/bin/llvm-link"
+  ];
+
+  meta = llvm_meta // {
+    homepage = "https://openmp.llvm.org/";
+    description = "Support for the OpenMP language";
+    longDescription = ''
+      The OpenMP subproject of LLVM contains the components required to build an
+      executable OpenMP program that are outside the compiler itself.
+      Contains the code for the runtime library against which code compiled by
+      "clang -fopenmp" must be linked before it can run and the library that
+      supports offload to target devices.
+    '';
+  };
+}
diff --git a/pkgs/development/compilers/llvm/15/openmp/fix-find-tool.patch b/pkgs/development/compilers/llvm/15/openmp/fix-find-tool.patch
new file mode 100644
index 0000000000000..103b054ed1763
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/openmp/fix-find-tool.patch
@@ -0,0 +1,18 @@
+diff --git a/libomptarget/DeviceRTL/CMakeLists.txt b/libomptarget/DeviceRTL/CMakeLists.txt
+index ce66214822a2..6ab7b33c95da 100644
+--- a/libomptarget/DeviceRTL/CMakeLists.txt
++++ b/libomptarget/DeviceRTL/CMakeLists.txt
+@@ -27,10 +27,10 @@ endif()
+ if (LLVM_DIR)
+   # Builds that use pre-installed LLVM have LLVM_DIR set.
+   # A standalone or LLVM_ENABLE_RUNTIMES=openmp build takes this route
+-  find_program(CLANG_TOOL clang PATHS ${LLVM_TOOLS_BINARY_DIR} NO_DEFAULT_PATH)
++  find_program(CLANG_TOOL clang PATHS ${LLVM_TOOLS_BINARY_DIR})
+   find_program(LINK_TOOL llvm-link PATHS ${LLVM_TOOLS_BINARY_DIR}
+-    NO_DEFAULT_PATH)
+-  find_program(OPT_TOOL opt PATHS ${LLVM_TOOLS_BINARY_DIR} NO_DEFAULT_PATH)
++    )
++  find_program(OPT_TOOL opt PATHS ${LLVM_TOOLS_BINARY_DIR})
+   if ((NOT CLANG_TOOL) OR (NOT LINK_TOOL) OR (NOT OPT_TOOL))
+     libomptarget_say("Not building DeviceRTL. Missing clang: ${CLANG_TOOL}, llvm-link: ${LINK_TOOL} or opt: ${OPT_TOOL}")
+     return()
diff --git a/pkgs/development/compilers/llvm/15/openmp/gnu-install-dirs.patch b/pkgs/development/compilers/llvm/15/openmp/gnu-install-dirs.patch
new file mode 100644
index 0000000000000..77a93208832a1
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/openmp/gnu-install-dirs.patch
@@ -0,0 +1,22 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index b6ddbe90516d..311ab1d50e7f 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -29,7 +29,7 @@ if (OPENMP_STANDALONE_BUILD)
+   set(OPENMP_LIBDIR_SUFFIX "" CACHE STRING
+     "Suffix of lib installation directory, e.g. 64 => lib64")
+   # Do not use OPENMP_LIBDIR_SUFFIX directly, use OPENMP_INSTALL_LIBDIR.
+-  set(OPENMP_INSTALL_LIBDIR "lib${OPENMP_LIBDIR_SUFFIX}")
++  set(OPENMP_INSTALL_LIBDIR "${CMAKE_INSTALL_LIBDIR}${OPENMP_LIBDIR_SUFFIX}")
+ 
+   # Group test settings.
+   set(OPENMP_TEST_C_COMPILER ${CMAKE_C_COMPILER} CACHE STRING
+@@ -40,7 +40,7 @@ if (OPENMP_STANDALONE_BUILD)
+ else()
+   set(OPENMP_ENABLE_WERROR ${LLVM_ENABLE_WERROR})
+   # If building in tree, we honor the same install suffix LLVM uses.
+-  set(OPENMP_INSTALL_LIBDIR "lib${LLVM_LIBDIR_SUFFIX}")
++  set(OPENMP_INSTALL_LIBDIR "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}")
+ 
+   if (NOT MSVC)
+     set(OPENMP_TEST_C_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang)
diff --git a/pkgs/development/compilers/llvm/15/openmp/run-lit-directly.patch b/pkgs/development/compilers/llvm/15/openmp/run-lit-directly.patch
new file mode 100644
index 0000000000000..1e952fdc36a8f
--- /dev/null
+++ b/pkgs/development/compilers/llvm/15/openmp/run-lit-directly.patch
@@ -0,0 +1,12 @@
+diff --git a/cmake/OpenMPTesting.cmake b/cmake/OpenMPTesting.cmake
+--- a/cmake/OpenMPTesting.cmake
++++ b/cmake/OpenMPTesting.cmake
+@@ -185,7 +185,7 @@ function(add_openmp_testsuite target comment)
+   if (${OPENMP_STANDALONE_BUILD})
+     set(LIT_ARGS ${OPENMP_LIT_ARGS} ${ARG_ARGS})
+     add_custom_target(${target}
+-      COMMAND ${PYTHON_EXECUTABLE} ${OPENMP_LLVM_LIT_EXECUTABLE} ${LIT_ARGS} ${ARG_UNPARSED_ARGUMENTS}
++      COMMAND ${OPENMP_LLVM_LIT_EXECUTABLE} ${LIT_ARGS} ${ARG_UNPARSED_ARGUMENTS}
+       COMMENT ${comment}
+       DEPENDS ${ARG_DEPENDS}
+       USES_TERMINAL
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 235b6c1229b33..fde9eda320401 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -13983,6 +13983,7 @@ with pkgs;
   clang_12 = llvmPackages_12.clang;
   clang_13 = llvmPackages_13.clang;
   clang_14 = llvmPackages_14.clang;
+  clang_15 = llvmPackages_15.clang;
 
   clang-tools = callPackage ../development/tools/clang-tools {
     llvmPackages = llvmPackages_latest;
@@ -14028,6 +14029,10 @@ with pkgs;
     llvmPackages = llvmPackages_14;
   };
 
+  clang-tools_15 = callPackage ../development/tools/clang-tools {
+    llvmPackages = llvmPackages_15;
+  };
+
   clang-analyzer = callPackage ../development/tools/analysis/clang-analyzer {
     llvmPackages = llvmPackages_latest;
     inherit (llvmPackages_latest) clang;
@@ -15010,6 +15015,7 @@ with pkgs;
   lld_12 = llvmPackages_12.lld;
   lld_13 = llvmPackages_13.lld;
   lld_14 = llvmPackages_14.lld;
+  lld_15 = llvmPackages_15.lld;
 
   lldb = llvmPackages_latest.lldb;
   lldb_5 = llvmPackages_5.lldb;
@@ -15022,6 +15028,7 @@ with pkgs;
   lldb_12 = llvmPackages_12.lldb;
   lldb_13 = llvmPackages_13.lldb;
   lldb_14 = llvmPackages_14.lldb;
+  lldb_15 = llvmPackages_15.lldb;
 
   llvm = llvmPackages.llvm;
   llvm_5  = llvmPackages_5.llvm;
@@ -15034,6 +15041,7 @@ with pkgs;
   llvm_12 = llvmPackages_12.llvm;
   llvm_13 = llvmPackages_13.llvm;
   llvm_14 = llvmPackages_14.llvm;
+  llvm_15 = llvmPackages_15.llvm;
 
   libllvm = llvmPackages.libllvm;
   llvm-manpages = llvmPackages.llvm-manpages;
@@ -15128,6 +15136,13 @@ with pkgs;
     targetLlvm = targetPackages.llvmPackages_14.llvm or llvmPackages_14.llvm;
   }));
 
+  llvmPackages_15 = recurseIntoAttrs (callPackage ../development/compilers/llvm/15 ({
+    inherit (stdenvAdapters) overrideCC;
+    buildLlvmTools = buildPackages.llvmPackages_15.tools;
+    targetLlvmLibraries = targetPackages.llvmPackages_15.libraries or llvmPackages_15.libraries;
+    targetLlvm = targetPackages.llvmPackages_15.llvm or llvmPackages_15.llvm;
+  }));
+
   llvmPackages_latest = llvmPackages_14;
 
   llvmPackages_rocm = recurseIntoAttrs (callPackage ../development/compilers/llvm/rocm { });