[LTO] Fix Veclib flags correctly pass to LTO flags

[paschalis-mpeis]

Flags -fveclib=name were not passed to LTO flags.
This pass fixes that by converting the -fveclib flags to their relevant names for opt's -vector-lib=name flags.

For example:
-fveclib=SLEEF would become -vector-library=sleefgnuabi and passed through the -plugin-opt flag.

[llvmbot]

@llvm/pr-subscribers-clang-driver

@llvm/pr-subscribers-clang

Author: Paschalis Mpeis (paschalis-mpeis)

Changes

Flags -fveclib=name were not passed to LTO flags.
This pass fixes that by converting the -fveclib flags to their relevant names for opt's -vector-lib=name flags.

For example:
-fveclib=SLEEF would become -vector-library=sleefgnuabi and passed through the -plugin-opt flag.

---

Full diff: https://github.com/llvm/llvm-project/pull/78749.diff

2 Files Affected:

• (modified) clang/lib/Driver/ToolChains/CommonArgs.cpp (+22)
• (modified) clang/test/Driver/fveclib.c (+28)

diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index 385f66f3782bc1..470145849e4187 100644
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -783,6 +783,28 @@ void tools::addLTOOptions(const ToolChain &ToolChain, const ArgList &Args,
                                          "-generate-arange-section"));
   }
 
+  // Pass vector library arguments to LTO.
+  Arg *ArgVecLib = Args.getLastArg(options::OPT_fveclib);
+  if (ArgVecLib && ArgVecLib->getNumValues() == 1) {
+    // Map the vector library names from clang front-end to opt front-end. The
+    // values are taken from the TargetLibraryInfo class command line options.
+    std::optional<StringRef> OptVal =
+        llvm::StringSwitch<std::optional<StringRef>>(ArgVecLib->getValue())
+            .Case("Accelerate", "Accelerate")
+            .Case("LIBMVEC", "LIBMVEC-X86")
+            .Case("MASSV", "MASSV")
+            .Case("SVML", "SVML")
+            .Case("SLEEF", "sleefgnuabi")
+            .Case("Darwin_libsystem_m", "Darwin_libsystem_m")
+            .Case("ArmPL", "ArmPL")
+            .Case("none", "none")
+            .Default(std::nullopt);
+
+    if (OptVal)
+      CmdArgs.push_back(Args.MakeArgString(
+          Twine(PluginOptPrefix) + "-vector-library=" + OptVal.value()));
+  }
+
   // Try to pass driver level flags relevant to LTO code generation down to
   // the plugin.
 
diff --git a/clang/test/Driver/fveclib.c b/clang/test/Driver/fveclib.c
index e2a7619e9b89f7..8ce7bcbb67ae0b 100644
--- a/clang/test/Driver/fveclib.c
+++ b/clang/test/Driver/fveclib.c
@@ -31,3 +31,31 @@
 
 // RUN: %clang -fveclib=Accelerate %s -nodefaultlibs -target arm64-apple-ios8.0.0 -### 2>&1 | FileCheck --check-prefix=CHECK-LINK-NODEFAULTLIBS %s
 // CHECK-LINK-NODEFAULTLIBS-NOT: "-framework" "Accelerate"
+
+
+/* Verify that the correct vector library is passed to LTO flags. */
+
+
+// RUN: %clang -### -fveclib=none -flto %s -v 2>&1  | FileCheck -check-prefix CHECK-LTO-NOLIB %s
+// CHECK-LTO-NOLIB: "-plugin-opt=-vector-library=none"
+
+// RUN: %clang -### -fveclib=Accelerate -flto %s -v 2>&1  | FileCheck -check-prefix CHECK-LTO-ACCELERATE %s
+// CHECK-LTO-ACCELERATE: "-plugin-opt=-vector-library=Accelerate"
+
+// RUN: %clang -### -fveclib=LIBMVEC -flto %s -v 2>&1  | FileCheck -check-prefix CHECK-LTO-LIBMVEC %s
+// CHECK-LTO-LIBMVEC: "-plugin-opt=-vector-library=LIBMVEC-X86"
+
+// RUN: %clang -### -fveclib=MASSV -flto %s -v 2>&1  | FileCheck -check-prefix CHECK-LTO-MASSV %s
+// CHECK-LTO-MASSV: "-plugin-opt=-vector-library=MASSV"
+
+// RUN: not %clang -### -fveclib=SVML -flto %s -v 2>&1  | FileCheck -check-prefix CHECK-LTO-SVML %s
+// CHECK-LTO-SVML: "-plugin-opt=-vector-library=SVML"
+
+// RUN: %clang -### -fveclib=SLEEF -flto %s -v 2>&1  | FileCheck -check-prefix CHECK-LTO-SLEEF %s
+// CHECK-LTO-SLEEF: "-plugin-opt=-vector-library=sleefgnuabi"
+
+// RUN: %clang -### -fveclib=Darwin_libsystem_m -flto %s -v 2>&1  | FileCheck -check-prefix CHECK-LTO-DARWIN %s
+// CHECK-LTO-DARWIN: "-plugin-opt=-vector-library=Darwin_libsystem_m"
+
+// RUN: %clang -### -fveclib=ArmPL -flto %s -v 2>&1  | FileCheck -check-prefix CHECK-LTO-ARMPL %s
+// CHECK-LTO-ARMPL: "-plugin-opt=-vector-library=ArmPL"

[david-arm]

Is it possible to refactor and reuse existing TargetLibraryInfo code, i.e. create a common static function that maps the values so that it can be called in multiple places?

[paschalis-mpeis]

Reusing code for mapping the strings is a great suggestion, however, TargetLibraryInfo statically creates some cl::opt (command line options) and I'm not sure ATM what would be a clean way to do this.

I would suggest such change (if is doable in a clean way) to be dealt in a separate patch.

[mgabka]

the TLI belongs to llvm world, while clang driver from what I can see is only linked with following llvm components:
set(LLVM_LINK_COMPONENTS
BinaryFormat
MC
Object
Option
ProfileData
Support
TargetParser
WindowsDriver
)
so I don't think it is possible to do it.

Unfortunately at the early stage when the tools::addLTOOptions function is called the CodeGenOptions are not even created, perhaps we could have a function defined which does the strings checking in include/llvm/Analysis/TargetLibraryInfo.h and include it in the CommonArgs.cpp? a least everything would be in one place? what do you think @david-arm ?

[david-arm]

Yes I think that would work, i.e. having a static function in TargetLibraryInfo.h that can be called in two places and doesn't have a dependency on the component/library. Having said that, I won't hold this patch up for this if it's too difficult!

[mgabka]

It LGTM, but probably worth to give some extra time in case anybody else thinks differently, it would be really good to have it on LLVM18 as well

[david-arm]

LGTM as well!