Auto merge of rust-lang#132167 - Zalathar:llvm-wrappers, r=jieyouxu

Replace some LLVMRust wrappers with calls to the LLVM C API

This PR removes the LLVMRust wrapper functions for getting/setting linkage and visibility, and replaces them with direct calls to the corresponding functions in LLVM's C API.

To make this convenient and sound, two pieces of supporting code have also been added:
- A simple proc-macro that derives `TryFrom<u32>` for fieldless enums
- A wrapper type for C enum values returned by LLVM functions, to ensure soundness if LLVM returns an enum value we don't know about

In a few places, the use of safe wrapper functions means that an `unsafe` block is no longer needed, so the affected code has changed its indentation level.

compiler/rustc_codegen_llvm/src/allocator.rs

@@ -77,20 +77,14 @@ pub(crate) unsafe fn codegen(
         // __rust_alloc_error_handler_should_panic
         let name = OomStrategy::SYMBOL;
         let ll_g = llvm::LLVMRustGetOrInsertGlobal(llmod, name.as_ptr().cast(), name.len(), i8);
-        llvm::LLVMRustSetVisibility(
-            ll_g,
-            llvm::Visibility::from_generic(tcx.sess.default_visibility()),
-        );
+        llvm::set_visibility(ll_g, llvm::Visibility::from_generic(tcx.sess.default_visibility()));
         let val = tcx.sess.opts.unstable_opts.oom.should_panic();
         let llval = llvm::LLVMConstInt(i8, val as u64, False);
         llvm::LLVMSetInitializer(ll_g, llval);
 
         let name = NO_ALLOC_SHIM_IS_UNSTABLE;
         let ll_g = llvm::LLVMRustGetOrInsertGlobal(llmod, name.as_ptr().cast(), name.len(), i8);
-        llvm::LLVMRustSetVisibility(
-            ll_g,
-            llvm::Visibility::from_generic(tcx.sess.default_visibility()),
-        );
+        llvm::set_visibility(ll_g, llvm::Visibility::from_generic(tcx.sess.default_visibility()));
         let llval = llvm::LLVMConstInt(i8, 0, False);
         llvm::LLVMSetInitializer(ll_g, llval);
     }
@@ -134,10 +128,7 @@ fn create_wrapper_function(
             None
         };
 
-        llvm::LLVMRustSetVisibility(
-            llfn,
-            llvm::Visibility::from_generic(tcx.sess.default_visibility()),
-        );
+        llvm::set_visibility(llfn, llvm::Visibility::from_generic(tcx.sess.default_visibility()));
 
         if tcx.sess.must_emit_unwind_tables() {
             let uwtable =
@@ -151,7 +142,7 @@ fn create_wrapper_function(
             // -> ! DIFlagNoReturn
             attributes::apply_to_llfn(callee, llvm::AttributePlace::Function, &[no_return]);
         }
-        llvm::LLVMRustSetVisibility(callee, llvm::Visibility::Hidden);
+        llvm::set_visibility(callee, llvm::Visibility::Hidden);
 
         let llbb = llvm::LLVMAppendBasicBlockInContext(llcx, llfn, c"entry".as_ptr());
 

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -1043,7 +1043,7 @@ unsafe fn embed_bitcode(
 
             let section = bitcode_section_name(cgcx);
             llvm::LLVMSetSection(llglobal, section.as_ptr().cast());
-            llvm::LLVMRustSetLinkage(llglobal, llvm::Linkage::PrivateLinkage);
+            llvm::set_linkage(llglobal, llvm::Linkage::PrivateLinkage);
             llvm::LLVMSetGlobalConstant(llglobal, llvm::True);
 
             let llconst = common::bytes_in_context(llcx, cmdline.as_bytes());
@@ -1061,7 +1061,7 @@ unsafe fn embed_bitcode(
                 c".llvmcmd"
             };
             llvm::LLVMSetSection(llglobal, section.as_ptr());
-            llvm::LLVMRustSetLinkage(llglobal, llvm::Linkage::PrivateLinkage);
+            llvm::set_linkage(llglobal, llvm::Linkage::PrivateLinkage);
         } else {
             // We need custom section flags, so emit module-level inline assembly.
             let section_flags = if cgcx.is_pe_coff { "n" } else { "e" };
@@ -1096,7 +1096,7 @@ fn create_msvc_imps(
         let ptr_ty = Type::ptr_llcx(llcx);
         let globals = base::iter_globals(llmod)
             .filter(|&val| {
-                llvm::LLVMRustGetLinkage(val) == llvm::Linkage::ExternalLinkage
+                llvm::get_linkage(val) == llvm::Linkage::ExternalLinkage
                     && llvm::LLVMIsDeclaration(val) == 0
             })
             .filter_map(|val| {
@@ -1115,7 +1115,7 @@ fn create_msvc_imps(
         for (imp_name, val) in globals {
             let imp = llvm::LLVMAddGlobal(llmod, ptr_ty, imp_name.as_ptr());
             llvm::LLVMSetInitializer(imp, val);
-            llvm::LLVMRustSetLinkage(imp, llvm::Linkage::ExternalLinkage);
+            llvm::set_linkage(imp, llvm::Linkage::ExternalLinkage);
         }
     }
 

compiler/rustc_codegen_llvm/src/callee.rs

@@ -95,9 +95,9 @@ pub(crate) fn get_fn<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'t
         // whether we are sharing generics or not. The important thing here is
         // that the visibility we apply to the declaration is the same one that
         // has been applied to the definition (wherever that definition may be).
-        unsafe {
-            llvm::LLVMRustSetLinkage(llfn, llvm::Linkage::ExternalLinkage);
 
+        llvm::set_linkage(llfn, llvm::Linkage::ExternalLinkage);
+        unsafe {
             let is_generic = instance.args.non_erasable_generics().next().is_some();
 
             let is_hidden = if is_generic {
@@ -135,7 +135,7 @@ pub(crate) fn get_fn<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'t
                         || !cx.tcx.is_reachable_non_generic(instance_def_id))
             };
             if is_hidden {
-                llvm::LLVMRustSetVisibility(llfn, llvm::Visibility::Hidden);
+                llvm::set_visibility(llfn, llvm::Visibility::Hidden);
             }
 
             // MinGW: For backward compatibility we rely on the linker to decide whether it

compiler/rustc_codegen_llvm/src/common.rs

@@ -219,8 +219,8 @@ impl<'ll, 'tcx> ConstCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                     llvm::LLVMSetInitializer(g, sc);
                     llvm::LLVMSetGlobalConstant(g, True);
                     llvm::LLVMSetUnnamedAddress(g, llvm::UnnamedAddr::Global);
-                    llvm::LLVMRustSetLinkage(g, llvm::Linkage::InternalLinkage);
                 }
+                llvm::set_linkage(g, llvm::Linkage::InternalLinkage);
                 (s.to_owned(), g)
             })
             .1;

compiler/rustc_codegen_llvm/src/consts.rs

@@ -172,29 +172,27 @@ fn check_and_apply_linkage<'ll, 'tcx>(
     if let Some(linkage) = attrs.import_linkage {
         debug!("get_static: sym={} linkage={:?}", sym, linkage);
 
-        unsafe {
-            // Declare a symbol `foo` with the desired linkage.
-            let g1 = cx.declare_global(sym, cx.type_i8());
-            llvm::LLVMRustSetLinkage(g1, base::linkage_to_llvm(linkage));
-
-            // Declare an internal global `extern_with_linkage_foo` which
-            // is initialized with the address of `foo`. If `foo` is
-            // discarded during linking (for example, if `foo` has weak
-            // linkage and there are no definitions), then
-            // `extern_with_linkage_foo` will instead be initialized to
-            // zero.
-            let mut real_name = "_rust_extern_with_linkage_".to_string();
-            real_name.push_str(sym);
-            let g2 = cx.define_global(&real_name, llty).unwrap_or_else(|| {
-                cx.sess().dcx().emit_fatal(SymbolAlreadyDefined {
-                    span: cx.tcx.def_span(def_id),
-                    symbol_name: sym,
-                })
-            });
-            llvm::LLVMRustSetLinkage(g2, llvm::Linkage::InternalLinkage);
-            llvm::LLVMSetInitializer(g2, g1);
-            g2
-        }
+        // Declare a symbol `foo` with the desired linkage.
+        let g1 = cx.declare_global(sym, cx.type_i8());
+        llvm::set_linkage(g1, base::linkage_to_llvm(linkage));
+
+        // Declare an internal global `extern_with_linkage_foo` which
+        // is initialized with the address of `foo`. If `foo` is
+        // discarded during linking (for example, if `foo` has weak
+        // linkage and there are no definitions), then
+        // `extern_with_linkage_foo` will instead be initialized to
+        // zero.
+        let mut real_name = "_rust_extern_with_linkage_".to_string();
+        real_name.push_str(sym);
+        let g2 = cx.define_global(&real_name, llty).unwrap_or_else(|| {
+            cx.sess().dcx().emit_fatal(SymbolAlreadyDefined {
+                span: cx.tcx.def_span(def_id),
+                symbol_name: sym,
+            })
+        });
+        llvm::set_linkage(g2, llvm::Linkage::InternalLinkage);
+        unsafe { llvm::LLVMSetInitializer(g2, g1) };
+        g2
     } else if cx.tcx.sess.target.arch == "x86"
         && let Some(dllimport) = crate::common::get_dllimport(cx.tcx, def_id, sym)
     {
@@ -224,23 +222,21 @@ impl<'ll> CodegenCx<'ll, '_> {
         align: Align,
         kind: Option<&str>,
     ) -> &'ll Value {
-        unsafe {
-            let gv = match kind {
-                Some(kind) if !self.tcx.sess.fewer_names() => {
-                    let name = self.generate_local_symbol_name(kind);
-                    let gv = self.define_global(&name, self.val_ty(cv)).unwrap_or_else(|| {
-                        bug!("symbol `{}` is already defined", name);
-                    });
-                    llvm::LLVMRustSetLinkage(gv, llvm::Linkage::PrivateLinkage);
-                    gv
-                }
-                _ => self.define_private_global(self.val_ty(cv)),
-            };
-            llvm::LLVMSetInitializer(gv, cv);
-            set_global_alignment(self, gv, align);
-            llvm::SetUnnamedAddress(gv, llvm::UnnamedAddr::Global);
-            gv
-        }
+        let gv = match kind {
+            Some(kind) if !self.tcx.sess.fewer_names() => {
+                let name = self.generate_local_symbol_name(kind);
+                let gv = self.define_global(&name, self.val_ty(cv)).unwrap_or_else(|| {
+                    bug!("symbol `{}` is already defined", name);
+                });
+                llvm::set_linkage(gv, llvm::Linkage::PrivateLinkage);
+                gv
+            }
+            _ => self.define_private_global(self.val_ty(cv)),
+        };
+        unsafe { llvm::LLVMSetInitializer(gv, cv) };
+        set_global_alignment(self, gv, align);
+        llvm::SetUnnamedAddress(gv, llvm::UnnamedAddr::Global);
+        gv
     }
 
     #[instrument(level = "debug", skip(self))]
@@ -292,9 +288,7 @@ impl<'ll> CodegenCx<'ll, '_> {
             let g = self.declare_global(sym, llty);
 
             if !self.tcx.is_reachable_non_generic(def_id) {
-                unsafe {
-                    llvm::LLVMRustSetVisibility(g, llvm::Visibility::Hidden);
-                }
+                llvm::set_visibility(g, llvm::Visibility::Hidden);
             }
 
             g
@@ -312,7 +306,7 @@ impl<'ll> CodegenCx<'ll, '_> {
             llvm::set_thread_local_mode(g, self.tls_model);
         }
 
-        let dso_local = unsafe { self.should_assume_dso_local(g, true) };
+        let dso_local = self.should_assume_dso_local(g, true);
         if dso_local {
             unsafe {
                 llvm::LLVMRustSetDSOLocal(g, true);
@@ -401,8 +395,8 @@ impl<'ll> CodegenCx<'ll, '_> {
                 let name = llvm::get_value_name(g).to_vec();
                 llvm::set_value_name(g, b"");
 
-                let linkage = llvm::LLVMRustGetLinkage(g);
-                let visibility = llvm::LLVMRustGetVisibility(g);
+                let linkage = llvm::get_linkage(g);
+                let visibility = llvm::get_visibility(g);
 
                 let new_g = llvm::LLVMRustGetOrInsertGlobal(
                     self.llmod,
@@ -411,8 +405,8 @@ impl<'ll> CodegenCx<'ll, '_> {
                     val_llty,
                 );
 
-                llvm::LLVMRustSetLinkage(new_g, linkage);
-                llvm::LLVMRustSetVisibility(new_g, visibility);
+                llvm::set_linkage(new_g, linkage);
+                llvm::set_visibility(new_g, visibility);
 
                 // The old global has had its name removed but is returned by
                 // get_static since it is in the instance cache. Provide an

compiler/rustc_codegen_llvm/src/context.rs

@@ -605,7 +605,7 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
         unsafe {
             let g = llvm::LLVMAddGlobal(self.llmod, self.val_ty(array), name.as_ptr());
             llvm::LLVMSetInitializer(g, array);
-            llvm::LLVMRustSetLinkage(g, llvm::Linkage::AppendingLinkage);
+            llvm::set_linkage(g, llvm::Linkage::AppendingLinkage);
             llvm::LLVMSetSection(g, c"llvm.metadata".as_ptr());
         }
     }

compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs

@@ -76,7 +76,7 @@ pub(crate) fn get_or_insert_gdb_debug_scripts_section_global<'ll>(
             llvm::LLVMSetInitializer(section_var, cx.const_bytes(section_contents));
             llvm::LLVMSetGlobalConstant(section_var, llvm::True);
             llvm::LLVMSetUnnamedAddress(section_var, llvm::UnnamedAddr::Global);
-            llvm::LLVMRustSetLinkage(section_var, llvm::Linkage::LinkOnceODRLinkage);
+            llvm::set_linkage(section_var, llvm::Linkage::LinkOnceODRLinkage);
             // This should make sure that the whole section is not larger than
             // the string it contains. Otherwise we get a warning from GDB.
             llvm::LLVMSetAlignment(section_var, 1);

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -785,13 +785,12 @@ fn codegen_msvc_try<'ll>(
         let type_info =
             bx.const_struct(&[type_info_vtable, bx.const_null(bx.type_ptr()), type_name], false);
         let tydesc = bx.declare_global("__rust_panic_type_info", bx.val_ty(type_info));
-        unsafe {
-            llvm::LLVMRustSetLinkage(tydesc, llvm::Linkage::LinkOnceODRLinkage);
-            if bx.cx.tcx.sess.target.supports_comdat() {
-                llvm::SetUniqueComdat(bx.llmod, tydesc);
-            }
-            llvm::LLVMSetInitializer(tydesc, type_info);
+
+        llvm::set_linkage(tydesc, llvm::Linkage::LinkOnceODRLinkage);
+        if bx.cx.tcx.sess.target.supports_comdat() {
+            llvm::SetUniqueComdat(bx.llmod, tydesc);
         }
+        unsafe { llvm::LLVMSetInitializer(tydesc, type_info) };
 
         // The flag value of 8 indicates that we are catching the exception by
         // reference instead of by value. We can't use catch by value because
@@ -1064,7 +1063,7 @@ fn gen_fn<'ll, 'tcx>(
     cx.set_frame_pointer_type(llfn);
     cx.apply_target_cpu_attr(llfn);
     // FIXME(eddyb) find a nicer way to do this.
-    unsafe { llvm::LLVMRustSetLinkage(llfn, llvm::Linkage::InternalLinkage) };
+    llvm::set_linkage(llfn, llvm::Linkage::InternalLinkage);
     let llbb = Builder::append_block(cx, llfn, "entry-block");
     let bx = Builder::build(cx, llbb);
     codegen(bx);