Auto merge of #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.

1 files changed, 4 insertions, 4 deletions

diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index afdd2b581b8..bf77fc56d08 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/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);
         }
     }