Add a safe wrapper for LLVMAppendModuleInlineAsm

This patch also changes the Rust-side declaration to take `*const c_uchar`
instead of `*const c_char`, to avoid the need for `AsCCharPtr`.

Author: Zalathar

compiler/rustc_codegen_llvm/src/asm.rs

@@ -435,13 +435,7 @@ impl<'tcx> AsmCodegenMethods<'tcx> for CodegenCx<'_, 'tcx> {
             template_str.push_str("\n.att_syntax\n");
         }
 
-        unsafe {
-            llvm::LLVMAppendModuleInlineAsm(
-                self.llmod,
-                template_str.as_c_char_ptr(),
-                template_str.len(),
-            );
-        }
+        llvm::append_module_inline_asm(self.llmod, template_str.as_bytes());
     }
 
     fn mangled_name(&self, instance: Instance<'tcx>) -> String {

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -1148,9 +1148,9 @@ unsafe fn embed_bitcode(
             // We need custom section flags, so emit module-level inline assembly.
             let section_flags = if cgcx.is_pe_coff { "n" } else { "e" };
             let asm = create_section_with_flags_asm(".llvmbc", section_flags, bitcode);
-            llvm::LLVMAppendModuleInlineAsm(llmod, asm.as_c_char_ptr(), asm.len());
+            llvm::append_module_inline_asm(llmod, &asm);
             let asm = create_section_with_flags_asm(".llvmcmd", section_flags, cmdline.as_bytes());
-            llvm::LLVMAppendModuleInlineAsm(llmod, asm.as_c_char_ptr(), asm.len());
+            llvm::append_module_inline_asm(llmod, &asm);
         }
     }
 }

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1014,8 +1014,12 @@ unsafe extern "C" {
     pub(crate) fn LLVMGetDataLayoutStr(M: &Module) -> *const c_char;
     pub(crate) fn LLVMSetDataLayout(M: &Module, Triple: *const c_char);
 
-    /// See Module::setModuleInlineAsm.
-    pub(crate) fn LLVMAppendModuleInlineAsm(M: &Module, Asm: *const c_char, Len: size_t);
+    /// Append inline assembly to a module. See `Module::appendModuleInlineAsm`.
+    pub(crate) fn LLVMAppendModuleInlineAsm(
+        M: &Module,
+        Asm: *const c_uchar, // See "PTR_LEN_STR".
+        Len: size_t,
+    );
 
     /// Create the specified uniqued inline asm string. See `InlineAsm::get()`.
     pub(crate) fn LLVMGetInlineAsm<'ll>(

compiler/rustc_codegen_llvm/src/llvm/mod.rs

@@ -440,3 +440,11 @@ pub(crate) fn set_dso_local<'ll>(v: &'ll Value) {
         LLVMRustSetDSOLocal(v, true);
     }
 }
+
+/// Safe wrapper for `LLVMAppendModuleInlineAsm`, which delegates to
+/// `Module::appendModuleInlineAsm`.
+pub(crate) fn append_module_inline_asm<'ll>(llmod: &'ll Module, asm: &[u8]) {
+    unsafe {
+        LLVMAppendModuleInlineAsm(llmod, asm.as_ptr(), asm.len());
+    }
+}