Always preserve user-written comments in assembly

Author: tgross35

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -436,7 +436,8 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
   Options.FunctionSections = FunctionSections;
   Options.UniqueSectionNames = UniqueSectionNames;
   Options.MCOptions.AsmVerbose = AsmComments;
-  Options.MCOptions.PreserveAsmComments = AsmComments;
+  // Always preserve comments that were written by the user
+  Options.MCOptions.PreserveAsmComments = true;
   Options.MCOptions.ABIName = ABIStr;
   if (SplitDwarfFile) {
     Options.MCOptions.SplitDwarfFile = SplitDwarfFile;

tests/assembly/asm-comments.rs

@@ -0,0 +1,12 @@
+//@ assembly-output: emit-asm
+//@ only-x86_64
+// Check that comments in assembly get passed
+
+#![crate_type = "lib"]
+
+// CHECK-LABEL: test_comments:
+#[no_mangle]
+pub fn test_comments() {
+    // CHECK: example comment
+    unsafe { core::arch::asm!("nop // example comment") };
+}