Replace the \01__gnu_mcount_nc to LLVM intrinsic for ARM

Current `-Zinstrument-mcount` for ARM32 use the `\01__gnu_mcount_nc`
directly for its instrumentation function.

However, the LLVM does not use this mcount function directly, but it wraps
it to intrinsic, `llvm.arm.gnu.eabi.mcount` and the transform pass also
only handle the intrinsic.

As a result, current `-Zinstrument-mcount` not work on ARM32.
Refer: https://github.com/namhyung/uftrace/issues/1764

This commit replaces the mcount name from native function to the
LLVM intrinsic so that the transform pass can handle it.

Signed-off-by: ChoKyuWon <kyuwoncho18@gmail.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/compiler/rustc_codegen_llvm/src/attributes.rs b/compiler/rustc_codegen_llvm/src/attributes.rs
index 39275272e42..57e7f86f703 100644
--- a/compiler/rustc_codegen_llvm/src/attributes.rs
+++ b/compiler/rustc_codegen_llvm/src/attributes.rs
@@ -128,7 +128,10 @@ fn instrument_function_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> SmallVec<[&'ll Attr
 
         // The function name varies on platforms.
         // See test/CodeGen/mcount.c in clang.
-        let mcount_name = cx.sess().target.mcount.as_ref();
+        let mcount_name = match &cx.sess().target.llvm_mcount_intrinsic {
+            Some(llvm_mcount_intrinsic) => llvm_mcount_intrinsic.as_ref(),
+            None => cx.sess().target.mcount.as_ref(),
+        };
 
         attrs.push(llvm::CreateAttrStringValue(
             cx.llcx,