[llvm] 50a4ab2 - [Coroutines] Create C++ noop coroutine with default function attributes (#134878)

[via llvm-commits]

Author: Victor Campos
Date: 2025-06-02T09:39:52+01:00
New Revision: 50a4ab2bc3288cb7876d93c859eebdc3c851c527

URL: https://github.com/llvm/llvm-project/commit/50a4ab2bc3288cb7876d93c859eebdc3c851c527
DIFF: https://github.com/llvm/llvm-project/commit/50a4ab2bc3288cb7876d93c859eebdc3c851c527.diff

LOG: [Coroutines] Create C++ noop coroutine with default function attributes (#134878)

This change makes the C++ noop coroutine to be built with attributes
based on the module flags. Among other things, this adds function
attributes related to the Pointer Authentication and Branch Target
Enforcement module flags, which are set by command-line options.

Before this patch, C++ programs built with either PAC-RET or BTI that
had the noop coroutine emitted could have a runtime error because this
function wasn't compatible with the rest of the program.

Added: 
    llvm/test/Transforms/Coroutines/coro-noop-pacbti.ll

Modified: 
    llvm/lib/Transforms/Coroutines/CoroEarly.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Coroutines/CoroEarly.cpp b/llvm/lib/Transforms/Coroutines/CoroEarly.cpp
index eea6dfba14e37..9ac145b10fe43 100644
--- a/llvm/lib/Transforms/Coroutines/CoroEarly.cpp
+++ b/llvm/lib/Transforms/Coroutines/CoroEarly.cpp
@@ -131,9 +131,10 @@ void Lowerer::lowerCoroNoop(IntrinsicInst *II) {
         StructType::create({FnPtrTy, FnPtrTy}, "NoopCoro.Frame");
 
     // Create a Noop function that does nothing.
-    Function *NoopFn =
-        Function::Create(FnTy, GlobalValue::LinkageTypes::PrivateLinkage,
-                         "__NoopCoro_ResumeDestroy", &M);
+    Function *NoopFn = Function::createWithDefaultAttr(
+        FnTy, GlobalValue::LinkageTypes::PrivateLinkage,
+        M.getDataLayout().getProgramAddressSpace(), "__NoopCoro_ResumeDestroy",
+        &M);
     NoopFn->setCallingConv(CallingConv::Fast);
     buildDebugInfoForNoopResumeDestroyFunc(NoopFn);
     auto *Entry = BasicBlock::Create(C, "entry", NoopFn);

diff  --git a/llvm/test/Transforms/Coroutines/coro-noop-pacbti.ll b/llvm/test/Transforms/Coroutines/coro-noop-pacbti.ll
new file mode 100644
index 0000000000000..4f302a6acc649
--- /dev/null
+++ b/llvm/test/Transforms/Coroutines/coro-noop-pacbti.ll
@@ -0,0 +1,23 @@
+
+; RUN: opt < %s -S -passes=coro-early | FileCheck %s
+
+; CHECK:      define private fastcc void @__NoopCoro_ResumeDestroy(ptr %0) #1 {
+; CHECK-NEXT: entry:
+; CHECK-NEXT:   ret void
+; CHECK-NEXT: }
+
+; CHECK:      attributes #1 = { "branch-target-enforcement" "sign-return-address"="all" "sign-return-address-key"="a_key" }
+
+define ptr @noop() {
+entry:
+  %n = call ptr @llvm.coro.noop()
+  ret ptr %n
+}
+
+declare ptr @llvm.coro.noop()
+
+!llvm.module.flags = !{!0, !1, !2}
+
+!0 = !{i32 8, !"branch-target-enforcement", i32 1}
+!1 = !{i32 8, !"sign-return-address", i32 1}
+!2 = !{i32 8, !"sign-return-address-all", i32 1}