[llvm] Skip tranformConstExprCastCall for naked function (PR #76496)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: None (hstk30-hw)

<details>
<summary>Changes</summary>

Fix this issue https://github.com/llvm/llvm-project/issues/72843 .

For naked function, assembly might be using an argument, or otherwise rely on the frame layout, so don't transformConstExprCastCall

---
Full diff: https://github.com/llvm/llvm-project/pull/76496.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp (+6) 
- (added) llvm/test/Transforms/InstCombine/cast-call-naked.ll (+16) 


``````````diff
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 3b7fe7fa226607..43d4496571be50 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3850,6 +3850,12 @@ bool InstCombinerImpl::transformConstExprCastCall(CallBase &Call) {
   if (Callee->hasFnAttribute("thunk"))
     return false;
 
+  // If this is a call to a naked function, the assembly might be
+  // using an argument, or otherwise rely on the frame layout,
+  // the function prototype will mismatch.
+  if (Callee->hasFnAttribute(Attribute::Naked))
+    return false;
+
   // If this is a musttail call, the callee's prototype must match the caller's
   // prototype with the exception of pointee types. The code below doesn't
   // implement that, so we can't do this transform.
diff --git a/llvm/test/Transforms/InstCombine/cast-call-naked.ll b/llvm/test/Transforms/InstCombine/cast-call-naked.ll
new file mode 100644
index 00000000000000..a0b0d48b44d4eb
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/cast-call-naked.ll
@@ -0,0 +1,16 @@
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+ 
+define dso_local void @naked_func() #0 {
+entry:
+  tail call void asm sideeffect "mov  r1, r0", ""()
+  unreachable
+}
+ 
+define i32 @main() {
+; CHECK:  call void @naked_func(i32 noundef 1)
+entry:
+  call void @naked_func(i32 noundef 1)
+  ret i32 0
+}
+ 
+attributes #0 = { naked }

``````````

</details>


https://github.com/llvm/llvm-project/pull/76496