[llvm] [MemCpyOpt] Combine alias metadatas when replacing byval arguments (PR #70580)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: DianQK (DianQK)

<details>
<summary>Changes</summary>

Fixes #<!-- -->70578.

---
Full diff: https://github.com/llvm/llvm-project/pull/70580.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp (+1) 
- (modified) llvm/test/Transforms/MemCpyOpt/memcpy.ll (+17) 


``````````diff
diff --git a/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp b/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
index b366ec5d4c35725..a31dedafdcbc449 100644
--- a/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ b/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -1864,6 +1864,7 @@ bool MemCpyOptPass::processByValArgument(CallBase &CB, unsigned ArgNo) {
                     << "  " << CB << "\n");
 
   // Otherwise we're good!  Update the byval argument.
+  combineAAMetadata(&CB, MDep);
   CB.setArgOperand(ArgNo, MDep->getSource());
   ++NumMemCpyInstr;
   return true;
diff --git a/llvm/test/Transforms/MemCpyOpt/memcpy.ll b/llvm/test/Transforms/MemCpyOpt/memcpy.ll
index f7c1c85517ffa32..7d3b4fdc1c111fe 100644
--- a/llvm/test/Transforms/MemCpyOpt/memcpy.ll
+++ b/llvm/test/Transforms/MemCpyOpt/memcpy.ll
@@ -393,6 +393,7 @@ declare void @f1(ptr nocapture sret(%struct.big))
 declare void @f2(ptr)
 
 declare void @f(ptr)
+declare void @f_byval(ptr byval(i32))
 declare void @f_full_readonly(ptr nocapture noalias readonly)
 
 define void @immut_param(ptr align 4 noalias %val) {
@@ -709,6 +710,22 @@ define void @immut_param_noalias_metadata(ptr align 4 byval(i32) %ptr) {
   ret void
 }
 
+define void @byval_param_noalias_metadata(ptr align 4 byval(i32) %ptr) {
+; CHECK-LABEL: @byval_param_noalias_metadata(
+; CHECK-NEXT:    store i32 1, ptr [[PTR:%.*]], align 4, !noalias !3
+; CHECK-NEXT:    call void @f_byval(ptr byval(i32) align 4 [[PTR]])
+; CHECK-NEXT:    ret void
+;
+  %tmp = alloca i32, align 4
+  store i32 1, ptr %ptr, !noalias !5
+  call void @llvm.memcpy.p0.p0.i64(ptr align 4 %tmp, ptr align 4 %ptr, i64 4, i1 false)
+  call void @f_byval(ptr align 4 byval(i32) %tmp), !alias.scope !5
+  ret void
+}
+
 !0 = !{!0}
 !1 = !{!1, !0}
 !2 = !{!1}
+!3 = !{!3}
+!4 = !{!4, !3}
+!5 = !{!4}

``````````

</details>


https://github.com/llvm/llvm-project/pull/70580