[InstCombine] Dont throw away noalias/alias scope metadata when inlining memcpys (#74805)

This was found in julia when we changed some operations from explicit
loads + stores to memcpys. While applying it to both the src and the
dest seems weird, thats what we do for normal TBAA.

Author: gbaraldi

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

@@ -172,10 +172,10 @@ Instruction *InstCombinerImpl::SimplifyAnyMemTransfer(AnyMemTransferInst *MI) {
 
   // If the memcpy has metadata describing the members, see if we can get the
   // TBAA tag describing our copy.
-  MDNode *CopyMD = nullptr;
-  if (MDNode *M = MI->getMetadata(LLVMContext::MD_tbaa)) {
-    CopyMD = M;
-  } else if (MDNode *M = MI->getMetadata(LLVMContext::MD_tbaa_struct)) {
+  AAMDNodes AACopyMD = MI->getAAMetadata();
+
+  if (MDNode *M = AACopyMD.TBAAStruct) {
+    AACopyMD.TBAAStruct = nullptr;
     if (M->getNumOperands() == 3 && M->getOperand(0) &&
         mdconst::hasa<ConstantInt>(M->getOperand(0)) &&
         mdconst::extract<ConstantInt>(M->getOperand(0))->isZero() &&
@@ -184,16 +184,15 @@ Instruction *InstCombinerImpl::SimplifyAnyMemTransfer(AnyMemTransferInst *MI) {
         mdconst::extract<ConstantInt>(M->getOperand(1))->getValue() ==
         Size &&
         M->getOperand(2) && isa<MDNode>(M->getOperand(2)))
-      CopyMD = cast<MDNode>(M->getOperand(2));
+      AACopyMD.TBAA = cast<MDNode>(M->getOperand(2));
   }
 
   Value *Src = MI->getArgOperand(1);
   Value *Dest = MI->getArgOperand(0);
   LoadInst *L = Builder.CreateLoad(IntType, Src);
   // Alignment from the mem intrinsic will be better, so use it.
   L->setAlignment(*CopySrcAlign);
-  if (CopyMD)
-    L->setMetadata(LLVMContext::MD_tbaa, CopyMD);
+  L->setAAMetadata(AACopyMD);
   MDNode *LoopMemParallelMD =
     MI->getMetadata(LLVMContext::MD_mem_parallel_loop_access);
   if (LoopMemParallelMD)
@@ -205,8 +204,7 @@ Instruction *InstCombinerImpl::SimplifyAnyMemTransfer(AnyMemTransferInst *MI) {
   StoreInst *S = Builder.CreateStore(L, Dest);
   // Alignment from the mem intrinsic will be better, so use it.
   S->setAlignment(*CopyDstAlign);
-  if (CopyMD)
-    S->setMetadata(LLVMContext::MD_tbaa, CopyMD);
+  S->setAAMetadata(AACopyMD);
   if (LoopMemParallelMD)
     S->setMetadata(LLVMContext::MD_mem_parallel_loop_access, LoopMemParallelMD);
   if (AccessGroupMD)

llvm/test/Transforms/InstCombine/memcpy-to-load.ll

@@ -79,3 +79,19 @@ define void @copy_16_bytes(ptr %d, ptr %s) {
   ret void
 }
 
+define void @copy_8_bytes_noalias(ptr %d, ptr %s) {
+; CHECK-LABEL: @copy_8_bytes_noalias(
+; CHECK-NEXT:    [[TMP1:%.*]] = load i64, ptr [[S:%.*]], align 1, !alias.scope [[META0:![0-9]+]], !noalias [[META3:![0-9]+]]
+; CHECK-NEXT:    store i64 [[TMP1]], ptr [[D:%.*]], align 1, !alias.scope [[META0]], !noalias [[META3]]
+; CHECK-NEXT:    ret void
+;
+  call void @llvm.memcpy.p0.p0.i32(ptr %d, ptr %s, i32 8, i1 false), !alias.scope !4, !noalias !5
+  ret void
+}
+
+!0 = distinct !{!0, !"The domain"}
+!1 = distinct !{!1}
+!2 = !{!2, !0}
+!3 = !{!3, !1}
+!4 = !{!2}
+!5 = !{!3}