[PATCH] Properly update AA metadata when performing call slot optimization

[Björn Steinbrink]

http://reviews.llvm.org/D7482

Files:
  lib/Transforms/Scalar/MemCpyOptimizer.cpp
  test/Transforms/MemCpyOpt/callslot_aa.ll

Index: lib/Transforms/Scalar/MemCpyOptimizer.cpp
===================================================================
--- lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -750,6 +750,14 @@
   // its dependence information by changing its parameter.
   MD->removeInstruction(C);
 
+  // Update AA metadata
+  unsigned KnownIDs[] = {
+    LLVMContext::MD_tbaa,
+    LLVMContext::MD_alias_scope,
+    LLVMContext::MD_noalias,
+  };
+  combineMetadata(C, cpy, KnownIDs);
+
   // Remove the memcpy.
   MD->removeInstruction(cpy);
   ++NumMemCpyInstr;
Index: test/Transforms/MemCpyOpt/callslot_aa.ll
===================================================================
--- /dev/null
+++ test/Transforms/MemCpyOpt/callslot_aa.ll
@@ -0,0 +1,22 @@
+; RUN: opt < %s -S -basicaa -memcpyopt | FileCheck %s
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+%T = type { i64, i64 }
+
+define void @test(i8* %src) {
+  %tmp = alloca i8
+  %dst = alloca i8
+; CHECK:   call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 1, i32 8, i1 false)
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %tmp, i8* %src, i64 1, i32 8, i1 false), !noalias !2
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dst, i8* %tmp, i64 1, i32 8, i1 false)
+
+  ret void
+}
+
+declare void @llvm.memcpy.p0i8.p0i8.i64(i8*, i8*, i64, i32, i1)
+
+; Check that the noalias for "dst" was removed by checking that the metadata is gone
+; CHECK-NOT: "dst"
+!0 = !{!0}
+!1 = distinct !{!1, !0, !"dst"}
+!2 = distinct !{!1}

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