Preserve TBAA tags when doing load PRE.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121921 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp
index d8629e68b8dd5a77a2da8f5ab6cd7f2cfa230ba9..5ac19dc9ebfdaafda00b458686721a0018bfb860 100644 (file)
--- a/lib/Transforms/Scalar/GVN.cpp
+++ b/lib/Transforms/Scalar/GVN.cpp
@@ -22,6 +22,7 @@
 #include "llvm/GlobalVariable.h"
 #include "llvm/Function.h"
 #include "llvm/IntrinsicInst.h"
+#include "llvm/LLVMContext.h"
 #include "llvm/Operator.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/ConstantFolding.h"
@@ -1659,9 +1660,13 @@ bool GVN::processNonLocalLoad(LoadInst *LI,
     BasicBlock *UnavailablePred = I->first;
     Value *LoadPtr = I->second;
 
-    Value *NewLoad = new LoadInst(LoadPtr, LI->getName()+".pre", false,
-                                  LI->getAlignment(),
-                                  UnavailablePred->getTerminator());
+    Instruction *NewLoad = new LoadInst(LoadPtr, LI->getName()+".pre", false,
+                                        LI->getAlignment(),
+                                        UnavailablePred->getTerminator());
+
+    // Transfer the old load's TBAA tag to the new load.
+    if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa))
+      NewLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
 
     // Add the newly created load.
     ValuesPerBlock.push_back(AvailableValueInBlock::get(UnavailablePred,

diff --git a/test/Transforms/GVN/preserve-tbaa.ll b/test/Transforms/GVN/preserve-tbaa.ll
new file mode 100644 (file)
index 0000000..2fcfc47
--- /dev/null
+++ b/test/Transforms/GVN/preserve-tbaa.ll
@@ -0,0 +1,28 @@
+; RUN: opt -tbaa -basicaa -gvn -S < %s | FileCheck %s
+
+target datalayout = "e-p:64:64:64"
+
+; GVN should preserve the TBAA tag on loads when doing PRE.
+
+; CHECK: @test
+; CHECK: %tmp33.pre = load i16* undef, align 2, !tbaa !0
+; CHECK: br label %for.body
+define void @test() nounwind {
+entry:
+  br i1 undef, label %bb.nph, label %for.end
+
+bb.nph:                                           ; preds = %entry
+  br label %for.body
+
+for.body:                                         ; preds = %for.body, %bb.nph
+  %tmp33 = load i16* undef, align 2, !tbaa !0
+  store i16 undef, i16* undef, align 2, !tbaa !0
+  br i1 false, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body, %entry
+  ret void
+}
+
+!0 = metadata !{metadata !"short", metadata !1}
+!1 = metadata !{metadata !"omnipotent char", metadata !2}
+!2 = metadata !{metadata !"Simple C/C++ TBAA", null}