[PATCH] D31865: MemorySSA: Make lifetime starts defs for mustaliased pointers

[Daniel Berlin via Phabricator via llvm-commits]

dberlin updated this revision to Diff 94683.
dberlin added a comment.

Small bugfix


https://reviews.llvm.org/D31865

Files:
  lib/Transforms/Utils/MemorySSA.cpp
  test/Transforms/Util/MemorySSA/lifetime-simple.ll


Index: test/Transforms/Util/MemorySSA/lifetime-simple.ll
===================================================================
--- test/Transforms/Util/MemorySSA/lifetime-simple.ll
+++ test/Transforms/Util/MemorySSA/lifetime-simple.ll
@@ -9,7 +9,7 @@
 ; CHECK:  1 = MemoryDef(liveOnEntry)
 ; CHECK-NEXT:   call void @llvm.lifetime.start(i64 32, i8* %P)
   call void @llvm.lifetime.start(i64 32, i8* %P)
-; CHECK:  MemoryUse(liveOnEntry)
+; CHECK:  MemoryUse(1)
 ; CHECK-NEXT:   %0 = load i8, i8* %P
   %0 = load i8, i8* %P
 ; CHECK:  2 = MemoryDef(1)
Index: lib/Transforms/Utils/MemorySSA.cpp
===================================================================
--- lib/Transforms/Utils/MemorySSA.cpp
+++ lib/Transforms/Utils/MemorySSA.cpp
@@ -214,12 +214,16 @@
                                      AliasAnalysis &AA) {
   Instruction *DefInst = MD->getMemoryInst();
   assert(DefInst && "Defining instruction not actually an instruction");
+  ImmutableCallSite UseCS(UseInst);
 
   if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(DefInst)) {
     // These intrinsics will show up as affecting memory, but they are just
     // markers.
     switch (II->getIntrinsicID()) {
     case Intrinsic::lifetime_start:
+      if (UseCS)
+        return false;
+      return AA.isMustAlias(MemoryLocation(II->getArgOperand(1)), UseLoc);
     case Intrinsic::lifetime_end:
     case Intrinsic::invariant_start:
     case Intrinsic::invariant_end:
@@ -230,7 +234,6 @@
     }
   }
 
-  ImmutableCallSite UseCS(UseInst);
   if (UseCS) {
     ModRefInfo I = AA.getModRefInfo(DefInst, UseCS);
     return I != MRI_NoModRef;
@@ -298,7 +301,6 @@
   Instruction *Inst = MD->getMemoryInst();
   if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
     switch (II->getIntrinsicID()) {
-    case Intrinsic::lifetime_start:
     case Intrinsic::lifetime_end:
       return AA.isMustAlias(MemoryLocation(II->getArgOperand(1)), Loc);
     default:


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