vendor/llvm/llvm-release_70-r339999

1 files changed, 7 insertions, 2 deletions

diff --git a/lib/Analysis/MemorySSA.cpp b/lib/Analysis/MemorySSA.cpp
index f57d490ce96e..b38c0c4f1439 100644
--- a/lib/Analysis/MemorySSA.cpp
+++ b/lib/Analysis/MemorySSA.cpp
@@ -258,13 +258,18 @@ static ClobberAlias instructionClobbersQuery(MemoryDef *MD,
 
   if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(DefInst)) {
     // These intrinsics will show up as affecting memory, but they are just
-    // markers.
+    // markers, mostly.
+    //
+    // FIXME: We probably don't actually want MemorySSA to model these at all
+    // (including creating MemoryAccesses for them): we just end up inventing
+    // clobbers where they don't really exist at all. Please see D43269 for
+    // context.
     switch (II->getIntrinsicID()) {
     case Intrinsic::lifetime_start:
       if (UseCS)
         return {false, NoAlias};
       AR = AA.alias(MemoryLocation(II->getArgOperand(1)), UseLoc);
-      return {AR == MustAlias, AR};
+      return {AR != NoAlias, AR};
     case Intrinsic::lifetime_end:
     case Intrinsic::invariant_start:
     case Intrinsic::invariant_end: