[PATCH] D134161: [MemorySSA] Reset location size if IsGuaranteedLoopInvariant after phi tranlation

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StephenFan created this revision.
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We set the Location size to beforeOrAfter if the Location value is not
guaranteed loop invariant. But in some cases, we need to reset the
location size if the location size is precise after phi tranlation of
location value. This will improve MemorySSA analysis results.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D134161

Files:
  llvm/include/llvm/Analysis/MemorySSA.h
  llvm/test/Analysis/MemorySSA/phi-translation.ll


Index: llvm/test/Analysis/MemorySSA/phi-translation.ll
===================================================================
--- llvm/test/Analysis/MemorySSA/phi-translation.ll
+++ llvm/test/Analysis/MemorySSA/phi-translation.ll
@@ -437,10 +437,10 @@
 ; CHECK-LABEL: merge:
 ; CHECK:       ; 3 = MemoryPhi({lhs,1},{rhs,2})
 ; CHECK-NEXT   %storemerge2 = phi i32 [ 2, %lhs ], [ 3, %rhs ]
-; TODO: Here the defining access could be liveOnEntry. Since all incoming
-; values of phi node can be phi translated.
-; CHECK:       ; MemoryUse(3)
-; CHECK-NEXT:    %lv = load i16, i16* %arrayidx, align 2
+; LIMIT:       ; MemoryUse(3)
+; LIMIT-NEXT:  %lv = load i16, i16* %arrayidx, align 2
+; NOLIMIT:     ; MemoryUse(liveOnEntry)
+; NOLIMIT-NEXT: %lv = load i16, i16* %arrayidx, align 2
 
 entry:
   br i1 %cmp, label %lhs, label %rhs
Index: llvm/include/llvm/Analysis/MemorySSA.h
===================================================================
--- llvm/include/llvm/Analysis/MemorySSA.h
+++ llvm/include/llvm/Analysis/MemorySSA.h
@@ -1252,7 +1252,9 @@
       // to unknown guarantees that any memory accesses that access locations
       // after the pointer are considered as clobbers, which is important to
       // catch loop carried dependences.
-      if (!IsGuaranteedLoopInvariant(const_cast<Value *>(Location.Ptr)))
+      bool GuaranteedLoopInvariant =
+          IsGuaranteedLoopInvariant(const_cast<Value *>(Location.Ptr));
+      if (!GuaranteedLoopInvariant)
         CurrentPair.second =
             Location.getWithNewSize(LocationSize::beforeOrAfterPointer());
       PHITransAddr Translator(
@@ -1266,6 +1268,10 @@
         if (TransAddr != Location.Ptr) {
           CurrentPair.second = CurrentPair.second.getWithNewPtr(TransAddr);
 
+          if (!GuaranteedLoopInvariant && IsGuaranteedLoopInvariant(TransAddr))
+            CurrentPair.second =
+                CurrentPair.second.getWithNewSize(Location.Size);
+
           if (TransAddr &&
               !IsGuaranteedLoopInvariant(const_cast<Value *>(TransAddr)))
             CurrentPair.second = CurrentPair.second.getWithNewSize(


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