[llvm] 040c60d - Fix a miscompile introduced by 99203f2.

[Richard Smith via llvm-commits]

Author: Richard Smith
Date: 2021-03-25T16:53:58-07:00
New Revision: 040c60d9b69e2ad570556f255a746929a4b10e82

URL: https://github.com/llvm/llvm-project/commit/040c60d9b69e2ad570556f255a746929a4b10e82
DIFF: https://github.com/llvm/llvm-project/commit/040c60d9b69e2ad570556f255a746929a4b10e82.diff

LOG: Fix a miscompile introduced by 99203f2.

getPointersDiff would previously round down the difference between two
pointers to a multiple of the element size of the pointee, which could
result in a pointer value being decreased a little.

Alexey Bataev has graciously agreed to add a testcase for this;
submitting the bugfix now to unblock.

Added: 
    

Modified: 
    llvm/lib/Analysis/LoopAccessAnalysis.cpp

Removed: 
    


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diff  --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index 56ac3051af15..2a6987848ca5 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -1204,7 +1204,8 @@ bool llvm::sortPtrAccesses(ArrayRef<Value *> VL, const DataLayout &DL,
   int Cnt = 1;
   bool IsConsecutive = true;
   for (auto *Ptr : VL.drop_front()) {
-    Optional<int> Diff = getPointersDiff(Ptr0, Ptr, DL, SE);
+    Optional<int> Diff =
+        getPointersDiff(Ptr0, Ptr, DL, SE, /*StrictCheck=*/true);
     if (!Diff)
       return false;