[PATCH] D33136: [ValueTracking] Don't let isAddOfNonZero look at adds with a PHI node as input

[Phabricator via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL305481: [BasicAA] Don't call isKnownNonEqual if we might be have gone through a PHINode. (authored by ctopper).

Changed prior to commit:
  https://reviews.llvm.org/D33136?vs=99173&id=102684#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D33136

Files:
  llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp


Index: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
===================================================================
--- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
+++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
@@ -1011,10 +1011,24 @@
     // equal each other so we can exit early.
     if (C1 && C2)
       return NoAlias;
-    if (isKnownNonEqual(GEP1->getOperand(GEP1->getNumOperands() - 1),
-                        GEP2->getOperand(GEP2->getNumOperands() - 1),
-                        DL))
-      return NoAlias;
+    {
+      Value *GEP1LastIdx = GEP1->getOperand(GEP1->getNumOperands() - 1);
+      Value *GEP2LastIdx = GEP2->getOperand(GEP2->getNumOperands() - 1);
+      if (isa<PHINode>(GEP1LastIdx) || isa<PHINode>(GEP2LastIdx)) {
+        // If one of the indices is a PHI node, be safe and only use
+        // computeKnownBits so we don't make any assumptions about the
+        // relationships between the two indices. This is important if we're
+        // asking about values from different loop iterations. See PR32314.
+        // TODO: We may be able to change the check so we only do this when
+        // we definitely looked through a PHINode.
+        KnownBits Known1 = computeKnownBits(GEP1LastIdx, DL);
+        KnownBits Known2 = computeKnownBits(GEP2LastIdx, DL);
+        if (Known1.Zero.intersects(Known2.One) ||
+            Known1.One.intersects(Known2.Zero))
+          return NoAlias;
+      } else if (isKnownNonEqual(GEP1LastIdx, GEP2LastIdx, DL))
+        return NoAlias;
+    }
     return MayAlias;
   } else if (!LastIndexedStruct || !C1 || !C2) {
     return MayAlias;


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D33136.102684.patch
Type: text/x-patch
Size: 1626 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20170615/69dd030d/attachment.bin>