From: Craig Topper <craig.topper@intel.com>
Date: Thu, 22 Jun 2017 19:04:14 +0000 (+0000)
Subject: [BasicAA] Add type check and Value equality check around code added in r305481.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=6de0dc01efdc79173abfe546dcf9cb5ea4271c12;p=llvm

[BasicAA] Add type check and Value equality check around code added in r305481.

This matches the checks done at the beginning of isKnownNonEqual that this code is partially emulating.

Without this we can get assertion failures due to the bit widths of the KnownBits not matching.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@306044 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index 5395762477f..b52a1d7b24d 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -1021,11 +1021,14 @@ static AliasResult aliasSameBasePointerGEPs(const GEPOperator *GEP1,
         // 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;
+        if (GEP1LastIdx != GEP2LastIdx &&
+            GEP1LastIdx->getType() == GEP2LastIdx->getType()) {
+          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;
     }