[llvm] ce066da - [BasicAA] Make sure types match in constant offset heuristic

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2021-03-28T21:38:09+02:00
New Revision: ce066da81c3e6175a02fa7ae831931b5e4126a2b

URL: https://github.com/llvm/llvm-project/commit/ce066da81c3e6175a02fa7ae831931b5e4126a2b
DIFF: https://github.com/llvm/llvm-project/commit/ce066da81c3e6175a02fa7ae831931b5e4126a2b.diff

LOG: [BasicAA] Make sure types match in constant offset heuristic

This can only happen if offset types that are larger than the
pointer size are involved. The previous implementation did not
assert in this case because it initialized the APInts to the
width of one of the variables -- though I strongly suspect it
did not compute correct results in this case.

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=32621
reported by fhahn.

Added: 
    

Modified: 
    llvm/lib/Analysis/BasicAliasAnalysis.cpp
    llvm/test/Analysis/BasicAA/q.bad.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index 4f41b28a3a0d..15e4946eb8fd 100644
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -1725,7 +1725,7 @@ bool BasicAAResult::constantOffsetHeuristic(
   const VariableGEPIndex &Var0 = VarIndices[0], &Var1 = VarIndices[1];
 
   if (Var0.ZExtBits != Var1.ZExtBits || Var0.SExtBits != Var1.SExtBits ||
-      Var0.Scale != -Var1.Scale)
+      Var0.Scale != -Var1.Scale || Var0.V->getType() != Var1.V->getType())
     return false;
 
   // We'll strip off the Extensions of Var0 and Var1 and do another round

diff  --git a/llvm/test/Analysis/BasicAA/q.bad.ll b/llvm/test/Analysis/BasicAA/q.bad.ll
index 0d22f37cc251..ac27143c57d1 100644
--- a/llvm/test/Analysis/BasicAA/q.bad.ll
+++ b/llvm/test/Analysis/BasicAA/q.bad.ll
@@ -178,3 +178,11 @@ define void @constantOffsetHeuristic_i8_i8(i8* %mem, i8 %val) {
   %c = bitcast i8* %c.8 to i32*
   ret void
 }
+
+; CHECK-LABEL: 
diff erent_large_bitwidths
+; MayAlias: i64* %p1, i64* %p2
+define void @
diff erent_large_bitwidths(i8* %a, i64 %i, i128 %j) {
+  %p1 = getelementptr i8, i8* %a, i64 %i
+  %p2 = getelementptr i8, i8* %a, i128 %j
+  ret void
+}