[llvm] 137568e - [InstCombine] Fixed UB in foldCtpop

[Dávid Bolvanský via llvm-commits]

Author: Dávid Bolvanský
Date: 2021-04-24T19:44:16+02:00
New Revision: 137568e5797c33c12d284cc325367ceaddf2441a

URL: https://github.com/llvm/llvm-project/commit/137568e5797c33c12d284cc325367ceaddf2441a
DIFF: https://github.com/llvm/llvm-project/commit/137568e5797c33c12d284cc325367ceaddf2441a.diff

LOG: [InstCombine] Fixed UB in foldCtpop

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 378682b7b9cd..72008dfa3b28 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -497,7 +497,7 @@ static Instruction *foldCtpop(IntrinsicInst &II, InstCombinerImpl &IC) {
   Type *Ty = II.getType();
   unsigned BitWidth = Ty->getScalarSizeInBits();
   Value *Op0 = II.getArgOperand(0);
-  Value *X;
+  Value *X, *Y;
 
   // ctpop(bitreverse(x)) -> ctpop(x)
   // ctpop(bswap(x)) -> ctpop(x)
@@ -505,8 +505,9 @@ static Instruction *foldCtpop(IntrinsicInst &II, InstCombinerImpl &IC) {
     return IC.replaceOperand(II, 0, X);
 
   // ctpop(rot(x)) -> ctpop(x)
-  if (match(Op0, m_FShl(m_Value(X), m_Specific(X), m_Value())) ||
-      match(Op0, m_FShr(m_Value(X), m_Specific(X), m_Value())))
+  if ((match(Op0, m_FShl(m_Value(X), m_Value(Y), m_Value())) ||
+       match(Op0, m_FShr(m_Value(X), m_Value(Y), m_Value()))) &&
+      X == Y)
     return IC.replaceOperand(II, 0, X);
 
   // ctpop(x | -x) -> bitwidth - cttz(x, false)