[InstSimplify] fold srem with sext bool divisor

llvm-svn: 335616

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 4f5bed91dcc..4a80558dd1b 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -1099,6 +1099,12 @@ Value *llvm::SimplifyUDivInst(Value *Op0, Value *Op1, const SimplifyQuery &Q) {
 /// If not, this returns null.
 static Value *SimplifySRemInst(Value *Op0, Value *Op1, const SimplifyQuery &Q,
                                unsigned MaxRecurse) {
+  // If the divisor is 0, the result is undefined, so assume the divisor is -1.
+  // srem Op0, (sext i1 X) --> srem Op0, -1 --> 0
+  Value *X;
+  if (match(Op1, m_SExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1))
+    return ConstantInt::getNullValue(Op0->getType());
+
   return simplifyRem(Instruction::SRem, Op0, Op1, Q, MaxRecurse);
 }