[InstCombine] fold udiv with sext bool divisor

Note: I didn't add a hasOneUse() check because the existing,
related fold doesn't have that check. I suspect that the
improved analysis and codegen make these some of the rare
canonicalization cases where we allow an increase in
instructions.

llvm-svn: 335597

1 files changed, 7 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index bb714d00d69..7a8f2c27adc 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -954,9 +954,15 @@ Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
 
   // Op0 / C where C is large (negative) --> zext (Op0 >= C)
   // TODO: Could use isKnownNegative() to handle non-constant values.
+  Type *Ty = I.getType();
   if (match(Op1, m_Negative())) {
     Value *Cmp = Builder.CreateICmpUGE(Op0, Op1);
-    return CastInst::CreateZExtOrBitCast(Cmp, I.getType());
+    return CastInst::CreateZExtOrBitCast(Cmp, Ty);
+  }
+  // Op0 / (sext i1 X) --> zext (Op0 == -1) (if X is 0, the div is undefined)
+  if (match(Op1, m_SExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)) {
+    Value *Cmp = Builder.CreateICmpEQ(Op0, ConstantInt::getAllOnesValue(Ty));
+    return CastInst::CreateZExtOrBitCast(Cmp, Ty);
   }
 
   if (Instruction *NarrowDiv = narrowUDivURem(I, Builder))