InstCombine: Flip the order of two urem transforms
There are two transforms in visitUrem that conflict with each other.
*) One, if a divisor is a power of two, subtracts one from the divisor
and turns it into a bitwise-and.
*) The other unwraps both operands if they are surrounded by zext
instructions.
Flipping the order allows the subtraction to go beneath the sign
extension.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181668 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 2494078..87d5621 100644
--- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -1027,6 +1027,12 @@
if (Instruction *common = commonIRemTransforms(I))
return common;
+ // (zext A) urem (zext B) --> zext (A urem B)
+ if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
+ if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
+ return new ZExtInst(Builder->CreateURem(ZOp0->getOperand(0), ZOp1),
+ I.getType());
+
// X urem Y -> X and Y-1, where Y is a power of 2,
if (isKnownToBeAPowerOfTwo(Op1, /*OrZero*/true)) {
Constant *N1 = Constant::getAllOnesValue(I.getType());
@@ -1034,12 +1040,6 @@
return BinaryOperator::CreateAnd(Op0, Add);
}
- // (zext A) urem (zext B) --> zext (A urem B)
- if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
- if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
- return new ZExtInst(Builder->CreateURem(ZOp0->getOperand(0), ZOp1),
- I.getType());
-
return 0;
}