Add combine: X sdiv (1 << Y) -> X udiv (1 << Y) when X doesn't have the
sign bit set.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76304 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 0c010cf..e9e5294 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -3104,11 +3104,22 @@
// unsigned inputs), turn this into a udiv.
if (I.getType()->isInteger()) {
APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
- if (MaskedValueIsZero(Op1, Mask) && MaskedValueIsZero(Op0, Mask)) {
- // X sdiv Y -> X udiv Y, iff X and Y don't have sign bit set
- return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
+ if (MaskedValueIsZero(Op0, Mask)) {
+ if (MaskedValueIsZero(Op1, Mask)) {
+ // X sdiv Y -> X udiv Y, iff X and Y don't have sign bit set
+ return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
+ }
+ ConstantInt *ShiftedInt;
+ if (match(Op1, m_Shl(m_ConstantInt(ShiftedInt), m_Value()), *Context) &&
+ ShiftedInt->getValue().isPowerOf2()) {
+ // X sdiv (1 << Y) -> X udiv (1 << Y) ( -> X u>> Y)
+ // Safe because the only negative value (1 << Y) can take on is
+ // INT_MIN, and X sdiv INT_MIN == X udiv INT_MIN == 0 if X doesn't have
+ // the sign bit set.
+ return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
+ }
}
- }
+ }
return 0;
}