diff options
| -rw-r--r-- | lib/Transforms/Scalar/InstructionCombining.cpp | 19 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/sdiv-shift.ll | 9 |
2 files changed, 24 insertions, 4 deletions
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 @@ Instruction *InstCombiner::visitSDiv(BinaryOperator &I) { // 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; } diff --git a/test/Transforms/InstCombine/sdiv-shift.ll b/test/Transforms/InstCombine/sdiv-shift.ll new file mode 100644 index 0000000..3fba05d --- /dev/null +++ b/test/Transforms/InstCombine/sdiv-shift.ll @@ -0,0 +1,9 @@ +; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep div + +define i32 @a(i16 zeroext %x, i32 %y) nounwind { +entry: + %conv = zext i16 %x to i32 + %s = shl i32 2, %y + %d = sdiv i32 %conv, %s + ret i32 %d +} |