Xor'ing both sides of icmp by sign-bit is equivalent to swapping signedness of
the predicate.
Also, make this optz'n apply in more cases where it's safe to do so.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54876 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 9e0a8e7..065507f 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -5241,6 +5241,20 @@
return new ICmpInst(I.getPredicate(), A, B);
}
+ ConstantInt *CI2;
+ // (icmp u/s (xor A SignBit), C) -> (icmp s/u A, (xor C SignBit))
+ if (!I.isEquality() &&
+ match(Op0, m_Xor(m_Value(A), m_ConstantInt(CI2)))) {
+ if (CI2->getValue().isSignBit()) {
+ const APInt &SignBit = CI2->getValue();
+ ICmpInst::Predicate Pred = I.isSignedPredicate()
+ ? I.getUnsignedPredicate()
+ : I.getSignedPredicate();
+ return new ICmpInst(Pred, A,
+ ConstantInt::get(CI->getValue() ^ SignBit));
+ }
+ }
+
// If we have a icmp le or icmp ge instruction, turn it into the appropriate
// icmp lt or icmp gt instruction. This allows us to rely on them being
// folded in the code below.
@@ -5491,35 +5505,49 @@
// See if it's the same type of instruction on the left and right.
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) {
- if (Op0I->getOpcode() == Op1I->getOpcode() && Op0I->hasOneUse() &&
- Op1I->hasOneUse() && Op0I->getOperand(1) == Op1I->getOperand(1) &&
- I.isEquality()) {
- switch (Op0I->getOpcode()) {
+ if (Op0I->getOpcode() == Op1I->getOpcode() &&
+ Op0I->getOperand(1) == Op1I->getOperand(1)) {
+ switch (Op0I->getOpcode()) {
default: break;
case Instruction::Add:
case Instruction::Sub:
case Instruction::Xor:
- // a+x icmp eq/ne b+x --> a icmp b
- return new ICmpInst(I.getPredicate(), Op0I->getOperand(0),
- Op1I->getOperand(0));
+ if (I.isEquality()) {
+ // icmp eq/ne a+x, b+x --> icmp eq/ne a, b
+ return new ICmpInst(I.getPredicate(), Op0I->getOperand(0),
+ Op1I->getOperand(0));
+ } else {
+ // icmp u/s (a ^ signbit), (b ^ signbit) --> icmp s/u a, b
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
+ if (CI->getValue().isSignBit()) {
+ ICmpInst::Predicate Pred = I.isSignedPredicate()
+ ? I.getUnsignedPredicate()
+ : I.getSignedPredicate();
+ return new ICmpInst(Pred, Op0I->getOperand(0),
+ Op1I->getOperand(0));
+ }
+ }
+ }
break;
case Instruction::Mul:
- if (ConstantInt *CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
- // a * Cst icmp eq/ne b * Cst --> a & Mask icmp b & Mask
- // Mask = -1 >> count-trailing-zeros(Cst).
- if (!CI->isZero() && !CI->isOne()) {
- const APInt &AP = CI->getValue();
- ConstantInt *Mask = ConstantInt::get(
- APInt::getLowBitsSet(AP.getBitWidth(),
- AP.getBitWidth() -
+ // a * Cst icmp eq/ne b * Cst --> a & Mask icmp b & Mask
+ // Mask = -1 >> count-trailing-zeros(Cst).
+ if (Op0I->hasOneUse() && Op1I->hasOneUse() && I.isEquality()) {
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
+ if (!CI->isZero() && !CI->isOne()) {
+ const APInt &AP = CI->getValue();
+ ConstantInt *Mask =
+ ConstantInt::get(APInt::getLowBitsSet(AP.getBitWidth(),
+ AP.getBitWidth() -
AP.countTrailingZeros()));
- Instruction *And1 = BinaryOperator::CreateAnd(Op0I->getOperand(0),
- Mask);
- Instruction *And2 = BinaryOperator::CreateAnd(Op1I->getOperand(0),
- Mask);
- InsertNewInstBefore(And1, I);
- InsertNewInstBefore(And2, I);
- return new ICmpInst(I.getPredicate(), And1, And2);
+ Instruction *And1 =
+ BinaryOperator::CreateAnd(Op0I->getOperand(0), Mask);
+ Instruction *And2 =
+ BinaryOperator::CreateAnd(Op1I->getOperand(0), Mask);
+ InsertNewInstBefore(And1, I);
+ InsertNewInstBefore(And2, I);
+ return new ICmpInst(I.getPredicate(), And1, And2);
+ }
}
}
break;