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Implement two xforms: 

1. ~(~X | Y) === (X & ~Y)
2. (A|B) & ~(A&B) -> A^B

This allows us to transform  ~(~(a|b) | (a&b)) -> a^b.

This implements PR1510 for scalar values.

llvm-svn: 37584
This commit is contained in:
Chris Lattner 2007-06-15 05:58:24 +00:00
parent a8de4cccd9
commit 481e28b1f5
1 changed files with 26 additions and 6 deletions
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32
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -3363,13 +3363,28 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
}
{
Value *A = 0, *B = 0;
if (match(Op0, m_Or(m_Value(A), m_Value(B))))
Value *A = 0, *B = 0, *C = 0, *D = 0;
if (match(Op0, m_Or(m_Value(A), m_Value(B)))) {
if (A == Op1 || B == Op1) // (A | ?) & A --> A
return ReplaceInstUsesWith(I, Op1);
if (match(Op1, m_Or(m_Value(A), m_Value(B))))
// (A|B) & ~(A&B) -> A^B
if (match(Op1, m_Not(m_And(m_Value(C), m_Value(D))))) {
if ((A == C && B == D) || (A == D && B == C))
return BinaryOperator::createXor(A, B);
}
}
if (match(Op1, m_Or(m_Value(A), m_Value(B)))) {
if (A == Op0 || B == Op0) // A & (A | ?) --> A
return ReplaceInstUsesWith(I, Op0);
// ~(A&B) & (A|B) -> A^B
if (match(Op0, m_Not(m_And(m_Value(C), m_Value(D))))) {
if ((A == C && B == D) || (A == D && B == C))
return BinaryOperator::createXor(A, B);
}
}
if (Op0->hasOneUse() &&
match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
@ -4137,15 +4152,20 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
return BinaryOperator::createAdd(Op0I->getOperand(1), ConstantRHS);
}
// ~(~X & Y) --> (X | ~Y)
if (Op0I->getOpcode() == Instruction::And && RHS->isAllOnesValue()) {
// ~(~X & Y) --> (X | ~Y) - De Morgan's Law
// ~(~X | Y) === (X & ~Y) - De Morgan's Law
if ((Op0I->getOpcode() == Instruction::And ||
Op0I->getOpcode() == Instruction::Or) && RHS->isAllOnesValue()) {
if (dyn_castNotVal(Op0I->getOperand(1))) Op0I->swapOperands();
if (Value *Op0NotVal = dyn_castNotVal(Op0I->getOperand(0))) {
Instruction *NotY =
BinaryOperator::createNot(Op0I->getOperand(1),
Op0I->getOperand(1)->getName()+".not");
InsertNewInstBefore(NotY, I);
return BinaryOperator::createOr(Op0NotVal, NotY);
if (Op0I->getOpcode() == Instruction::And)
return BinaryOperator::createOr(Op0NotVal, NotY);
else
return BinaryOperator::createAnd(Op0NotVal, NotY);
}
}