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Simplify some code, reducing calls to MaskedValueIsZero. Implement a minor

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optimization where we reduce the number of bits in AND masks when possible.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26056 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-02-08 07:34:50 +00:00
parent 917707a73f
commit 7560c3af83
1 changed files with 32 additions and 16 deletions
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48
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -1930,28 +1930,44 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
return &I;
if (ConstantIntegral *AndRHS = dyn_cast<ConstantIntegral>(Op1)) {
// and X, -1 == X
if (AndRHS->isAllOnesValue())
uint64_t AndRHSMask = AndRHS->getZExtValue();
uint64_t TypeMask = Op0->getType()->getIntegralTypeMask();
if (AndRHSMask == TypeMask) // and X, -1 == X
return ReplaceInstUsesWith(I, Op0);
else if (AndRHSMask == 0) // and X, 0 == 0
return ReplaceInstUsesWith(I, AndRHS);
// and (and X, c1), c2 -> and (x, c1&c2). Handle this case here, before
// calling MaskedValueIsZero, to avoid inefficient cases where we traipse
// through many levels of ands.
// calling ComputeMaskedNonZeroBits, to avoid inefficient cases where we
// traipse through many levels of ands.
{
Value *X = 0; ConstantInt *C1 = 0;
if (match(Op0, m_And(m_Value(X), m_ConstantInt(C1))))
return BinaryOperator::createAnd(X, ConstantExpr::getAnd(C1, AndRHS));
}
if (MaskedValueIsZero(Op0, AndRHS->getZExtValue())) // LHS & RHS == 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// Figure out which of the input bits are not known to be zero, and which
// bits are known to be zero.
uint64_t NonZeroBits = ComputeMaskedNonZeroBits(Op0, TypeMask);
uint64_t ZeroBits = NonZeroBits^TypeMask;
// If the mask is not masking out any bits, there is no reason to do the
// and in the first place.
uint64_t NotAndRHS = // ~ANDRHS
AndRHS->getZExtValue()^Op0->getType()->getIntegralTypeMask();
if (MaskedValueIsZero(Op0, NotAndRHS))
// If the mask is not masking out any bits (i.e. all of the zeros in the
// mask are already known to be zero), there is no reason to do the and in
// the first place.
uint64_t NotAndRHS = AndRHSMask^TypeMask;
if ((NotAndRHS & ZeroBits) == NotAndRHS)
return ReplaceInstUsesWith(I, Op0);
// If the AND mask contains bits that are known zero, remove them. A
// special case is when there are no bits in common, in which case we
// implicitly turn this into an AND X, 0, which is later simplified into 0.
if ((AndRHSMask & NonZeroBits) != AndRHSMask) {
Constant *NewRHS =
ConstantUInt::get(Type::ULongTy, AndRHSMask & NonZeroBits);
I.setOperand(1, ConstantExpr::getCast(NewRHS, I.getType()));
return &I;
}
// Optimize a variety of ((val OP C1) & C2) combinations...
if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
@ -1963,9 +1979,9 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
case Instruction::Or:
// (X ^ V) & C2 --> (X & C2) iff (V & C2) == 0
// (X | V) & C2 --> (X & C2) iff (V & C2) == 0
if (MaskedValueIsZero(Op0LHS, AndRHS->getZExtValue()))
if (MaskedValueIsZero(Op0LHS, AndRHSMask))
return BinaryOperator::createAnd(Op0RHS, AndRHS);
if (MaskedValueIsZero(Op0RHS, AndRHS->getZExtValue()))
if (MaskedValueIsZero(Op0RHS, AndRHSMask))
return BinaryOperator::createAnd(Op0LHS, AndRHS);
// If the mask is only needed on one incoming arm, push it up.
@ -1992,8 +2008,8 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
break;
case Instruction::And:
// (X & V) & C2 --> 0 iff (V & C2) == 0
if (MaskedValueIsZero(Op0LHS, AndRHS->getZExtValue()) ||
MaskedValueIsZero(Op0RHS, AndRHS->getZExtValue()))
if (MaskedValueIsZero(Op0LHS, AndRHSMask) ||
MaskedValueIsZero(Op0RHS, AndRHSMask))
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
break;
case Instruction::Add:
@ -2028,7 +2044,7 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
if (SrcTy->getPrimitiveSizeInBits() >=
I.getType()->getPrimitiveSizeInBits() &&
CastOp->getNumOperands() == 2)
if (ConstantInt *AndCI =dyn_cast<ConstantInt>(CastOp->getOperand(1)))
if (ConstantInt *AndCI = dyn_cast<ConstantInt>(CastOp->getOperand(1)))
if (CastOp->getOpcode() == Instruction::And) {
// Change: and (cast (and X, C1) to T), C2
// into : and (cast X to T), trunc(C1)&C2