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Pattern match a setcc of boolean value with 0 as a truncate.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154322 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola
2012-04-09 16:06:03 +00:00
parent f08c7abd15
commit decbc43f72
2 changed files with 81 additions and 10 deletions
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57
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -4408,6 +4408,44 @@ SDValue DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
return SDValue();
}
// isTruncateOf - If N is a truncate of some other value, return true, record
// the value being truncated in Op and which of Op's bits are zero in KnownZero.
// This function computes KnownZero to avoid a duplicated call to
// ComputeMaskedBits in the caller.
static bool isTruncateOf(SelectionDAG &DAG, SDValue N, SDValue &Op,
APInt &KnownZero) {
APInt KnownOne;
if (N->getOpcode() == ISD::TRUNCATE) {
Op = N->getOperand(0);
DAG.ComputeMaskedBits(Op, KnownZero, KnownOne);
return true;
}
if (N->getOpcode() != ISD::SETCC || N->getValueType(0) != MVT::i1 ||
cast<CondCodeSDNode>(N->getOperand(2))->get() != ISD::SETNE)
return false;
SDValue Op0 = N->getOperand(0);
SDValue Op1 = N->getOperand(1);
assert(Op0.getValueType() == Op1.getValueType());
ConstantSDNode *COp0 = dyn_cast<ConstantSDNode>(Op0);
ConstantSDNode *COp1 = dyn_cast<ConstantSDNode>(Op1);
if (COp0 && COp0->getZExtValue() == 0)
Op = Op1;
else if (COp1 && COp1->getZExtValue() == 0)
Op = Op0;
else
return false;
DAG.ComputeMaskedBits(Op, KnownZero, KnownOne);
if (!(KnownZero | APInt(Op.getValueSizeInBits(), 1)).isAllOnesValue())
return false;
return true;
}
SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
SDValue N0 = N->getOperand(0);
EVT VT = N->getValueType(0);
@ -4425,15 +4463,16 @@ SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
// (zext (truncate x)) -> (truncate x)
// This is valid when the truncated bits of x are already zero.
// FIXME: We should extend this to work for vectors too.
if (N0.getOpcode() == ISD::TRUNCATE && !VT.isVector()) {
SDValue Op = N0.getOperand(0);
APInt TruncatedBits
= APInt::getBitsSet(Op.getValueSizeInBits(),
N0.getValueSizeInBits(),
std::min(Op.getValueSizeInBits(),
VT.getSizeInBits()));
APInt KnownZero, KnownOne;
DAG.ComputeMaskedBits(Op, KnownZero, KnownOne);
SDValue Op;
APInt KnownZero;
if (!VT.isVector() && isTruncateOf(DAG, N0, Op, KnownZero)) {
APInt TruncatedBits =
(Op.getValueSizeInBits() == N0.getValueSizeInBits()) ?
APInt(Op.getValueSizeInBits(), 0) :
APInt::getBitsSet(Op.getValueSizeInBits(),
N0.getValueSizeInBits(),
std::min(Op.getValueSizeInBits(),
VT.getSizeInBits()));
if (TruncatedBits == (KnownZero & TruncatedBits)) {
if (VT.bitsGT(Op.getValueType()))
return DAG.getNode(ISD::ZERO_EXTEND, N->getDebugLoc(), VT, Op);