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Generalize (zext (truncate x)) and (sext (truncate x)) folding to work when

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the src/dst are not the same size.  This catches things like "truncate
32-bit X to 8 bits, then zext to 16", which happens a bit on X86.

llvm-svn: 30557
This commit is contained in:
Chris Lattner 2006-09-21 06:00:20 +00:00
parent 437703d4c9
commit eb12877970
1 changed files with 24 additions and 9 deletions
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33
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -1766,12 +1766,18 @@ SDOperand DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
if (N0.getOpcode() == ISD::SIGN_EXTEND || N0.getOpcode() == ISD::ANY_EXTEND)
return DAG.getNode(ISD::SIGN_EXTEND, VT, N0.getOperand(0));
// fold (sext (truncate x)) -> (sextinreg x) iff x size == sext size.
if (N0.getOpcode() == ISD::TRUNCATE && N0.getOperand(0).getValueType() == VT&&
(!AfterLegalize ||
TLI.isOperationLegal(ISD::SIGN_EXTEND_INREG, N0.getValueType())))
return DAG.getNode(ISD::SIGN_EXTEND_INREG, VT, N0.getOperand(0),
// fold (sext (truncate x)) -> (sextinreg x).
if (N0.getOpcode() == ISD::TRUNCATE &&
(!AfterLegalize || TLI.isOperationLegal(ISD::SIGN_EXTEND_INREG, VT))) {
SDOperand Op = N0.getOperand(0);
if (Op.getValueType() < VT) {
Op = DAG.getNode(ISD::ANY_EXTEND, VT, Op);
} else if (Op.getValueType() > VT) {
Op = DAG.getNode(ISD::TRUNCATE, VT, Op);
}
return DAG.getNode(ISD::SIGN_EXTEND_INREG, VT, Op,
DAG.getValueType(N0.getValueType()));
}
// fold (sext (load x)) -> (sext (truncate (sextload x)))
if (N0.getOpcode() == ISD::LOAD && N0.hasOneUse() &&
@ -1812,10 +1818,19 @@ SDOperand DAGCombiner::visitZERO_EXTEND(SDNode *N) {
// fold (zext (aext x)) -> (zext x)
if (N0.getOpcode() == ISD::ZERO_EXTEND || N0.getOpcode() == ISD::ANY_EXTEND)
return DAG.getNode(ISD::ZERO_EXTEND, VT, N0.getOperand(0));
// fold (zext (truncate x)) -> (zextinreg x) iff x size == zext size.
if (N0.getOpcode() == ISD::TRUNCATE && N0.getOperand(0).getValueType() == VT&&
(!AfterLegalize || TLI.isOperationLegal(ISD::AND, N0.getValueType())))
return DAG.getZeroExtendInReg(N0.getOperand(0), N0.getValueType());
// fold (zext (truncate x)) -> (and x, mask)
if (N0.getOpcode() == ISD::TRUNCATE &&
(!AfterLegalize || TLI.isOperationLegal(ISD::AND, VT))) {
SDOperand Op = N0.getOperand(0);
if (Op.getValueType() < VT) {
Op = DAG.getNode(ISD::ANY_EXTEND, VT, Op);
} else if (Op.getValueType() > VT) {
Op = DAG.getNode(ISD::TRUNCATE, VT, Op);
}
return DAG.getZeroExtendInReg(Op, N0.getValueType());
}
// fold (zext (load x)) -> (zext (truncate (zextload x)))
if (N0.getOpcode() == ISD::LOAD && N0.hasOneUse() &&
(!AfterLegalize||TLI.isOperationLegal(ISD::ZEXTLOAD, N0.getValueType()))){