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Temporarily revert r48491. It's breaking test/CodeGen/X86/xorl.ll.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48510 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling
2008-03-18 22:29:51 +00:00
parent d3bf1aef3f
commit 2974e49019
3 changed files with 87 additions and 27 deletions
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26
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@@ -2374,32 +2374,6 @@ SDOperand DAGCombiner::visitSRA(SDNode *N) {
DAG.getValueType(EVT));
}
// fold sra (shl X, m), result_size - n
// -> (sign_extend (trunc (shl X, result_size - n - m))) for
// result_size - n != m. If truncate is free for the target sext(shl) is
// likely to result in better code.
if (N0.getOpcode() == ISD::SHL) {
// Get the two constanst of the shifts, CN0 = m, CN = n.
const ConstantSDNode *N01C = dyn_cast<ConstantSDNode>(N0.getOperand(1));
if (N01C && N1C) {
// Determine if the truncate type's bitsize would correspond to
// an integer type for this target.
unsigned VTValSize = MVT::getSizeInBits(VT);
MVT::ValueType TruncVT = MVT::getIntegerType(VTValSize - N1C->getValue());
unsigned ShiftAmt = N1C->getValue() - N01C->getValue();
// If the shift wouldn't be a noop, the truncated type is an actual type,
// and the truncate is free, then proceed with the transform.
if (ShiftAmt != 0 &&
!MVT::isExtendedVT(TruncVT) && TLI.isTruncateFree(VT, TruncVT)) {
SDOperand Amt = DAG.getConstant(ShiftAmt, TLI.getShiftAmountTy());
SDOperand Shift = DAG.getNode(ISD::SRL, VT, N0.getOperand(0), Amt);
SDOperand Trunc = DAG.getNode(ISD::TRUNCATE, TruncVT, Shift);
return DAG.getNode(ISD::SIGN_EXTEND, N->getValueType(0), Trunc);
}
}
}
// fold (sra (sra x, c1), c2) -> (sra x, c1+c2)
if (N1C && N0.getOpcode() == ISD::SRA) {
if (ConstantSDNode *C1 = dyn_cast<ConstantSDNode>(N0.getOperand(1))) {