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Pull shifts by a constant through multiplies (a form of reassociation),

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implementing Regression/CodeGen/X86/mul-shift-reassoc.ll


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26440 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-03-01 03:44:24 +00:00
parent cf6a9fbd9b
commit 0b1a85f110
1 changed files with 27 additions and 0 deletions
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27
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -726,6 +726,33 @@ SDOperand DAGCombiner::visitMUL(SDNode *N) {
DAG.getConstant(Log2_64(-N1C->getSignExtended()),
TLI.getShiftAmountTy())));
}
// (mul (shl X, c1), c2) -> (mul X, c2 << c1)
if (N1C && N0.getOpcode() == ISD::SHL &&
isa<ConstantSDNode>(N0.getOperand(1))) {
SDOperand C3 = DAG.getNode(ISD::SHL, VT, N1, N0.getOperand(1));
return DAG.getNode(ISD::MUL, VT, N0.getOperand(0), C3);
}
// Change (mul (shl X, C), Y) -> (shl (mul X, Y), C) when the shift has one
// use.
{
SDOperand Sh(0,0), Y(0,0);
// Check for both (mul (shl X, C), Y) and (mul Y, (shl X, C)).
if (N0.getOpcode() == ISD::SHL && isa<ConstantSDNode>(N0.getOperand(1)) &&
N0.Val->hasOneUse()) {
Sh = N0; Y = N1;
} else if (N1.getOpcode() == ISD::SHL &&
isa<ConstantSDNode>(N1.getOperand(1)) && N1.Val->hasOneUse()) {
Sh = N1; Y = N0;
}
if (Sh.Val) {
SDOperand Mul = DAG.getNode(ISD::MUL, VT, Sh.getOperand(0), Y);
return DAG.getNode(ISD::SHL, VT, Mul, Sh.getOperand(1));
}
}
// reassociate mul
SDOperand RMUL = ReassociateOps(ISD::MUL, N0, N1);
if (RMUL.Val != 0)