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handle combining A / (B << N) into A >>u (log2(B)+N) when B is a power of 2 

llvm-svn: 26000
This commit is contained in:
Nate Begeman 2006-02-05 07:20:23 +00:00
parent a28b764886
commit 25d178bece
1 changed files with 13 additions and 2 deletions
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15
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -778,15 +778,26 @@ SDOperand DAGCombiner::visitUDIV(SDNode *N) {
return DAG.getNode(ISD::UDIV, VT, N0, N1);
// fold (udiv x, (1 << c)) -> x >>u c
if (N1C && isPowerOf2_64(N1C->getValue()))
return DAG.getNode(ISD::SRL, N->getValueType(0), N0,
return DAG.getNode(ISD::SRL, VT, N0,
DAG.getConstant(Log2_64(N1C->getValue()),
TLI.getShiftAmountTy()));
// fold (udiv x, (shl c, y)) -> x >>u (log2(c)+y) iff c is power of 2
if (N1.getOpcode() == ISD::SHL) {
if (ConstantSDNode *SHC = dyn_cast<ConstantSDNode>(N1.getOperand(0))) {
if (isPowerOf2_64(SHC->getValue())) {
MVT::ValueType ADDVT = N1.getOperand(1).getValueType();
return DAG.getNode(ISD::SRL, VT, N0,
DAG.getNode(ISD::ADD, ADDVT, N1.getOperand(1),
DAG.getConstant(Log2_64(SHC->getValue()),
ADDVT)));
}
}
}
// fold (udiv x, c) -> alternate
if (N1C && N1C->getValue() && !TLI.isIntDivCheap()) {
SDOperand Op = BuildUDIV(N);
if (Op.Val) return Op;
}
return SDOperand();
}