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Fold extract_element(cst) to cst 

llvm-svn: 30478
This commit is contained in:
Chris Lattner 2006-09-19 05:02:39 +00:00
parent 4c059f4962
commit 5a42ebcff3
1 changed files with 8 additions and 2 deletions
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10
llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
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@ -1330,12 +1330,18 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,
break;
}
case ISD::EXTRACT_ELEMENT:
assert(N2C && (unsigned)N2C->getValue() < 2 && "Bad EXTRACT_ELEMENT!");
// EXTRACT_ELEMENT of BUILD_PAIR is often formed while legalize is expanding
// 64-bit integers into 32-bit parts. Instead of building the extract of
// the BUILD_PAIR, only to have legalize rip it apart, just do it now.
if (N2C && N1.getOpcode() == ISD::BUILD_PAIR) {
assert((unsigned)N2C->getValue() < 2 && "Bad EXTRACT_ELEMENT!");
if (N1.getOpcode() == ISD::BUILD_PAIR)
return N1.getOperand(N2C->getValue());
// EXTRACT_ELEMENT of a constant int is also very common.
if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(N1)) {
unsigned Shift = MVT::getSizeInBits(VT) * N2C->getValue();
return getConstant(C->getValue() >> Shift, VT);
}
break;