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Fold extract_element(cst) to cst
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30478 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -1330,12 +1330,18 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,
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break;
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}
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case ISD::EXTRACT_ELEMENT:
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assert(N2C && (unsigned)N2C->getValue() < 2 && "Bad EXTRACT_ELEMENT!");
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// EXTRACT_ELEMENT of BUILD_PAIR is often formed while legalize is expanding
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// 64-bit integers into 32-bit parts. Instead of building the extract of
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// the BUILD_PAIR, only to have legalize rip it apart, just do it now.
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if (N2C && N1.getOpcode() == ISD::BUILD_PAIR) {
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assert((unsigned)N2C->getValue() < 2 && "Bad EXTRACT_ELEMENT!");
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if (N1.getOpcode() == ISD::BUILD_PAIR)
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return N1.getOperand(N2C->getValue());
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// EXTRACT_ELEMENT of a constant int is also very common.
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if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(N1)) {
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unsigned Shift = MVT::getSizeInBits(VT) * N2C->getValue();
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return getConstant(C->getValue() >> Shift, VT);
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}
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break;
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