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Generalize the ARM DAG combiner of mul with constants to all power-of-two cases.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103901 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -3613,44 +3613,31 @@ static SDValue PerformMULCombine(SDNode *N,
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ShiftAmt = ShiftAmt & (32 - 1);
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SDValue V = N->getOperand(0);
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DebugLoc DL = N->getDebugLoc();
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SDValue NewAdd;
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// FIXME: Handle arbitrary powers of 2.
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switch (MulAmt >> ShiftAmt) {
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case 3: // 2 + 1
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NewAdd = DAG.getNode(ISD::ADD, DL, VT,
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V, DAG.getNode(ISD::SHL, DL, VT,
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V, DAG.getConstant(1, MVT::i32)));
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break;
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case 5: // 4 + 1
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NewAdd = DAG.getNode(ISD::ADD, DL, VT,
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V, DAG.getNode(ISD::SHL, DL, VT,
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V, DAG.getConstant(2, MVT::i32)));
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break;
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case 7: // 8 - 1
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NewAdd = DAG.getNode(ISD::SUB, DL, VT,
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DAG.getNode(ISD::SHL, DL, VT,
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V, DAG.getConstant(3, MVT::i32)),
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V);
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break;
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case 9: // 8 + 1
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NewAdd = DAG.getNode(ISD::ADD, DL, VT,
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V, DAG.getNode(ISD::SHL, DL, VT,
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V, DAG.getConstant(3, MVT::i32)));
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break;
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default: return SDValue();
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}
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if (ShiftAmt != 0) {
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SDValue NewShift = DAG.getNode(ISD::SHL, DL, VT, NewAdd,
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DAG.getConstant(ShiftAmt, MVT::i32));
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// Do not add new nodes to DAG combiner worklist.
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DCI.CombineTo(N, NewShift, false);
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SDValue Res;
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MulAmt >>= ShiftAmt;
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if (isPowerOf2_32(MulAmt - 1)) {
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// (mul x, 2^N + 1) => (add (shl x, N), x)
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Res = DAG.getNode(ISD::ADD, DL, VT,
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V, DAG.getNode(ISD::SHL, DL, VT,
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V, DAG.getConstant(Log2_32(MulAmt-1),
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MVT::i32)));
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} else if (isPowerOf2_32(MulAmt + 1)) {
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// (mul x, 2^N - 1) => (sub (shl x, N), x)
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Res = DAG.getNode(ISD::SUB, DL, VT,
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DAG.getNode(ISD::SHL, DL, VT,
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V, DAG.getConstant(Log2_32(MulAmt+1),
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MVT::i32)),
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V);
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} else
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return SDValue();
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}
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if (ShiftAmt != 0)
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Res = DAG.getNode(ISD::SHL, DL, VT, Res,
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DAG.getConstant(ShiftAmt, MVT::i32));
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// Do not add new nodes to DAG combiner worklist.
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DCI.CombineTo(N, NewAdd, false);
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DCI.CombineTo(N, Res, false);
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return SDValue();
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}
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