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| author | Craig Topper <craig.topper@intel.com> | 2018-07-25 01:15:35 +0000 |
|---|---|---|
| committer | Craig Topper <craig.topper@intel.com> | 2018-07-25 01:15:35 +0000 |
| commit | 5be253d9886479f158904feeeebdce62a34019d4 (patch) | |
| tree | 3f3fd9c9e5d3593311a7f5bfbbe389f0d46f6d09 /llvm/lib | |
| parent | bae7367cd9942e832eaffe105ea42c170a0ed810 (diff) | |
| download | bcm5719-llvm-5be253d9886479f158904feeeebdce62a34019d4.tar.gz bcm5719-llvm-5be253d9886479f158904feeeebdce62a34019d4.zip | |
[X86] Expand mul by pow2 + 2 using a shift and two adds similar to what we do for pow2 - 2.
llvm-svn: 337874
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Target/X86/X86ISelLowering.cpp | 26 |
1 files changed, 15 insertions, 11 deletions
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp index c1fb981e739..fc29069ffdd 100644 --- a/llvm/lib/Target/X86/X86ISelLowering.cpp +++ b/llvm/lib/Target/X86/X86ISelLowering.cpp @@ -33920,35 +33920,39 @@ static SDValue combineMul(SDNode *N, SelectionDAG &DAG, int64_t SignMulAmt = C->getSExtValue(); if ((SignMulAmt != INT64_MIN) && (SignMulAmt != INT64_MAX) && (SignMulAmt != -INT64_MAX)) { - int NumSign = SignMulAmt > 0 ? 1 : -1; - bool IsPowerOf2_64PlusOne = isPowerOf2_64(NumSign * SignMulAmt - 1); - bool IsPowerOf2_64MinusOne = isPowerOf2_64(NumSign * SignMulAmt + 1); - bool IsPowerOf2_64MinusTwo = isPowerOf2_64(NumSign * SignMulAmt + 2); - if (IsPowerOf2_64PlusOne) { + int64_t AbsMulAmt = SignMulAmt < 0 ? -SignMulAmt : SignMulAmt; + if (isPowerOf2_64(AbsMulAmt - 1)) { // (mul x, 2^N + 1) => (add (shl x, N), x) NewMul = DAG.getNode( ISD::ADD, DL, VT, N->getOperand(0), DAG.getNode(ISD::SHL, DL, VT, N->getOperand(0), - DAG.getConstant(Log2_64(NumSign * SignMulAmt - 1), DL, + DAG.getConstant(Log2_64(AbsMulAmt - 1), DL, MVT::i8))); // To negate, subtract the number from zero if (SignMulAmt < 0) NewMul = DAG.getNode(ISD::SUB, DL, VT, DAG.getConstant(0, DL, VT), NewMul); - } else if (IsPowerOf2_64MinusOne) { + } else if (isPowerOf2_64(AbsMulAmt + 1)) { // (mul x, 2^N - 1) => (sub (shl x, N), x) NewMul = DAG.getNode(ISD::SHL, DL, VT, N->getOperand(0), - DAG.getConstant(Log2_64(NumSign * SignMulAmt + 1), + DAG.getConstant(Log2_64(AbsMulAmt + 1), DL, MVT::i8)); // To negate, reverse the operands of the subtract. if (SignMulAmt < 0) NewMul = DAG.getNode(ISD::SUB, DL, VT, N->getOperand(0), NewMul); else NewMul = DAG.getNode(ISD::SUB, DL, VT, NewMul, N->getOperand(0)); - } else if (IsPowerOf2_64MinusTwo && NumSign == 1) { - // (mul x, 2^N - 1) => (sub (shl x, N), x) + } else if (SignMulAmt >= 0 && isPowerOf2_64(AbsMulAmt - 2)) { + // (mul x, 2^N + 2) => (add (add (shl x, N), x), x) + NewMul = DAG.getNode(ISD::SHL, DL, VT, N->getOperand(0), + DAG.getConstant(Log2_64(AbsMulAmt - 2), + DL, MVT::i8)); + NewMul = DAG.getNode(ISD::ADD, DL, VT, NewMul, N->getOperand(0)); + NewMul = DAG.getNode(ISD::ADD, DL, VT, NewMul, N->getOperand(0)); + } else if (SignMulAmt >= 0 && isPowerOf2_64(AbsMulAmt + 2)) { + // (mul x, 2^N - 2) => (sub (sub (shl x, N), x), x) NewMul = DAG.getNode(ISD::SHL, DL, VT, N->getOperand(0), - DAG.getConstant(Log2_64(NumSign * SignMulAmt + 2), + DAG.getConstant(Log2_64(AbsMulAmt + 2), DL, MVT::i8)); NewMul = DAG.getNode(ISD::SUB, DL, VT, NewMul, N->getOperand(0)); NewMul = DAG.getNode(ISD::SUB, DL, VT, NewMul, N->getOperand(0)); |
