diff options
Diffstat (limited to 'llvm/lib/CodeGen')
| -rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index ce4297def73..26b9bc2b025 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -350,6 +350,7 @@ namespace { SDValue visitFREM(SDNode *N); SDValue visitFSQRT(SDNode *N); SDValue visitFCOPYSIGN(SDNode *N); + SDValue visitFPOW(SDNode *N); SDValue visitSINT_TO_FP(SDNode *N); SDValue visitUINT_TO_FP(SDNode *N); SDValue visitFP_TO_SINT(SDNode *N); @@ -1568,6 +1569,7 @@ SDValue DAGCombiner::visit(SDNode *N) { case ISD::FREM: return visitFREM(N); case ISD::FSQRT: return visitFSQRT(N); case ISD::FCOPYSIGN: return visitFCOPYSIGN(N); + case ISD::FPOW: return visitFPOW(N); case ISD::SINT_TO_FP: return visitSINT_TO_FP(N); case ISD::UINT_TO_FP: return visitUINT_TO_FP(N); case ISD::FP_TO_SINT: return visitFP_TO_SINT(N); @@ -11566,6 +11568,45 @@ SDValue DAGCombiner::visitFCOPYSIGN(SDNode *N) { return SDValue(); } +SDValue DAGCombiner::visitFPOW(SDNode *N) { + ConstantFPSDNode *ExponentC = isConstOrConstSplatFP(N->getOperand(1)); + if (!ExponentC) + return SDValue(); + + // Try to convert x ** (1/4) into square roots. + // x ** (1/2) is canonicalized to sqrt, so we do not bother with that case. + // TODO: This could be extended (using a target hook) to handle smaller + // power-of-2 fractional exponents. + if (ExponentC->getValueAPF().isExactlyValue(0.25)) { + // pow(-0.0, 0.25) = +0.0; sqrt(sqrt(-0.0)) = -0.0. + // pow(-inf, 0.25) = +inf; sqrt(sqrt(-inf)) = NaN. + // For regular numbers, rounding may cause the results to differ. + // Therefore, we require { nsz ninf afn } for this transform. + // TODO: We could select out the special cases if we don't have nsz/ninf. + SDNodeFlags Flags = N->getFlags(); + if (!Flags.hasNoSignedZeros() || !Flags.hasNoInfs() || + !Flags.hasApproximateFuncs()) + return SDValue(); + + // Don't double the number of libcalls. We are trying to inline fast code. + EVT VT = N->getValueType(0); + if (!DAG.getTargetLoweringInfo().isOperationLegalOrCustom(ISD::FSQRT, VT)) + return SDValue(); + + // Assume that libcalls are the smallest code. + // TODO: This restriction should probably be lifted for vectors. + if (DAG.getMachineFunction().getFunction().optForSize()) + return SDValue(); + + // pow(X, 0.25) --> sqrt(sqrt(X)) + SDLoc DL(N); + SDValue Sqrt = DAG.getNode(ISD::FSQRT, DL, VT, N->getOperand(0), Flags); + return DAG.getNode(ISD::FSQRT, DL, VT, Sqrt, Flags); + } + + return SDValue(); +} + static SDValue foldFPToIntToFP(SDNode *N, SelectionDAG &DAG, const TargetLowering &TLI) { // This optimization is guarded by a function attribute because it may produce |
