From 39fb1d08dce7b7c78a9633ce32c5610d72d1996a Mon Sep 17 00:00:00 2001 From: Lang Hames Date: Tue, 19 Jun 2012 22:51:23 +0000 Subject: Add DAG-combines for aggressive FMA formation. This patch adds DAG combines to form FMAs from pairs of FADD + FMUL or FSUB + FMUL. The combines are performed when: (a) Either AllowExcessFPPrecision option (-enable-excess-fp-precision for llc) OR UnsafeFPMath option (-enable-unsafe-fp-math) are set, and (b) TargetLoweringInfo::isFMAFasterThanMulAndAdd(VT) is true for the type of the FADD/FSUB, and (c) The FMUL only has one user (the FADD/FSUB). If your target has fast FMA instructions you can make use of these combines by overriding TargetLoweringInfo::isFMAFasterThanMulAndAdd(VT) to return true for types supported by your FMA instruction, and adding patterns to match ISD::FMA to your FMA instructions. llvm-svn: 158757 --- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 43 +++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) (limited to 'llvm/lib/CodeGen') diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 369d927112f..3517b7cfbe3 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -5633,6 +5633,26 @@ SDValue DAGCombiner::visitFADD(SDNode *N) { DAG.getNode(ISD::FADD, N->getDebugLoc(), VT, N0.getOperand(1), N1)); + // FADD -> FMA combines: + if ((DAG.getTarget().Options.AllowExcessFPPrecision || + DAG.getTarget().Options.UnsafeFPMath) && + DAG.getTarget().getTargetLowering()->isFMAFasterThanMulAndAdd(VT) && + TLI.isOperationLegal(ISD::FMA, VT)) { + + // fold (fadd (fmul x, y), z) -> (fma x, y, z) + if (N0.getOpcode() == ISD::FMUL && N0->hasOneUse()) { + return DAG.getNode(ISD::FMA, N->getDebugLoc(), VT, + N0.getOperand(0), N0.getOperand(1), N1); + } + + // fold (fadd x, (fmul y, z)) -> (fma x, y, z) + // Note: Commutes FADD operands. + if (N1.getOpcode() == ISD::FMUL && N1->hasOneUse()) { + return DAG.getNode(ISD::FMA, N->getDebugLoc(), VT, + N1.getOperand(0), N1.getOperand(1), N0); + } + } + return SDValue(); } @@ -5690,6 +5710,29 @@ SDValue DAGCombiner::visitFSUB(SDNode *N) { } } + // FSUB -> FMA combines: + if ((DAG.getTarget().Options.AllowExcessFPPrecision || + DAG.getTarget().Options.UnsafeFPMath) && + DAG.getTarget().getTargetLowering()->isFMAFasterThanMulAndAdd(VT) && + TLI.isOperationLegal(ISD::FMA, VT)) { + + // fold (fsub (fmul x, y), z) -> (fma x, y, (fneg z)) + if (N0.getOpcode() == ISD::FMUL && N0->hasOneUse()) { + return DAG.getNode(ISD::FMA, N->getDebugLoc(), VT, + N0.getOperand(0), N0.getOperand(1), + DAG.getNode(ISD::FNEG, N1->getDebugLoc(), VT, N1)); + } + + // fold (fsub x, (fmul y, z)) -> (fma (fneg y), z, x) + // Note: Commutes FSUB operands. + if (N1.getOpcode() == ISD::FMUL && N1->hasOneUse()) { + return DAG.getNode(ISD::FMA, N->getDebugLoc(), VT, + DAG.getNode(ISD::FNEG, N1->getDebugLoc(), VT, + N1.getOperand(0)), + N1.getOperand(1), N0); + } + } + return SDValue(); } -- cgit v1.2.3