diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -11898,19 +11898,43 @@ }; // fold (fsub (fmul x, y), z) -> (fma x, y, (fneg z)) - if (isContractableFMUL(N0) && (Aggressive || N0->hasOneUse())) { - return DAG.getNode(PreferredFusedOpcode, SL, VT, - N0.getOperand(0), N0.getOperand(1), - DAG.getNode(ISD::FNEG, SL, VT, N1), Flags); - } + auto tryToFoldXYSubZ = [&](SDValue XY, SDValue Z) { + if (isContractableFMUL(XY) && (Aggressive || XY->hasOneUse())) { + return DAG.getNode(PreferredFusedOpcode, SL, VT, XY.getOperand(0), + XY.getOperand(1), DAG.getNode(ISD::FNEG, SL, VT, Z), + Flags); + } + return SDValue(); + }; // fold (fsub x, (fmul y, z)) -> (fma (fneg y), z, x) // Note: Commutes FSUB operands. - if (isContractableFMUL(N1) && (Aggressive || N1->hasOneUse())) { - return DAG.getNode(PreferredFusedOpcode, SL, VT, - DAG.getNode(ISD::FNEG, SL, VT, - N1.getOperand(0)), - N1.getOperand(1), N0, Flags); + auto tryToFoldXSubYZ = [&](SDValue X, SDValue YZ) { + if (isContractableFMUL(YZ) && (Aggressive || YZ->hasOneUse())) { + return DAG.getNode(PreferredFusedOpcode, SL, VT, + DAG.getNode(ISD::FNEG, SL, VT, YZ.getOperand(0)), + YZ.getOperand(1), X, Flags); + } + return SDValue(); + }; + + // If we have two choices trying to fold (fsub (fmul u, v), (fmul x, y)), + // prefer to fold the multiply with fewer uses. + if (Aggressive && isContractableFMUL(N0) && isContractableFMUL(N1) && + (N0.getNode()->use_size() > N1.getNode()->use_size())) { + // fold (fsub x, (fmul y, z)) -> (fma (fneg y), z, x) + if (SDValue V = tryToFoldXSubYZ(N0, N1)) + return V; + // fold (fsub (fmul x, y), z) -> (fma x, y, (fneg z)) + if (SDValue V = tryToFoldXYSubZ(N0, N1)) + return V; + } else { + // fold (fsub (fmul x, y), z) -> (fma x, y, (fneg z)) + if (SDValue V = tryToFoldXYSubZ(N0, N1)) + return V; + // fold (fsub x, (fmul y, z)) -> (fma (fneg y), z, x) + if (SDValue V = tryToFoldXSubYZ(N0, N1)) + return V; } // fold (fsub (fneg (fmul, x, y)), z) -> (fma (fneg x), y, (fneg z)) diff --git a/llvm/test/CodeGen/PowerPC/fma-precision.ll b/llvm/test/CodeGen/PowerPC/fma-precision.ll --- a/llvm/test/CodeGen/PowerPC/fma-precision.ll +++ b/llvm/test/CodeGen/PowerPC/fma-precision.ll @@ -5,10 +5,10 @@ define double @fsub1(double %a, double %b, double %c, double %d) { ; CHECK-LABEL: fsub1: ; CHECK: # %bb.0: # %entry -; CHECK-NEXT: xsmuldp 3, 4, 3 ; CHECK-NEXT: xsmuldp 0, 2, 1 -; CHECK-NEXT: xsmsubadp 3, 2, 1 -; CHECK-NEXT: xsmuldp 1, 0, 3 +; CHECK-NEXT: fmr 1, 0 +; CHECK-NEXT: xsnmsubadp 1, 4, 3 +; CHECK-NEXT: xsmuldp 1, 0, 1 ; CHECK-NEXT: blr entry: %mul = fmul fast double %b, %a diff --git a/llvm/test/CodeGen/PowerPC/recipest.ll b/llvm/test/CodeGen/PowerPC/recipest.ll --- a/llvm/test/CodeGen/PowerPC/recipest.ll +++ b/llvm/test/CodeGen/PowerPC/recipest.ll @@ -177,12 +177,11 @@ ; CHECK-NEXT: fmuls 1, 1, 0 ; CHECK-NEXT: fmadds 1, 1, 0, 4 ; CHECK-NEXT: fmuls 0, 0, 5 -; CHECK-NEXT: fres 5, 2 +; CHECK-NEXT: fmuls 0, 0, 1 +; CHECK-NEXT: fres 1, 2 ; CHECK-NEXT: fmuls 4, 0, 1 -; CHECK-NEXT: fmuls 4, 4, 5 -; CHECK-NEXT: fmuls 2, 2, 4 -; CHECK-NEXT: fmsubs 0, 0, 1, 2 -; CHECK-NEXT: fmadds 0, 5, 0, 4 +; CHECK-NEXT: fnmsubs 0, 2, 4, 0 +; CHECK-NEXT: fmadds 0, 1, 0, 4 ; CHECK-NEXT: fmuls 1, 3, 0 ; CHECK-NEXT: blr %x = call fast float @llvm.sqrt.f32(float %a)