Index: llvm/lib/Target/X86/X86ISelLowering.cpp =================================================================== --- llvm/lib/Target/X86/X86ISelLowering.cpp +++ llvm/lib/Target/X86/X86ISelLowering.cpp @@ -28139,26 +28139,32 @@ TLI.getSetCCResultType(DAG.getDataLayout(), *DAG.getContext(), VT); unsigned BitWidth = VT.getScalarSizeInBits(); - if (Opcode == ISD::USUBSAT && !TLI.isOperationLegal(ISD::UMAX, VT)) { - // Handle a special-case with a bit-hack instead of cmp+select: - // usubsat X, SMIN --> (X ^ SMIN) & (X s>> BW-1) - ConstantSDNode *C = isConstOrConstSplat(Y, true); - if (C && C->getAPIntValue().isSignMask()) { - SDValue SignMask = DAG.getConstant(C->getAPIntValue(), DL, VT); - SDValue ShiftAmt = DAG.getConstant(BitWidth - 1, DL, VT); - SDValue Xor = DAG.getNode(ISD::XOR, DL, VT, X, SignMask); - SDValue Sra = DAG.getNode(ISD::SRA, DL, VT, X, ShiftAmt); - return DAG.getNode(ISD::AND, DL, VT, Xor, Sra); - } - - // usubsat X, Y --> (X >u Y) ? X - Y : 0 - SDValue Sub = DAG.getNode(ISD::SUB, DL, VT, X, Y); - SDValue Cmp = DAG.getSetCC(DL, SetCCResultType, X, Y, ISD::SETUGT); - // TODO: Move this to DAGCombiner? - if (SetCCResultType == VT && - DAG.ComputeNumSignBits(Cmp) == VT.getScalarSizeInBits()) - return DAG.getNode(ISD::AND, DL, VT, Cmp, Sub); - return DAG.getSelect(DL, VT, Cmp, Sub, DAG.getConstant(0, DL, VT)); + if (Opcode == ISD::USUBSAT) { + if (!TLI.isOperationLegal(ISD::UMAX, VT) || useVPTERNLOG(Subtarget, VT)) { + // Handle a special-case with a bit-hack instead of cmp+select: + // usubsat X, SMIN --> (X ^ SMIN) & (X s>> BW-1) + // If the target can use VPTERNLOG, DAGToDAG will match this as + // "vpsra + vpternlog" which is better than "vpmax + vpsub" with a + // "broadcast" constant load. + ConstantSDNode *C = isConstOrConstSplat(Y, true); + if (C && C->getAPIntValue().isSignMask()) { + SDValue SignMask = DAG.getConstant(C->getAPIntValue(), DL, VT); + SDValue ShiftAmt = DAG.getConstant(BitWidth - 1, DL, VT); + SDValue Xor = DAG.getNode(ISD::XOR, DL, VT, X, SignMask); + SDValue Sra = DAG.getNode(ISD::SRA, DL, VT, X, ShiftAmt); + return DAG.getNode(ISD::AND, DL, VT, Xor, Sra); + } + } + if (!TLI.isOperationLegal(ISD::UMAX, VT)) { + // usubsat X, Y --> (X >u Y) ? X - Y : 0 + SDValue Sub = DAG.getNode(ISD::SUB, DL, VT, X, Y); + SDValue Cmp = DAG.getSetCC(DL, SetCCResultType, X, Y, ISD::SETUGT); + // TODO: Move this to DAGCombiner? + if (SetCCResultType == VT && + DAG.ComputeNumSignBits(Cmp) == VT.getScalarSizeInBits()) + return DAG.getNode(ISD::AND, DL, VT, Cmp, Sub); + return DAG.getSelect(DL, VT, Cmp, Sub, DAG.getConstant(0, DL, VT)); + } } if ((Opcode == ISD::SADDSAT || Opcode == ISD::SSUBSAT) && Index: llvm/test/CodeGen/X86/psubus.ll =================================================================== --- llvm/test/CodeGen/X86/psubus.ll +++ llvm/test/CodeGen/X86/psubus.ll @@ -162,9 +162,8 @@ ; ; AVX512-LABEL: usubsat_custom: ; AVX512: # %bb.0: -; AVX512-NEXT: vpbroadcastd {{.*#+}} xmm1 = [2147483648,2147483648,2147483648,2147483648] -; AVX512-NEXT: vpmaxud %xmm1, %xmm0, %xmm0 -; AVX512-NEXT: vpsubd %xmm1, %xmm0, %xmm0 +; AVX512-NEXT: vpsrad $31, %xmm0, %xmm1 +; AVX512-NEXT: vpternlogd $72, {{\.?LCPI[0-9]+_[0-9]+}}(%rip){1to4}, %xmm1, %xmm0 ; AVX512-NEXT: retq %res = call <4 x i32> @llvm.usub.sat.v4i32(<4 x i32> %x, <4 x i32> ) ret <4 x i32> %res