diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp index c65ddc6c28986..1b25d91d9a316 100644 --- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp @@ -10877,6 +10877,18 @@ SDValue TargetLowering::expandAddSubSat(SDNode *Node, SelectionDAG &DAG) const { assert(VT == RHS.getValueType() && "Expected operands to be the same type"); assert(VT.isInteger() && "Expected operands to be integers"); + // usub.sat(a, 1) -> sub(a, zext(a != 0)) + if (Opcode == ISD::USUBSAT && !VT.isVector() && isOneConstant(RHS)) { + LHS = DAG.getFreeze(LHS); + SDValue Zero = DAG.getConstant(0, dl, VT); + EVT BoolVT = getSetCCResultType(DAG.getDataLayout(), *DAG.getContext(), VT); + SDValue IsNonZero = DAG.getSetCC(dl, BoolVT, LHS, Zero, ISD::SETNE); + SDValue Subtrahend = DAG.getBoolExtOrTrunc(IsNonZero, dl, VT, BoolVT); + Subtrahend = + DAG.getNode(ISD::AND, dl, VT, Subtrahend, DAG.getConstant(1, dl, VT)); + return DAG.getNode(ISD::SUB, dl, VT, LHS, Subtrahend); + } + // usub.sat(a, b) -> umax(a, b) - b if (Opcode == ISD::USUBSAT && isOperationLegal(ISD::UMAX, VT)) { SDValue Max = DAG.getNode(ISD::UMAX, dl, VT, LHS, RHS); diff --git a/llvm/test/CodeGen/AArch64/and-mask-removal.ll b/llvm/test/CodeGen/AArch64/and-mask-removal.ll index 5046c0571ad2b..855fe5caf97b2 100644 --- a/llvm/test/CodeGen/AArch64/and-mask-removal.ll +++ b/llvm/test/CodeGen/AArch64/and-mask-removal.ll @@ -483,9 +483,9 @@ define i64 @pr58109(i8 signext %0) { ; CHECK-SD-LABEL: pr58109: ; CHECK-SD: ; %bb.0: ; CHECK-SD-NEXT: add w8, w0, #1 -; CHECK-SD-NEXT: and w8, w8, #0xff -; CHECK-SD-NEXT: subs w8, w8, #1 -; CHECK-SD-NEXT: csel w0, wzr, w8, lo +; CHECK-SD-NEXT: ands w8, w8, #0xff +; CHECK-SD-NEXT: cset w9, ne +; CHECK-SD-NEXT: sub w0, w8, w9 ; CHECK-SD-NEXT: ret ; ; CHECK-GI-LABEL: pr58109: diff --git a/llvm/test/CodeGen/RISCV/usub_sat.ll b/llvm/test/CodeGen/RISCV/usub_sat.ll index 33056682dcc79..7084885a0ee2c 100644 --- a/llvm/test/CodeGen/RISCV/usub_sat.ll +++ b/llvm/test/CodeGen/RISCV/usub_sat.ll @@ -185,3 +185,31 @@ define zeroext i4 @func3(i4 zeroext %x, i4 zeroext %y) nounwind { %tmp = call i4 @llvm.usub.sat.i4(i4 %x, i4 %y); ret i4 %tmp; } + +define signext i32 @sat_dec_i32(i32 signext %x) nounwind { +; RV32I-LABEL: sat_dec_i32: +; RV32I: # %bb.0: +; RV32I-NEXT: snez a1, a0 +; RV32I-NEXT: sub a0, a0, a1 +; RV32I-NEXT: ret +; +; RV64I-LABEL: sat_dec_i32: +; RV64I: # %bb.0: +; RV64I-NEXT: snez a1, a0 +; RV64I-NEXT: subw a0, a0, a1 +; RV64I-NEXT: ret +; +; RV32IZbb-LABEL: sat_dec_i32: +; RV32IZbb: # %bb.0: +; RV32IZbb-NEXT: snez a1, a0 +; RV32IZbb-NEXT: sub a0, a0, a1 +; RV32IZbb-NEXT: ret +; +; RV64IZbb-LABEL: sat_dec_i32: +; RV64IZbb: # %bb.0: +; RV64IZbb-NEXT: snez a1, a0 +; RV64IZbb-NEXT: subw a0, a0, a1 +; RV64IZbb-NEXT: ret + %tmp = call i32 @llvm.usub.sat.i32(i32 %x, i32 1) + ret i32 %tmp +} diff --git a/llvm/test/CodeGen/X86/combine-sub-usat.ll b/llvm/test/CodeGen/X86/combine-sub-usat.ll index e601c5733bd42..7ec4e062930db 100644 --- a/llvm/test/CodeGen/X86/combine-sub-usat.ll +++ b/llvm/test/CodeGen/X86/combine-sub-usat.ll @@ -116,9 +116,9 @@ define <8 x i16> @combine_zero_v8i16(<8 x i16> %a0) { define i32 @combine_dec_i32(i32 %a0) { ; CHECK-LABEL: combine_dec_i32: ; CHECK: # %bb.0: -; CHECK-NEXT: xorl %eax, %eax -; CHECK-NEXT: subl $1, %edi -; CHECK-NEXT: cmovael %edi, %eax +; CHECK-NEXT: movl %edi, %eax +; CHECK-NEXT: cmpl $1, %edi +; CHECK-NEXT: adcl $-1, %eax ; CHECK-NEXT: retq %1 = call i32 @llvm.usub.sat.i32(i32 %a0, i32 1) ret i32 %1