IR: add SubWithFlags op (arm64 subs)

with 8/16-bit handling to keep everything uniform.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>

FEXCore/Source/Interface/Core/JIT/Arm64/ALUOps.cpp

@@ -200,6 +200,21 @@ DEF_OP(SubShift) {
   sub(EmitSize, GetReg(Node), GetReg(Op->Src1.ID()), GetReg(Op->Src2.ID()), ConvertIRShiftType(Op->Shift), Op->ShiftAmount);
 }
 
+DEF_OP(SubWithFlags) {
+  auto Op = IROp->C<IR::IROp_SubWithFlags>();
+  const uint8_t OpSize = IROp->Size;
+
+  LOGMAN_THROW_AA_FMT(OpSize == 4 || OpSize == 8, "Unsupported {} size: {}", __func__, OpSize);
+  const auto EmitSize = OpSize == IR::i64Bit ? ARMEmitter::Size::i64Bit : ARMEmitter::Size::i32Bit;
+
+  uint64_t Const;
+  if (IsInlineConstant(Op->Src2, &Const)) {
+    subs(EmitSize, GetReg(Node), GetZeroableReg(Op->Src1), Const);
+  } else {
+    subs(EmitSize, GetReg(Node), GetZeroableReg(Op->Src1), GetReg(Op->Src2.ID()));
+  }
+}
+
 DEF_OP(SubNZCV) {
   auto Op = IROp->C<IR::IROp_SubNZCV>();
   const uint8_t OpSize = IROp->Size;

FEXCore/Source/Interface/IR/IR.json

@@ -1021,6 +1021,14 @@
           "_Shift != ShiftType::ROR"
         ]
       },
+      "GPR = SubWithFlags OpSize:#Size, GPR:$Src1, GPR:$Src2": {
+        "Desc": [ "Integer Sub. Truncates and sets NZCV per SubNZCV"],
+        "DestSize": "Size",
+        "HasSideEffects": true,
+        "EmitValidation": [
+          "Size == FEXCore::IR::OpSize::i32Bit || Size == FEXCore::IR::OpSize::i64Bit"
+        ]
+      },
       "SubNZCV OpSize:#Size, GPR:$Src1, GPR:$Src2": {
         "Desc": ["Set NZCV for the difference of two GPRs. ",
                  "Carry flag uses arm64 definition, inverted x86.",

FEXCore/Source/Interface/IR/Passes/ConstProp.cpp

@@ -965,6 +965,7 @@ bool ConstProp::ConstantInlining(IREmitter *IREmit, const IRListView& CurrentIR)
       case OP_SUB:
       case OP_ADDNZCV:
       case OP_SUBNZCV:
+      case OP_SUBWITHFLAGS:
       {
         auto Op = IROp->C<IR::IROp_Add>();
 
@@ -979,7 +980,7 @@ bool ConstProp::ConstantInlining(IREmitter *IREmit, const IRListView& CurrentIR)
 
             Changed = true;
           }
-        } else if (IROp->Op == OP_SUBNZCV) {
+        } else if (IROp->Op == OP_SUBNZCV || IROp->Op == OP_SUBWITHFLAGS) {
           // If the first source is zero, we can use a NEGS instruction.
           uint64_t Constant1{};
           if (IREmit->IsValueConstant(Op->Header.Args[0], &Constant1)) {

FEXCore/Source/Interface/IR/Passes/RedundantFlagCalculationElimination.cpp

@@ -128,6 +128,13 @@ DeadFlagCalculationEliminination::Classify(IROp_Header *IROp)
         .Replacement = OP_AND,
       };
 
+    case OP_SUBWITHFLAGS:
+      return {
+        .Write = FLAG_NZCV,
+        .CanReplace = true,
+        .Replacement = OP_SUB,
+      };
+
     case OP_ADDNZCV:
     case OP_SUBNZCV:
     case OP_TESTNZ: