FEXCore: Rework X87 tag word handling

The FXSAVE and FSAVE tag words are written out in different formats,
with FXSAVE using an abridged version that lacks the zero/special/valid
distinction. Switch to using this abridged version internally for
simplicity, and to allow the calculation of zero/special/valid
distinction to be deferred until an fxsave instruction (in the future,
currently the distinction is ignored and only valid/empty states are
possible).

FEXCore/Source/Interface/Core/OpcodeDispatcher.h

@@ -1811,14 +1811,12 @@ private:
   /**  @} */
 
   OrderedNode * GetX87Top();
-  enum class X87Tag {
-    Valid   = 0b00,
-    Zero    = 0b01,
-    Special = 0b10,
-    Empty   = 0b11
-  };
-  void SetX87TopTag(OrderedNode *Value, X87Tag Tag);
-  OrderedNode *GetX87FTW(OrderedNode *Value);
+  void SetX87ValidTag(OrderedNode *Value, bool Valid);
+  OrderedNode *GetX87ValidTag(OrderedNode *Value);
+  OrderedNode *GetX87Tag(OrderedNode *Value, OrderedNode *AbridgedFTW);
+  OrderedNode *GetX87Tag(OrderedNode *Value);
+  void SetX87FTW(OrderedNode *FTW);
+  OrderedNode *GetX87FTW();
   void SetX87Top(OrderedNode *Value);
 
   bool DestIsLockedMem(FEXCore::X86Tables::DecodedOp Op) const {

FEXCore/Source/Interface/Core/OpcodeDispatcher/Vector.cpp

@@ -2622,10 +2622,10 @@ void OpDispatchBuilder::SaveX87State(OpcodeArgs, OrderedNode *MemBase) {
   }
 
   {
-    // FTW
+    // Abridged FTW
     OrderedNode *MemLocation = _Add(OpSize, MemBase, _Constant(4));
-    auto FTW = _LoadContext(2, GPRClass, offsetof(FEXCore::Core::CPUState, FTW));
-    _StoreMem(GPRClass, 2, MemLocation, FTW, 2);
+    auto AbridgedFTW = _LoadContext(1, GPRClass, offsetof(FEXCore::Core::CPUState, AbridgedFTW));
+    _StoreMem(GPRClass, 1, MemLocation, AbridgedFTW, 2);
   }
 
   // BYTE | 0 1 | 2 3 | 4   | 5     | 6 7 | 8 9 | a b | c d | e f |
@@ -2826,10 +2826,10 @@ void OpDispatchBuilder::RestoreX87State(OrderedNode *MemBase) {
   }
 
   {
-    // FTW
+    // Abridged FTW
     OrderedNode *MemLocation = _Add(OpSize, MemBase, _Constant(4));
-    auto NewFTW = _LoadMem(GPRClass, 2, MemLocation, 2);
-    _StoreContext(2, GPRClass, NewFTW, offsetof(FEXCore::Core::CPUState, FTW));
+    auto NewAbridgedFTW = _LoadMem(GPRClass, 1, MemLocation, 2);
+    _StoreContext(1, GPRClass, NewAbridgedFTW, offsetof(FEXCore::Core::CPUState, AbridgedFTW));
   }
 
   for (uint32_t i = 0; i < Core::CPUState::NUM_MMS; ++i) {

FEXCore/Source/Interface/Core/OpcodeDispatcher/X87.cpp

@@ -12,6 +12,7 @@ $end_info$
 #include <FEXCore/Core/X86Enums.h>
 #include <FEXCore/Utils/EnumUtils.h>
 #include <FEXCore/Utils/LogManager.h>
+#include <FEXCore/Utils/FPState.h>
 #include <FEXCore/IR/IREmitter.h>
 
 #include <stddef.h>
@@ -28,28 +29,59 @@ OrderedNode *OpDispatchBuilder::GetX87Top() {
   return _LoadContext(1, GPRClass, offsetof(FEXCore::Core::CPUState, flags) + FEXCore::X86State::X87FLAG_TOP_LOC);
 }
 
-void OpDispatchBuilder::SetX87TopTag(OrderedNode *Value, X87Tag Tag) {
+void OpDispatchBuilder::SetX87ValidTag(OrderedNode *Value, bool Valid) {
   // if we are popping then we must first mark this location as empty
-  auto FTW = _LoadContext(2, GPRClass, offsetof(FEXCore::Core::CPUState, FTW));
-  OrderedNode *Mask = _Constant(0b11);
-  // TODO: This can all be done with OpSize::i32Bit.
-  auto TopOffset = _Lshl(IR::SizeToOpSize(std::max<uint8_t>(4, GetOpSize(Value))), Value, _Constant(1));
-  Mask = _Lshl(OpSize::i64Bit, Mask, TopOffset);
-  OrderedNode *NewFTW = _Andn(OpSize::i64Bit, FTW, Mask);
-  if (Tag != X87Tag::Valid) {
-    auto TagVal = _Lshl(OpSize::i64Bit, _Constant(ToUnderlying(Tag)), TopOffset);
-    NewFTW = _Or(OpSize::i64Bit, NewFTW, TagVal);
-  }
-
-  _StoreContext(2, GPRClass, NewFTW, offsetof(FEXCore::Core::CPUState, FTW));
+  OrderedNode *AbridgedFTW = _LoadContext(1, GPRClass, offsetof(FEXCore::Core::CPUState, AbridgedFTW));
+  OrderedNode *RegMask = _Lshl(OpSize::i32Bit, _Constant(1), Value);
+  OrderedNode *NewAbridgedFTW = Valid ? _Or(OpSize::i32Bit, AbridgedFTW, RegMask) : _Andn(OpSize::i32Bit, AbridgedFTW, RegMask);
+  _StoreContext(1, GPRClass, NewAbridgedFTW, offsetof(FEXCore::Core::CPUState, AbridgedFTW));
 }
 
-OrderedNode *OpDispatchBuilder::GetX87FTW(OrderedNode *Value) {
-  auto FTW = _LoadContext(2, GPRClass, offsetof(FEXCore::Core::CPUState, FTW));
-  OrderedNode *Mask = _Constant(0b11);
-  auto TopOffset = _Lshl(OpSize::i32Bit, Value, _Constant(1));
-  auto NewFTW = _Lshr(OpSize::i32Bit, FTW, TopOffset);
-  return _And(OpSize::i64Bit, NewFTW, Mask);
+OrderedNode *OpDispatchBuilder::GetX87ValidTag(OrderedNode *Value) {
+  OrderedNode *AbridgedFTW = _LoadContext(1, GPRClass, offsetof(FEXCore::Core::CPUState, AbridgedFTW));
+  return _And(OpSize::i32Bit, _Lshr(OpSize::i32Bit, AbridgedFTW, Value), _Constant(1));
+}
+
+OrderedNode *OpDispatchBuilder::GetX87Tag(OrderedNode *Value, OrderedNode *AbridgedFTW) {
+  OrderedNode *RegValid = _And(OpSize::i32Bit, _Lshr(OpSize::i32Bit, AbridgedFTW, Value), _Constant(1));
+  OrderedNode *X87Empty = _Constant(static_cast<uint8_t>(FPState::X87Tag::Empty));
+  OrderedNode *X87Valid = _Constant(static_cast<uint8_t>(FPState::X87Tag::Valid));
+
+  return _Select(FEXCore::IR::COND_EQ,
+    RegValid, _Constant(0),
+    X87Empty, X87Valid);
+}
+
+OrderedNode *OpDispatchBuilder::GetX87Tag(OrderedNode *Value) {
+  OrderedNode *AbridgedFTW = _LoadContext(1, GPRClass, offsetof(FEXCore::Core::CPUState, AbridgedFTW));
+  return GetX87Tag(Value, AbridgedFTW);
+}
+
+void OpDispatchBuilder::SetX87FTW(OrderedNode *FTW) {
+  OrderedNode *X87Empty = _Constant(static_cast<uint8_t>(FPState::X87Tag::Empty));
+  OrderedNode *NewAbridgedFTW = _Constant(0);
+
+  for (int i = 0; i < 8; i++) {
+    OrderedNode *RegTag = _And(OpSize::i32Bit, _Lshr(OpSize::i32Bit, FTW, _Constant(i * 2)), _Constant(0b11));
+    OrderedNode *RegValid = _Select(FEXCore::IR::COND_EQ,
+      RegTag, X87Empty,
+      _Constant(0), _Constant(1));
+    NewAbridgedFTW = _Or(OpSize::i32Bit, NewAbridgedFTW, _Lshl(OpSize::i32Bit, RegValid, _Constant(i)));
+  }
+
+  _StoreContext(1, GPRClass, NewAbridgedFTW, offsetof(FEXCore::Core::CPUState, AbridgedFTW));
+}
+
+OrderedNode *OpDispatchBuilder::GetX87FTW() {
+  OrderedNode *AbridgedFTW = _LoadContext(1, GPRClass, offsetof(FEXCore::Core::CPUState, AbridgedFTW));
+  OrderedNode *FTW = _Constant(0);
+
+  for (int i = 0; i < 8; i++) {
+    const auto RegTag = GetX87Tag(_Constant(i), AbridgedFTW);
+    FTW = _Or(OpSize::i32Bit, FTW, _Lshl(OpSize::i32Bit, RegTag, _Constant(i * 2)));
+  }
+
+  return FTW;
 }
 
 void OpDispatchBuilder::SetX87Top(OrderedNode *Value) {
@@ -119,7 +151,7 @@ void OpDispatchBuilder::FLD(OpcodeArgs) {
   }
 
   auto top = _And(OpSize::i64Bit, _Sub(OpSize::i64Bit, orig_top, _Constant(1)), mask);
-  SetX87TopTag(top, X87Tag::Valid);
+  SetX87ValidTag(top, true);
   SetX87Top(top);
   // Write to ST[TOP]
   _StoreContextIndexed(converted, top, 16, MMBaseOffset(), 16, FPRClass);
@@ -138,7 +170,7 @@ void OpDispatchBuilder::FBLD(OpcodeArgs) {
   auto orig_top = GetX87Top();
   auto mask = _Constant(7);
   auto top = _And(OpSize::i64Bit, _Sub(OpSize::i64Bit, orig_top, _Constant(1)), mask);
-  SetX87TopTag(top, X87Tag::Valid);
+  SetX87ValidTag(top, true);
   SetX87Top(top);
 
   // Read from memory
@@ -156,7 +188,7 @@ void OpDispatchBuilder::FBSTP(OpcodeArgs) {
   StoreResult_WithOpSize(FPRClass, Op, Op->Dest, converted, 10, 1);
 
   // if we are popping then we must first mark this location as empty
-  SetX87TopTag(orig_top, X87Tag::Empty);
+  SetX87ValidTag(orig_top, false);
   auto top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
   SetX87Top(top);
 }
@@ -166,7 +198,7 @@ void OpDispatchBuilder::FLD_Const(OpcodeArgs) {
   // Update TOP
   auto orig_top = GetX87Top();
   auto top = _And(OpSize::i64Bit, _Sub(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
-  SetX87TopTag(top, X87Tag::Valid);
+  SetX87ValidTag(top, true);
   SetX87Top(top);
 
   auto low = _Constant(Lower);
@@ -196,7 +228,7 @@ void OpDispatchBuilder::FILD(OpcodeArgs) {
   // Update TOP
   auto orig_top = GetX87Top();
   auto top = _And(OpSize::i64Bit, _Sub(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
-  SetX87TopTag(top, X87Tag::Valid);
+  SetX87ValidTag(top, true);
   SetX87Top(top);
 
   size_t read_width = GetSrcSize(Op);
@@ -246,7 +278,7 @@ void OpDispatchBuilder::FST(OpcodeArgs) {
 
   if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(orig_top, X87Tag::Empty);
+    SetX87ValidTag(orig_top, false);
     // Set the new top now
     auto top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
     SetX87Top(top);
@@ -272,7 +304,7 @@ void OpDispatchBuilder::FIST(OpcodeArgs) {
 
   if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(orig_top, X87Tag::Empty);
+    SetX87ValidTag(orig_top, false);
     // Set the new top now
     auto top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
     SetX87Top(top);
@@ -321,7 +353,7 @@ void OpDispatchBuilder::FADD(OpcodeArgs) {
 
   if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(top, X87Tag::Empty);
+    SetX87ValidTag(top, false);
     // Set the new top now
     top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, _Constant(1)), mask);
     SetX87Top(top);
@@ -384,7 +416,7 @@ void OpDispatchBuilder::FMUL(OpcodeArgs) {
 
   if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(top, X87Tag::Empty);
+    SetX87ValidTag(top, false);
     // Set the new top now
     top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, _Constant(1)), mask);
     SetX87Top(top);
@@ -453,7 +485,7 @@ void OpDispatchBuilder::FDIV(OpcodeArgs) {
 
   if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(top, X87Tag::Empty);
+    SetX87ValidTag(top, false);
     // Set the new top now
     top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, _Constant(1)), mask);
     SetX87Top(top);
@@ -537,7 +569,7 @@ void OpDispatchBuilder::FSUB(OpcodeArgs) {
 
   if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(top, X87Tag::Empty);
+    SetX87ValidTag(top, false);
     // Set the new top now
 
     top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, _Constant(1)), mask);
@@ -645,7 +677,7 @@ void OpDispatchBuilder::FRNDINT(OpcodeArgs) {
 void OpDispatchBuilder::FXTRACT(OpcodeArgs) {
   auto orig_top = GetX87Top();
   auto top = _And(OpSize::i64Bit, _Sub(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
-  SetX87TopTag(top, X87Tag::Valid);
+  SetX87ValidTag(top, true);
   SetX87Top(top);
 
   auto a = _LoadContextIndexed(orig_top, 16, MMBaseOffset(), 16, FPRClass);
@@ -673,8 +705,8 @@ void OpDispatchBuilder::FNINIT(OpcodeArgs) {
   SetRFLAG<FEXCore::X86State::X87FLAG_C2_LOC>(Zero);
   SetRFLAG<FEXCore::X86State::X87FLAG_C3_LOC>(Zero);
 
-  // Tags all get set to 0b11
-  _StoreContext(2, GPRClass, _Constant(0xFFFF), offsetof(FEXCore::Core::CPUState, FTW));
+  // Tags all get marked as invalid
+  _StoreContext(1, GPRClass, Zero, offsetof(FEXCore::Core::CPUState, AbridgedFTW));
 }
 
 template<size_t width, bool Integer, OpDispatchBuilder::FCOMIFlags whichflags, bool poptwice>
@@ -735,16 +767,16 @@ void OpDispatchBuilder::FCOMI(OpcodeArgs) {
 
   if constexpr (poptwice) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(top, X87Tag::Empty);
+    SetX87ValidTag(top, false);
     top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, _Constant(1)), mask);
-    SetX87TopTag(top, X87Tag::Empty);
+    SetX87ValidTag(top, false);
     // Set the new top now
     top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, _Constant(1)), mask);
     SetX87Top(top);
   }
   else if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(top, X87Tag::Empty);
+    SetX87ValidTag(top, false);
     // Set the new top now
     top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, _Constant(1)), mask);
     SetX87Top(top);
@@ -806,7 +838,7 @@ void OpDispatchBuilder::FST(OpcodeArgs) {
 
   if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(top, X87Tag::Empty);
+    SetX87ValidTag(top, false);
     top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, _Constant(1)), _Constant(7));
     SetX87Top(top);
   }
@@ -892,7 +924,7 @@ void OpDispatchBuilder::X87ModifySTP<true>(OpcodeArgs);
 void OpDispatchBuilder::X87SinCos(OpcodeArgs) {
   auto orig_top = GetX87Top();
   auto top = _And(OpSize::i64Bit, _Sub(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
-  SetX87TopTag(top, X87Tag::Valid);
+  SetX87ValidTag(top, true);
   SetX87Top(top);
 
   auto a = _LoadContextIndexed(orig_top, 16, MMBaseOffset(), 16, FPRClass);
@@ -913,7 +945,7 @@ void OpDispatchBuilder::X87FYL2X(OpcodeArgs) {
 
   auto orig_top = GetX87Top();
   // if we are popping then we must first mark this location as empty
-  SetX87TopTag(orig_top, X87Tag::Empty);
+  SetX87ValidTag(orig_top, false);
   auto top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
   SetX87Top(top);
 
@@ -937,7 +969,7 @@ void OpDispatchBuilder::X87FYL2X(OpcodeArgs) {
 void OpDispatchBuilder::X87TAN(OpcodeArgs) {
   auto orig_top = GetX87Top();
   auto top = _And(OpSize::i64Bit, _Sub(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
-  SetX87TopTag(top, X87Tag::Valid);
+  SetX87ValidTag(top, true);
   SetX87Top(top);
 
   auto a = _LoadContextIndexed(orig_top, 16, MMBaseOffset(), 16, FPRClass);
@@ -960,7 +992,7 @@ void OpDispatchBuilder::X87TAN(OpcodeArgs) {
 void OpDispatchBuilder::X87ATAN(OpcodeArgs) {
   auto orig_top = GetX87Top();
   // if we are popping then we must first mark this location as empty
-  SetX87TopTag(orig_top, X87Tag::Empty);
+  SetX87ValidTag(orig_top, false);
   auto top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
   SetX87Top(top);
 
@@ -989,8 +1021,7 @@ void OpDispatchBuilder::X87LDENV(OpcodeArgs) {
   {
     // FTW
     OrderedNode *MemLocation = _Add(OpSize::i64Bit, Mem, _Constant(Size * 2));
-    auto NewFTW = _LoadMem(GPRClass, Size, MemLocation, Size);
-    _StoreContext(2, GPRClass, NewFTW, offsetof(FEXCore::Core::CPUState, FTW));
+    SetX87FTW(_LoadMem(GPRClass, Size, MemLocation, Size));
   }
 }
 
@@ -1033,8 +1064,7 @@ void OpDispatchBuilder::X87FNSTENV(OpcodeArgs) {
   {
     // FTW
     OrderedNode *MemLocation = _Add(OpSize::i64Bit, Mem, _Constant(Size * 2));
-    auto FTW = _LoadContext(2, GPRClass, offsetof(FEXCore::Core::CPUState, FTW));
-    _StoreMem(GPRClass, Size, MemLocation, FTW, Size);
+    _StoreMem(GPRClass, Size, MemLocation, GetX87FTW(), Size);
   }
 
   {
@@ -1123,8 +1153,7 @@ void OpDispatchBuilder::X87FNSAVE(OpcodeArgs) {
   {
     // FTW
     OrderedNode *MemLocation = _Add(OpSize::i64Bit, Mem, _Constant(Size * 2));
-    auto FTW = _LoadContext(2, GPRClass, offsetof(FEXCore::Core::CPUState, FTW));
-    _StoreMem(GPRClass, Size, MemLocation, FTW, Size);
+    _StoreMem(GPRClass, Size, MemLocation, GetX87FTW(), Size);
   }
 
   {
@@ -1192,8 +1221,7 @@ void OpDispatchBuilder::X87FRSTOR(OpcodeArgs) {
   {
     // FTW
     OrderedNode *MemLocation = _Add(OpSize::i64Bit, Mem, _Constant(Size * 2));
-    auto NewFTW = _LoadMem(GPRClass, Size, MemLocation, Size);
-    _StoreContext(2, GPRClass, NewFTW, offsetof(FEXCore::Core::CPUState, FTW));
+    SetX87FTW(_LoadMem(GPRClass, Size, MemLocation, Size));
   }
 
   OrderedNode *ST0Location = _Add(OpSize::i64Bit, Mem, _Constant(Size * 7));
@@ -1241,20 +1269,16 @@ void OpDispatchBuilder::X87FXAM(OpcodeArgs) {
 
   // Claim this is a normal number
   // We don't support anything else
-  auto FTW = GetX87FTW(top);
-  auto X87Zero = _Constant(0b11);
+  auto TopValid = GetX87ValidTag(top);
   auto ZeroConst = _Constant(0);
   auto OneConst = _Constant(1);
 
-  // In the case of Zero 0b11 then C3:C2:C0 is 0b101
+  // In the case of top being invalid then C3:C2:C0 is 0b101
   auto C3 = _Select(FEXCore::IR::COND_EQ,
-    FTW, X87Zero,
-    OneConst, ZeroConst);
-
-  auto C2 = _Select(FEXCore::IR::COND_EQ,
-    FTW, X87Zero,
+    TopValid, OneConst,
     ZeroConst, OneConst);
 
+  auto C2 = TopValid;
   auto C0 = C3; // Mirror C3 until something other than zero is supported
   SetRFLAG<FEXCore::X86State::X87FLAG_C0_LOC>(C0);
   SetRFLAG<FEXCore::X86State::X87FLAG_C2_LOC>(C2);
@@ -1350,7 +1374,7 @@ void OpDispatchBuilder::X87FCMOV(OpcodeArgs) {
 
 void OpDispatchBuilder::X87EMMS(OpcodeArgs) {
   // Tags all get set to 0b11
-  _StoreContext(2, GPRClass, _Constant(0xFFFF), offsetof(FEXCore::Core::CPUState, FTW));
+  _StoreContext(1, GPRClass, _Constant(0), offsetof(FEXCore::Core::CPUState, AbridgedFTW));
 }
 
 void OpDispatchBuilder::X87FFREE(OpcodeArgs) {
@@ -1362,7 +1386,7 @@ void OpDispatchBuilder::X87FFREE(OpcodeArgs) {
   top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, offset), _Constant(7));
 
   // Set this argument's tag as empty now
-  SetX87TopTag(top, X87Tag::Empty);
+  SetX87ValidTag(top, false);
 }
 
 }

FEXCore/Source/Interface/Core/OpcodeDispatcher/X87F64.cpp

@@ -24,8 +24,11 @@ class OrderedNode;
 
 //Functions in X87.cpp (no change required)
 //GetX87Top
-//SetX87TopTag
-//GetX87FTW
+//SetX87ValidTag
+//GetX87ValidTag
+//GetX87Tag (will need changing once special tag handling is implemented)
+//SetX87FTW
+//GetX87FTW (will need changing once special tag handling is implemented)
 //SetX87Top
 //X87ModifySTP
 //EMMS
@@ -57,8 +60,8 @@ void OpDispatchBuilder::FNINITF64(OpcodeArgs) {
   SetRFLAG<FEXCore::X86State::X87FLAG_C2_LOC>(Zero);
   SetRFLAG<FEXCore::X86State::X87FLAG_C3_LOC>(Zero);
 
-  // Tags all get set to 0b11
-  _StoreContext(2, GPRClass, _Constant(0xFFFF), offsetof(FEXCore::Core::CPUState, FTW));
+  // Tags all get marked as invalid
+  _StoreContext(1, GPRClass, Zero, offsetof(FEXCore::Core::CPUState, AbridgedFTW));
 }
 
 void OpDispatchBuilder::X87LDENVF64(OpcodeArgs) {
@@ -86,8 +89,7 @@ void OpDispatchBuilder::X87LDENVF64(OpcodeArgs) {
   {
     // FTW
     OrderedNode *MemLocation = _Add(OpSize::i64Bit, Mem, _Constant(Size * 2));
-    auto NewFTW = _LoadMem(GPRClass, Size, MemLocation, Size);
-    _StoreContext(2, GPRClass, NewFTW, offsetof(FEXCore::Core::CPUState, FTW));
+    SetX87FTW(_LoadMem(GPRClass, Size, MemLocation, Size));
   }
 }
 
@@ -140,7 +142,7 @@ void OpDispatchBuilder::FLDF64(OpcodeArgs) {
   }
 
   auto top = _And(OpSize::i64Bit, _Sub(OpSize::i64Bit, orig_top, _Constant(1)), mask);
-  SetX87TopTag(top, X87Tag::Valid);
+  SetX87ValidTag(top, true);
   SetX87Top(top);
   // Write to ST[TOP]
   _StoreContextIndexed(converted, top, 8, MMBaseOffset(), 16, FPRClass);
@@ -158,7 +160,7 @@ void OpDispatchBuilder::FBLDF64(OpcodeArgs) {
   auto orig_top = GetX87Top();
   auto mask = _Constant(7);
   auto top = _And(OpSize::i64Bit, _Sub(OpSize::i64Bit, orig_top, _Constant(1)), mask);
-  SetX87TopTag(top, X87Tag::Valid);
+  SetX87ValidTag(top, true);
   SetX87Top(top);
 
   // Read from memory
@@ -178,7 +180,7 @@ void OpDispatchBuilder::FBSTPF64(OpcodeArgs) {
   StoreResult_WithOpSize(FPRClass, Op, Op->Dest, converted, 10, 1);
 
   // if we are popping then we must first mark this location as empty
-  SetX87TopTag(orig_top, X87Tag::Empty);
+  SetX87ValidTag(orig_top, false);
   auto top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
   SetX87Top(top);
 }
@@ -188,7 +190,7 @@ void OpDispatchBuilder::FLDF64_Const(OpcodeArgs) {
   // Update TOP
   auto orig_top = GetX87Top();
   auto top = _And(OpSize::i64Bit, _Sub(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
-  SetX87TopTag(top, X87Tag::Valid);
+  SetX87ValidTag(top, true);
   SetX87Top(top);
   auto data = _VCastFromGPR(8, 8, _Constant(num));
   // Write to ST[TOP]
@@ -214,7 +216,7 @@ void OpDispatchBuilder::FILDF64(OpcodeArgs) {
   // Update TOP
   auto orig_top = GetX87Top();
   auto top = _And(OpSize::i64Bit, _Sub(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
-  SetX87TopTag(top, X87Tag::Valid);
+  SetX87ValidTag(top, true);
   SetX87Top(top);
 
   size_t read_width = GetSrcSize(Op);
@@ -247,7 +249,7 @@ void OpDispatchBuilder::FSTF64(OpcodeArgs) {
 
   if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(orig_top, X87Tag::Empty);
+    SetX87ValidTag(orig_top, false);
     // Set the new top now
     auto top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
     SetX87Top(top);
@@ -276,7 +278,7 @@ void OpDispatchBuilder::FISTF64(OpcodeArgs) {
 
   if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(orig_top, X87Tag::Empty);
+    SetX87ValidTag(orig_top, false);
     // Set the new top now
     auto top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
     SetX87Top(top);
@@ -326,7 +328,7 @@ void OpDispatchBuilder::FADDF64(OpcodeArgs) {
   auto result = _VFAdd(8, 8, a, b);
   if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(top, X87Tag::Empty);
+    SetX87ValidTag(top, false);
     // Set the new top now
     top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, _Constant(1)), mask);
     SetX87Top(top);
@@ -390,7 +392,7 @@ void OpDispatchBuilder::FMULF64(OpcodeArgs) {
 
   if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(top, X87Tag::Empty);
+    SetX87ValidTag(top, false);
     // Set the new top now
     top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, _Constant(1)), mask);
     SetX87Top(top);
@@ -460,7 +462,7 @@ void OpDispatchBuilder::FDIVF64(OpcodeArgs) {
 
   if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(top, X87Tag::Empty);
+    SetX87ValidTag(top, false);
     // Set the new top now
     top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, _Constant(1)), mask);
     SetX87Top(top);
@@ -546,7 +548,7 @@ void OpDispatchBuilder::FSUBF64(OpcodeArgs) {
 
   if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(top, X87Tag::Empty);
+    SetX87ValidTag(top, false);
     // Set the new top now
 
     top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, _Constant(1)), mask);
@@ -645,7 +647,7 @@ void OpDispatchBuilder::FRNDINTF64(OpcodeArgs) {
 void OpDispatchBuilder::FXTRACTF64(OpcodeArgs) {
   auto orig_top = GetX87Top();
   auto top = _And(OpSize::i64Bit, _Sub(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
-  SetX87TopTag(top, X87Tag::Valid);
+  SetX87ValidTag(top, true);
   SetX87Top(top);
 
   auto a = _LoadContextIndexed(orig_top, 8, MMBaseOffset(), 16, FPRClass);
@@ -724,16 +726,16 @@ void OpDispatchBuilder::FCOMIF64(OpcodeArgs) {
 
   if constexpr (poptwice) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(top, X87Tag::Empty);
+    SetX87ValidTag(top, false);
     top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, _Constant(1)), mask);
-    SetX87TopTag(top, X87Tag::Empty);
+    SetX87ValidTag(top, false);
     // Set the new top now
     top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, _Constant(1)), mask);
     SetX87Top(top);
   }
   else if ((Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_POP) != 0) {
     // if we are popping then we must first mark this location as empty
-    SetX87TopTag(top, X87Tag::Empty);
+    SetX87ValidTag(top, false);
     // Set the new top now
     top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, top, _Constant(1)), mask);
     SetX87Top(top);
@@ -832,7 +834,7 @@ void OpDispatchBuilder::X87BinaryOpF64<IR::OP_F64SCALE>(OpcodeArgs);
 void OpDispatchBuilder::X87SinCosF64(OpcodeArgs) {
   auto orig_top = GetX87Top();
   auto top = _And(OpSize::i64Bit, _Sub(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
-  SetX87TopTag(top, X87Tag::Valid);
+  SetX87ValidTag(top, true);
   SetX87Top(top);
 
   auto a = _LoadContextIndexed(orig_top, 8, MMBaseOffset(), 16, FPRClass);
@@ -853,7 +855,7 @@ void OpDispatchBuilder::X87FYL2XF64(OpcodeArgs) {
 
   auto orig_top = GetX87Top();
   // if we are popping then we must first mark this location as empty
-  SetX87TopTag(orig_top, X87Tag::Empty);
+  SetX87ValidTag(orig_top, false);
   auto top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
   SetX87Top(top);
 
@@ -874,7 +876,7 @@ void OpDispatchBuilder::X87FYL2XF64(OpcodeArgs) {
 void OpDispatchBuilder::X87TANF64(OpcodeArgs) {
   auto orig_top = GetX87Top();
   auto top = _And(OpSize::i64Bit, _Sub(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
-  SetX87TopTag(top, X87Tag::Valid);
+  SetX87ValidTag(top, true);
   SetX87Top(top);
 
   auto a = _LoadContextIndexed(orig_top, 8, MMBaseOffset(), 16, FPRClass);
@@ -894,7 +896,7 @@ void OpDispatchBuilder::X87TANF64(OpcodeArgs) {
 void OpDispatchBuilder::X87ATANF64(OpcodeArgs) {
   auto orig_top = GetX87Top();
   // if we are popping then we must first mark this location as empty
-  SetX87TopTag(orig_top, X87Tag::Empty);
+  SetX87ValidTag(orig_top, false);
   auto top = _And(OpSize::i64Bit, _Add(OpSize::i64Bit, orig_top, _Constant(1)), _Constant(7));
   SetX87Top(top);
 
@@ -949,8 +951,7 @@ void OpDispatchBuilder::X87FNSAVEF64(OpcodeArgs) {
   {
     // FTW
     OrderedNode *MemLocation = _Add(OpSize::i64Bit, Mem, _Constant(Size * 2));
-    auto FTW = _LoadContext(2, GPRClass, offsetof(FEXCore::Core::CPUState, FTW));
-    _StoreMem(GPRClass, Size, MemLocation, FTW, Size);
+    _StoreMem(GPRClass, Size, MemLocation, GetX87FTW(), Size);
   }
 
   {
@@ -1032,8 +1033,7 @@ void OpDispatchBuilder::X87FRSTORF64(OpcodeArgs) {
   {
     // FTW
     OrderedNode *MemLocation = _Add(OpSize::i64Bit, Mem, _Constant(Size * 2));
-    auto NewFTW = _LoadMem(GPRClass, Size, MemLocation, Size);
-    _StoreContext(2, GPRClass, NewFTW, offsetof(FEXCore::Core::CPUState, FTW));
+    SetX87FTW(_LoadMem(GPRClass, Size, MemLocation, Size));
   }
 
   OrderedNode *ST0Location = _Add(OpSize::i64Bit, Mem, _Constant(Size * 7));
@@ -1085,20 +1085,16 @@ void OpDispatchBuilder::X87FXAMF64(OpcodeArgs) {
 
   // Claim this is a normal number
   // We don't support anything else
-  auto FTW = GetX87FTW(top);
-  auto X87Zero = _Constant(0b11);
+  auto TopValid = GetX87ValidTag(top);
   auto ZeroConst = _Constant(0);
   auto OneConst = _Constant(1);
 
-  // In the case of Zero 0b11 then C3:C2:C0 is 0b101
+  // In the case of top being invalid then C3:C2:C0 is 0b101
   auto C3 = _Select(FEXCore::IR::COND_EQ,
-    FTW, X87Zero,
-    OneConst, ZeroConst);
-
-  auto C2 = _Select(FEXCore::IR::COND_EQ,
-    FTW, X87Zero,
+    TopValid, OneConst,
     ZeroConst, OneConst);
 
+  auto C2 = TopValid;
   auto C0 = C3; // Mirror C3 until something other than zero is supported
   SetRFLAG<FEXCore::X86State::X87FLAG_C0_LOC>(C0);
   SetRFLAG<FEXCore::X86State::X87FLAG_C2_LOC>(C2);

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

@@ -306,11 +306,11 @@ namespace {
       FEXCore::IR::InvalidClass,
     });
 
-    // FTW
+    // AbridgedFTW
     ContextClassification->emplace_back(ContextMemberInfo {
       ContextMemberClassification {
-        offsetof(FEXCore::Core::CPUState, FTW),
-        sizeof(FEXCore::Core::CPUState::FTW),
+        offsetof(FEXCore::Core::CPUState, AbridgedFTW),
+        sizeof(FEXCore::Core::CPUState::AbridgedFTW),
       },
       ACCESS_NONE,
       FEXCore::IR::InvalidClass,

FEXCore/include/FEXCore/Core/CoreState.h

@@ -108,9 +108,9 @@ namespace FEXCore::Core {
       uint32_t base;
     } gdt[32]{};
     uint16_t FCW { 0x37F };
-    uint16_t FTW { 0xFFFF };
+    uint8_t AbridgedFTW{};
 
-    uint32_t _pad2[1];
+    uint8_t _pad2[5];
     // Reference counter for FEX's per-thread deferred signals.
     // Counts the nesting depth of program sections that cause signals to be deferred.
     NonAtomicRefCounter<uint64_t> DeferredSignalRefCount;

FEXCore/include/FEXCore/Utils/FPState.h

@@ -0,0 +1,12 @@
+#pragma once
+
+#include <cstdint>
+
+namespace FEXCore::FPState {
+  enum class X87Tag : uint8_t {
+    Valid   = 0b00,
+    Zero    = 0b01,
+    Special = 0b10,
+    Empty   = 0b11
+  };
+}