Merge pull request #7113 from lioncash/mask

Gekko: Centralize bitmasking of the FPSCR within UReg_FPSCR

Source/Core/Core/PowerPC/Gekko.h

@@ -474,8 +474,37 @@ union UReg_FPSCR
   };
   u32 Hex = 0;
 
+  // The FPSCR's 20th bit (11th from a little endian perspective)
+  // is defined as reserved and set to zero. Attempts to modify it
+  // are ignored by hardware, so we do the same.
+  static constexpr u32 mask = 0xFFFFF7FF;
+
   UReg_FPSCR() = default;
-  explicit UReg_FPSCR(u32 hex_) : Hex{hex_} {}
+  explicit UReg_FPSCR(u32 hex_) : Hex{hex_ & mask} {}
+
+  UReg_FPSCR& operator=(u32 value)
+  {
+    Hex = value & mask;
+    return *this;
+  }
+
+  UReg_FPSCR& operator|=(u32 value)
+  {
+    Hex |= value & mask;
+    return *this;
+  }
+
+  UReg_FPSCR& operator&=(u32 value)
+  {
+    Hex &= value;
+    return *this;
+  }
+
+  UReg_FPSCR& operator^=(u32 value)
+  {
+    Hex ^= value & mask;
+    return *this;
+  }
 
   void ClearFIFR()
   {

Source/Core/Core/PowerPC/Interpreter/Interpreter_SystemRegisters.cpp

@@ -62,20 +62,14 @@ void Interpreter::mtfsb0x(UGeckoInstruction inst)
 void Interpreter::mtfsb1x(UGeckoInstruction inst)
 {
   const u32 bit = inst.CRBD;
+  const u32 b = 0x80000000 >> bit;
 
-  // Bit 20 in the FPSCR is reserved and defined as zero,
-  // so we ensure that we don't set it.
-  if (bit != 20)
-  {
-    const u32 b = 0x80000000 >> bit;
+  if (b & FPSCR_ANY_X)
+    SetFPException(b);
+  else
+    FPSCR |= b;
 
-    if (b & FPSCR_ANY_X)
-      SetFPException(b);
-    else
-      FPSCR.Hex |= b;
-
-    FPSCRtoFPUSettings(FPSCR);
-  }
+  FPSCRtoFPUSettings(FPSCR);
 
   if (inst.Rc)
     Helper_UpdateCR1();
@@ -83,14 +77,12 @@ void Interpreter::mtfsb1x(UGeckoInstruction inst)
 
 void Interpreter::mtfsfix(UGeckoInstruction inst)
 {
-  // Bit 20 of the FPSCR is reserved and defined as zero on hardware,
-  // so ensure that we don't set it.
   const u32 field = inst.CRFD;
-  const u32 pre_shifted_mask = field == 4 ? 0x70000000 : 0xF0000000;
+  const u32 pre_shifted_mask = 0xF0000000;
   const u32 mask = (pre_shifted_mask >> (4 * field));
   const u32 imm = (inst.hex << 16) & pre_shifted_mask;
 
-  FPSCR.Hex = (FPSCR.Hex & ~mask) | (imm >> (4 * field));
+  FPSCR = (FPSCR.Hex & ~mask) | (imm >> (4 * field));
 
   FPSCRtoFPUSettings(FPSCR);
 
@@ -108,13 +100,7 @@ void Interpreter::mtfsfx(UGeckoInstruction inst)
       m |= (0xFU << (i * 4));
   }
 
-  // Bit 20 of the FPSCR is defined as always being zero
-  // (bit 11 in a little endian context), so ensure that
-  // we don't actually set that bit.
-  if ((fm & 0b100) != 0)
-    m &= 0xFFFFF7FF;
-
-  FPSCR.Hex = (FPSCR.Hex & ~m) | (static_cast<u32>(riPS0(inst.FB)) & m);
+  FPSCR = (FPSCR.Hex & ~m) | (static_cast<u32>(riPS0(inst.FB)) & m);
   FPSCRtoFPUSettings(FPSCR);
 
   if (inst.Rc)

Source/Core/DolphinQt2/Debugger/RegisterWidget.cpp

@@ -290,7 +290,7 @@ void RegisterWidget::PopulateTable()
 
   // FPSCR
   AddRegister(22, 5, RegisterType::fpscr, "FPSCR", [] { return PowerPC::ppcState.fpscr.Hex; },
-              [](u64 value) { PowerPC::ppcState.fpscr.Hex = value; });
+              [](u64 value) { PowerPC::ppcState.fpscr = static_cast<u32>(value); });
 
   // MSR
   AddRegister(23, 5, RegisterType::msr, "MSR", [] { return PowerPC::ppcState.msr.Hex; },

Source/Core/DolphinWX/Debugger/RegisterView.cpp

@@ -124,7 +124,7 @@ void SetSpecialRegValue(int reg, u32 value)
     PowerPC::SetXER(UReg_XER(value));
     break;
   case 5:
-    PowerPC::ppcState.fpscr.Hex = value;
+    PowerPC::ppcState.fpscr = value;
     break;
   case 6:
     PowerPC::ppcState.msr.Hex = value;