Arm64Emitter: Pull FillSpecialRegs bools into a struct

Makes this easily expandable over time without modifying the prototype,
and lets us be a little more informative at call sites.

FEXCore/Source/Interface/Core/ArchHelpers/Arm64Emitter.cpp

@@ -633,7 +633,7 @@ void Arm64Emitter::PopCalleeSavedRegisters() {
   }
 }
 
-void Arm64Emitter::FillSpecialRegs(ARMEmitter::Register TmpReg, ARMEmitter::Register TmpReg2, bool SetFIZ, bool SetPredRegs) {
+void Arm64Emitter::FillSpecialRegs(ARMEmitter::Register TmpReg, ARMEmitter::Register TmpReg2, const FillSpecialRegsOptions& Options) {
 #ifndef VIXL_SIMULATOR
   if (EmitterCTX->HostFeatures.SupportsAFP) {
     // Enable AFP features when filling JIT state.
@@ -649,7 +649,7 @@ void Arm64Emitter::FillSpecialRegs(ARMEmitter::Register TmpReg, ARMEmitter::Regi
         (1U << 2) |   // NEP
           (1U << 1)); // AH
 
-    if (SetFIZ) {
+    if (Options.SetFIZ) {
       // Insert MXCSR.DAZ in to FIZ
       ldr(TmpReg2.W(), STATE.R(), offsetof(FEXCore::Core::CPUState, mxcsr));
       bfxil(ARMEmitter::Size::i64Bit, TmpReg, TmpReg2, 6, 1);
@@ -659,7 +659,7 @@ void Arm64Emitter::FillSpecialRegs(ARMEmitter::Register TmpReg, ARMEmitter::Regi
   }
 #endif
 
-  if (SetPredRegs && EmitterCTX->HostFeatures.SupportsSVE()) {
+  if (Options.SetPredRegs && EmitterCTX->HostFeatures.SupportsSVE()) {
     // Set up predicate registers.
     // We don't bother spilling these in SpillStaticRegs,
     // since all that matters is we restore them on a fill.
@@ -822,7 +822,7 @@ void Arm64Emitter::FillStaticRegs(FillStaticRegOptions Options) {
     msr(ARMEmitter::SystemRegister::NZCV, TmpReg);
   }
 
-  FillSpecialRegs(TmpReg, TmpReg2, true, Options.FPRs);
+  FillSpecialRegs(TmpReg, TmpReg2, {.SetFIZ = true, .SetPredRegs = Options.FPRs});
 
   if (Options.FPRs) {
     if (EmitterCTX->HostFeatures.SupportsAVX && EmitterCTX->HostFeatures.SupportsSVE256) {

FEXCore/Source/Interface/Core/ArchHelpers/Arm64Emitter.h

@@ -129,7 +129,19 @@ protected:
   std::span<const ARMEmitter::VRegister> GeneralFPRegisters {};
   uint32_t PairRegisters = 0;
 
-  void FillSpecialRegs(ARMEmitter::Register TmpReg, ARMEmitter::Register TmpReg2, bool SetFIZ, bool SetPredRegs);
+  struct FillSpecialRegsOptions {
+    // Whether or not to set the FPCR.FIZ (flush inputs to zero) bit in the FPCR to
+    // the current value of the emulated MXCSR.DAZ bit.
+    // Will only attempt to do so, even when set to true, if and only if the host system
+    // supports FEAT_AFP.
+    bool SetFIZ {};
+
+    // Whether or not FillSpecialRegs should load our SVE predicate temporaries
+    // with certain canned values that accelerate some operations. Will (obviously)
+    // not load predicates, even if set to true, on host systems that do not support SVE.
+    bool SetPredRegs {};
+  };
+  void FillSpecialRegs(ARMEmitter::Register TmpReg, ARMEmitter::Register TmpReg2, const FillSpecialRegsOptions& Options);
 
   // Correlate an ARM register back to an x86 register index.
   // Returning REG_INVALID if there was no mapping.

FEXCore/Source/Interface/Core/Dispatcher/Dispatcher.cpp

@@ -121,7 +121,7 @@ void Dispatcher::EmitDispatcher() {
 
   ldr(REG_CALLRET_SP, STATE_PTR(CpuStateFrame, State.callret_sp));
 
-  FillSpecialRegs(TMP1, TMP2, false, true);
+  FillSpecialRegs(TMP1, TMP2, {.SetFIZ = false, .SetPredRegs = true});
 
   // As ARM64EC uses this as an entrypoint for both guest calls and host returns, opportunistically try to return
   // using the call-ret stack to avoid unbalancing it.