use much faster exp2/cos approximations in ffmpeg, large decrease in cpu usage on my machine on decoder thread

properly byteswap r13 for spinlock
Add PPCOpcodeBits
stub out broken fpscr updating in ppc_hir_builder. it's just code that repeatedly does nothing right now.
add note about 0 opcode bytes being executed to ppc_frontend
Add assert to check that function end is greater than function start, can happen with malformed functions
Disable prefetch and cachecontrol by default, automatic hardware prefetchers already do the job for the most part
minor cleanup in simplification_pass, dont loop optimizations, let the pass manager do it for us
Add experimental "delay_via_maybeyield" cvar, which uses MaybeYield to "emulate" the db16cyc instruction
Add much faster/simpler way of directly calling guest functions, no longer have to do a byte by byte search through the generated code
Generate label string ids on the fly
Fix unused function warnings for prefetch on clang, fix many other clang warnings
Eliminated majority of CallNativeSafes by replacing them with naive generic code paths.
^ Vector rotate left, vector shift left, vector shift right, vector shift arithmetic right, and vector average are included
These naive paths are implemented small loops that stash the two inputs to the stack and load them in gprs from there, they are not particularly fast but should be an order of magnitude faster than callnativesafe
to a host function, which would involve a call, stashing all volatile registers, an indirect call, potentially setting up a stack frame for the arrays that the inputs get stashed to, the actual operations, a return, loading all volatile registers, a return, etc
Added the fast SHR_V128 path back in
Implement signed vector average byte, signed vector average word. previously we were emitting no code for them. signed vector average byte appears in many games
Fix bug with signed vector average 32, we were doing unsigned shift, turning negative values into big positive ones potentially

src/xenia/cpu/backend/x64/x64_emitter.h

@@ -172,7 +172,9 @@ enum XmmConst {
   XMMLVLShuffle,
   XMMLVRCmp16,
   XMMSTVLShuffle,
-  XMMSTVRSwapMask  // swapwordmask with bit 7 set
+  XMMSTVRSwapMask,  // swapwordmask with bit 7 set
+  XMMVSRShlByteshuf,
+  XMMVSRMask
 
 };
 using amdfx::xopcompare_e;
@@ -190,13 +192,6 @@ class XbyakAllocator : public Xbyak::Allocator {
   virtual bool useProtect() const { return false; }
 };
 
-class ResolvableGuestCall {
- public:
-  bool is_jump_;
-  uintptr_t destination_;
-  // rgcid
-  unsigned offset_;
-};
 class X64Emitter;
 using TailEmitCallback = std::function<void(X64Emitter& e, Xbyak::Label& lbl)>;
 struct TailEmitter {
@@ -220,7 +215,6 @@ class X64Emitter : public Xbyak::CodeGenerator {
             uint32_t debug_info_flags, FunctionDebugInfo* debug_info,
             void** out_code_address, size_t* out_code_size,
             std::vector<SourceMapEntry>* out_source_map);
-  void InjectCallAddresses(void* new_execute_addr);
 
  public:
   // Reserved:  rsp, rsi, rdi
@@ -230,7 +224,7 @@ class X64Emitter : public Xbyak::CodeGenerator {
   //            xmm4-xmm15 (save to get xmm3)
   static const int GPR_COUNT = 7;
   static const int XMM_COUNT = 12;
-
+  static constexpr size_t kStashOffset = 32;
   static void SetupReg(const hir::Value* v, Xbyak::Reg8& r) {
     auto idx = gpr_reg_map_[v->reg.index];
     r = Xbyak::Reg8(idx);
@@ -410,8 +404,6 @@ class X64Emitter : public Xbyak::CodeGenerator {
 
   static const uint32_t gpr_reg_map_[GPR_COUNT];
   static const uint32_t xmm_reg_map_[XMM_COUNT];
-  uint32_t current_rgc_id_ = 0xEEDDF00F;
-  std::vector<ResolvableGuestCall> call_sites_;
   /*
     set to true if the low 32 bits of membase == 0.
     only really advantageous if you are storing 32 bit 0 to a displaced address,