CPU/Recompiler: Optimize away nops completely

35% performance improvement for PGXP CPU mode in Racing Lagoon.

src/core/cpu_recompiler_code_generator.cpp

@@ -65,6 +65,13 @@ bool CodeGenerator::CompileBlock(CodeBlock* block, CodeBlock::HostCodePointer* o
 
 bool CodeGenerator::CompileInstruction(const CodeBlockInstruction& cbi)
 {
+  if (IsNopInstruction(cbi.instruction))
+  {
+    InstructionPrologue(cbi, 1);
+    InstructionEpilogue(cbi);
+    return true;
+  }
+
   bool result;
   switch (cbi.instruction.op)
   {

src/core/cpu_recompiler_code_generator.h

@@ -214,6 +214,7 @@ private:
   //////////////////////////////////////////////////////////////////////////
   bool CompileInstruction(const CodeBlockInstruction& cbi);
   bool Compile_Fallback(const CodeBlockInstruction& cbi);
+  bool Compile_Nop(const CodeBlockInstruction& cbi);
   bool Compile_Bitwise(const CodeBlockInstruction& cbi);
   bool Compile_Shift(const CodeBlockInstruction& cbi);
   bool Compile_Load(const CodeBlockInstruction& cbi);

src/core/cpu_types.cpp

@@ -13,6 +13,12 @@ const char* GetRegName(Reg reg)
   return s_reg_names[static_cast<u8>(reg)];
 }
 
+bool IsNopInstruction(const Instruction& instruction)
+{
+  // TODO: Handle other types of nop.
+  return (instruction.bits == 0);
+}
+
 bool IsBranchInstruction(const Instruction& instruction)
 {
   switch (instruction.op)

src/core/cpu_types.h

@@ -220,6 +220,7 @@ union Instruction
 };
 
 // Instruction helpers.
+bool IsNopInstruction(const Instruction& instruction);
 bool IsBranchInstruction(const Instruction& instruction);
 bool IsUnconditionalBranchInstruction(const Instruction& instruction);
 bool IsDirectBranchInstruction(const Instruction& instruction);