Thumbulator optimizations.

Pre-decode ROM image and turn instruction dispatch into a switch.

src/emucore/CartBUS.cxx

@@ -67,7 +67,7 @@ CartridgeBUS::CartridgeBUS(const BytePtr& image, uInt32 size,
   // Create Thumbulator ARM emulator
   bool devSettings = settings.getBool("dev.settings");
   myThumbEmulator = make_unique<Thumbulator>(
-    reinterpret_cast<uInt16*>(myImage), reinterpret_cast<uInt16*>(myBUSRAM),
+    reinterpret_cast<uInt16*>(myImage), reinterpret_cast<uInt16*>(myBUSRAM), 32768,
     devSettings ? settings.getBool("dev.thumb.trapfatal") : false, Thumbulator::ConfigureFor::BUS, this
   );
 

src/emucore/CartCDF.cxx

@@ -70,7 +70,7 @@ CartridgeCDF::CartridgeCDF(const BytePtr& image, uInt32 size,
   // Create Thumbulator ARM emulator
   bool devSettings = settings.getBool("dev.settings");
   myThumbEmulator = make_unique<Thumbulator>(
-    reinterpret_cast<uInt16*>(myImage), reinterpret_cast<uInt16*>(myCDFRAM),
+    reinterpret_cast<uInt16*>(myImage), reinterpret_cast<uInt16*>(myCDFRAM), 32768,
     devSettings ? settings.getBool("dev.thumb.trapfatal") : false, myVersion ?
     Thumbulator::ConfigureFor::CDF1 : Thumbulator::ConfigureFor::CDF, this);
 

src/emucore/CartDPCPlus.cxx

@@ -58,6 +58,7 @@ CartridgeDPCPlus::CartridgeDPCPlus(const BytePtr& image, uInt32 size,
   myThumbEmulator = make_unique<Thumbulator>
       (reinterpret_cast<uInt16*>(myImage),
        reinterpret_cast<uInt16*>(myDPCRAM),
+       32768,
        devSettings ? settings.getBool("dev.thumb.trapfatal") : false,
        Thumbulator::ConfigureFor::DPCplus,
        this);

src/emucore/Thumbulator.hxx

@@ -53,7 +53,7 @@ class Thumbulator
       DPCplus   // cartridges of type DPC+
     };
 
-    Thumbulator(const uInt16* rom, uInt16* ram, bool traponfatal,
+    Thumbulator(const uInt16* rom, uInt16* ram, uInt32 romSize, bool traponfatal,
                 Thumbulator::ConfigureFor configurefor, Cartridge* cartridge);
 
     /**
@@ -88,6 +88,58 @@ class Thumbulator
     */
     void setConsoleTiming(ConsoleTiming timing);
 
+  private:
+
+    enum class Op : uInt8 {
+      invalid,
+      adc,
+      add1, add2, add3, add4, add5, add6, add7,
+      and_,
+      asr1, asr2,
+      b1, b2,
+      bic,
+      bkpt,
+      blx1, blx2,
+      bx,
+      cmn,
+      cmp1, cmp2, cmp3,
+      cps,
+      cpy,
+      eor,
+      ldmia,
+      ldr1, ldr2, ldr3, ldr4,
+      ldrb1, ldrb2,
+      ldrh1, ldrh2,
+      ldrsb,
+      ldrsh,
+      lsl1, lsl2,
+      lsr1, lsr2,
+      mov1, mov2, mov3,
+      mul,
+      mvn,
+      neg,
+      orr,
+      pop,
+      push,
+      rev,
+      rev16,
+      revsh,
+      ror,
+      sbc,
+      setend,
+      stmia,
+      str1, str2, str3,
+      strb1, strb2,
+      strh1, strh2,
+      sub1, sub2, sub3, sub4,
+      swi,
+      sxtb,
+      sxth,
+      tst,
+      uxtb,
+      uxth
+    };
+
   private:
     uInt32 read_register(uInt32 reg);
     void write_register(uInt32 reg, uInt32 data);
@@ -100,6 +152,8 @@ class Thumbulator
     void write32(uInt32 addr, uInt32 data);
     void updateTimer(uInt32 cycles);
 
+    static Op decodeInstructionWord(uint16_t inst);
+
     void do_zflag(uInt32 x);
     void do_nflag(uInt32 x);
     void do_cflag(uInt32 a, uInt32 b, uInt32 c);
@@ -120,6 +174,8 @@ class Thumbulator
 
   private:
     const uInt16* rom;
+    uInt16 romSize;
+    const unique_ptr<Op[]> decodedRom;
     uInt16* ram;
 
     uInt32 reg_norm[16]; // normal execution mode, do not have a thread mode