As a first step towards implementing thumb2, add code for...

src/arm/simulator-arm.cc

Index: src/arm/simulator-arm.cc
===================================================================
--- src/arm/simulator-arm.cc	(revision 3473)
+++ src/arm/simulator-arm.cc	(working copy)
@@ -421,6 +421,7 @@
   stack_ = reinterpret_cast<char*>(malloc(stack_size));
   pc_modified_ = false;
   icount_ = 0;
+  thumb_mode_ = false;
   break_pc_ = NULL;
   break_instr_ = 0;
 
@@ -2074,6 +2075,12 @@
                            reinterpret_cast<byte*>(instr));
     PrintF("  0x%08x  %s\n", instr, buffer.start());
   }
+  // Temporary special-casing of our particular ARM/THUMB switch

[Erik Corry, 2009/12/17 14:05:50]

I think this can be moved to where it fits (in the sub instruction somewhere).

+  if ((unsigned)instr->InstructionBits() == 0xe24ff003) {
+    thumb_mode_ = true;
+    set_register(pc, reinterpret_cast<int32_t>(instr) + Instr::kInstrSize);
+    return;
+  }
   if (instr->ConditionField() == special_condition) {
     DecodeUnconditional(instr);
   } else if (ConditionallyExecute(instr)) {
@@ -2118,6 +2125,11 @@
   }
 }
 
+void Simulator::InstructionDecode(ThumbInstr* instr) {
+  // For now, assume all thumb instructions are an aligned switch back to ARM

[Erik Corry, 2009/12/17 14:05:50]

Please assert this is true.

+  set_register(pc, reinterpret_cast<int32_t>(instr) + Instr::kInstrSize);
+  thumb_mode_ = false;
+}
 
 void Simulator::Execute() {
   // Get the PC to simulate. Cannot use the accessor here as we need the
@@ -2128,9 +2140,14 @@
     // Fast version of the dispatch loop without checking whether the simulator
     // should be stopping at a particular executed instruction.
     while (program_counter != end_sim_pc) {
-      Instr* instr = reinterpret_cast<Instr*>(program_counter);
+      if (thumb_mode_) {
+        ThumbInstr* instr = reinterpret_cast<ThumbInstr*>(program_counter);
+        InstructionDecode(instr);
+      } else {
+        Instr* instr = reinterpret_cast<Instr*>(program_counter);
+        InstructionDecode(instr);
+      }
       icount_++;
-      InstructionDecode(instr);
       program_counter = get_pc();
     }
   } else {