MIPS: Refactor simulator and add selection instructions for r6.

src/mips/constants-mips.cc

Index: src/mips/constants-mips.cc
diff --git a/src/mips/constants-mips.cc b/src/mips/constants-mips.cc
index 30e4b2e003bce967e7c2ce868b6150797b529c02..419462311a4a0063e80f2922e92478fae70de539 100644
--- a/src/mips/constants-mips.cc
+++ b/src/mips/constants-mips.cc
@@ -252,6 +252,8 @@ Instruction::Type Instruction::InstructionType() const {
         case MOVZ:
         case MOVN:
         case MOVCI:
+        case SELEQZ_S:
+        case SELNEZ_S:
           return kRegisterType;
         default:
           return kUnsupported;
@@ -280,6 +282,8 @@ Instruction::Type Instruction::InstructionType() const {
         case BC1:   // Branch on coprocessor condition.
         case BC1EQZ:
         case BC1NEZ:
+        case SELEQZ_C:
+        case SELNEZ_C:
           return kImmediateType;
         default:
           return kRegisterType;