MIPS: Let the register allocator handle the context register.

src/mips/assembler-mips.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 54 matching lines @@
 // mode. This way we get the compile-time error checking in debug mode
 // and best performance in optimized code.
 
 
 // -----------------------------------------------------------------------------
 // Implementation of Register and FPURegister.
 
 // Core register.
 struct Register {
   static const int kNumRegisters = v8::internal::kNumRegisters;
-  static const int kMaxNumAllocatableRegisters = 14;  // v0 through t7.
+  static const int kMaxNumAllocatableRegisters = 14;  // v0 through t6 and cp.
   static const int kSizeInBytes = 4;
+  static const int kCpRegister = 23;  // cp (s7) is the 23rd register.
 
   inline static int NumAllocatableRegisters();
 
   static int ToAllocationIndex(Register reg) {
-    return reg.code() - 2;  // zero_reg and 'at' are skipped.
+    ASSERT((reg.code() - 2) < (kMaxNumAllocatableRegisters - 1) ||
+           reg.is(from_code(kCpRegister)));
+    return reg.is(from_code(kCpRegister)) ?
+           kMaxNumAllocatableRegisters - 1 :  // Return last index for 'cp'.
+           reg.code() - 2;  // zero_reg and 'at' are skipped.
   }
 
   static Register FromAllocationIndex(int index) {
     ASSERT(index >= 0 && index < kMaxNumAllocatableRegisters);
-    return from_code(index + 2);  // zero_reg and 'at' are skipped.
+    return index == kMaxNumAllocatableRegisters - 1 ?
+           from_code(kCpRegister) :  // Last index is always the 'cp' register.
+           from_code(index + 2);  // zero_reg and 'at' are skipped.
   }
 
   static const char* AllocationIndexToString(int index) {
     ASSERT(index >= 0 && index < kMaxNumAllocatableRegisters);
     const char* const names[] = {
       "v0",
       "v1",
       "a0",
       "a1",
       "a2",
       "a3",
       "t0",
       "t1",
       "t2",
       "t3",
       "t4",
       "t5",
       "t6",
-      "t7",
+      "s7",
     };
     return names[index];
   }
 
   static Register from_code(int code) {
     Register r = { code };
     return r;
   }
 
   bool is_valid() const { return 0 <= code_ && code_ < kNumRegisters; }
@@ skipping 1095 matching lines @@
 class EnsureSpace BASE_EMBEDDED {
  public:
   explicit EnsureSpace(Assembler* assembler) {
     assembler->CheckBuffer();
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_ARM_ASSEMBLER_MIPS_H_