MIPS: Add big-endian support for MIPS.

src/mips/assembler-mips.h

Index: src/mips/assembler-mips.h
diff --git a/src/mips/assembler-mips.h b/src/mips/assembler-mips.h
index ea956e1355244d94d30544b9620ecd9462a68227..0afcb6e5399cdeb22ab5261383483dc9104e7ba5 100644
--- a/src/mips/assembler-mips.h
+++ b/src/mips/assembler-mips.h
@@ -77,6 +77,16 @@ struct Register {
   static const int kSizeInBytes = 4;
   static const int kCpRegister = 23;  // cp (s7) is the 23rd register.
 
+#if defined(V8_TARGET_LITTLE_ENDIAN)
+  static const int kMantissaOffset = 0;
+  static const int kExponentOffset = 4;
+#elif defined(V8_TARGET_BIG_ENDIAN)
+  static const int kMantissaOffset = 4;
+  static const int kExponentOffset = 0;
+#else
+#error Unknown endianness
+#endif
+
   inline static int NumAllocatableRegisters();
 
   static int ToAllocationIndex(Register reg) {