MIPS64: Add big-endian support for mips64.

src/mips64/macro-assembler-mips64.h

Index: src/mips64/macro-assembler-mips64.h
diff --git a/src/mips64/macro-assembler-mips64.h b/src/mips64/macro-assembler-mips64.h
index b374d43b797742b54f33bf2b547c23561cf3d776..00075492ef8022e24be9f0c85f98bc798e6a288c 100644
--- a/src/mips64/macro-assembler-mips64.h
+++ b/src/mips64/macro-assembler-mips64.h
@@ -1455,6 +1455,12 @@ const Operand& rt = Operand(zero_reg), BranchDelaySlot bd = PROTECT
   // -------------------------------------------------------------------------
   // Smi utilities.
 
+#if defined(V8_TARGET_LITTLE_ENDIAN)
+#define SmiWordOffset(offset) (offset + kPointerSize / 2)
+#else
+#define SmiWordOffset(offset) offset
+#endif
+
   // Test for overflow < 0: use BranchOnOverflow() or BranchOnNoOverflow().
   void SmiTagCheckOverflow(Register reg, Register overflow);
   void SmiTagCheckOverflow(Register dst, Register src, Register overflow);