Implement byte swapping instructions on MIPS32 and 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 27a34b32bfa12f6a9110214ffdee5a86b6ff8459..69ad88724f8bad154035abf2dc091663ac29012e 100644
--- a/src/mips64/macro-assembler-mips64.h
+++ b/src/mips64/macro-assembler-mips64.h
@@ -722,6 +722,10 @@ class MacroAssembler: public Assembler {
   // ---------------------------------------------------------------------------
   // Pseudo-instructions.
 
+  // Change endianness
+  void ByteSwapSigned(Register reg, int operand_size);
+  void ByteSwapUnsigned(Register reg, int operand_size);
+
   void mov(Register rd, Register rt) { or_(rd, rt, zero_reg); }
 
   void Ulh(Register rd, const MemOperand& rs);