MIPS:[turbofan] Use Nor instruction for bit negation instead of xori.

src/compiler/mips64/code-generator-mips64.cc

Index: src/compiler/mips64/code-generator-mips64.cc
diff --git a/src/compiler/mips64/code-generator-mips64.cc b/src/compiler/mips64/code-generator-mips64.cc
index 6c0ee1a020ac6e7644c0c0d360278e4bd0156791..5b47b69a4784926103547365489c2649704bb557 100644
--- a/src/compiler/mips64/code-generator-mips64.cc
+++ b/src/compiler/mips64/code-generator-mips64.cc
@@ -678,7 +678,12 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       __ Or(i.OutputRegister(), i.InputRegister(0), i.InputOperand(1));
       break;
     case kMips64Nor:
-      __ Nor(i.OutputRegister(), i.InputRegister(0), i.InputOperand(1));
+      if (instr->InputAt(1)->IsRegister()) {
+        __ Nor(i.OutputRegister(), i.InputRegister(0), i.InputOperand(1));
+      } else {
+        DCHECK(i.InputOperand(1).immediate() == 0);
+        __ Nor(i.OutputRegister(), i.InputRegister(0), zero_reg);
+      }
       break;
     case kMips64Xor:
       __ Xor(i.OutputRegister(), i.InputRegister(0), i.InputOperand(1));