[turbofan] Added the optional Float64RoundTiesEven operator to turbofan.

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 117e8cafd0b2d1dcbfbbcdd90617e7d64a6999e2..e0e291311c35f3efba7207c5168ee728fd1c5640 100644
--- a/src/compiler/mips64/code-generator-mips64.cc
+++ b/src/compiler/mips64/code-generator-mips64.cc
@@ -213,6 +213,13 @@ class OutOfLineCeil final : public OutOfLineRound {
 };
 
 
+class OutOfLineTiesEven final : public OutOfLineRound {
+ public:
+  OutOfLineTiesEven(CodeGenerator* gen, DoubleRegister result)
+      : OutOfLineRound(gen, result) {}
+};
+
+
 class OutOfLineRecordWrite final : public OutOfLineCode {
  public:
   OutOfLineRecordWrite(CodeGenerator* gen, Register object, Register index,
@@ -861,6 +868,10 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       ASSEMBLE_ROUND_DOUBLE_TO_DOUBLE(ceil_l_d, Ceil);
       break;
     }
+    case kMips64Float64RoundTiesEven: {
+      ASSEMBLE_ROUND_DOUBLE_TO_DOUBLE(round_l_d, TiesEven);
+      break;
+    }
     case kMips64Float64Max: {
       // (b < a) ? a : b
       if (kArchVariant == kMips64r6) {