MIPS: Use BOVC/BNVC for overflow checking on r6.

src/crankshaft/mips/lithium-codegen-mips.cc

 // Copyright 2012 the V8 project authors. All rights reserved.7
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1836 matching lines @@
 
   if (!can_overflow) {
     if (right->IsStackSlot()) {
       Register right_reg = EmitLoadRegister(right, at);
       __ Addu(ToRegister(result), ToRegister(left), Operand(right_reg));
     } else {
       DCHECK(right->IsRegister() || right->IsConstantOperand());
       __ Addu(ToRegister(result), ToRegister(left), ToOperand(right));
     }
   } else {  // can_overflow.
-    Register overflow = scratch0();
     Register scratch = scratch1();
+    Label no_overflow;
     if (right->IsStackSlot()) {
       Register right_reg = EmitLoadRegister(right, scratch);
-      __ AdduAndCheckForOverflow(ToRegister(result),
-                                 ToRegister(left),
-                                 right_reg,
-                                 overflow);  // Reg at also used as scratch.
+      __ AdduAndCheckForOverflow(ToRegister(result), ToRegister(left),
+                                 right_reg, nullptr,
+                                 &no_overflow);  // Reg at also used as scratch.
     } else {
       DCHECK(right->IsRegister() || right->IsConstantOperand());
       __ AdduAndCheckForOverflow(ToRegister(result), ToRegister(left),
-                                 ToOperand(right), overflow, scratch);
+                                 ToOperand(right), nullptr, &no_overflow,
+                                 scratch);
     }
-    DeoptimizeIf(lt, instr, Deoptimizer::kOverflow, overflow,
-                 Operand(zero_reg));
+    DeoptimizeIf(al, instr);
+    __ bind(&no_overflow);
   }
 }
 
 
 void LCodeGen::DoMathMinMax(LMathMinMax* instr) {
   LOperand* left = instr->left();
   LOperand* right = instr->right();
   HMathMinMax::Operation operation = instr->hydrogen()->operation();
   Condition condition = (operation == HMathMinMax::kMathMin) ? le : ge;
   if (instr->hydrogen()->representation().IsSmiOrInteger32()) {
@@ skipping 3946 matching lines @@
   __ Push(at, ToRegister(instr->function()));
   CallRuntime(Runtime::kPushBlockContext, 2, instr);
   RecordSafepoint(Safepoint::kNoLazyDeopt);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8