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

src/full-codegen/mips/full-codegen-mips.cc

Index: src/full-codegen/mips/full-codegen-mips.cc
diff --git a/src/full-codegen/mips/full-codegen-mips.cc b/src/full-codegen/mips/full-codegen-mips.cc
index 3a322ea315c863e48ed991e728f303bd60dc59a5..08ba63ffb3ad976bf1aaf3f86788e773f1d83da3 100644
--- a/src/full-codegen/mips/full-codegen-mips.cc
+++ b/src/full-codegen/mips/full-codegen-mips.cc
@@ -2363,8 +2363,7 @@ void FullCodeGenerator::EmitInlineSmiBinaryOp(BinaryOperation* expr,
       break;
     }
     case Token::ADD:
-      __ AdduAndCheckForOverflow(v0, left, right, scratch1);
-      __ BranchOnOverflow(&stub_call, scratch1);
+      __ AdduAndCheckForOverflow(v0, left, right, &stub_call, nullptr);
       break;
     case Token::SUB:
       __ SubuAndCheckForOverflow(v0, left, right, scratch1);
@@ -4031,8 +4030,8 @@ void FullCodeGenerator::EmitFastOneByteArrayJoin(CallRuntime* expr) {
   __ lbu(scratch1, FieldMemOperand(scratch1, Map::kInstanceTypeOffset));
   __ JumpIfInstanceTypeIsNotSequentialOneByte(scratch1, scratch2, &bailout);
   __ lw(scratch1, FieldMemOperand(string, SeqOneByteString::kLengthOffset));
-  __ AdduAndCheckForOverflow(string_length, string_length, scratch1, scratch3);
-  __ BranchOnOverflow(&bailout, scratch3);
+  __ AdduAndCheckForOverflow(string_length, string_length, scratch1, &bailout,
+                             nullptr);
   __ Branch(&loop, lt, element, Operand(elements_end));
 
   // If array_length is 1, return elements[0], a string.
@@ -4065,8 +4064,8 @@ void FullCodeGenerator::EmitFastOneByteArrayJoin(CallRuntime* expr) {
   __ Branch(&bailout, ne, scratch3, Operand(zero_reg));
   __ And(scratch3, scratch2, Operand(0x80000000));
   __ Branch(&bailout, ne, scratch3, Operand(zero_reg));
-  __ AdduAndCheckForOverflow(string_length, string_length, scratch2, scratch3);
-  __ BranchOnOverflow(&bailout, scratch3);
+  __ AdduAndCheckForOverflow(string_length, string_length, scratch2, &bailout,
+                             nullptr);
   __ SmiUntag(string_length);
 
   // Bailout for large object allocations.
@@ -4536,10 +4535,8 @@ void FullCodeGenerator::VisitCountOperation(CountOperation* expr) {
     }
 
     Register scratch1 = a1;
-    Register scratch2 = t0;
     __ li(scratch1, Operand(Smi::FromInt(count_value)));
-    __ AdduAndCheckForOverflow(v0, v0, scratch1, scratch2);
-    __ BranchOnNoOverflow(&done, scratch2);
+    __ AdduAndCheckForOverflow(v0, v0, scratch1, nullptr, &done);
     // Call stub. Undo operation first.
     __ Move(v0, a0);
     __ jmp(&stub_call);