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

src/mips/assembler-mips.cc

Index: src/mips/assembler-mips.cc
diff --git a/src/mips/assembler-mips.cc b/src/mips/assembler-mips.cc
index 1962e9aa31a755d72e275fcbdada018ea880f2cb..42d93e1817b21944e7f699af459c0a1daba6d00c 100644
--- a/src/mips/assembler-mips.cc
+++ b/src/mips/assembler-mips.cc
@@ -1336,17 +1336,23 @@ void Assembler::bne(Register rs, Register rt, int16_t offset) {
 
 void Assembler::bovc(Register rs, Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
-  DCHECK(!(rs.is(zero_reg)));
-  DCHECK(rs.code() >= rt.code());
-  GenInstrImmediate(ADDI, rs, rt, offset, CompactBranchType::COMPACT_BRANCH);
+  DCHECK(!rs.is(zero_reg));
+  if (rs.code() >= rt.code()) {
+    GenInstrImmediate(ADDI, rs, rt, offset, CompactBranchType::COMPACT_BRANCH);
+  } else {
+    GenInstrImmediate(ADDI, rt, rs, offset, CompactBranchType::COMPACT_BRANCH);
+  }
 }
 
 
 void Assembler::bnvc(Register rs, Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
-  DCHECK(!(rs.is(zero_reg)));
-  DCHECK(rs.code() >= rt.code());
-  GenInstrImmediate(DADDI, rs, rt, offset, CompactBranchType::COMPACT_BRANCH);
+  DCHECK(!rs.is(zero_reg));
+  if (rs.code() >= rt.code()) {
+    GenInstrImmediate(DADDI, rs, rt, offset, CompactBranchType::COMPACT_BRANCH);
+  } else {
+    GenInstrImmediate(DADDI, rt, rs, offset, CompactBranchType::COMPACT_BRANCH);
+  }
 }