Optimize redundant HCompareMap instructions with known successors.

src/mips/lithium-mips.cc

Index: src/mips/lithium-mips.cc
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index 6b1b982dc0106a0c3a08bd2389bb16fdd6881fa9..bb8e7502d80e4a19b5499778ceb2ce536344da4a 100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -945,6 +945,9 @@ LInstruction* LChunkBuilder::DoBranch(HBranch* instr) {
 
 
 LInstruction* LChunkBuilder::DoCompareMap(HCompareMap* instr) {
+  LInstruction* goto_instr = CheckElideControlInstruction(instr);
+  if (goto_instr != NULL) return goto_instr;
+
   ASSERT(instr->value()->representation().IsTagged());
   LOperand* value = UseRegisterAtStart(instr->value());
   LOperand* temp = TempRegister();