Introduce %_IsMinusZero.

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index 281589e32cc7f42f7992369df3755281b5a542dd..c93d94124b1a7ddea900cbd4f7a5723b8429ac7f 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1672,6 +1672,15 @@ LInstruction* LChunkBuilder::DoCompareHoleAndBranch(
 }
 
 
+LInstruction* LChunkBuilder::DoCompareMinusZeroAndBranch(
+    HCompareMinusZeroAndBranch* instr) {
+  LInstruction* goto_instr = CheckElideControlInstruction(instr);
+  if (goto_instr != NULL) return goto_instr;
+  LOperand* value = UseRegister(instr->value());
+  return new(zone()) LCompareMinusZeroAndBranch(value);
+}
+
+
 LInstruction* LChunkBuilder::DoIsObjectAndBranch(HIsObjectAndBranch* instr) {
   ASSERT(instr->value()->representation().IsTagged());
   return new(zone()) LIsObjectAndBranch(UseRegisterAtStart(instr->value()));