MIPS: Don't emit code for instructions that are hiding behind an HSoftDeoptimize

Port r13412 (36df819b)

BUG=
TEST=

Review URL: https://codereview.chromium.org/12022005
Patch from Akos Palfi <palfia@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13422 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/lithium-codegen-mips.cc

@@ -5620,6 +5620,11 @@ void LCodeGen::DoDeoptimize(LDeoptimize* instr) {
 }
 
 
+void LCodeGen::DoDummyUse(LDummyUse* instr) {
+  // Nothing to see here, move on!
+}
+
+
 void LCodeGen::DoDeleteProperty(LDeleteProperty* instr) {
   Register object = ToRegister(instr->object());
   Register key = ToRegister(instr->key());

src/mips/lithium-mips.cc

@@ -682,6 +682,11 @@ LInstruction* LChunkBuilder::DoBlockEntry(HBlockEntry* instr) {
 }
 
 
+LInstruction* LChunkBuilder::DoDummyUse(HDummyUse* instr) {
+  return DefineAsRegister(new(zone()) LDummyUse(UseAny(instr->value())));
+}
+
+
 LInstruction* LChunkBuilder::DoSoftDeoptimize(HSoftDeoptimize* instr) {
   return AssignEnvironment(new(zone()) LDeoptimize);
 }

src/mips/lithium-mips.h

@@ -93,6 +93,7 @@ class LCodeGen;
   V(Deoptimize)                                 \
   V(DivI)                                       \
   V(DoubleToI)                                  \
+  V(DummyUse)                                   \
   V(ElementsKind)                               \
   V(FastLiteral)                                \
   V(FixedArrayBaseLength)                       \
@@ -401,6 +402,15 @@ class LLazyBailout: public LTemplateInstruction<0, 0, 0> {
 };
 
 
+class LDummyUse: public LTemplateInstruction<1, 1, 0> {
+ public:
+  explicit LDummyUse(LOperand* value) {
+    inputs_[0] = value;
+  }
+  DECLARE_CONCRETE_INSTRUCTION(DummyUse, "dummy-use")
+};
+
+
 class LDeoptimize: public LTemplateInstruction<0, 0, 0> {
  public:
   DECLARE_CONCRETE_INSTRUCTION(Deoptimize, "deoptimize")