MIPS: Remove extranous holder load in some prototype-chain checking cases

Port r14136 (d091bc0e)

BUG=

Review URL: https://codereview.chromium.org/13636002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14142 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/lithium-codegen-mips.cc

@@ -5207,7 +5207,6 @@ void LCodeGen::DoClampTToUint8(LClampTToUint8* instr) {
 
 
 void LCodeGen::DoCheckPrototypeMaps(LCheckPrototypeMaps* instr) {
-  ASSERT(instr->temp()->Equals(instr->result()));
   Register prototype_reg = ToRegister(instr->temp());
   Register map_reg = ToRegister(instr->temp2());
 
@@ -5220,8 +5219,6 @@ void LCodeGen::DoCheckPrototypeMaps(LCheckPrototypeMaps* instr) {
     for (int i = 0; i < maps->length(); i++) {
       prototype_maps_.Add(maps->at(i), info()->zone());
     }
-    __ LoadHeapObject(prototype_reg,
-                      prototypes->at(prototypes->length() - 1));
   } else {
     for (int i = 0; i < prototypes->length(); i++) {
       __ LoadHeapObject(prototype_reg, prototypes->at(i));

src/mips/lithium-mips.cc

@@ -1807,7 +1807,7 @@ LInstruction* LChunkBuilder::DoCheckPrototypeMaps(HCheckPrototypeMaps* instr) {
   LUnallocated* temp1 = TempRegister();
   LOperand* temp2 = TempRegister();
   LCheckPrototypeMaps* result = new(zone()) LCheckPrototypeMaps(temp1, temp2);
-  return AssignEnvironment(Define(result, temp1));
+  return AssignEnvironment(result);
 }
 
 

src/mips/lithium-mips.h

@@ -2184,7 +2184,7 @@ class LCheckMaps: public LTemplateInstruction<0, 1, 0> {
 };
 
 
-class LCheckPrototypeMaps: public LTemplateInstruction<1, 0, 2> {
+class LCheckPrototypeMaps: public LTemplateInstruction<0, 0, 2> {
  public:
   LCheckPrototypeMaps(LOperand* temp, LOperand* temp2)  {
     temps_[0] = temp;