Optimization: Do not assign an environment to LBranch when are sure that we will never deopt later.

src/ia32/lithium-ia32.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1024 matching lines @@
   HValue* v = instr->value();
   if (v->EmitAtUses()) {
     ASSERT(v->IsConstant());
     ASSERT(!v->representation().IsDouble());
     HBasicBlock* successor = HConstant::cast(v)->ToBoolean()
         ? instr->FirstSuccessor()
         : instr->SecondSuccessor();
     return new LGoto(successor->block_id());
   }
   ToBooleanStub::Types expected = instr->expected_input_types();
+  // We need a temporary register when we have to access the map *or* we have
+  // no type info yet, in which case we handle all cases (including the ones
+  // involving maps).
   bool needs_temp = expected.NeedsMap() || expected.IsEmpty();
   LOperand* temp = needs_temp ? TempRegister() : NULL;
-  return AssignEnvironment(new LBranch(UseRegister(v), temp));
+  LInstruction* branch = new LBranch(UseRegister(v), temp);
+  // When we handle all cases, we never deopt, so we don't need to assign the
+  // environment then.
+  return expected.IsAll() ? branch : AssignEnvironment(branch);
 }
 
 
 LInstruction* LChunkBuilder::DoCompareMap(HCompareMap* instr) {
   ASSERT(instr->value()->representation().IsTagged());
   LOperand* value = UseRegisterAtStart(instr->value());
   return new LCmpMapAndBranch(value);
 }
 
 
@@ skipping 1201 matching lines @@
   LOperand* key = UseOrConstantAtStart(instr->key());
   LOperand* object = UseOrConstantAtStart(instr->object());
   LIn* result = new LIn(context, key, object);
   return MarkAsCall(DefineFixed(result, eax), instr);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32