Improve and simplify removal of unreachable code

src/x64/lithium-x64.cc

 // Copyright 2012 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 979 matching lines @@
 LInstruction* LChunkBuilder::DoDebugBreak(HDebugBreak* instr) {
   return new(zone()) LDebugBreak();
 }
 
 
 LInstruction* LChunkBuilder::DoBranch(HBranch* instr) {
   HValue* value = instr->value();
   if (value->EmitAtUses()) {
     ASSERT(value->IsConstant());
     ASSERT(!value->representation().IsDouble());
-    HBasicBlock* successor = HConstant::cast(value)->BooleanValue()
-        ? instr->FirstSuccessor()
-        : instr->SecondSuccessor();
-    return new(zone()) LGoto(successor->block_id());
+    return ElideControlInstruction(instr,
+                                   HConstant::cast(value)->BooleanValue());
   }
 
   LBranch* result = new(zone()) LBranch(UseRegister(value));
   // Tagged values that are not known smis or booleans require a
   // deoptimization environment. If the instruction is generic no
   // environment is needed since all cases are handled.
   ToBooleanStub::Types expected = instr->expected_input_types();
   Representation rep = value->representation();
   HType type = value->type();
   if (rep.IsTagged() && !type.IsSmi() && !type.IsBoolean() &&
@@ skipping 616 matching lines @@
       left = UseRegisterAtStart(instr->left());
       right = UseRegisterAtStart(instr->right());
     }
     return new(zone()) LCompareNumericAndBranch(left, right);
   }
 }
 
 
 LInstruction* LChunkBuilder::DoCompareObjectEqAndBranch(
     HCompareObjectEqAndBranch* instr) {
+  if (instr->left()->IsConstant() && instr->right()->IsConstant()) {
+    bool comparison_result =
+        HConstant::cast(instr->left())->SameConstantObject(
+            HConstant::cast(instr->right()));
+    return ElideControlInstruction(instr, comparison_result);
+  }
+
   LOperand* left = UseRegisterAtStart(instr->left());
   LOperand* right = UseRegisterOrConstantAtStart(instr->right());
   return new(zone()) LCmpObjectEqAndBranch(left, right);
 }
 
 
 LInstruction* LChunkBuilder::DoCompareHoleAndBranch(
     HCompareHoleAndBranch* instr) {
   LOperand* object = UseRegisterAtStart(instr->object());
   return new(zone()) LCmpHoleAndBranch(object);
@@ skipping 882 matching lines @@
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64