Improve dead code elimination by transitively marking live code and removing all dead code. Replace…

src/hydrogen-instructions.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 630 matching lines @@
 
 void HValue::SetOperandAt(int index, HValue* value) {
   RegisterUse(index, value);
   InternalSetOperandAt(index, value);
 }
 
 
 void HValue::DeleteAndReplaceWith(HValue* other) {
   // We replace all uses first, so Delete can assert that there are none.
   if (other != NULL) ReplaceAllUsesWith(other);
-  ASSERT(HasNoUses());
   Kill();
   DeleteFromGraph();
 }
 
 
 void HValue::ReplaceAllUsesWith(HValue* other) {
   while (use_list_ != NULL) {
     HUseListNode* list_node = use_list_;
     HValue* value = list_node->value();
     ASSERT(!value->block()->IsStartBlock());
@@ skipping 1229 matching lines @@
     HValue* value = OperandAt(i);
     stream->Add(" ");
     value->PrintNameTo(stream);
     stream->Add(" ");
   }
   stream->Add(" uses%d_%di_%dd_%dt",
               UseCount(),
               int32_non_phi_uses() + int32_indirect_uses(),
               double_non_phi_uses() + double_indirect_uses(),
               tagged_non_phi_uses() + tagged_indirect_uses());
   stream->Add("%s%s]",

[Sven Panne, 2013/05/07 13:32:10]

Do we never print phis marked as dead by DCE? If this is the case, removing this
piece information is OK here (at least if you adapt the format pattern ;-). If
not, print it.

[titzer, 2013/05/13 13:29:38]

Done.

-              is_live() ? "_live" : "",
               IsConvertibleToInteger() ? "" : "_ncti");
 }
 
 
 void HPhi::AddInput(HValue* value) {
   inputs_.Add(NULL, value->block()->zone());
   SetOperandAt(OperandCount() - 1, value);
   // Mark phis that may have 'arguments' directly or indirectly as an operand.
   if (!CheckFlag(kIsArguments) && value->CheckFlag(kIsArguments)) {
     SetFlag(kIsArguments);
@@ skipping 1709 matching lines @@
 
 
 void HCheckFunction::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
 }
 
 #endif
 
 } }  // namespace v8::internal