Eliminatable CheckMaps replaced with if(true) or if(false).

src/hydrogen.cc

 // Copyright 2013 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 295 matching lines @@
   const HBasicBlock* current = this;
   int result  = (current->IsLoopHeader()) ? 1 : 0;
   while (current->parent_loop_header() != NULL) {
     current = current->parent_loop_header();
     result++;
   }
   return result;
 }
 
 
+void HBasicBlock::ReplaceControlWithGotoSuccessor(int succ) {
+  ASSERT(IsFinished());
+  ASSERT(end()->SuccessorCount() == 2);  // Only this case is supported yet.
+  ASSERT(succ < end()->SuccessorCount());
+
+  // Replace control instruction with if(true) or if(false).
+  HConstant* value = (succ == 0)
+      ? graph()->GetConstantTrue()
+      : graph()->GetConstantFalse();
+
+  HBranch* new_branch = HBranch::New(
+      zone(),
+      NULL,
+      value,

[titzer, 2014/01/14 13:40:32]

Why not always if(true) {succ} else {1 - succ}?

[Igor Sheludko, 2014/01/14 15:28:00]

Done.

+      ToBooleanStub::Types(ToBooleanStub::BOOLEAN),
+      end()->SuccessorAt(0),
+      end()->SuccessorAt(1));
+
+  int unreachable_succ = 1 - succ;
+
+  MarkSuccEdgeUnreachable(unreachable_succ);
+
+  end()->DeleteAndReplaceWith(end()->ActualValue());
+  new_branch->InsertAfter(last());
+  end_ = new_branch;
+}
+
+
 void HBasicBlock::PostProcessLoopHeader(IterationStatement* stmt) {
   ASSERT(IsLoopHeader());
 
   SetJoinId(stmt->EntryId());
   if (predecessors()->length() == 1) {
     // This is a degenerated loop.
     DetachLoopInformation();
     return;
   }
 
   // Only the first entry into the loop is from outside the loop. All other
   // entries must be back edges.
   for (int i = 1; i < predecessors()->length(); ++i) {
     loop_information()->RegisterBackEdge(predecessors()->at(i));
   }
 }
 
 
+void HBasicBlock::MarkSuccEdgeUnreachable(int succ) {
+  ASSERT(IsFinished());
+  HBasicBlock* succ_block = end()->SuccessorAt(succ);
+
+  ASSERT(succ_block->predecessors()->length() == 1);
+  succ_block->MarkUnreachable();
+}
+
+
 void HBasicBlock::RegisterPredecessor(HBasicBlock* pred) {
   if (HasPredecessor()) {
     // Only loop header blocks can have a predecessor added after
     // instructions have been added to the block (they have phis for all
     // values in the environment, these phis may be eliminated later).
     ASSERT(IsLoopHeader() || first_ == NULL);
     HEnvironment* incoming_env = pred->last_environment();
     if (IsLoopHeader()) {
       ASSERT(phis()->length() == incoming_env->length());
       for (int i = 0; i < phis_.length(); ++i) {
@@ skipping 10628 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal