Preliminary support for block contexts in hydrogen.

src/hydrogen.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "hydrogen.h"
 
 #include <algorithm>
 
 #include "v8.h"
 #include "allocation-site-scopes.h"
@@ skipping 4235 matching lines @@
     CHECK_ALIVE(Visit(stmt));
     if (stmt->IsJump()) break;
   }
 }
 
 
 void HOptimizedGraphBuilder::VisitBlock(Block* stmt) {
   ASSERT(!HasStackOverflow());
   ASSERT(current_block() != NULL);
   ASSERT(current_block()->HasPredecessor());
-  if (stmt->scope() != NULL) {
-    return Bailout(kScopedBlock);
+
+  Scope* outer_scope = scope();
+  Scope* scope = stmt->scope();
+  BreakAndContinueInfo break_info(stmt, outer_scope);
+
+  { BreakAndContinueScope push(&break_info, this);
+    if (scope != NULL) {
+      // Load the function object.
+      Scope* declaration_scope = scope->DeclarationScope();
+      HInstruction* function;
+
+      HValue* outer_context = environment()->context();
+      if (declaration_scope->is_global_scope() ||
+          declaration_scope->is_eval_scope()) {
+        function = new(zone()) HLoadContextSlot(
+            outer_context, Context::CLOSURE_INDEX, HLoadContextSlot::kNoCheck);
+      } else {
+        function = New<HThisFunction>();
+      }
+      AddInstruction(function);
+      // Allocate a block context and store it to the stack frame.
+      HInstruction* inner_context = Add<HAllocateBlockContext>(
+          outer_context, function, scope->GetScopeInfo());
+      HInstruction* instr = Add<HStoreFrameContext>(inner_context);
+      if (instr->HasObservableSideEffects()) {
+        AddSimulate(stmt->EntryId(), REMOVABLE_SIMULATE);
+      }
+      set_scope(scope);

[rossberg, 2014/06/04 12:54:53]

Hm, can pushing/popping the scope perhaps be factored into
BreakAndContinueScope, or a separate BlockScope abstraction?

[ulan, 2014/06/04 14:02:05]

Done.

+      environment()->BindContext(inner_context);
+      VisitDeclarations(scope->declarations());
+      AddSimulate(stmt->DeclsId(), REMOVABLE_SIMULATE);
+    }
+    CHECK_BAILOUT(VisitStatements(stmt->statements()));
   }
-  BreakAndContinueInfo break_info(stmt);
-  { BreakAndContinueScope push(&break_info, this);
-    CHECK_BAILOUT(VisitStatements(stmt->statements()));
+  set_scope(outer_scope);
+  if (scope != NULL && current_block() != NULL) {
+    HValue* inner_context = environment()->context();
+    HValue* outer_context = Add<HLoadNamedField>(
+        inner_context, static_cast<HValue*>(NULL),
+        HObjectAccess::ForContextSlot(Context::PREVIOUS_INDEX));
+
+    HInstruction* instr = Add<HStoreFrameContext>(outer_context);
+    if (instr->HasObservableSideEffects()) {
+      AddSimulate(stmt->ExitId(), REMOVABLE_SIMULATE);
+    }
+    environment()->BindContext(outer_context);
   }
   HBasicBlock* break_block = break_info.break_block();
   if (break_block != NULL) {
     if (current_block() != NULL) Goto(break_block);
     break_block->SetJoinId(stmt->ExitId());
     set_current_block(break_block);
   }
 }
 
 
@@ skipping 48 matching lines @@
 
     HBasicBlock* join = CreateJoin(cond_true, cond_false, stmt->IfId());
     set_current_block(join);
   }
 }
 
 
 HBasicBlock* HOptimizedGraphBuilder::BreakAndContinueScope::Get(
     BreakableStatement* stmt,
     BreakType type,
+    Scope** scope,
     int* drop_extra) {
   *drop_extra = 0;
   BreakAndContinueScope* current = this;
   while (current != NULL && current->info()->target() != stmt) {
     *drop_extra += current->info()->drop_extra();
     current = current->next();
   }
   ASSERT(current != NULL);  // Always found (unless stack is malformed).
+  *scope = current->info()->scope();
 
   if (type == BREAK) {
     *drop_extra += current->info()->drop_extra();
   }
 
   HBasicBlock* block = NULL;
   switch (type) {
     case BREAK:
       block = current->info()->break_block();
       if (block == NULL) {
@@ skipping 13 matching lines @@
 
   return block;
 }
 
 
 void HOptimizedGraphBuilder::VisitContinueStatement(
     ContinueStatement* stmt) {
   ASSERT(!HasStackOverflow());
   ASSERT(current_block() != NULL);
   ASSERT(current_block()->HasPredecessor());
+  Scope* outer_scope = NULL;
+  Scope* inner_scope = scope();
   int drop_extra = 0;
   HBasicBlock* continue_block = break_scope()->Get(
-      stmt->target(), BreakAndContinueScope::CONTINUE, &drop_extra);
+      stmt->target(), BreakAndContinueScope::CONTINUE,
+      &outer_scope, &drop_extra);
+  HValue* context = environment()->context();
   Drop(drop_extra);
+  int context_pop_count = inner_scope->ContextChainLength(outer_scope);
+  if (context_pop_count > 0) {
+    while (context_pop_count-- > 0) {
+      HInstruction* context_instruction = Add<HLoadNamedField>(
+          context, static_cast<HValue*>(NULL),
+          HObjectAccess::ForContextSlot(Context::PREVIOUS_INDEX));
+      context = context_instruction;
+    }
+    HInstruction* instr = Add<HStoreFrameContext>(context);
+    if (instr->HasObservableSideEffects()) {
+      AddSimulate(stmt->target()->EntryId(), REMOVABLE_SIMULATE);
+    }
+    environment()->BindContext(context);
+  }
+
   Goto(continue_block);
   set_current_block(NULL);
 }
 
 
 void HOptimizedGraphBuilder::VisitBreakStatement(BreakStatement* stmt) {
   ASSERT(!HasStackOverflow());
   ASSERT(current_block() != NULL);
   ASSERT(current_block()->HasPredecessor());
+  Scope* outer_scope = NULL;
+  Scope* inner_scope = scope();
   int drop_extra = 0;
   HBasicBlock* break_block = break_scope()->Get(
-      stmt->target(), BreakAndContinueScope::BREAK, &drop_extra);
+      stmt->target(), BreakAndContinueScope::BREAK,
+      &outer_scope, &drop_extra);
+  HValue* context = environment()->context();
   Drop(drop_extra);
+  int context_pop_count = inner_scope->ContextChainLength(outer_scope);
+  if (context_pop_count > 0) {
+    while (context_pop_count-- > 0) {
+      HInstruction* context_instruction = Add<HLoadNamedField>(
+          context, static_cast<HValue*>(NULL),
+          HObjectAccess::ForContextSlot(Context::PREVIOUS_INDEX));
+      context = context_instruction;
+    }
+    HInstruction* instr = Add<HStoreFrameContext>(context);
+    if (instr->HasObservableSideEffects()) {
+      AddSimulate(stmt->target()->ExitId(), REMOVABLE_SIMULATE);
+    }
+    environment()->BindContext(context);
+  }
   Goto(break_block);
   set_current_block(NULL);
 }
 
 
 void HOptimizedGraphBuilder::VisitReturnStatement(ReturnStatement* stmt) {
   ASSERT(!HasStackOverflow());
   ASSERT(current_block() != NULL);
   ASSERT(current_block()->HasPredecessor());
   FunctionState* state = function_state();
@@ skipping 134 matching lines @@
 
   // Save the current block to use for the default or to join with the
   // exit.
   HBasicBlock* last_block = current_block();
   Drop(1);  // tag_value
 
   // 2. Loop over the clauses and the linked list of tests in lockstep,
   // translating the clause bodies.
   HBasicBlock* fall_through_block = NULL;
 
-  BreakAndContinueInfo break_info(stmt);
+  BreakAndContinueInfo break_info(stmt, scope());
   { BreakAndContinueScope push(&break_info, this);
     for (int i = 0; i < clause_count; ++i) {
       CaseClause* clause = clauses->at(i);
 
       // Identify the block where normal (non-fall-through) control flow
       // goes to.
       HBasicBlock* normal_block = NULL;
       if (clause->is_default()) {
         if (last_block == NULL) continue;
         normal_block = last_block;
@@ skipping 26 matching lines @@
   } else {
     if (fall_through_block != NULL) Goto(fall_through_block, break_block);
     if (last_block != NULL) Goto(last_block, break_block);
     break_block->SetJoinId(stmt->ExitId());
     set_current_block(break_block);
   }
 }
 
 
 void HOptimizedGraphBuilder::VisitLoopBody(IterationStatement* stmt,
-                                           HBasicBlock* loop_entry,
-                                           BreakAndContinueInfo* break_info) {
-  BreakAndContinueScope push(break_info, this);
+                                           HBasicBlock* loop_entry) {
   Add<HSimulate>(stmt->StackCheckId());
   HStackCheck* stack_check =
       HStackCheck::cast(Add<HStackCheck>(HStackCheck::kBackwardsBranch));
   ASSERT(loop_entry->IsLoopHeader());
   loop_entry->loop_information()->set_stack_check(stack_check);
   CHECK_BAILOUT(Visit(stmt->body()));
 }
 
 
 void HOptimizedGraphBuilder::VisitDoWhileStatement(DoWhileStatement* stmt) {
   ASSERT(!HasStackOverflow());
   ASSERT(current_block() != NULL);
   ASSERT(current_block()->HasPredecessor());
   ASSERT(current_block() != NULL);
   HBasicBlock* loop_entry = BuildLoopEntry(stmt);
 
-  BreakAndContinueInfo break_info(stmt);
-  CHECK_BAILOUT(VisitLoopBody(stmt, loop_entry, &break_info));
+  BreakAndContinueInfo break_info(stmt, scope());
+  {
+    BreakAndContinueScope push(&break_info, this);
+    CHECK_BAILOUT(VisitLoopBody(stmt, loop_entry));
+  }
   HBasicBlock* body_exit =
       JoinContinue(stmt, current_block(), break_info.continue_block());
   HBasicBlock* loop_successor = NULL;
   if (body_exit != NULL && !stmt->cond()->ToBooleanIsTrue()) {
     set_current_block(body_exit);
     loop_successor = graph()->CreateBasicBlock();
     if (stmt->cond()->ToBooleanIsFalse()) {
       loop_entry->loop_information()->stack_check()->Eliminate();
       Goto(loop_successor);
       body_exit = NULL;
@@ skipping 40 matching lines @@
       body_entry->SetJoinId(stmt->BodyId());
       set_current_block(body_entry);
     }
     if (loop_successor->HasPredecessor()) {
       loop_successor->SetJoinId(stmt->ExitId());
     } else {
       loop_successor = NULL;
     }
   }
 
-  BreakAndContinueInfo break_info(stmt);
+  BreakAndContinueInfo break_info(stmt, scope());
   if (current_block() != NULL) {
-    CHECK_BAILOUT(VisitLoopBody(stmt, loop_entry, &break_info));
+    BreakAndContinueScope push(&break_info, this);
+    CHECK_BAILOUT(VisitLoopBody(stmt, loop_entry));
   }
   HBasicBlock* body_exit =
       JoinContinue(stmt, current_block(), break_info.continue_block());
   HBasicBlock* loop_exit = CreateLoop(stmt,
                                       loop_entry,
                                       body_exit,
                                       loop_successor,
                                       break_info.break_block());
   set_current_block(loop_exit);
 }
@@ skipping 18 matching lines @@
       body_entry->SetJoinId(stmt->BodyId());
       set_current_block(body_entry);
     }
     if (loop_successor->HasPredecessor()) {
       loop_successor->SetJoinId(stmt->ExitId());
     } else {
       loop_successor = NULL;
     }
   }
 
-  BreakAndContinueInfo break_info(stmt);
+  BreakAndContinueInfo break_info(stmt, scope());
   if (current_block() != NULL) {
-    CHECK_BAILOUT(VisitLoopBody(stmt, loop_entry, &break_info));
+    BreakAndContinueScope push(&break_info, this);
+    CHECK_BAILOUT(VisitLoopBody(stmt, loop_entry));
   }
   HBasicBlock* body_exit =
       JoinContinue(stmt, current_block(), break_info.continue_block());
 
   if (stmt->next() != NULL && body_exit != NULL) {
     set_current_block(body_exit);
     CHECK_BAILOUT(Visit(stmt->next()));
     body_exit = current_block();
   }
 
@@ skipping 78 matching lines @@
       environment()->ExpressionStackAt(0),
       FAST_ELEMENTS);
 
   // Check if the expected map still matches that of the enumerable.
   // If not just deoptimize.
   Add<HCheckMapValue>(environment()->ExpressionStackAt(4),
                       environment()->ExpressionStackAt(3));
 
   Bind(each_var, key);
 
-  BreakAndContinueInfo break_info(stmt, 5);
-  CHECK_BAILOUT(VisitLoopBody(stmt, loop_entry, &break_info));
+  BreakAndContinueInfo break_info(stmt, scope(), 5);
+  {
+    BreakAndContinueScope push(&break_info, this);
+    CHECK_BAILOUT(VisitLoopBody(stmt, loop_entry));
+  }
 
   HBasicBlock* body_exit =
       JoinContinue(stmt, current_block(), break_info.continue_block());
 
   if (body_exit != NULL) {
     set_current_block(body_exit);
 
     HValue* current_index = Pop();
     Push(AddUncasted<HAdd>(current_index, graph()->GetConstant1()));
     body_exit = current_block();
@@ skipping 124 matching lines @@
     return kUseGeneric;
   }
 
   return kUseCell;
 }
 
 
 HValue* HOptimizedGraphBuilder::BuildContextChainWalk(Variable* var) {
   ASSERT(var->IsContextSlot());
   HValue* context = environment()->context();
-  int length = current_info()->scope()->ContextChainLength(var->scope());
+  int length = scope()->ContextChainLength(var->scope());
   while (length-- > 0) {
     context = Add<HLoadNamedField>(
         context, static_cast<HValue*>(NULL),
         HObjectAccess::ForContextSlot(Context::PREVIOUS_INDEX));
   }
   return context;
 }
 
 
 void HOptimizedGraphBuilder::VisitVariableProxy(VariableProxy* expr) {
@@ skipping 63 matching lines @@
       if (value == graph()->GetConstantHole()) {
         ASSERT(IsDeclaredVariableMode(variable->mode()) &&
                variable->mode() != VAR);
         return Bailout(kReferenceToUninitializedVariable);
       }
       return ast_context()->ReturnValue(value);
     }
 
     case Variable::CONTEXT: {
       HValue* context = BuildContextChainWalk(variable);
-      HLoadContextSlot* instr = new(zone()) HLoadContextSlot(context, variable);
+      HLoadContextSlot::Mode mode;
+      switch (variable->mode()) {
+        case LET:
+        case CONST:
+          mode = HLoadContextSlot::kCheckDeoptimize;
+          break;
+        case CONST_LEGACY:
+          mode = HLoadContextSlot::kCheckReturnUndefined;
+          break;
+        default:
+          mode = HLoadContextSlot::kNoCheck;
+          break;
+      }
+      HLoadContextSlot* instr =
+          new(zone()) HLoadContextSlot(context, variable->index(), mode);
       return ast_context()->ReturnInstruction(instr, expr->id());
     }
 
     case Variable::LOOKUP:
       return Bailout(kReferenceToAVariableWhichRequiresDynamicLookup);
   }
 }
 
 
 void HOptimizedGraphBuilder::VisitLiteral(Literal* expr) {
@@ skipping 2422 matching lines @@
   }
 
   // Capture the state before invoking the inlined function for deopt in the
   // inlined function. This simulate has no bailout-id since it's not directly
   // reachable for deopt, and is only used to capture the state. If the simulate
   // becomes reachable by merging, the ast id of the simulate merged into it is
   // adopted.
   Add<HSimulate>(BailoutId::None());
 
   current_block()->UpdateEnvironment(inner_env);
-
+  Scope* saved_scope = scope();
+  set_scope(target_info.scope());
   HEnterInlined* enter_inlined =
       Add<HEnterInlined>(return_id, target, arguments_count, function,
                          function_state()->inlining_kind(),
                          function->scope()->arguments(),
                          arguments_object);
   function_state()->set_entry(enter_inlined);
 
   VisitDeclarations(target_info.scope()->declarations());
   VisitStatements(function->body());
+  set_scope(saved_scope);
   if (HasStackOverflow()) {
     // Bail out if the inline function did, as we cannot residualize a call
     // instead.
     TraceInline(target, caller, "inline graph construction failed");
     target_shared->DisableOptimization(kInliningBailedOut);
     inline_bailout_ = true;
     delete target_state;
     return true;
   }
 
@@ skipping 3677 matching lines @@
       frame_type_(JS_FUNCTION),
       parameter_count_(0),
       specials_count_(1),
       local_count_(0),
       outer_(outer),
       entry_(NULL),
       pop_count_(0),
       push_count_(0),
       ast_id_(BailoutId::None()),
       zone_(zone) {
-  Initialize(scope->num_parameters() + 1, scope->num_stack_slots(), 0);
+  Scope* declaration_scope = scope->DeclarationScope();
+  Initialize(declaration_scope->num_parameters() + 1,
+             declaration_scope->num_stack_slots(), 0);
 }
 
 
 HEnvironment::HEnvironment(Zone* zone, int parameter_count)
     : values_(0, zone),
       frame_type_(STUB),
       parameter_count_(parameter_count),
       specials_count_(1),
       local_count_(0),
       outer_(NULL),
@@ skipping 592 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal