v8::internal::compiler::JSContextSpecializer Class Reference

#include <js-context-specialization.h>

Collaboration diagram for v8::internal::compiler::JSContextSpecializer:

Public Member Functions
	JSContextSpecializer (CompilationInfo *info, JSGraph *jsgraph, Node *context)
void	SpecializeToContext ()
Reduction	ReduceJSLoadContext (Node *node)
Reduction	ReduceJSStoreContext (Node *node)

Private Attributes
CompilationInfo *	info_
JSGraph *	jsgraph_
Node *	context_

Detailed Description

Definition at line 19 of file js-context-specialization.h.

Constructor & Destructor Documentation

JSContextSpecializer()

v8::internal::compiler::JSContextSpecializer::JSContextSpecializer ( CompilationInfo *  info, JSGraph *  jsgraph, Node *  context  )

inline

Definition at line 21 of file js-context-specialization.h.

      : info_(info), jsgraph_(jsgraph), context_(context) {}

Member Function Documentation

ReduceJSLoadContext()

Reduction v8::internal::compiler::JSContextSpecializer::ReduceJSLoadContext

(

Node *

node

)

Definition at line 61 of file js-context-specialization.cc.

                                                              {
  DCHECK_EQ(IrOpcode::kJSLoadContext, node->opcode());
 
  HeapObjectMatcher<Context> m(NodeProperties::GetValueInput(node, 0));
  // If the context is not constant, no reduction can occur.
  if (!m.HasValue()) {
    return Reducer::NoChange();
  }
 
  ContextAccess access = OpParameter<ContextAccess>(node);
 
  // Find the right parent context.
  Context* context = *m.Value().handle();
  for (int i = access.depth(); i > 0; --i) {
    context = context->previous();
  }
 
  // If the access itself is mutable, only fold-in the parent.
  if (!access.immutable()) {
    // The access does not have to look up a parent, nothing to fold.
    if (access.depth() == 0) {
      return Reducer::NoChange();
    }
    const Operator* op = jsgraph_->javascript()->LoadContext(
        0, access.index(), access.immutable());
    node->set_op(op);
    Handle<Object> context_handle = Handle<Object>(context, info_->isolate());
    node->ReplaceInput(0, jsgraph_->Constant(context_handle));
    return Reducer::Changed(node);
  }
  Handle<Object> value =
      Handle<Object>(context->get(access.index()), info_->isolate());
 
  // Even though the context slot is immutable, the context might have escaped
  // before the function to which it belongs has initialized the slot.
  // We must be conservative and check if the value in the slot is currently the
  // hole or undefined. If it is neither of these, then it must be initialized.
  if (value->IsUndefined() || value->IsTheHole()) {
    return Reducer::NoChange();
  }
 
  // Success. The context load can be replaced with the constant.
  // TODO(titzer): record the specialization for sharing code across multiple
  // contexts that have the same value in the corresponding context slot.
  return Reducer::Replace(jsgraph_->Constant(value));
}

References v8::internal::compiler::Reducer::Changed(), v8::internal::compiler::JSGraph::Constant(), DCHECK_EQ, v8::internal::compiler::ContextAccess::depth(), v8::internal::FixedArray::get(), v8::internal::compiler::NodeProperties::GetValueInput(), v8::internal::compiler::ContextAccess::immutable(), v8::internal::compiler::ContextAccess::index(), info_, v8::internal::CompilationInfo::isolate(), v8::internal::compiler::JSGraph::javascript(), jsgraph_, v8::internal::compiler::JSOperatorBuilder::LoadContext(), v8::internal::compiler::Reducer::NoChange(), v8::internal::Context::previous(), and v8::internal::compiler::Reducer::Replace().

Referenced by v8::internal::compiler::ContextSpecializationVisitor::Post().

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ReduceJSStoreContext()

Reduction v8::internal::compiler::JSContextSpecializer::ReduceJSStoreContext

(

Node *

node

)

Definition at line 109 of file js-context-specialization.cc.

                                                               {
  DCHECK_EQ(IrOpcode::kJSStoreContext, node->opcode());
 
  HeapObjectMatcher<Context> m(NodeProperties::GetValueInput(node, 0));
  // If the context is not constant, no reduction can occur.
  if (!m.HasValue()) {
    return Reducer::NoChange();
  }
 
  ContextAccess access = OpParameter<ContextAccess>(node);
 
  // The access does not have to look up a parent, nothing to fold.
  if (access.depth() == 0) {
    return Reducer::NoChange();
  }
 
  // Find the right parent context.
  Context* context = *m.Value().handle();
  for (int i = access.depth(); i > 0; --i) {
    context = context->previous();
  }
 
  const Operator* op = jsgraph_->javascript()->StoreContext(0, access.index());
  node->set_op(op);
  Handle<Object> new_context_handle = Handle<Object>(context, info_->isolate());
  node->ReplaceInput(0, jsgraph_->Constant(new_context_handle));
 
  return Reducer::Changed(node);
}

References v8::internal::compiler::Reducer::Changed(), v8::internal::compiler::JSGraph::Constant(), DCHECK_EQ, v8::internal::compiler::ContextAccess::depth(), v8::internal::compiler::NodeProperties::GetValueInput(), v8::internal::compiler::ContextAccess::index(), info_, v8::internal::CompilationInfo::isolate(), v8::internal::compiler::JSGraph::javascript(), jsgraph_, v8::internal::compiler::Reducer::NoChange(), v8::internal::Context::previous(), and v8::internal::compiler::JSOperatorBuilder::StoreContext().

Referenced by v8::internal::compiler::ContextSpecializationVisitor::Post().

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SpecializeToContext()

void v8::internal::compiler::JSContextSpecializer::SpecializeToContext

(

)

Definition at line 52 of file js-context-specialization.cc.

                                               {
  NodeProperties::ReplaceWithValue(context_,
                                   jsgraph_->Constant(info_->context()));
 
  ContextSpecializationVisitor visitor(this);
  jsgraph_->graph()->VisitNodeInputsFromEnd(&visitor);
}

References v8::internal::compiler::JSGraph::Constant(), v8::internal::CompilationInfo::context(), context_, v8::internal::compiler::JSGraph::graph(), info_, jsgraph_, v8::internal::compiler::NodeProperties::ReplaceWithValue(), and v8::internal::compiler::Graph::VisitNodeInputsFromEnd().

Referenced by v8::internal::compiler::Pipeline::GenerateCode().

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Member Data Documentation

context_

Node* v8::internal::compiler::JSContextSpecializer::context_

private

Definition at line 31 of file js-context-specialization.h.

Referenced by SpecializeToContext().

info_

CompilationInfo* v8::internal::compiler::JSContextSpecializer::info_

private

Definition at line 29 of file js-context-specialization.h.

Referenced by ReduceJSLoadContext(), ReduceJSStoreContext(), and SpecializeToContext().

jsgraph_

JSGraph* v8::internal::compiler::JSContextSpecializer::jsgraph_

private

Definition at line 30 of file js-context-specialization.h.

Referenced by ReduceJSLoadContext(), ReduceJSStoreContext(), and SpecializeToContext().

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The documentation for this class was generated from the following files:

• /mnt/V8SourceCode/src/compiler/js-context-specialization.h
• /mnt/V8SourceCode/src/compiler/js-context-specialization.cc