blob: c92ccda730fbe604d04434ab7f7abf6257748eb0 [file] [log] [blame]
// Copyright 2012 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 "src/v8.h"
#include "src/rewriter.h"
#include "src/ast.h"
#include "src/compiler.h"
#include "src/scopes.h"
namespace v8 {
namespace internal {
class Processor: public AstVisitor {
public:
Processor(Variable* result, Zone* zone)
: result_(result),
result_assigned_(false),
is_set_(false),
in_try_(false),
factory_(zone) {
InitializeAstVisitor(zone);
}
virtual ~Processor() { }
void Process(ZoneList<Statement*>* statements);
bool result_assigned() const { return result_assigned_; }
AstNodeFactory<AstNullVisitor>* factory() {
return &factory_;
}
private:
Variable* result_;
// We are not tracking result usage via the result_'s use
// counts (we leave the accurate computation to the
// usage analyzer). Instead we simple remember if
// there was ever an assignment to result_.
bool result_assigned_;
// To avoid storing to .result all the time, we eliminate some of
// the stores by keeping track of whether or not we're sure .result
// will be overwritten anyway. This is a bit more tricky than what I
// was hoping for
bool is_set_;
bool in_try_;
AstNodeFactory<AstNullVisitor> factory_;
Expression* SetResult(Expression* value) {
result_assigned_ = true;
VariableProxy* result_proxy = factory()->NewVariableProxy(result_);
return factory()->NewAssignment(
Token::ASSIGN, result_proxy, value, RelocInfo::kNoPosition);
}
// Node visitors.
#define DEF_VISIT(type) \
virtual void Visit##type(type* node);
AST_NODE_LIST(DEF_VISIT)
#undef DEF_VISIT
void VisitIterationStatement(IterationStatement* stmt);
DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
};
void Processor::Process(ZoneList<Statement*>* statements) {
for (int i = statements->length() - 1; i >= 0; --i) {
Visit(statements->at(i));
}
}
void Processor::VisitBlock(Block* node) {
// An initializer block is the rewritten form of a variable declaration
// with initialization expressions. The initializer block contains the
// list of assignments corresponding to the initialization expressions.
// While unclear from the spec (ECMA-262, 3rd., 12.2), the value of
// a variable declaration with initialization expression is 'undefined'
// with some JS VMs: For instance, using smjs, print(eval('var x = 7'))
// returns 'undefined'. To obtain the same behavior with v8, we need
// to prevent rewriting in that case.
if (!node->is_initializer_block()) Process(node->statements());
}
void Processor::VisitModuleStatement(ModuleStatement* node) {
bool set_after_body = is_set_;
Visit(node->body());
is_set_ = is_set_ && set_after_body;
}
void Processor::VisitExpressionStatement(ExpressionStatement* node) {
// Rewrite : <x>; -> .result = <x>;
if (!is_set_ && !node->expression()->IsThrow()) {
node->set_expression(SetResult(node->expression()));
if (!in_try_) is_set_ = true;
}
}
void Processor::VisitIfStatement(IfStatement* node) {
// Rewrite both then and else parts (reversed).
bool save = is_set_;
Visit(node->else_statement());
bool set_after_then = is_set_;
is_set_ = save;
Visit(node->then_statement());
is_set_ = is_set_ && set_after_then;
}
void Processor::VisitIterationStatement(IterationStatement* node) {
// Rewrite the body.
bool set_after_loop = is_set_;
Visit(node->body());
is_set_ = is_set_ && set_after_loop;
}
void Processor::VisitDoWhileStatement(DoWhileStatement* node) {
VisitIterationStatement(node);
}
void Processor::VisitWhileStatement(WhileStatement* node) {
VisitIterationStatement(node);
}
void Processor::VisitForStatement(ForStatement* node) {
VisitIterationStatement(node);
}
void Processor::VisitForInStatement(ForInStatement* node) {
VisitIterationStatement(node);
}
void Processor::VisitForOfStatement(ForOfStatement* node) {
VisitIterationStatement(node);
}
void Processor::VisitTryCatchStatement(TryCatchStatement* node) {
// Rewrite both try and catch blocks (reversed order).
bool set_after_catch = is_set_;
Visit(node->catch_block());
is_set_ = is_set_ && set_after_catch;
bool save = in_try_;
in_try_ = true;
Visit(node->try_block());
in_try_ = save;
}
void Processor::VisitTryFinallyStatement(TryFinallyStatement* node) {
// Rewrite both try and finally block (reversed order).
Visit(node->finally_block());
bool save = in_try_;
in_try_ = true;
Visit(node->try_block());
in_try_ = save;
}
void Processor::VisitSwitchStatement(SwitchStatement* node) {
// Rewrite statements in all case clauses in reversed order.
ZoneList<CaseClause*>* clauses = node->cases();
bool set_after_switch = is_set_;
for (int i = clauses->length() - 1; i >= 0; --i) {
CaseClause* clause = clauses->at(i);
Process(clause->statements());
}
is_set_ = is_set_ && set_after_switch;
}
void Processor::VisitContinueStatement(ContinueStatement* node) {
is_set_ = false;
}
void Processor::VisitBreakStatement(BreakStatement* node) {
is_set_ = false;
}
void Processor::VisitWithStatement(WithStatement* node) {
bool set_after_body = is_set_;
Visit(node->statement());
is_set_ = is_set_ && set_after_body;
}
// Do nothing:
void Processor::VisitVariableDeclaration(VariableDeclaration* node) {}
void Processor::VisitFunctionDeclaration(FunctionDeclaration* node) {}
void Processor::VisitModuleDeclaration(ModuleDeclaration* node) {}
void Processor::VisitImportDeclaration(ImportDeclaration* node) {}
void Processor::VisitExportDeclaration(ExportDeclaration* node) {}
void Processor::VisitModuleLiteral(ModuleLiteral* node) {}
void Processor::VisitModuleVariable(ModuleVariable* node) {}
void Processor::VisitModulePath(ModulePath* node) {}
void Processor::VisitModuleUrl(ModuleUrl* node) {}
void Processor::VisitEmptyStatement(EmptyStatement* node) {}
void Processor::VisitReturnStatement(ReturnStatement* node) {}
void Processor::VisitDebuggerStatement(DebuggerStatement* node) {}
// Expressions are never visited yet.
#define DEF_VISIT(type) \
void Processor::Visit##type(type* expr) { UNREACHABLE(); }
EXPRESSION_NODE_LIST(DEF_VISIT)
#undef DEF_VISIT
// Assumes code has been parsed. Mutates the AST, so the AST should not
// continue to be used in the case of failure.
bool Rewriter::Rewrite(CompilationInfo* info) {
FunctionLiteral* function = info->function();
ASSERT(function != NULL);
Scope* scope = function->scope();
ASSERT(scope != NULL);
if (!scope->is_global_scope() && !scope->is_eval_scope()) return true;
ZoneList<Statement*>* body = function->body();
if (!body->is_empty()) {
Variable* result = scope->NewTemporary(
info->isolate()->factory()->dot_result_string());
Processor processor(result, info->zone());
processor.Process(body);
if (processor.HasStackOverflow()) return false;
if (processor.result_assigned()) {
ASSERT(function->end_position() != RelocInfo::kNoPosition);
// Set the position of the assignment statement one character past the
// source code, such that it definitely is not in the source code range
// of an immediate inner scope. For example in
// eval('with ({x:1}) x = 1');
// the end position of the function generated for executing the eval code
// coincides with the end of the with scope which is the position of '1'.
int pos = function->end_position();
VariableProxy* result_proxy = processor.factory()->NewVariableProxy(
result->name(), false, result->interface(), pos);
result_proxy->BindTo(result);
Statement* result_statement =
processor.factory()->NewReturnStatement(result_proxy, pos);
body->Add(result_statement, info->zone());
}
}
return true;
}
} } // namespace v8::internal