1// Copyright 2006-2008 the V8 project authors. All rights reserved.
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3// modification, are permitted provided that the following conditions are
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5//
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8//     * Redistributions in binary form must reproduce the above
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22// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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27
28#include "v8.h"
29
30#include "ast.h"
31#include "func-name-inferrer.h"
32#include "scopes.h"
33#include "rewriter.h"
34
35namespace v8 {
36namespace internal {
37
38
39class AstOptimizer: public AstVisitor {
40 public:
41  explicit AstOptimizer() : has_function_literal_(false) {}
42  explicit AstOptimizer(Handle<String> enclosing_name)
43      : has_function_literal_(false) {
44    func_name_inferrer_.PushEnclosingName(enclosing_name);
45  }
46
47  void Optimize(ZoneList<Statement*>* statements);
48
49 private:
50  // Used for loop condition analysis.  Cleared before visiting a loop
51  // condition, set when a function literal is visited.
52  bool has_function_literal_;
53  // Helper object for function name inferring.
54  FuncNameInferrer func_name_inferrer_;
55
56  // Helpers
57  void OptimizeArguments(ZoneList<Expression*>* arguments);
58
59  // Node visitors.
60#define DEF_VISIT(type) \
61  virtual void Visit##type(type* node);
62  AST_NODE_LIST(DEF_VISIT)
63#undef DEF_VISIT
64
65  DISALLOW_COPY_AND_ASSIGN(AstOptimizer);
66};
67
68
69void AstOptimizer::Optimize(ZoneList<Statement*>* statements) {
70  int len = statements->length();
71  for (int i = 0; i < len; i++) {
72    Visit(statements->at(i));
73  }
74}
75
76
77void AstOptimizer::OptimizeArguments(ZoneList<Expression*>* arguments) {
78  for (int i = 0; i < arguments->length(); i++) {
79    Visit(arguments->at(i));
80  }
81}
82
83
84void AstOptimizer::VisitBlock(Block* node) {
85  Optimize(node->statements());
86}
87
88
89void AstOptimizer::VisitExpressionStatement(ExpressionStatement* node) {
90  Visit(node->expression());
91}
92
93
94void AstOptimizer::VisitIfStatement(IfStatement* node) {
95  Visit(node->condition());
96  Visit(node->then_statement());
97  if (node->HasElseStatement()) {
98    Visit(node->else_statement());
99  }
100}
101
102
103void AstOptimizer::VisitDoWhileStatement(DoWhileStatement* node) {
104  Visit(node->cond());
105  Visit(node->body());
106}
107
108
109void AstOptimizer::VisitWhileStatement(WhileStatement* node) {
110  has_function_literal_ = false;
111  Visit(node->cond());
112  node->may_have_function_literal_ = has_function_literal_;
113  Visit(node->body());
114}
115
116
117void AstOptimizer::VisitForStatement(ForStatement* node) {
118  if (node->init() != NULL) {
119    Visit(node->init());
120  }
121  if (node->cond() != NULL) {
122    has_function_literal_ = false;
123    Visit(node->cond());
124    node->may_have_function_literal_ = has_function_literal_;
125  }
126  Visit(node->body());
127  if (node->next() != NULL) {
128    Visit(node->next());
129  }
130}
131
132
133void AstOptimizer::VisitForInStatement(ForInStatement* node) {
134  Visit(node->each());
135  Visit(node->enumerable());
136  Visit(node->body());
137}
138
139
140void AstOptimizer::VisitTryCatchStatement(TryCatchStatement* node) {
141  Visit(node->try_block());
142  Visit(node->catch_var());
143  Visit(node->catch_block());
144}
145
146
147void AstOptimizer::VisitTryFinallyStatement(TryFinallyStatement* node) {
148  Visit(node->try_block());
149  Visit(node->finally_block());
150}
151
152
153void AstOptimizer::VisitSwitchStatement(SwitchStatement* node) {
154  Visit(node->tag());
155  for (int i = 0; i < node->cases()->length(); i++) {
156    CaseClause* clause = node->cases()->at(i);
157    if (!clause->is_default()) {
158      Visit(clause->label());
159    }
160    Optimize(clause->statements());
161  }
162}
163
164
165void AstOptimizer::VisitContinueStatement(ContinueStatement* node) {
166  USE(node);
167}
168
169
170void AstOptimizer::VisitBreakStatement(BreakStatement* node) {
171  USE(node);
172}
173
174
175void AstOptimizer::VisitDeclaration(Declaration* node) {
176  // Will not be reached by the current optimizations.
177  USE(node);
178}
179
180
181void AstOptimizer::VisitEmptyStatement(EmptyStatement* node) {
182  USE(node);
183}
184
185
186void AstOptimizer::VisitReturnStatement(ReturnStatement* node) {
187  Visit(node->expression());
188}
189
190
191void AstOptimizer::VisitWithEnterStatement(WithEnterStatement* node) {
192  Visit(node->expression());
193}
194
195
196void AstOptimizer::VisitWithExitStatement(WithExitStatement* node) {
197  USE(node);
198}
199
200
201void AstOptimizer::VisitDebuggerStatement(DebuggerStatement* node) {
202  USE(node);
203}
204
205
206void AstOptimizer::VisitFunctionLiteral(FunctionLiteral* node) {
207  has_function_literal_ = true;
208
209  if (node->name()->length() == 0) {
210    // Anonymous function.
211    func_name_inferrer_.AddFunction(node);
212  }
213}
214
215
216void AstOptimizer::VisitFunctionBoilerplateLiteral(
217    FunctionBoilerplateLiteral* node) {
218  USE(node);
219}
220
221
222void AstOptimizer::VisitConditional(Conditional* node) {
223  Visit(node->condition());
224  Visit(node->then_expression());
225  Visit(node->else_expression());
226}
227
228
229void AstOptimizer::VisitSlot(Slot* node) {
230  USE(node);
231}
232
233
234void AstOptimizer::VisitVariableProxy(VariableProxy* node) {
235  Variable* var = node->AsVariable();
236  if (var != NULL) {
237    if (var->type()->IsKnown()) {
238      node->type()->CopyFrom(var->type());
239    } else if (node->type()->IsLikelySmi()) {
240      var->type()->SetAsLikelySmi();
241    }
242
243    if (!var->is_this() &&
244        !Heap::result_symbol()->Equals(*var->name())) {
245      func_name_inferrer_.PushName(var->name());
246    }
247  }
248}
249
250
251void AstOptimizer::VisitLiteral(Literal* node) {
252  Handle<Object> literal = node->handle();
253  if (literal->IsSmi()) {
254    node->type()->SetAsLikelySmi();
255  } else if (literal->IsString()) {
256    Handle<String> lit_str(Handle<String>::cast(literal));
257    if (!Heap::prototype_symbol()->Equals(*lit_str)) {
258      func_name_inferrer_.PushName(lit_str);
259    }
260  }
261}
262
263
264void AstOptimizer::VisitRegExpLiteral(RegExpLiteral* node) {
265  USE(node);
266}
267
268
269void AstOptimizer::VisitArrayLiteral(ArrayLiteral* node) {
270  for (int i = 0; i < node->values()->length(); i++) {
271    Visit(node->values()->at(i));
272  }
273}
274
275void AstOptimizer::VisitObjectLiteral(ObjectLiteral* node) {
276  for (int i = 0; i < node->properties()->length(); i++) {
277    ScopedFuncNameInferrer scoped_fni(&func_name_inferrer_);
278    scoped_fni.Enter();
279    Visit(node->properties()->at(i)->key());
280    Visit(node->properties()->at(i)->value());
281  }
282}
283
284
285void AstOptimizer::VisitCatchExtensionObject(CatchExtensionObject* node) {
286  Visit(node->key());
287  Visit(node->value());
288}
289
290
291void AstOptimizer::VisitAssignment(Assignment* node) {
292  ScopedFuncNameInferrer scoped_fni(&func_name_inferrer_);
293  switch (node->op()) {
294    case Token::INIT_VAR:
295    case Token::INIT_CONST:
296    case Token::ASSIGN:
297      // No type can be infered from the general assignment.
298
299      // Don't infer if it is "a = function(){...}();"-like expression.
300      if (node->value()->AsCall() == NULL) {
301        scoped_fni.Enter();
302      }
303      break;
304    case Token::ASSIGN_BIT_OR:
305    case Token::ASSIGN_BIT_XOR:
306    case Token::ASSIGN_BIT_AND:
307    case Token::ASSIGN_SHL:
308    case Token::ASSIGN_SAR:
309    case Token::ASSIGN_SHR:
310      node->type()->SetAsLikelySmiIfUnknown();
311      node->target()->type()->SetAsLikelySmiIfUnknown();
312      node->value()->type()->SetAsLikelySmiIfUnknown();
313      break;
314    case Token::ASSIGN_ADD:
315    case Token::ASSIGN_SUB:
316    case Token::ASSIGN_MUL:
317    case Token::ASSIGN_DIV:
318    case Token::ASSIGN_MOD:
319      if (node->type()->IsLikelySmi()) {
320        node->target()->type()->SetAsLikelySmiIfUnknown();
321        node->value()->type()->SetAsLikelySmiIfUnknown();
322      }
323      break;
324    default:
325      UNREACHABLE();
326      break;
327  }
328
329  Visit(node->target());
330  Visit(node->value());
331
332  switch (node->op()) {
333    case Token::INIT_VAR:
334    case Token::INIT_CONST:
335    case Token::ASSIGN:
336      // Pure assignment copies the type from the value.
337      node->type()->CopyFrom(node->value()->type());
338      break;
339    case Token::ASSIGN_BIT_OR:
340    case Token::ASSIGN_BIT_XOR:
341    case Token::ASSIGN_BIT_AND:
342    case Token::ASSIGN_SHL:
343    case Token::ASSIGN_SAR:
344    case Token::ASSIGN_SHR:
345      // Should have been setup above already.
346      break;
347    case Token::ASSIGN_ADD:
348    case Token::ASSIGN_SUB:
349    case Token::ASSIGN_MUL:
350    case Token::ASSIGN_DIV:
351    case Token::ASSIGN_MOD:
352      if (node->type()->IsUnknown()) {
353        if (node->target()->type()->IsLikelySmi() ||
354            node->value()->type()->IsLikelySmi()) {
355          node->type()->SetAsLikelySmi();
356        }
357      }
358      break;
359    default:
360      UNREACHABLE();
361      break;
362  }
363
364  // Since this is an assignment. We have to propagate this node's type to the
365  // variable.
366  VariableProxy* proxy = node->target()->AsVariableProxy();
367  if (proxy != NULL) {
368    Variable* var = proxy->AsVariable();
369    if (var != NULL) {
370      StaticType* var_type = var->type();
371      if (var_type->IsUnknown()) {
372        var_type->CopyFrom(node->type());
373      } else if (var_type->IsLikelySmi()) {
374        // We do not reset likely types to Unknown.
375      }
376    }
377  }
378}
379
380
381void AstOptimizer::VisitThrow(Throw* node) {
382  Visit(node->exception());
383}
384
385
386void AstOptimizer::VisitProperty(Property* node) {
387  Visit(node->obj());
388  Visit(node->key());
389}
390
391
392void AstOptimizer::VisitCall(Call* node) {
393  Visit(node->expression());
394  OptimizeArguments(node->arguments());
395}
396
397
398void AstOptimizer::VisitCallNew(CallNew* node) {
399  Visit(node->expression());
400  OptimizeArguments(node->arguments());
401}
402
403
404void AstOptimizer::VisitCallRuntime(CallRuntime* node) {
405  ScopedFuncNameInferrer scoped_fni(&func_name_inferrer_);
406  if (Factory::InitializeVarGlobal_symbol()->Equals(*node->name()) &&
407      node->arguments()->length() >= 2 &&
408      node->arguments()->at(1)->AsFunctionLiteral() != NULL) {
409      scoped_fni.Enter();
410  }
411  OptimizeArguments(node->arguments());
412}
413
414
415void AstOptimizer::VisitUnaryOperation(UnaryOperation* node) {
416  Visit(node->expression());
417}
418
419
420void AstOptimizer::VisitCountOperation(CountOperation* node) {
421  // Count operations assume that they work on Smis.
422  node->type()->SetAsLikelySmiIfUnknown();
423  node->expression()->type()->SetAsLikelySmiIfUnknown();
424  Visit(node->expression());
425}
426
427
428void AstOptimizer::VisitBinaryOperation(BinaryOperation* node) {
429  // Depending on the operation we can propagate this node's type down the
430  // AST nodes.
431  switch (node->op()) {
432    case Token::COMMA:
433    case Token::OR:
434    case Token::AND:
435      break;
436    case Token::BIT_OR:
437    case Token::BIT_XOR:
438    case Token::BIT_AND:
439    case Token::SHL:
440    case Token::SAR:
441    case Token::SHR:
442      node->type()->SetAsLikelySmiIfUnknown();
443      node->left()->type()->SetAsLikelySmiIfUnknown();
444      node->right()->type()->SetAsLikelySmiIfUnknown();
445      break;
446    case Token::ADD:
447    case Token::SUB:
448    case Token::MUL:
449    case Token::DIV:
450    case Token::MOD:
451      if (node->type()->IsLikelySmi()) {
452        node->left()->type()->SetAsLikelySmiIfUnknown();
453        node->right()->type()->SetAsLikelySmiIfUnknown();
454      }
455      break;
456    default:
457      UNREACHABLE();
458      break;
459  }
460
461  Visit(node->left());
462  Visit(node->right());
463
464  // After visiting the operand nodes we have to check if this node's type
465  // can be updated. If it does, then we can push that information down
466  // towards the leafs again if the new information is an upgrade over the
467  // previous type of the operand nodes.
468  if (node->type()->IsUnknown()) {
469    if (node->left()->type()->IsLikelySmi() ||
470        node->right()->type()->IsLikelySmi()) {
471      node->type()->SetAsLikelySmi();
472    }
473    if (node->type()->IsLikelySmi()) {
474      // The type of this node changed to LIKELY_SMI. Propagate this knowledge
475      // down through the nodes.
476      if (node->left()->type()->IsUnknown()) {
477        node->left()->type()->SetAsLikelySmi();
478        Visit(node->left());
479      }
480      if (node->right()->type()->IsUnknown()) {
481        node->right()->type()->SetAsLikelySmi();
482        Visit(node->right());
483      }
484    }
485  }
486}
487
488
489void AstOptimizer::VisitCompareOperation(CompareOperation* node) {
490  if (node->type()->IsKnown()) {
491    // Propagate useful information down towards the leafs.
492    node->left()->type()->SetAsLikelySmiIfUnknown();
493    node->right()->type()->SetAsLikelySmiIfUnknown();
494  }
495
496  Visit(node->left());
497  Visit(node->right());
498
499  // After visiting the operand nodes we have to check if this node's type
500  // can be updated. If it does, then we can push that information down
501  // towards the leafs again if the new information is an upgrade over the
502  // previous type of the operand nodes.
503  if (node->type()->IsUnknown()) {
504    if (node->left()->type()->IsLikelySmi() ||
505        node->right()->type()->IsLikelySmi()) {
506      node->type()->SetAsLikelySmi();
507    }
508    if (node->type()->IsLikelySmi()) {
509      // The type of this node changed to LIKELY_SMI. Propagate this knowledge
510      // down through the nodes.
511      if (node->left()->type()->IsUnknown()) {
512        node->left()->type()->SetAsLikelySmi();
513        Visit(node->left());
514      }
515      if (node->right()->type()->IsUnknown()) {
516        node->right()->type()->SetAsLikelySmi();
517        Visit(node->right());
518      }
519    }
520  }
521}
522
523
524void AstOptimizer::VisitThisFunction(ThisFunction* node) {
525  USE(node);
526}
527
528
529class Processor: public AstVisitor {
530 public:
531  explicit Processor(VariableProxy* result)
532      : result_(result),
533        result_assigned_(false),
534        is_set_(false),
535        in_try_(false) {
536  }
537
538  void Process(ZoneList<Statement*>* statements);
539  bool result_assigned() const  { return result_assigned_; }
540
541 private:
542  VariableProxy* result_;
543
544  // We are not tracking result usage via the result_'s use
545  // counts (we leave the accurate computation to the
546  // usage analyzer). Instead we simple remember if
547  // there was ever an assignment to result_.
548  bool result_assigned_;
549
550  // To avoid storing to .result all the time, we eliminate some of
551  // the stores by keeping track of whether or not we're sure .result
552  // will be overwritten anyway. This is a bit more tricky than what I
553  // was hoping for
554  bool is_set_;
555  bool in_try_;
556
557  Expression* SetResult(Expression* value) {
558    result_assigned_ = true;
559    return new Assignment(Token::ASSIGN, result_, value,
560                          RelocInfo::kNoPosition);
561  }
562
563  // Node visitors.
564#define DEF_VISIT(type) \
565  virtual void Visit##type(type* node);
566  AST_NODE_LIST(DEF_VISIT)
567#undef DEF_VISIT
568
569  void VisitIterationStatement(IterationStatement* stmt);
570};
571
572
573void Processor::Process(ZoneList<Statement*>* statements) {
574  for (int i = statements->length() - 1; i >= 0; --i) {
575    Visit(statements->at(i));
576  }
577}
578
579
580void Processor::VisitBlock(Block* node) {
581  // An initializer block is the rewritten form of a variable declaration
582  // with initialization expressions. The initializer block contains the
583  // list of assignments corresponding to the initialization expressions.
584  // While unclear from the spec (ECMA-262, 3rd., 12.2), the value of
585  // a variable declaration with initialization expression is 'undefined'
586  // with some JS VMs: For instance, using smjs, print(eval('var x = 7'))
587  // returns 'undefined'. To obtain the same behavior with v8, we need
588  // to prevent rewriting in that case.
589  if (!node->is_initializer_block()) Process(node->statements());
590}
591
592
593void Processor::VisitExpressionStatement(ExpressionStatement* node) {
594  // Rewrite : <x>; -> .result = <x>;
595  if (!is_set_) {
596    node->set_expression(SetResult(node->expression()));
597    if (!in_try_) is_set_ = true;
598  }
599}
600
601
602void Processor::VisitIfStatement(IfStatement* node) {
603  // Rewrite both then and else parts (reversed).
604  bool save = is_set_;
605  Visit(node->else_statement());
606  bool set_after_then = is_set_;
607  is_set_ = save;
608  Visit(node->then_statement());
609  is_set_ = is_set_ && set_after_then;
610}
611
612
613void Processor::VisitIterationStatement(IterationStatement* node) {
614  // Rewrite the body.
615  bool set_after_loop = is_set_;
616  Visit(node->body());
617  is_set_ = is_set_ && set_after_loop;
618}
619
620
621void Processor::VisitDoWhileStatement(DoWhileStatement* node) {
622  VisitIterationStatement(node);
623}
624
625
626void Processor::VisitWhileStatement(WhileStatement* node) {
627  VisitIterationStatement(node);
628}
629
630
631void Processor::VisitForStatement(ForStatement* node) {
632  VisitIterationStatement(node);
633}
634
635
636void Processor::VisitForInStatement(ForInStatement* node) {
637  VisitIterationStatement(node);
638}
639
640
641void Processor::VisitTryCatchStatement(TryCatchStatement* node) {
642  // Rewrite both try and catch blocks (reversed order).
643  bool set_after_catch = is_set_;
644  Visit(node->catch_block());
645  is_set_ = is_set_ && set_after_catch;
646  bool save = in_try_;
647  in_try_ = true;
648  Visit(node->try_block());
649  in_try_ = save;
650}
651
652
653void Processor::VisitTryFinallyStatement(TryFinallyStatement* node) {
654  // Rewrite both try and finally block (reversed order).
655  Visit(node->finally_block());
656  bool save = in_try_;
657  in_try_ = true;
658  Visit(node->try_block());
659  in_try_ = save;
660}
661
662
663void Processor::VisitSwitchStatement(SwitchStatement* node) {
664  // Rewrite statements in all case clauses in reversed order.
665  ZoneList<CaseClause*>* clauses = node->cases();
666  bool set_after_switch = is_set_;
667  for (int i = clauses->length() - 1; i >= 0; --i) {
668    CaseClause* clause = clauses->at(i);
669    Process(clause->statements());
670  }
671  is_set_ = is_set_ && set_after_switch;
672}
673
674
675void Processor::VisitContinueStatement(ContinueStatement* node) {
676  is_set_ = false;
677}
678
679
680void Processor::VisitBreakStatement(BreakStatement* node) {
681  is_set_ = false;
682}
683
684
685// Do nothing:
686void Processor::VisitDeclaration(Declaration* node) {}
687void Processor::VisitEmptyStatement(EmptyStatement* node) {}
688void Processor::VisitReturnStatement(ReturnStatement* node) {}
689void Processor::VisitWithEnterStatement(WithEnterStatement* node) {}
690void Processor::VisitWithExitStatement(WithExitStatement* node) {}
691void Processor::VisitDebuggerStatement(DebuggerStatement* node) {}
692
693
694// Expressions are never visited yet.
695void Processor::VisitFunctionLiteral(FunctionLiteral* node) {
696  USE(node);
697  UNREACHABLE();
698}
699
700
701void Processor::VisitFunctionBoilerplateLiteral(
702    FunctionBoilerplateLiteral* node) {
703  USE(node);
704  UNREACHABLE();
705}
706
707
708void Processor::VisitConditional(Conditional* node) {
709  USE(node);
710  UNREACHABLE();
711}
712
713
714void Processor::VisitSlot(Slot* node) {
715  USE(node);
716  UNREACHABLE();
717}
718
719
720void Processor::VisitVariableProxy(VariableProxy* node) {
721  USE(node);
722  UNREACHABLE();
723}
724
725
726void Processor::VisitLiteral(Literal* node) {
727  USE(node);
728  UNREACHABLE();
729}
730
731
732void Processor::VisitRegExpLiteral(RegExpLiteral* node) {
733  USE(node);
734  UNREACHABLE();
735}
736
737
738void Processor::VisitArrayLiteral(ArrayLiteral* node) {
739  USE(node);
740  UNREACHABLE();
741}
742
743
744void Processor::VisitObjectLiteral(ObjectLiteral* node) {
745  USE(node);
746  UNREACHABLE();
747}
748
749
750void Processor::VisitCatchExtensionObject(CatchExtensionObject* node) {
751  USE(node);
752  UNREACHABLE();
753}
754
755
756void Processor::VisitAssignment(Assignment* node) {
757  USE(node);
758  UNREACHABLE();
759}
760
761
762void Processor::VisitThrow(Throw* node) {
763  USE(node);
764  UNREACHABLE();
765}
766
767
768void Processor::VisitProperty(Property* node) {
769  USE(node);
770  UNREACHABLE();
771}
772
773
774void Processor::VisitCall(Call* node) {
775  USE(node);
776  UNREACHABLE();
777}
778
779
780void Processor::VisitCallNew(CallNew* node) {
781  USE(node);
782  UNREACHABLE();
783}
784
785
786void Processor::VisitCallRuntime(CallRuntime* node) {
787  USE(node);
788  UNREACHABLE();
789}
790
791
792void Processor::VisitUnaryOperation(UnaryOperation* node) {
793  USE(node);
794  UNREACHABLE();
795}
796
797
798void Processor::VisitCountOperation(CountOperation* node) {
799  USE(node);
800  UNREACHABLE();
801}
802
803
804void Processor::VisitBinaryOperation(BinaryOperation* node) {
805  USE(node);
806  UNREACHABLE();
807}
808
809
810void Processor::VisitCompareOperation(CompareOperation* node) {
811  USE(node);
812  UNREACHABLE();
813}
814
815
816void Processor::VisitThisFunction(ThisFunction* node) {
817  USE(node);
818  UNREACHABLE();
819}
820
821
822bool Rewriter::Process(FunctionLiteral* function) {
823  HistogramTimerScope timer(&Counters::rewriting);
824  Scope* scope = function->scope();
825  if (scope->is_function_scope()) return true;
826
827  ZoneList<Statement*>* body = function->body();
828  if (body->is_empty()) return true;
829
830  VariableProxy* result = scope->NewTemporary(Factory::result_symbol());
831  Processor processor(result);
832  processor.Process(body);
833  if (processor.HasStackOverflow()) return false;
834
835  if (processor.result_assigned()) body->Add(new ReturnStatement(result));
836  return true;
837}
838
839
840bool Rewriter::Optimize(FunctionLiteral* function) {
841  ZoneList<Statement*>* body = function->body();
842
843  if (FLAG_optimize_ast && !body->is_empty()) {
844    HistogramTimerScope timer(&Counters::ast_optimization);
845    AstOptimizer optimizer(function->name());
846    optimizer.Optimize(body);
847    if (optimizer.HasStackOverflow()) {
848      return false;
849    }
850  }
851  return true;
852}
853
854
855} }  // namespace v8::internal
856