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| 1 // Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file |
| 2 // for details. All rights reserved. Use of this source code is governed by a |
| 3 // BSD-style license that can be found in the LICENSE file. |
| 4 |
| 5 #ifndef VM_AST_TRANSFORMER_H_ |
| 6 #define VM_AST_TRANSFORMER_H_ |
| 7 |
| 8 #include "platform/assert.h" |
| 9 #include "vm/ast.h" |
| 10 |
| 11 namespace dart { |
| 12 |
| 13 class ParsedFunction; |
| 14 |
| 15 // Translate an AstNode containing an expression (that itself contains one or |
| 16 // more awaits) into a sequential representation where subexpressions are |
| 17 // evaluated sequentially into intermediates. Those intermediates are stored |
| 18 // within a context. |
| 19 // |
| 20 // This allows a function to be suspended and resumed from within evaluating an |
| 21 // expression. The evaluation is split among a so-called preamble and the |
| 22 // evaluation of the resulting expression (which is only a single load). |
| 23 // |
| 24 // Example (minimalistic): |
| 25 // |
| 26 // var a = (await bar()) + foo(); |
| 27 // |
| 28 // This translates to a premable similar to: |
| 29 // |
| 30 // var t_1, t_2, t_3, t_4; // All stored in a context. |
| 31 // t_1 = bar(); |
| 32 // :result_param = t_1; |
| 33 // <continuation logic> |
| 34 // t_2 = :result_param; |
| 35 // t_3 = foo(); |
| 36 // t_4 = t_2.operator+(t_3); |
| 37 // |
| 38 // and a resulting expression of a load of t_4. |
| 39 // |
| 40 class AwaitTransformer : public AstNodeVisitor { |
| 41 public: |
| 42 AwaitTransformer(SequenceNode* preamble, |
| 43 const Library& library, |
| 44 ParsedFunction* const parsed_function) |
| 45 : preamble_(preamble), |
| 46 temp_cnt_(0), |
| 47 library_(library), |
| 48 parsed_function_(parsed_function), |
| 49 isolate_(Isolate::Current()) {} |
| 50 |
| 51 #define DECLARE_VISIT(BaseName) \ |
| 52 virtual void Visit##BaseName##Node(BaseName##Node* node); |
| 53 |
| 54 FOR_EACH_NODE(DECLARE_VISIT) |
| 55 #undef DECLARE_VISIT |
| 56 |
| 57 AstNode* Transform(AstNode* expr); |
| 58 |
| 59 private: |
| 60 LocalVariable* EnsureCurrentTempVar(); |
| 61 LocalVariable* AddToPreambleNewTempVar(AstNode* node); |
| 62 ArgumentListNode* TransformArguments(ArgumentListNode* node); |
| 63 AstNode* LazyTransform(const Token::Kind kind, |
| 64 AstNode* new_left, |
| 65 AstNode* right); |
| 66 |
| 67 void NextTempVar() { temp_cnt_++; } |
| 68 |
| 69 Isolate* isolate() const { return isolate_; } |
| 70 |
| 71 SequenceNode* preamble_; |
| 72 int temp_cnt_; |
| 73 AstNode* result_; |
| 74 const Library& library_; |
| 75 ParsedFunction* const parsed_function_; |
| 76 |
| 77 Isolate* isolate_; |
| 78 |
| 79 DISALLOW_COPY_AND_ASSIGN(AwaitTransformer); |
| 80 }; |
| 81 |
| 82 } // namespace dart |
| 83 |
| 84 #endif // VM_AST_TRANSFORMER_H_ |
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