| // Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| #ifndef VM_AST_TRANSFORMER_H_ |
| #define VM_AST_TRANSFORMER_H_ |
| |
| #include "platform/assert.h" |
| #include "vm/ast.h" |
| |
| namespace dart { |
| |
| class Thread; |
| |
| // Translate an AstNode containing an expression (that itself contains one or |
| // more awaits) into a sequential representation where subexpressions are |
| // evaluated sequentially into intermediates. Those intermediates are stored |
| // within a context. |
| // |
| // This allows a function to be suspended and resumed from within evaluating an |
| // expression. The evaluation is split among a so-called preamble and the |
| // evaluation of the resulting expression (which is only a single load). |
| // |
| // Example (minimalistic): |
| // |
| // var a = (await bar()) + foo(); |
| // |
| // This translates to a premable similar to: |
| // |
| // var t_1, t_2, t_3, t_4; // All stored in a context. |
| // t_1 = bar(); |
| // :result_param = t_1; |
| // <continuation logic> |
| // t_2 = :result_param; |
| // t_3 = foo(); |
| // t_4 = t_2.operator+(t_3); |
| // |
| // and a resulting expression of a load of t_4. |
| // |
| class AwaitTransformer : public AstNodeVisitor { |
| public: |
| AwaitTransformer(SequenceNode* preamble, LocalScope* async_temp_scope); |
| |
| #define DECLARE_VISIT(BaseName) \ |
| virtual void Visit##BaseName##Node(BaseName##Node* node); |
| |
| FOR_EACH_NODE(DECLARE_VISIT) |
| #undef DECLARE_VISIT |
| |
| AstNode* Transform(AstNode* expr); |
| |
| private: |
| LocalVariable* EnsureCurrentTempVar(); |
| LocalVariable* AddToPreambleNewTempVar(AstNode* node); |
| ArgumentListNode* TransformArguments(ArgumentListNode* node); |
| AstNode* LazyTransform(const Token::Kind kind, |
| AstNode* new_left, |
| AstNode* right); |
| LocalScope* ChainNewScope(LocalScope* parent); |
| LocalVariable* GetVariableInScope(LocalScope* scope, const String& symbol); |
| |
| void NextTempVar() { temp_cnt_++; } |
| |
| Thread* thread() const { return thread_; } |
| |
| SequenceNode* preamble_; |
| int32_t temp_cnt_; |
| AstNode* result_; |
| LocalScope* async_temp_scope_; |
| |
| Thread* thread_; |
| |
| DISALLOW_COPY_AND_ASSIGN(AwaitTransformer); |
| }; |
| |
| } // namespace dart |
| |
| #endif // VM_AST_TRANSFORMER_H_ |