1 // Copyright 2014 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #ifndef V8_AST_AST_NUMBERING_H_
6 #define V8_AST_AST_NUMBERING_H_
7 
8 namespace v8 {
9 namespace internal {
10 
11 // Forward declarations.
12 class FunctionLiteral;
13 class Isolate;
14 class Zone;
15 
16 namespace AstNumbering {
17 // Assign type feedback IDs, bailout IDs, and generator yield IDs to an AST node
18 // tree; perform catch prediction for TryStatements.
19 bool Renumber(Isolate* isolate, Zone* zone, FunctionLiteral* function);
20 }
21 
22 // Some details on yield IDs
23 // -------------------------
24 //
25 // In order to assist Ignition in generating bytecode for a generator function,
26 // we assign a unique number (the yield ID) to each Yield node in its AST. We
27 // also annotate loops with the number of yields they contain (loop.yield_count)
28 // and the smallest ID of those (loop.first_yield_id), and we annotate the
29 // function itself with the number of yields it contains (function.yield_count).
30 //
31 // The way in which we choose the IDs is simply by enumerating the Yield nodes.
32 // Ignition relies on the following properties:
33 // - For each loop l and each yield y of l:
34 //     l.first_yield_id  <=  y.yield_id  <  l.first_yield_id + l.yield_count
35 // - For the generator function f itself and each yield y of f:
36 //                    0  <=  y.yield_id  <  f.yield_count
37 
38 }  // namespace internal
39 }  // namespace v8
40 
41 #endif  // V8_AST_AST_NUMBERING_H_
42