source: src/AST/porting.md @ 89c2f7c9

arm-ehcleanup-dtorsenumforall-pointer-decayjacob/cs343-translationjenkins-sandboxnew-astnew-ast-unique-exprpthread-emulationqualifiedEnum
Last change on this file since 89c2f7c9 was 89c2f7c9, checked in by Aaron Moss <a3moss@…>, 4 years ago

Merge branch 'master' of plg.uwaterloo.ca:software/cfa/cfa-cc

  • Property mode set to 100644
File size: 8.5 KB
Line 
1# Porting notes for new AST #
2
3## Pointer Types ##
4* raw pointer `T*` is used for construction, but not storage
5* `ast::ptr_base<T,R>` is a pointer to AST node `T` with reference type `R`
6  * specialization: strong pointer `ast::ptr<T>` is used for an ownership relationship
7  * specialization: weak pointer `ast::readonly<T>` is used for an observation relationship
8  * added `ast::ptr_base<T,R>::as<S>()` with same semantics as `dynamic_cast<S*>(p)`
9
10## Visitors ##
11* `Visitor` and `Mutator` are combined into a single `ast::Visitor` class
12  * Base nodes now override `const Node * accept( Visitor & v ) const = 0` with, e.g. `const Stmt * accept( Visitor & v ) const override = 0`
13* `PassVisitor` is replaced with `ast::Pass`
14
15## Structural Changes ##
16`CodeLocation` has been devolved from `BaseSyntaxNode` to `ast::ParseNode`
17* excludes `ast::Type` from carrying location information
18* `CodeLocation` is a mandatory constructor field for `ast::ParseNode`
19  * all subclass constructors must fill it; by convention, from their first argument
20
21`N->print(std::ostream&)` is a visitor now, port these methods to `ast::Print` class
22* **TODO** write this visitor
23* **TODO** write `std::ostream& operator<< ( std::ostream& out, const Node* node )` in `Node.hpp` in terms of `ast::Print`
24* `Declaration::printShort` should also be integrated
25
26`clone` is private to `Node` now
27* still needs to be overriden to return appropriate type
28  * e.g. `private: virtual Stmt * clone() const override = 0;`
29  * because friendship is not inherited, all implementations of clone need
30      /// Must be copied in ALL derived classes
31      template<typename node_t>
32      friend auto mutate(const node_t * node);
33
34All leaves of the `Node` inheritance tree are now declared `final`
35* e.g. `class CompoundStmt final : public Stmt`
36* allows compiler to optimize virtual calls to static calls if given static type
37
38Pulled `FuncSpecifiers`, `StorageClasses`, `CVQualifiers` out of `Type` into their own headers
39* Made `BFCommon` a `MakeBitfield` macro in its own header
40  * added default and field-init constructors to macro
41
42Prefer move semantics for containers passed to node constructors
43
44## Code Style ##
45
46### Files ###
47* Headers have a `.hpp` suffix
48* Source code has a `.cpp` suffix
49* All source has the project-standard leading and trailing comments
50* prefer `#pragma once` over `#ifdef` guards
51* namespaces that cover entire files don't get indented
52
53### Documentation ###
54* class, method, and field comments should use doxygen-style `///` prefix
55  * should be included on all classes
56  * should be included on any method declaration that doesn't have an obvious behaviour from either naming convention (e.g. constructor, print operator, implement visitor pattern) or an inline implementation
57* use explanatory comments with `//` wherever appropriate
58  * older comments should be maintained in porting process wherever possible
59
60### Naming ###
61* Preserve names from previous AST whenever reasonable, and get team consensus on any changes.
62* Strong justification required for private fields
63  * No `get_` prefix on getters (including for generated fields)
64    * exception is `DeclWithType::get_type()`
65* Notable changes:
66  * for concision and consistency with subclasses:
67    * `Declaration` => `ast::Decl`
68        * `DeclarationWithType` => `ast::DeclWithType`
69        * `Expression` => `ast::Expr`
70        * `Initializer` => `ast::Init`
71    * `Statement` => `ast::Stmt`
72        * any field names should follow a similar renaming
73  * because they don't really belong to `Type` (and for consistency with `Linkage::Spec`):
74    * `Type::StorageClasses` => `ast::Storage::Classes`
75          * `Type::Extern` etc. => `ast::Storage::Extern` etc.
76        * `Type::FuncSpecifiers` => `ast::Function::Specs`
77          * `Type::Inline` etc. => `ast::Function::Inline` etc.
78        * `Type::Qualifiers` => `ast::CV::Qualifiers`
79          * `Type::Const` etc. => `ast::CV::Const`
80          * couldn't break name-dependency loop without pulling `Qualifiers` out of `Type`
81        * `LinkageSpec::Spec` => `ast::Linkage::Spec`
82          * `LinkageSpec::Mangle` etc. => `ast::Linkage::Mangle` etc.
83          * `LinkageSpec::linkageUpdate` => `ast::Linkage::update`
84          * `LinkageSpec::linkageName` => `ast::Linkage::name`
85          * `LinkageSpec::isMangled(Spec)` etc. => `Spec.is_mangled` etc.
86          * `LinkageSpec::Intrinsic` etc. => `ast::Linkage::Intrinsic` etc.
87* Boolean constructor parameters get replaced with a dedicated flag enum:
88  * e.g. `bool isVarLen;` => `enum LengthFlag { FixedLen, VariableLen };` `LengthFlag isVarLen;`
89  * field can be *read* in the existing boolean contexts, but requires documentation to write
90  * suggest naming all flag enums `FooFlag` to hint at boolean nature
91
92## Specific Nodes ##
93`Decl`
94* `storageClasses` => `storage`
95* `declFromId()` => `fromId()`
96  * not 100% sure about the return type here...
97
98`DeclWithType`
99* When `SymTab::Validate::Pass2` is rewritten, update comment on `mangleName` with new name of pass
100* `get_scopedMangleName()` => `scopedMangleName()`
101* `get_type()` now returns `const Type*` so can't be inadvertently mutated
102  * still with `get_` name so it doesn't conflict with subclass field names
103
104`ObjectDecl`
105* changed constructor parameter order for better defaults
106  * allows `newObject` as just default settings
107
108`TypeDecl`
109* moved `TypeDecl::Kind` to `ast::TypeVar::Kind`
110
111`EnumDecl`
112* **TODO** rebuild `eval` for new AST (re: `valueOf` implementation)
113
114`Expr`
115* Merged `inferParams`/`resnSlots` into union, as suggested by comment in old version
116  * does imply get_/set_ API, and some care about moving backward
117
118`Init`
119* `bool maybeConstruct` => `enum ConstructFlag { DoConstruct, MaybeConstruct }`
120
121`Label`
122* `get_statement()` exclusively used for code location, replaced with `CodeLocation` field
123
124`CaseStmt`
125* `_isDefault` has been removed
126  * `isDefault` calculates value from `cond`
127  * default may not have a condition. I believe case (!default) requires a condition.
128
129`BranchStmt`
130* `Type` -> `Kind` and `type` -> `kind`
131* Constructors no longer throw SemanticErrorException:
132  * `label` constructor claims it is now considered a syntax error, replaced with assert.
133  * `computedTarget` constructor assumes `Goto`, other check would have SegFaulted.
134
135`TryStmt`
136* `block` -> `body` and `finallyBlock` -> `finally`
137
138`FinallyStmt`
139* `block` -> `body`
140
141`CompoundStmt`
142* **TODO** port copy operator
143  * Needs to be an almost-shallow clone, where the declarations are cloned only if needed
144  * **TODO** port `DeclReplacer`
145* Still a `std::list` for children, rather than `std::vector`
146  * allows more-efficient splicing for purposes of later code generation
147
148`Type`
149* `CV::Qualifiers` moved to end of constructor parameter list, defaulted to `{}`
150  * `ReferenceToType` puts a defaulted list of attributes after qualifiers
151* `forall` field split off into `ParameterizedType` subclass
152  * any type that needs it can inherit from `ParameterizedType`
153    * currently `FunctionType`, `ReferenceToType`
154* `get_qualifiers()` replaced with accessor `qualifiers()` and mutator `set_qualifiers()`
155  * `get_const()` etc. replaced with `is_const()` etc. variants
156* `referenceDepth()` now returns `unsigned` rather than `int`
157* A number of features only supported on aggregates pushed down to `ReferenceToType`:
158  * `attributes`: per docs [1] GCC only supports type attributes on aggregates and typedefs
159    * suggest adding a `TypeWithAttributes` wrapper type if this proves insufficient
160  * `getAggr()` => `aggr()`
161    * also now returns `const AggregateDecl *`
162* `genericSubstitution()` moved to own visitor **TODO** write
163
164`BasicType`
165* **TODO** move `kind`, `typeNames` into code generator
166
167`ReferenceToType`
168* deleted `get_baseParameters()` from children
169  * replace with `aggr() ? aggr()->parameters : nullptr`
170* hoisted `lookup` implementation into parent, made non-virtual
171  * also changed to return vector rather than filling; change back if any great win for reuse
172* `baseStruct` etc. renamed to `base`
173
174`PointerType`/`ArrayType`
175* `is_array()` => `isArray()`
176* `bool isVarLen;` => `enum LengthFlag { FixedLen, VariableLen }; LengthFlag isVarLen;`
177* `bool isStatic;` => `enum DimensionFlag { DynamicDim, StaticDim }; DimensionFlag isStatic;`
178
179`FunctionType`
180* `bool isVarArgs;` => `enum ArgumentFlag { FixedArgs, VariableArgs }; ArgumentFlag isVarArgs;`
181
182`TypeInstType`
183* `bool isFtype` => `TypeVar::Kind kind`
184
185`TypeofType`
186* `bool is_basetypeof` => `enum Kind { Typeof, Basetypeof } kind;`
187
188`TupleType`
189* removed `value_type` typedef due to likely error
190  * if readded, should be `const Type *`
191
192`AttrType`
193* did not port due to deprecation of feature
194  * feature is `type@thing` e.g. `int@MAX`
195
196[1] https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Type-Attributes.html#Type-Attributes
197
Note: See TracBrowser for help on using the repository browser.