1 // backend.h -- Go frontend interface to backend -*- C++ -*-
3 // Copyright 2011 The Go Authors. All rights reserved.
4 // Use of this source code is governed by a BSD-style
5 // license that can be found in the LICENSE file.
10 // Pointers to these types are created by the backend, passed to the
11 // frontend, and passed back to the backend. The types must be
12 // defined by the backend using these names.
14 // The backend representation of a type.
17 // The backend represention of an expression.
20 // The backend representation of a statement.
23 // The backend representation of a function definition.
26 // The backend representation of a block.
29 // The backend representation of a variable.
32 // The backend representation of a label.
35 // The backend interface. This is a pure abstract class that a
36 // specific backend will implement.
41 virtual ~Backend() { }
43 // Name/type/location. Used for function parameters, struct fields,
45 struct Btyped_identifier
52 : name(), btype(NULL), location(UNKNOWN_LOCATION)
55 Btyped_identifier(const std::string& a_name, Btype* a_btype,
57 : name(a_name), btype(a_btype), location(a_location)
63 // Produce an error type. Actually the backend could probably just
64 // crash if this is called.
68 // Get a void type. This is used in (at least) two ways: 1) as the
69 // return type of a function with no result parameters; 2)
70 // unsafe.Pointer is represented as *void.
74 // Get the unnamed boolean type.
78 // Get an unnamed integer type with the given signedness and number
81 integer_type(bool is_unsigned, int bits) = 0;
83 // Get an unnamed floating point type with the given number of bits
86 float_type(int bits) = 0;
88 // Get an unnamed complex type with the given number of bits (64 or 128).
90 complex_type(int bits) = 0;
92 // Get a pointer type.
94 pointer_type(Btype* to_type) = 0;
96 // Get a function type. The receiver, parameter, and results are
97 // generated from the types in the Function_type. The Function_type
98 // is provided so that the names are available.
100 function_type(const Btyped_identifier& receiver,
101 const std::vector<Btyped_identifier>& parameters,
102 const std::vector<Btyped_identifier>& results,
103 Location location) = 0;
105 // Get a struct type.
107 struct_type(const std::vector<Btyped_identifier>& fields) = 0;
109 // Get an array type.
111 array_type(Btype* element_type, Bexpression* length) = 0;
113 // Create a placeholder pointer type. This is used for a named
114 // pointer type, since in Go a pointer type may refer to itself.
115 // NAME is the name of the type, and the location is where the named
116 // type is defined. This function is also used for unnamed function
117 // types with multiple results, in which case the type has no name
118 // and NAME will be empty. FOR_FUNCTION is true if this is for a Go
119 // function type, which corresponds to a C/C++ pointer to function
120 // type. The return value will later be passed as the first
121 // parameter to set_placeholder_pointer_type or
122 // set_placeholder_function_type.
124 placeholder_pointer_type(const std::string& name, Location,
125 bool for_function) = 0;
127 // Fill in a placeholder pointer type as a pointer. This takes a
128 // type returned by placeholder_pointer_type and arranges for it to
129 // point to to_type. Returns true on success, false on failure.
131 set_placeholder_pointer_type(Btype* placeholder, Btype* to_type) = 0;
133 // Fill in a placeholder pointer type as a function. This takes a
134 // type returned by placeholder_pointer_type and arranges for it to
135 // become a real Go function type (which corresponds to a C/C++
136 // pointer to function type). FT will be something returned by the
137 // function_type method. Returns true on success, false on failure.
139 set_placeholder_function_type(Btype* placeholder, Btype* ft) = 0;
141 // Create a placeholder struct type. This is used for a named
142 // struct type, as with placeholder_pointer_type.
144 placeholder_struct_type(const std::string& name, Location) = 0;
146 // Fill in a placeholder struct type. This takes a type returned by
147 // placeholder_struct_type and arranges for it to become a real
148 // struct type. The parameter is as for struct_type. Returns true
149 // on success, false on failure.
151 set_placeholder_struct_type(Btype* placeholder,
152 const std::vector<Btyped_identifier>& fields)
155 // Create a placeholder array type. This is used for a named array
156 // type, as with placeholder_pointer_type, to handle cases like
159 placeholder_array_type(const std::string& name, Location) = 0;
161 // Fill in a placeholder array type. This takes a type returned by
162 // placeholder_array_type and arranges for it to become a real array
163 // type. The parameters are as for array_type. Returns true on
164 // success, false on failure.
166 set_placeholder_array_type(Btype* placeholder, Btype* element_type,
167 Bexpression* length) = 0;
169 // Return a named version of a type. The location is the location
170 // of the type definition. This will not be called for a type
171 // created via placeholder_pointer_type, placeholder_struct_type, or
172 // placeholder_array_type.. (It may be called for a pointer,
173 // struct, or array type in a case like "type P *byte; type Q P".)
175 named_type(const std::string& name, Btype*, Location) = 0;
177 // Create a marker for a circular pointer type. Go pointer and
178 // function types can refer to themselves in ways that are not
179 // permitted in C/C++. When a circular type is found, this function
180 // is called for the circular reference. This permits the backend
181 // to decide how to handle such a type. PLACEHOLDER is the
182 // placeholder type which has already been created; if the backend
183 // is prepared to handle a circular pointer type, it may simply
184 // return PLACEHOLDER. FOR_FUNCTION is true if this is for a
187 // For "type P *P" the sequence of calls will be
188 // bt1 = placeholder_pointer_type();
189 // bt2 = circular_pointer_type(bt1, false);
190 // set_placeholder_pointer_type(bt1, bt2);
192 circular_pointer_type(Btype* placeholder, bool for_function) = 0;
194 // Return whether the argument could be a special type created by
195 // circular_pointer_type. This is used to introduce explicit type
196 // conversions where needed. If circular_pointer_type returns its
197 // PLACEHOLDER parameter, this may safely always return false.
199 is_circular_pointer_type(Btype*) = 0;
201 // Return the size of a type.
203 type_size(Btype*) = 0;
205 // Return the alignment of a type.
207 type_alignment(Btype*) = 0;
209 // Return the alignment of a struct field of this type. This is
210 // normally the same as type_alignment, but not always.
212 type_field_alignment(Btype*) = 0;
214 // Return the offset of field INDEX in a struct type. INDEX is the
215 // entry in the FIELDS std::vector parameter of struct_type or
216 // set_placeholder_struct_type.
218 type_field_offset(Btype*, size_t index) = 0;
222 // Return an expression for a zero value of the given type. This is
223 // used for cases such as local variable initialization and
224 // converting nil to other types.
226 zero_expression(Btype*) = 0;
230 // Create an error statement. This is used for cases which should
231 // not occur in a correct program, in order to keep the compilation
232 // going without crashing.
234 error_statement() = 0;
236 // Create an expression statement.
238 expression_statement(Bexpression*) = 0;
240 // Create a variable initialization statement. This initializes a
241 // local variable at the point in the program flow where it is
244 init_statement(Bvariable* var, Bexpression* init) = 0;
246 // Create an assignment statement.
248 assignment_statement(Bexpression* lhs, Bexpression* rhs,
251 // Create a return statement, passing the representation of the
252 // function and the list of values to return.
254 return_statement(Bfunction*, const std::vector<Bexpression*>&,
257 // Create an if statement. ELSE_BLOCK may be NULL.
259 if_statement(Bexpression* condition, Bblock* then_block, Bblock* else_block,
262 // Create a switch statement where the case values are constants.
263 // CASES and STATEMENTS must have the same number of entries. If
264 // VALUE matches any of the list in CASES[i], which will all be
265 // integers, then STATEMENTS[i] is executed. STATEMENTS[i] will
266 // either end with a goto statement or will fall through into
267 // STATEMENTS[i + 1]. CASES[i] is empty for the default clause,
268 // which need not be last.
270 switch_statement(Bexpression* value,
271 const std::vector<std::vector<Bexpression*> >& cases,
272 const std::vector<Bstatement*>& statements,
275 // Create a single statement from two statements.
277 compound_statement(Bstatement*, Bstatement*) = 0;
279 // Create a single statement from a list of statements.
281 statement_list(const std::vector<Bstatement*>&) = 0;
285 // Create a block. The frontend will call this function when it
286 // starts converting a block within a function. FUNCTION is the
287 // current function. ENCLOSING is the enclosing block; it will be
288 // NULL for the top-level block in a function. VARS is the list of
289 // local variables defined within this block; each entry will be
290 // created by the local_variable function. START_LOCATION is the
291 // location of the start of the block, more or less the location of
292 // the initial curly brace. END_LOCATION is the location of the end
293 // of the block, more or less the location of the final curly brace.
294 // The statements will be added after the block is created.
296 block(Bfunction* function, Bblock* enclosing,
297 const std::vector<Bvariable*>& vars,
298 Location start_location, Location end_location) = 0;
300 // Add the statements to a block. The block is created first. Then
301 // the statements are created. Then the statements are added to the
302 // block. This will called exactly once per block. The vector may
303 // be empty if there are no statements.
305 block_add_statements(Bblock*, const std::vector<Bstatement*>&) = 0;
307 // Return the block as a statement. This is used to include a block
308 // in a list of statements.
310 block_statement(Bblock*) = 0;
314 // Create an error variable. This is used for cases which should
315 // not occur in a correct program, in order to keep the compilation
316 // going without crashing.
318 error_variable() = 0;
320 // Create a global variable. PACKAGE_NAME is the name of the
321 // package where the variable is defined. UNIQUE_PREFIX is the
322 // prefix for that package, from the -fgo-prefix option. NAME is
323 // the name of the variable. BTYPE is the type of the variable.
324 // IS_EXTERNAL is true if the variable is defined in some other
325 // package. IS_HIDDEN is true if the variable is not exported (name
326 // begins with a lower case letter). LOCATION is where the variable
329 global_variable(const std::string& package_name,
330 const std::string& unique_prefix,
331 const std::string& name,
335 Location location) = 0;
337 // A global variable will 1) be initialized to zero, or 2) be
338 // initialized to a constant value, or 3) be initialized in the init
339 // function. In case 2, the frontend will call
340 // global_variable_set_init to set the initial value. If this is
341 // not called, the backend should initialize a global variable to 0.
342 // The init function may then assign a value to it.
344 global_variable_set_init(Bvariable*, Bexpression*) = 0;
346 // Create a local variable. The frontend will create the local
347 // variables first, and then create the block which contains them.
348 // FUNCTION is the function in which the variable is defined. NAME
349 // is the name of the variable. TYPE is the type. IS_ADDRESS_TAKEN
350 // is true if the address of this variable is taken (this implies
351 // that the address does not escape the function, as otherwise the
352 // variable would be on the heap). LOCATION is where the variable
353 // is defined. For each local variable the frontend will call
354 // init_statement to set the initial value.
356 local_variable(Bfunction* function, const std::string& name, Btype* type,
357 bool is_address_taken, Location location) = 0;
359 // Create a function parameter. This is an incoming parameter, not
360 // a result parameter (result parameters are treated as local
361 // variables). The arguments are as for local_variable.
363 parameter_variable(Bfunction* function, const std::string& name,
364 Btype* type, bool is_address_taken,
365 Location location) = 0;
367 // Create a temporary variable. A temporary variable has no name,
368 // just a type. We pass in FUNCTION and BLOCK in case they are
369 // needed. If INIT is not NULL, the variable should be initialized
370 // to that value. Otherwise the initial value is irrelevant--the
371 // backend does not have to explicitly initialize it to zero.
372 // ADDRESS_IS_TAKEN is true if the programs needs to take the
373 // address of this temporary variable. LOCATION is the location of
374 // the statement or expression which requires creating the temporary
375 // variable, and may not be very useful. This function should
376 // return a variable which can be referenced later and should set
377 // *PSTATEMENT to a statement which initializes the variable.
379 temporary_variable(Bfunction*, Bblock*, Btype*, Bexpression* init,
380 bool address_is_taken, Location location,
381 Bstatement** pstatement) = 0;
383 // Create a named immutable initialized data structure. This is
384 // used for type descriptors and map descriptors. This returns a
385 // Bvariable because it corresponds to an initialized const global
388 // NAME is the name to use for the initialized global variable which
389 // this call will create.
391 // IS_COMMON is true if NAME may be defined by several packages, and
392 // the linker should merge all such definitions. If IS_COMMON is
393 // false, NAME should be defined in only one file. In general
394 // IS_COMMON will be true for the type descriptor of an unnamed type
395 // or a builtin type.
397 // TYPE will be a struct type; the type of the returned expression
398 // must be a pointer to this struct type.
400 // We must create the named structure before we know its
401 // initializer, because the initializer may refer to its own
402 // address. After calling this the frontend will call
403 // immutable_struct_set_init.
405 immutable_struct(const std::string& name, bool is_common, Btype* type,
408 // Set the initial value of a variable created by immutable_struct.
409 // The NAME, IS_COMMON, TYPE, and location parameters are the same
410 // ones passed to immutable_struct. INITIALIZER will be a composite
411 // literal of type TYPE. It will not contain any function calls or
412 // anything else which can not be put into a read-only data section.
413 // It may contain the address of variables created by
416 immutable_struct_set_init(Bvariable*, const std::string& name,
417 bool is_common, Btype* type, Location,
418 Bexpression* initializer) = 0;
420 // Create a reference to a named immutable initialized data
421 // structure defined in some other package. This will be a
422 // structure created by a call to immutable_struct with the same
423 // NAME and TYPE and with IS_COMMON passed as false. This
424 // corresponds to an extern const global variable in C.
426 immutable_struct_reference(const std::string& name, Btype* type,
431 // Create a new label. NAME will be empty if this is a label
432 // created by the frontend for a loop construct. The location is
433 // where the the label is defined.
435 label(Bfunction*, const std::string& name, Location) = 0;
437 // Create a statement which defines a label. This statement will be
438 // put into the codestream at the point where the label should be
441 label_definition_statement(Blabel*) = 0;
443 // Create a goto statement to a label.
445 goto_statement(Blabel*, Location) = 0;
447 // Create an expression for the address of a label. This is used to
448 // get the return address of a deferred function which may call
451 label_address(Blabel*, Location) = 0;
454 // The backend interface has to define this function.
456 extern Backend* go_get_backend();
458 // FIXME: Temporary helper functions while converting to new backend
461 extern Btype* tree_to_type(tree);
462 extern Bexpression* tree_to_expr(tree);
463 extern Bstatement* tree_to_stat(tree);
464 extern Bfunction* tree_to_function(tree);
465 extern Bblock* tree_to_block(tree);
466 extern tree type_to_tree(Btype*);
467 extern tree expr_to_tree(Bexpression*);
468 extern tree stat_to_tree(Bstatement*);
469 extern tree block_to_tree(Bblock*);
470 extern tree var_to_tree(Bvariable*);
472 #endif // !defined(GO_BACKEND_H)