1 // backend.h -- Go frontend interface to backend -*- C++ -*-
2
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.
6
7 #ifndef GO_BACKEND_H
8 #define GO_BACKEND_H
9
10 #include <gmp.h>
11 #include <mpfr.h>
12 #include <mpc.h>
13
14 #include "operator.h"
15
16 // Pointers to these types are created by the backend, passed to the
17 // frontend, and passed back to the backend. The types must be
18 // defined by the backend using these names.
19
20 // The backend representation of a type.
21 class Btype;
22
23 // The backend represention of an expression.
24 class Bexpression;
25
26 // The backend representation of a statement.
27 class Bstatement;
28
29 // The backend representation of a function definition or declaration.
30 class Bfunction;
31
32 // The backend representation of a block.
33 class Bblock;
34
35 // The backend representation of a variable.
36 class Bvariable;
37
38 // The backend representation of a label.
39 class Blabel;
40
41 // The backend interface. This is a pure abstract class that a
42 // specific backend will implement.
43
44 class Backend
45 {
46 public:
47 virtual ~Backend() { }
48
49 // Name/type/location. Used for function parameters, struct fields,
50 // interface methods.
51 struct Btyped_identifier
52 {
53 std::string name;
54 Btype* btype;
55 Location location;
56
57 Btyped_identifier()
58 : name(), btype(NULL), location(Linemap::unknown_location())
59 { }
60
61 Btyped_identifier(const std::string& a_name, Btype* a_btype,
62 Location a_location)
63 : name(a_name), btype(a_btype), location(a_location)
64 { }
65 };
66
67 // Types.
68
69 // Produce an error type. Actually the backend could probably just
70 // crash if this is called.
71 virtual Btype*
72 error_type() = 0;
73
74 // Get a void type. This is used in (at least) two ways: 1) as the
75 // return type of a function with no result parameters; 2)
76 // unsafe.Pointer is represented as *void.
77 virtual Btype*
78 void_type() = 0;
79
80 // Get the unnamed boolean type.
81 virtual Btype*
82 bool_type() = 0;
83
84 // Get an unnamed integer type with the given signedness and number
85 // of bits.
86 virtual Btype*
87 integer_type(bool is_unsigned, int bits) = 0;
88
89 // Get an unnamed floating point type with the given number of bits
90 // (32 or 64).
91 virtual Btype*
92 float_type(int bits) = 0;
93
94 // Get an unnamed complex type with the given number of bits (64 or 128).
95 virtual Btype*
96 complex_type(int bits) = 0;
97
98 // Get a pointer type.
99 virtual Btype*
100 pointer_type(Btype* to_type) = 0;
101
102 // Get a function type. The receiver, parameter, and results are
103 // generated from the types in the Function_type. The Function_type
104 // is provided so that the names are available. This should return
105 // not the type of a Go function (which is a pointer to a struct)
106 // but the type of a C function pointer (which will be used as the
107 // type of the first field of the struct). If there is more than
108 // one result, RESULT_STRUCT is a struct type to hold the results,
109 // and RESULTS may be ignored; if there are zero or one results,
110 // RESULT_STRUCT is NULL.
111 virtual Btype*
112 function_type(const Btyped_identifier& receiver,
113 const std::vector<Btyped_identifier>& parameters,
114 const std::vector<Btyped_identifier>& results,
115 Btype* result_struct,
116 Location location) = 0;
117
118 // Get a struct type.
119 virtual Btype*
120 struct_type(const std::vector<Btyped_identifier>& fields) = 0;
121
122 // Get an array type.
123 virtual Btype*
124 array_type(Btype* element_type, Bexpression* length) = 0;
125
126 // Create a placeholder pointer type. This is used for a named
127 // pointer type, since in Go a pointer type may refer to itself.
128 // NAME is the name of the type, and the location is where the named
129 // type is defined. This function is also used for unnamed function
130 // types with multiple results, in which case the type has no name
131 // and NAME will be empty. FOR_FUNCTION is true if this is for a C
132 // pointer to function type. A Go func type is represented as a
133 // pointer to a struct, and the first field of the struct is a C
134 // pointer to function. The return value will later be passed as
135 // the first parameter to set_placeholder_pointer_type or
136 // set_placeholder_function_type.
137 virtual Btype*
138 placeholder_pointer_type(const std::string& name, Location,
139 bool for_function) = 0;
140
141 // Fill in a placeholder pointer type as a pointer. This takes a
142 // type returned by placeholder_pointer_type and arranges for it to
143 // point to the type that TO_TYPE points to (that is, PLACEHOLDER
144 // becomes the same type as TO_TYPE). Returns true on success,
145 // false on failure.
146 virtual bool
147 set_placeholder_pointer_type(Btype* placeholder, Btype* to_type) = 0;
148
149 // Fill in a placeholder pointer type as a function. This takes a
150 // type returned by placeholder_pointer_type and arranges for it to
151 // become a real Go function type (which corresponds to a C/C++
152 // pointer to function type). FT will be something returned by the
153 // function_type method. Returns true on success, false on failure.
154 virtual bool
155 set_placeholder_function_type(Btype* placeholder, Btype* ft) = 0;
156
157 // Create a placeholder struct type. This is used for a named
158 // struct type, as with placeholder_pointer_type. It is also used
159 // for interface types, in which case NAME will be the empty string.
160 virtual Btype*
161 placeholder_struct_type(const std::string& name, Location) = 0;
162
163 // Fill in a placeholder struct type. This takes a type returned by
164 // placeholder_struct_type and arranges for it to become a real
165 // struct type. The parameter is as for struct_type. Returns true
166 // on success, false on failure.
167 virtual bool
168 set_placeholder_struct_type(Btype* placeholder,
169 const std::vector<Btyped_identifier>& fields)
170 = 0;
171
172 // Create a placeholder array type. This is used for a named array
173 // type, as with placeholder_pointer_type, to handle cases like
174 // type A []*A.
175 virtual Btype*
176 placeholder_array_type(const std::string& name, Location) = 0;
177
178 // Fill in a placeholder array type. This takes a type returned by
179 // placeholder_array_type and arranges for it to become a real array
180 // type. The parameters are as for array_type. Returns true on
181 // success, false on failure.
182 virtual bool
183 set_placeholder_array_type(Btype* placeholder, Btype* element_type,
184 Bexpression* length) = 0;
185
186 // Return a named version of a type. The location is the location
187 // of the type definition. This will not be called for a type
188 // created via placeholder_pointer_type, placeholder_struct_type, or
189 // placeholder_array_type.. (It may be called for a pointer,
190 // struct, or array type in a case like "type P *byte; type Q P".)
191 virtual Btype*
192 named_type(const std::string& name, Btype*, Location) = 0;
193
194 // Create a marker for a circular pointer type. Go pointer and
195 // function types can refer to themselves in ways that are not
196 // permitted in C/C++. When a circular type is found, this function
197 // is called for the circular reference. This permits the backend
198 // to decide how to handle such a type. PLACEHOLDER is the
199 // placeholder type which has already been created; if the backend
200 // is prepared to handle a circular pointer type, it may simply
201 // return PLACEHOLDER. FOR_FUNCTION is true if this is for a
202 // function type.
203 //
204 // For "type P *P" the sequence of calls will be
205 // bt1 = placeholder_pointer_type();
206 // bt2 = circular_pointer_type(bt1, false);
207 // set_placeholder_pointer_type(bt1, bt2);
208 virtual Btype*
209 circular_pointer_type(Btype* placeholder, bool for_function) = 0;
210
211 // Return whether the argument could be a special type created by
212 // circular_pointer_type. This is used to introduce explicit type
213 // conversions where needed. If circular_pointer_type returns its
214 // PLACEHOLDER parameter, this may safely always return false.
215 virtual bool
216 is_circular_pointer_type(Btype*) = 0;
217
218 // Return the size of a type.
219 virtual int64_t
220 type_size(Btype*) = 0;
221
222 // Return the alignment of a type.
223 virtual int64_t
224 type_alignment(Btype*) = 0;
225
226 // Return the alignment of a struct field of this type. This is
227 // normally the same as type_alignment, but not always.
228 virtual int64_t
229 type_field_alignment(Btype*) = 0;
230
231 // Return the offset of field INDEX in a struct type. INDEX is the
232 // entry in the FIELDS std::vector parameter of struct_type or
233 // set_placeholder_struct_type.
234 virtual int64_t
235 type_field_offset(Btype*, size_t index) = 0;
236
237 // Expressions.
238
239 // Return an expression for a zero value of the given type. This is
240 // used for cases such as local variable initialization and
241 // converting nil to other types.
242 virtual Bexpression*
243 zero_expression(Btype*) = 0;
244
245 // Create an error expression. This is used for cases which should
246 // not occur in a correct program, in order to keep the compilation
247 // going without crashing.
248 virtual Bexpression*
249 error_expression() = 0;
250
251 // Create a nil pointer expression.
252 virtual Bexpression*
253 nil_pointer_expression() = 0;
254
255 // Create a reference to a variable.
256 virtual Bexpression*
257 var_expression(Bvariable* var, Location) = 0;
258
259 // Create an expression that indirects through the pointer expression EXPR
260 // (i.e., return the expression for *EXPR). KNOWN_VALID is true if the pointer
261 // is known to point to a valid memory location. BTYPE is the expected type
262 // of the indirected EXPR.
263 virtual Bexpression*
264 indirect_expression(Btype* btype, Bexpression* expr, bool known_valid,
265 Location) = 0;
266
267 // Return an expression that declares a constant named NAME with the
268 // constant value VAL in BTYPE.
269 virtual Bexpression*
270 named_constant_expression(Btype* btype, const std::string& name,
271 Bexpression* val, Location) = 0;
272
273 // Return an expression for the multi-precision integer VAL in BTYPE.
274 virtual Bexpression*
275 integer_constant_expression(Btype* btype, mpz_t val) = 0;
276
277 // Return an expression for the floating point value VAL in BTYPE.
278 virtual Bexpression*
279 float_constant_expression(Btype* btype, mpfr_t val) = 0;
280
281 // Return an expression for the complex value VAL in BTYPE.
282 virtual Bexpression*
283 complex_constant_expression(Btype* btype, mpc_t val) = 0;
284
285 // Return an expression for the string value VAL.
286 virtual Bexpression*
287 string_constant_expression(const std::string& val) = 0;
288
289 // Return an expression for the boolean value VAL.
290 virtual Bexpression*
291 boolean_constant_expression(bool val) = 0;
292
293 // Return an expression for the real part of BCOMPLEX.
294 virtual Bexpression*
295 real_part_expression(Bexpression* bcomplex, Location) = 0;
296
297 // Return an expression for the imaginary part of BCOMPLEX.
298 virtual Bexpression*
299 imag_part_expression(Bexpression* bcomplex, Location) = 0;
300
301 // Return an expression for the complex number (BREAL, BIMAG).
302 virtual Bexpression*
303 complex_expression(Bexpression* breal, Bexpression* bimag, Location) = 0;
304
305 // Return an expression that converts EXPR to TYPE.
306 virtual Bexpression*
307 convert_expression(Btype* type, Bexpression* expr, Location) = 0;
308
309 // Create an expression for the address of a function. This is used to
310 // get the address of the code for a function.
311 virtual Bexpression*
312 function_code_expression(Bfunction*, Location) = 0;
313
314 // Create an expression that takes the address of an expression.
315 virtual Bexpression*
316 address_expression(Bexpression*, Location) = 0;
317
318 // Return an expression for the field at INDEX in BSTRUCT.
319 virtual Bexpression*
320 struct_field_expression(Bexpression* bstruct, size_t index, Location) = 0;
321
322 // Create an expression that executes BSTAT before BEXPR.
323 virtual Bexpression*
324 compound_expression(Bstatement* bstat, Bexpression* bexpr, Location) = 0;
325
326 // Return an expression that executes THEN_EXPR if CONDITION is true, or
327 // ELSE_EXPR otherwise and returns the result as type BTYPE, within the
328 // specified function FUNCTION. ELSE_EXPR may be NULL. BTYPE may be NULL.
329 virtual Bexpression*
330 conditional_expression(Bfunction* function, Btype* btype,
331 Bexpression* condition, Bexpression* then_expr,
332 Bexpression* else_expr, Location) = 0;
333
334 // Return an expression for the unary operation OP EXPR.
335 // Supported values of OP are (from operators.h):
336 // MINUS, NOT, XOR.
337 virtual Bexpression*
338 unary_expression(Operator op, Bexpression* expr, Location) = 0;
339
340 // Return an expression for the binary operation LEFT OP RIGHT.
341 // Supported values of OP are (from operators.h):
342 // EQEQ, NOTEQ, LT, LE, GT, GE, PLUS, MINUS, OR, XOR, MULT, DIV, MOD,
343 // LSHIFT, RSHIFT, AND, NOT.
344 virtual Bexpression*
345 binary_expression(Operator op, Bexpression* left, Bexpression* right,
346 Location) = 0;
347
348 // Return an expression that constructs BTYPE with VALS. BTYPE must be the
349 // backend representation a of struct. VALS must be in the same order as the
350 // corresponding fields in BTYPE.
351 virtual Bexpression*
352 constructor_expression(Btype* btype, const std::vector<Bexpression*>& vals,
353 Location) = 0;
354
355 // Return an expression that constructs an array of BTYPE with INDEXES and
356 // VALS. INDEXES and VALS must have the same amount of elements. Each index
357 // in INDEXES must be in the same order as the corresponding value in VALS.
358 virtual Bexpression*
359 array_constructor_expression(Btype* btype,
360 const std::vector<unsigned long>& indexes,
361 const std::vector<Bexpression*>& vals,
362 Location) = 0;
363
364 // Return an expression for the address of BASE[INDEX].
365 // BASE has a pointer type. This is used for slice indexing.
366 virtual Bexpression*
367 pointer_offset_expression(Bexpression* base, Bexpression* index,
368 Location) = 0;
369
370 // Return an expression for ARRAY[INDEX] as an l-value. ARRAY is a valid
371 // fixed-length array, not a slice.
372 virtual Bexpression*
373 array_index_expression(Bexpression* array, Bexpression* index, Location) = 0;
374
375 // Create an expression for a call to FN with ARGS, taking place within
376 // caller CALLER.
377 virtual Bexpression*
378 call_expression(Bfunction *caller, Bexpression* fn,
379 const std::vector<Bexpression*>& args,
380 Bexpression* static_chain, Location) = 0;
381
382 // Statements.
383
384 // Create an error statement. This is used for cases which should
385 // not occur in a correct program, in order to keep the compilation
386 // going without crashing.
387 virtual Bstatement*
388 error_statement() = 0;
389
390 // Create an expression statement within the specified function.
391 virtual Bstatement*
392 expression_statement(Bfunction*, Bexpression*) = 0;
393
394 // Create a variable initialization statement in the specified
395 // function. This initializes a local variable at the point in the
396 // program flow where it is declared.
397 virtual Bstatement*
398 init_statement(Bfunction*, Bvariable* var, Bexpression* init) = 0;
399
400 // Create an assignment statement within the specified function.
401 virtual Bstatement*
402 assignment_statement(Bfunction*, Bexpression* lhs, Bexpression* rhs,
403 Location) = 0;
404
405 // Create a return statement, passing the representation of the
406 // function and the list of values to return.
407 virtual Bstatement*
408 return_statement(Bfunction*, const std::vector<Bexpression*>&,
409 Location) = 0;
410
411 // Create an if statement within a function. ELSE_BLOCK may be NULL.
412 virtual Bstatement*
413 if_statement(Bfunction*, Bexpression* condition,
414 Bblock* then_block, Bblock* else_block,
415 Location) = 0;
416
417 // Create a switch statement where the case values are constants.
418 // CASES and STATEMENTS must have the same number of entries. If
419 // VALUE matches any of the list in CASES[i], which will all be
420 // integers, then STATEMENTS[i] is executed. STATEMENTS[i] will
421 // either end with a goto statement or will fall through into
422 // STATEMENTS[i + 1]. CASES[i] is empty for the default clause,
423 // which need not be last. FUNCTION is the current function.
424 virtual Bstatement*
425 switch_statement(Bfunction* function, Bexpression* value,
426 const std::vector<std::vector<Bexpression*> >& cases,
427 const std::vector<Bstatement*>& statements,
428 Location) = 0;
429
430 // Create a single statement from two statements.
431 virtual Bstatement*
432 compound_statement(Bstatement*, Bstatement*) = 0;
433
434 // Create a single statement from a list of statements.
435 virtual Bstatement*
436 statement_list(const std::vector<Bstatement*>&) = 0;
437
438 // Create a statement that attempts to execute BSTAT and calls EXCEPT_STMT if
439 // an exception occurs. EXCEPT_STMT may be NULL. FINALLY_STMT may be NULL and
440 // if not NULL, it will always be executed. This is used for handling defers
441 // in Go functions. In C++, the resulting code is of this form:
442 // try { BSTAT; } catch { EXCEPT_STMT; } finally { FINALLY_STMT; }
443 virtual Bstatement*
444 exception_handler_statement(Bstatement* bstat, Bstatement* except_stmt,
445 Bstatement* finally_stmt, Location) = 0;
446
447 // Blocks.
448
449 // Create a block. The frontend will call this function when it
450 // starts converting a block within a function. FUNCTION is the
451 // current function. ENCLOSING is the enclosing block; it will be
452 // NULL for the top-level block in a function. VARS is the list of
453 // local variables defined within this block; each entry will be
454 // created by the local_variable function. START_LOCATION is the
455 // location of the start of the block, more or less the location of
456 // the initial curly brace. END_LOCATION is the location of the end
457 // of the block, more or less the location of the final curly brace.
458 // The statements will be added after the block is created.
459 virtual Bblock*
460 block(Bfunction* function, Bblock* enclosing,
461 const std::vector<Bvariable*>& vars,
462 Location start_location, Location end_location) = 0;
463
464 // Add the statements to a block. The block is created first. Then
465 // the statements are created. Then the statements are added to the
466 // block. This will called exactly once per block. The vector may
467 // be empty if there are no statements.
468 virtual void
469 block_add_statements(Bblock*, const std::vector<Bstatement*>&) = 0;
470
471 // Return the block as a statement. This is used to include a block
472 // in a list of statements.
473 virtual Bstatement*
474 block_statement(Bblock*) = 0;
475
476 // Variables.
477
478 // Create an error variable. This is used for cases which should
479 // not occur in a correct program, in order to keep the compilation
480 // going without crashing.
481 virtual Bvariable*
482 error_variable() = 0;
483
484 // Bit flags to pass to the various methods that return Bvariable*.
485 // Not all flags are meaningful for all methods.
486
487 // Set if the variable's address is taken. For a local variable
488 // this implies that the address does not escape the function, as
489 // otherwise the variable would be on the heap.
490 static const unsigned int variable_address_is_taken = 1 << 0;
491
492 // Set if the variable is defined in some other package. Only
493 // meaningful for the global_variable method. At most one of
494 // is_external, is_hidden, and is_common may be set.
495 static const unsigned int variable_is_external = 1 << 1;
496
497 // Set if the variable is not exported, and as such is only defined
498 // in the current package. Only meaningful for global_variable,
499 // implicit_variable, and immutable_struct. At most one of
500 // is_external, is_hidden, and is_common may be set.
501 static const unsigned variable_is_hidden = 1 << 2;
502
503 // Set if the variable should be treated as a common variable:
504 // multiple definitions with different sizes permitted in different
505 // object files, all merged into the largest definition at link
506 // time. Only meaningful for implicit_variable and immutable_struct.
507 // At most one of is_external, is_hidden, and is_common may be set.
508 static const unsigned int variable_is_common = 1 << 3;
509
510 // Set if the variable should be put into a unique section if
511 // possible; this is intended to permit the linker to garbage
512 // collect the value if it is not referenced. Only meaningful for
513 // global_variable.
514 static const unsigned int variable_in_unique_section = 1 << 4;
515
516 // Set if the variable should be treated as immutable. Only
517 // meaningful for implicit_variable. For example, this is set for
518 // slice initializers if the values must be copied to the heap.
519 static const unsigned int variable_is_constant = 1 << 5;
520
521 // Create a global variable. NAME is the package-qualified name of
522 // the variable. ASM_NAME is the encoded identifier for the
523 // variable, incorporating the package, and made safe for the
524 // assembler. BTYPE is the type of the variable. FLAGS is the bit
525 // flags defined above. LOCATION is where the variable was defined.
526 virtual Bvariable*
527 global_variable(const std::string& name, const std::string& asm_name,
528 Btype* btype, unsigned int flags, Location location) = 0;
529
530 // A global variable will 1) be initialized to zero, or 2) be
531 // initialized to a constant value, or 3) be initialized in the init
532 // function. In case 2, the frontend will call
533 // global_variable_set_init to set the initial value. If this is
534 // not called, the backend should initialize a global variable to 0.
535 // The init function may then assign a value to it.
536 virtual void
537 global_variable_set_init(Bvariable*, Bexpression*) = 0;
538
539 // Create a local variable. The frontend will create the local
540 // variables first, and then create the block which contains them.
541 // FUNCTION is the function in which the variable is defined. NAME
542 // is the name of the variable. TYPE is the type. DECL_VAR, if not
543 // null, gives the location at which the value of this variable may
544 // be found, typically used to create an inner-scope reference to an
545 // outer-scope variable, to extend the lifetime of the variable beyond
546 // the inner scope. FLAGS is the bit flags defined above.
547 // LOCATION is where the variable is defined. For each local variable
548 // the frontend will call init_statement to set the initial value.
549 virtual Bvariable*
550 local_variable(Bfunction* function, const std::string& name, Btype* type,
551 Bvariable* decl_var, unsigned int flags,
552 Location location) = 0;
553
554 // Create a function parameter. This is an incoming parameter, not
555 // a result parameter (result parameters are treated as local
556 // variables). The arguments are as for local_variable.
557 virtual Bvariable*
558 parameter_variable(Bfunction* function, const std::string& name,
559 Btype* type, unsigned int flags, Location location) = 0;
560
561 // Create a static chain parameter. This is the closure parameter.
562 virtual Bvariable*
563 static_chain_variable(Bfunction* function, const std::string& name,
564 Btype* type, unsigned int flags,
565 Location location) = 0;
566
567 // Create a temporary variable. A temporary variable has no name,
568 // just a type. We pass in FUNCTION and BLOCK in case they are
569 // needed. If INIT is not NULL, the variable should be initialized
570 // to that value. Otherwise the initial value is irrelevant--the
571 // backend does not have to explicitly initialize it to zero.
572 // FLAGS is the bit flags defined above. LOCATION is the location of
573 // the statement or expression which requires creating the temporary
574 // variable, and may not be very useful. This function should
575 // return a variable which can be referenced later and should set
576 // *PSTATEMENT to a statement which initializes the variable.
577 virtual Bvariable*
578 temporary_variable(Bfunction*, Bblock*, Btype*, Bexpression* init,
579 unsigned int flags, Location location,
580 Bstatement** pstatement) = 0;
581
582 // Create an implicit variable that is compiler-defined. This is
583 // used when generating GC data and roots, when storing the values
584 // of a slice constructor, and for the zero value of types. This returns a
585 // Bvariable because it corresponds to an initialized variable in C.
586 //
587 // NAME is the name to use for the initialized variable this will create.
588 //
589 // ASM_NAME is encoded assembler-friendly version of the name, or the
590 // empty string if no encoding is needed.
591 //
592 // TYPE is the type of the implicit variable.
593 //
594 // FLAGS is the bit flags defined above.
595 //
596 // If ALIGNMENT is not zero, it is the desired alignment of the variable.
597 virtual Bvariable*
598 implicit_variable(const std::string& name, const std::string& asm_name,
599 Btype* type, unsigned int flags, int64_t alignment) = 0;
600
601
602 // Set the initial value of a variable created by implicit_variable.
603 // This must be called even if there is no initializer, i.e., INIT is NULL.
604 // The NAME, TYPE, and FLAGS parameters are the same ones passed to
605 // implicit_variable. INIT will be a composite literal of type
606 // TYPE. It will not contain any function calls or anything else
607 // that can not be put into a read-only data section. It may
608 // contain the address of variables created by implicit_variable.
609 //
610 // If variable_is_common is set in FLAGS, INIT will be NULL, and the
611 // variable should be initialized to all zeros.
612 virtual void
613 implicit_variable_set_init(Bvariable*, const std::string& name, Btype* type,
614 unsigned int flags, Bexpression* init) = 0;
615
616 // Create a reference to a named implicit variable defined in some
617 // other package. This will be a variable created by a call to
618 // implicit_variable with the same NAME, ASM_NAME and TYPE and with
619 // variable_is_common not set in FLAGS. This corresponds to an
620 // extern global variable in C.
621 virtual Bvariable*
622 implicit_variable_reference(const std::string& name,
623 const std::string& asm_name,
624 Btype* type) = 0;
625
626 // Create a named immutable initialized data structure. This is
627 // used for type descriptors, map descriptors, and function
628 // descriptors. This returns a Bvariable because it corresponds to
629 // an initialized const variable in C.
630 //
631 // NAME is the name to use for the initialized global variable which
632 // this call will create.
633 //
634 // ASM_NAME is the encoded, assembler-friendly version of NAME, or
635 // the empty string if no encoding is needed.
636 //
637 // FLAGS is the bit flags defined above. The variable_is_common
638 // flag will be set if NAME may be defined by several packages, and
639 // the linker should merge all such definitions. If the
640 // variable_is_common flag is not set, NAME should be defined in
641 // only one file. In general variable_is_common will be set for the
642 // type descriptor of an unnamed type or a builtin type.
643 //
644 // TYPE will be a struct type; the type of the returned expression
645 // must be a pointer to this struct type.
646 //
647 // We must create the named structure before we know its
648 // initializer, because the initializer may refer to its own
649 // address. After calling this the frontend will call
650 // immutable_struct_set_init.
651 virtual Bvariable*
652 immutable_struct(const std::string& name, const std::string& asm_name,
653 unsigned int flags, Btype* type, Location) = 0;
654
655 // Set the initial value of a variable created by immutable_struct.
656 // The NAME, FLAGS, TYPE, and location parameters are the same ones
657 // passed to immutable_struct. INITIALIZER will be a composite
658 // literal of type TYPE. It will not contain any function calls or
659 // anything else that can not be put into a read-only data section.
660 // It may contain the address of variables created by
661 // immutable_struct.
662 virtual void
663 immutable_struct_set_init(Bvariable*, const std::string& name,
664 unsigned int flags, Btype* type,
665 Location, Bexpression* initializer) = 0;
666
667 // Create a reference to a named immutable initialized data
668 // structure defined in some other package. This will be a
669 // structure created by a call to immutable_struct with the same
670 // NAME, ASM_NAME and TYPE and with variable_is_common not set in
671 // flags. This corresponds to an extern const global variable in C.
672 virtual Bvariable*
673 immutable_struct_reference(const std::string& name,
674 const std::string& asm_name,
675 Btype* type, Location) = 0;
676
677 // Labels.
678
679 // Create a new label. NAME will be empty if this is a label
680 // created by the frontend for a loop construct. The location is
681 // where the label is defined.
682 virtual Blabel*
683 label(Bfunction*, const std::string& name, Location) = 0;
684
685 // Create a statement which defines a label. This statement will be
686 // put into the codestream at the point where the label should be
687 // defined.
688 virtual Bstatement*
689 label_definition_statement(Blabel*) = 0;
690
691 // Create a goto statement to a label.
692 virtual Bstatement*
693 goto_statement(Blabel*, Location) = 0;
694
695 // Create an expression for the address of a label. This is used to
696 // get the return address of a deferred function which may call
697 // recover.
698 virtual Bexpression*
699 label_address(Blabel*, Location) = 0;
700
701 // Functions.
702
703 // Create an error function. This is used for cases which should
704 // not occur in a correct program, in order to keep the compilation
705 // going without crashing.
706 virtual Bfunction*
707 error_function() = 0;
708
709 // Bit flags to pass to the function method.
710
711 // Set if the function should be visible outside of the current
712 // compilation unit.
713 static const unsigned int function_is_visible = 1 << 0;
714
715 // Set if this is a function declaration rather than a definition;
716 // the definition will be in another compilation unit.
717 static const unsigned int function_is_declaration = 1 << 1;
718
719 // Set if the function can be inlined. This is normally set, but is
720 // false for functions that may not be inlined because they call
721 // recover and must be visible for correct panic recovery.
722 static const unsigned int function_is_inlinable = 1 << 2;
723
724 // Set if the function may not split the stack. This is set for the
725 // implementation of recover itself, among other things.
726 static const unsigned int function_no_split_stack = 1 << 3;
727
728 // Set if the function does not return. This is set for the
729 // implementation of panic.
730 static const unsigned int function_does_not_return = 1 << 4;
731
732 // Set if the function should be put in a unique section if
733 // possible. This is used for field tracking.
734 static const unsigned int function_in_unique_section = 1 << 5;
735
736 // Set if the function should be available for inlining in the
737 // backend, but should not be emitted as a standalone function. Any
738 // call to the function that is not inlined should be treated as a
739 // call to a function defined in a different compilation unit. This
740 // is like a C99 function marked inline but not extern.
741 static const unsigned int function_only_inline = 1 << 6;
742
743 // Declare or define a function of FNTYPE.
744 // NAME is the Go name of the function. ASM_NAME, if not the empty
745 // string, is the name that should be used in the symbol table; this
746 // will be non-empty if a magic extern comment is used. FLAGS is
747 // bit flags described above.
748 virtual Bfunction*
749 function(Btype* fntype, const std::string& name, const std::string& asm_name,
750 unsigned int flags, Location) = 0;
751
752 // Create a statement that runs all deferred calls for FUNCTION. This should
753 // be a statement that looks like this in C++:
754 // finish:
755 // try { DEFER_RETURN; } catch { CHECK_DEFER; goto finish; }
756 virtual Bstatement*
757 function_defer_statement(Bfunction* function, Bexpression* undefer,
758 Bexpression* check_defer, Location) = 0;
759
760 // Record PARAM_VARS as the variables to use for the parameters of FUNCTION.
761 // This will only be called for a function definition. Returns true on
762 // success, false on failure.
763 virtual bool
764 function_set_parameters(Bfunction* function,
765 const std::vector<Bvariable*>& param_vars) = 0;
766
767 // Set the function body for FUNCTION using the code in CODE_STMT. Returns
768 // true on success, false on failure.
769 virtual bool
770 function_set_body(Bfunction* function, Bstatement* code_stmt) = 0;
771
772 // Look up a named built-in function in the current backend implementation.
773 // Returns NULL if no built-in function by that name exists.
774 virtual Bfunction*
775 lookup_builtin(const std::string&) = 0;
776
777 // Utility.
778
779 // Write the definitions for all TYPE_DECLS, CONSTANT_DECLS,
780 // FUNCTION_DECLS, and VARIABLE_DECLS declared globally.
781 virtual void
782 write_global_definitions(const std::vector<Btype*>& type_decls,
783 const std::vector<Bexpression*>& constant_decls,
784 const std::vector<Bfunction*>& function_decls,
785 const std::vector<Bvariable*>& variable_decls) = 0;
786
787 // Write SIZE bytes of export data from BYTES to the proper
788 // section in the output object file.
789 virtual void
790 write_export_data(const char* bytes, unsigned int size) = 0;
791 };
792
793 #endif // !defined(GO_BACKEND_H)