1/*****************************************************************************/
2/* */
3/* function.c */
4/* */
5/* Parse function entry/body/exit */
6/* */
7/* */
8/* */
9/* (C) 2000-2015, Ullrich von Bassewitz */
10/* Roemerstrasse 52 */
11/* D-70794 Filderstadt */
12/* EMail: uz@cc65.org */
13/* */
14/* */
15/* This software is provided 'as-is', without any expressed or implied */
16/* warranty. In no event will the authors be held liable for any damages */
17/* arising from the use of this software. */
18/* */
19/* Permission is granted to anyone to use this software for any purpose, */
20/* including commercial applications, and to alter it and redistribute it */
21/* freely, subject to the following restrictions: */
22/* */
23/* 1. The origin of this software must not be misrepresented; you must not */
24/* claim that you wrote the original software. If you use this software */
25/* in a product, an acknowledgment in the product documentation would be */
26/* appreciated but is not required. */
27/* 2. Altered source versions must be plainly marked as such, and must not */
28/* be misrepresented as being the original software. */
29/* 3. This notice may not be removed or altered from any source */
30/* distribution. */
31/* */
32/*****************************************************************************/
33
34
35
36/* common */
37#include "check.h"
38#include "xmalloc.h"
39
40/* cc65 */
41#include "asmcode.h"
42#include "asmlabel.h"
43#include "codegen.h"
44#include "error.h"
45#include "funcdesc.h"
46#include "global.h"
47#include "litpool.h"
48#include "locals.h"
49#include "scanner.h"
50#include "stackptr.h"
51#include "standard.h"
52#include "stmt.h"
53#include "symtab.h"
54#include "function.h"
55
56
57
58/*****************************************************************************/
59/* Data */
60/*****************************************************************************/
61
62
63
64/* Pointer to current function */
65Function* CurrentFunc = 0;
66
67
68
69/*****************************************************************************/
70/* Subroutines working with struct Function */
71/*****************************************************************************/
72
73
74
75static Function* NewFunction (struct SymEntry* Sym)
76/* Create a new function activation structure and return it */
77{
78 /* Allocate a new structure */
79 Function* F = (Function*) xmalloc (sizeof (Function));
80
81 /* Initialize the fields */
82 F->FuncEntry = Sym;
83 F->ReturnType = GetFuncReturn (Sym->Type);
84 F->Desc = GetFuncDesc (Sym->Type);
85 F->Reserved = 0;
86 F->RetLab = GetLocalLabel ();
87 F->TopLevelSP = 0;
88 F->RegOffs = RegisterSpace;
89 F->Flags = IsTypeVoid (F->ReturnType) ? FF_VOID_RETURN : FF_NONE;
90
91 InitCollection (&F->LocalsBlockStack);
92
93 /* Return the new structure */
94 return F;
95}
96
97
98
99static void FreeFunction (Function* F)
100/* Free a function activation structure */
101{
102 DoneCollection (&F->LocalsBlockStack);
103 xfree (F);
104}
105
106
107
108const char* F_GetFuncName (const Function* F)
109/* Return the name of the current function */
110{
111 return F->FuncEntry->Name;
112}
113
114
115
116unsigned F_GetParamCount (const Function* F)
117/* Return the parameter count for the current function */
118{
119 return F->Desc->ParamCount;
120}
121
122
123
124unsigned F_GetParamSize (const Function* F)
125/* Return the parameter size for the current function */
126{
127 return F->Desc->ParamSize;
128}
129
130
131
132Type* F_GetReturnType (Function* F)
133/* Get the return type for the function */
134{
135 return F->ReturnType;
136}
137
138
139
140int F_HasVoidReturn (const Function* F)
141/* Return true if the function does not have a return value */
142{
143 return (F->Flags & FF_VOID_RETURN) != 0;
144}
145
146
147
148void F_ReturnFound (Function* F)
149/* Mark the function as having a return statement */
150{
151 F->Flags |= FF_HAS_RETURN;
152}
153
154
155
156int F_HasReturn (const Function* F)
157/* Return true if the function contains a return statement*/
158{
159 return (F->Flags & FF_HAS_RETURN) != 0;
160}
161
162
163
164int F_IsMainFunc (const Function* F)
165/* Return true if this is the main function */
166{
167 return (F->Flags & FF_IS_MAIN) != 0;
168}
169
170
171
172int F_IsVariadic (const Function* F)
173/* Return true if this is a variadic function */
174{
175 return (F->Desc->Flags & FD_VARIADIC) != 0;
176}
177
178
179
180int F_IsOldStyle (const Function* F)
181/* Return true if this is an old style (K&R) function */
182{
183 return (F->Desc->Flags & FD_OLDSTYLE) != 0;
184}
185
186
187
188int F_HasOldStyleIntRet (const Function* F)
189/* Return true if this is an old style (K&R) function with an implicit int return */
190{
191 return (F->Desc->Flags & FD_OLDSTYLE_INTRET) != 0;
192}
193
194
195
196unsigned F_GetRetLab (const Function* F)
197/* Return the return jump label */
198{
199 return F->RetLab;
200}
201
202
203
204int F_GetTopLevelSP (const Function* F)
205/* Get the value of the stack pointer on function top level */
206{
207 return F->TopLevelSP;
208}
209
210
211
212int F_ReserveLocalSpace (Function* F, unsigned Size)
213/* Reserve (but don't allocate) the given local space and return the stack
214** offset.
215*/
216{
217 F->Reserved += Size;
218 return StackPtr - F->Reserved;
219}
220
221
222
223int F_GetStackPtr (const Function* F)
224/* Return the current stack pointer including reserved (but not allocated)
225** space on the stack.
226*/
227{
228 return StackPtr - F->Reserved;
229}
230
231
232
233void F_AllocLocalSpace (Function* F)
234/* Allocate any local space previously reserved. The function will do
235** nothing if there is no reserved local space.
236*/
237{
238 if (F->Reserved > 0) {
239
240 /* Create space on the stack */
241 g_space (F->Reserved);
242
243 /* Correct the stack pointer */
244 StackPtr -= F->Reserved;
245
246 /* Nothing more reserved */
247 F->Reserved = 0;
248 }
249}
250
251
252
253int F_AllocRegVar (Function* F, const Type* Type)
254/* Allocate a register variable for the given variable type. If the allocation
255** was successful, return the offset of the register variable in the register
256** bank (zero page storage). If there is no register space left, return -1.
257*/
258{
259 /* Allow register variables only on top level and if enabled */
260 if (IS_Get (&EnableRegVars) && GetLexicalLevel () == LEX_LEVEL_FUNCTION) {
261
262 /* Get the size of the variable */
263 unsigned Size = CheckedSizeOf (Type);
264
265 /* Do we have space left? */
266 if (F->RegOffs >= Size) {
267 /* Space left. We allocate the variables from high to low addresses,
268 ** so the addressing is compatible with the saved values on stack.
269 ** This allows shorter code when saving/restoring the variables.
270 */
271 F->RegOffs -= Size;
272 return F->RegOffs;
273 }
274 }
275
276 /* No space left or no allocation */
277 return -1;
278}
279
280
281
282static void F_RestoreRegVars (Function* F)
283/* Restore the register variables for the local function if there are any. */
284{
285 const SymEntry* Sym;
286
287 /* If we don't have register variables in this function, bail out early */
288 if (F->RegOffs == RegisterSpace) {
289 return;
290 }
291
292 /* Save the accumulator if needed */
293 if (!F_HasVoidReturn (F)) {
294 g_save (CF_CHAR | CF_FORCECHAR);
295 }
296
297 /* Get the first symbol from the function symbol table */
298 Sym = F->FuncEntry->V.F.Func->SymTab->SymHead;
299
300 /* Walk through all symbols checking for register variables */
301 while (Sym) {
302 if (SymIsRegVar (Sym)) {
303
304 /* Check for more than one variable */
305 int Offs = Sym->V.R.SaveOffs;
306 unsigned Bytes = CheckedSizeOf (Sym->Type);
307
308 while (1) {
309
310 /* Find next register variable */
311 const SymEntry* NextSym = Sym->NextSym;
312 while (NextSym && !SymIsRegVar (NextSym)) {
313 NextSym = NextSym->NextSym;
314 }
315
316 /* If we have a next one, compare the stack offsets */
317 if (NextSym) {
318
319 /* We have a following register variable. Get the size */
320 int Size = CheckedSizeOf (NextSym->Type);
321
322 /* Adjacent variable? */
323 if (NextSym->V.R.SaveOffs + Size != Offs) {
324 /* No */
325 break;
326 }
327
328 /* Adjacent variable */
329 Bytes += Size;
330 Offs -= Size;
331 Sym = NextSym;
332
333 } else {
334 break;
335 }
336 }
337
338 /* Restore the memory range */
339 g_restore_regvars (Offs, Sym->V.R.RegOffs, Bytes);
340
341 }
342
343 /* Check next symbol */
344 Sym = Sym->NextSym;
345 }
346
347 /* Restore the accumulator if needed */
348 if (!F_HasVoidReturn (F)) {
349 g_restore (CF_CHAR | CF_FORCECHAR);
350 }
351}
352
353
354
355static void F_EmitDebugInfo (void)
356/* Emit debug infos for the current function */
357{
358 if (DebugInfo) {
359 /* Get the current function */
360 const SymEntry* Sym = CurrentFunc->FuncEntry;
361
362 /* Output info for the function itself */
363 AddTextLine ("\t.dbg\tfunc, \"%s\", \"00\", %s, \"%s\"",
364 Sym->Name,
365 (Sym->Flags & SC_EXTERN)? "extern" : "static",
366 Sym->AsmName);
367 }
368}
369
370
371
372/*****************************************************************************/
373/* code */
374/*****************************************************************************/
375
376
377
378void NewFunc (SymEntry* Func)
379/* Parse argument declarations and function body. */
380{
381 int C99MainFunc = 0;/* Flag for C99 main function returning int */
382 SymEntry* Param;
383
384 /* Get the function descriptor from the function entry */
385 FuncDesc* D = Func->V.F.Func;
386
387 /* Allocate the function activation record for the function */
388 CurrentFunc = NewFunction (Func);
389
390 /* Reenter the lexical level */
391 ReenterFunctionLevel (D);
392
393 /* Check if the function header contains unnamed parameters. These are
394 ** only allowed in cc65 mode.
395 */
396 if ((D->Flags & FD_UNNAMED_PARAMS) != 0 && (IS_Get (&Standard) != STD_CC65)) {
397 Error ("Parameter name omitted");
398 }
399
400 /* Declare two special functions symbols: __fixargs__ and __argsize__.
401 ** The latter is different depending on the type of the function (variadic
402 ** or not).
403 */
404 AddConstSym ("__fixargs__", type_uint, SC_DEF | SC_CONST, D->ParamSize);
405 if (D->Flags & FD_VARIADIC) {
406 /* Variadic function. The variable must be const. */
407 static const Type T[] = { TYPE(T_UCHAR | T_QUAL_CONST), TYPE(T_END) };
408 AddLocalSym ("__argsize__", T, SC_DEF | SC_REF | SC_AUTO, 0);
409 } else {
410 /* Non variadic */
411 AddConstSym ("__argsize__", type_uchar, SC_DEF | SC_CONST, D->ParamSize);
412 }
413
414 /* Function body now defined */
415 Func->Flags |= SC_DEF;
416
417 /* Special handling for main() */
418 if (strcmp (Func->Name, "main") == 0) {
419
420 /* Mark this as the main function */
421 CurrentFunc->Flags |= FF_IS_MAIN;
422
423 /* Main cannot be a fastcall function */
424 if (IsQualFastcall (Func->Type)) {
425 Error ("'main' cannot be declared as __fastcall__");
426 }
427
428 /* If cc65 extensions aren't enabled, don't allow a main function that
429 ** doesn't return an int.
430 */
431 if (IS_Get (&Standard) != STD_CC65 && CurrentFunc->ReturnType[0].C != T_INT) {
432 Error ("'main' must always return an int");
433 }
434
435 /* Add a forced import of a symbol that is contained in the startup
436 ** code. This will force the startup code to be linked in.
437 */
438 g_importstartup ();
439
440 /* If main() takes parameters, generate a forced import to a function
441 ** that will setup these parameters. This way, programs that do not
442 ** need the additional code will not get it.
443 */
444 if (D->ParamCount > 0 || (D->Flags & FD_VARIADIC) != 0) {
445 g_importmainargs ();
446
447 /* The start-up code doesn't fast-call main(). */
448 Func->Type->C |= T_QUAL_CDECL;
449 }
450
451 /* Determine if this is a main function in a C99 environment that
452 ** returns an int.
453 */
454 if (IsTypeInt (F_GetReturnType (CurrentFunc)) &&
455 IS_Get (&Standard) == STD_C99) {
456 C99MainFunc = 1;
457 }
458 }
459
460 /* Allocate code and data segments for this function */
461 Func->V.F.Seg = PushSegments (Func);
462
463 /* Allocate a new literal pool */
464 PushLiteralPool (Func);
465
466 /* If this is a fastcall function, push the last parameter onto the stack */
467 if ((D->Flags & FD_VARIADIC) == 0 && D->ParamCount > 0 &&
468 (AutoCDecl ?
469 IsQualFastcall (Func->Type) :
470 !IsQualCDecl (Func->Type))) {
471 unsigned Flags;
472
473 /* Generate the push */
474 if (IsTypeFunc (D->LastParam->Type)) {
475 /* Pointer to function */
476 Flags = CF_PTR;
477 } else {
478 Flags = TypeOf (D->LastParam->Type) | CF_FORCECHAR;
479 }
480 g_push (Flags, 0);
481 }
482
483 /* Generate function entry code if needed */
484 g_enter (TypeOf (Func->Type), F_GetParamSize (CurrentFunc));
485
486 /* If stack checking code is requested, emit a call to the helper routine */
487 if (IS_Get (&CheckStack)) {
488 g_stackcheck ();
489 }
490
491 /* Setup the stack */
492 StackPtr = 0;
493
494 /* Walk through the parameter list and allocate register variable space
495 ** for parameters declared as register. Generate code to swap the contents
496 ** of the register bank with the save area on the stack.
497 */
498 Param = D->SymTab->SymHead;
499 while (Param && (Param->Flags & SC_PARAM) != 0) {
500
501 /* Check for a register variable */
502 if (SymIsRegVar (Param)) {
503
504 /* Allocate space */
505 int Reg = F_AllocRegVar (CurrentFunc, Param->Type);
506
507 /* Could we allocate a register? */
508 if (Reg < 0) {
509 /* No register available: Convert parameter to auto */
510 CvtRegVarToAuto (Param);
511 } else {
512 /* Remember the register offset */
513 Param->V.R.RegOffs = Reg;
514
515 /* Generate swap code */
516 g_swap_regvars (Param->V.R.SaveOffs, Reg, CheckedSizeOf (Param->Type));
517 }
518 }
519
520 /* Next parameter */
521 Param = Param->NextSym;
522 }
523
524 /* Need a starting curly brace */
525 ConsumeLCurly ();
526
527 /* Make sure there is always something on the stack of local variable blocks */
528 CollAppend (&CurrentFunc->LocalsBlockStack, 0);
529
530 /* Parse local variable declarations if any */
531 DeclareLocals ();
532
533 /* Remember the current stack pointer. All variables allocated elsewhere
534 ** must be dropped when doing a return from an inner block.
535 */
536 CurrentFunc->TopLevelSP = StackPtr;
537
538 /* Now process statements in this block */
539 while (CurTok.Tok != TOK_RCURLY && CurTok.Tok != TOK_CEOF) {
540 Statement (0);
541 }
542
543 /* If this is not a void function, and not the main function in a C99
544 ** environment returning int, output a warning if we didn't see a return
545 ** statement.
546 */
547 if (!F_HasVoidReturn (CurrentFunc) && !F_HasReturn (CurrentFunc) && !C99MainFunc) {
548 Warning ("Control reaches end of non-void function");
549 }
550
551 /* If this is the main function in a C99 environment returning an int, let
552 ** it always return zero. Note: Actual return statements jump to the return
553 ** label defined below.
554 ** The code is removed by the optimizer if unused.
555 */
556 if (C99MainFunc) {
557 g_getimmed (CF_INT | CF_CONST, 0, 0);
558 }
559
560 /* Output the function exit code label */
561 g_defcodelabel (F_GetRetLab (CurrentFunc));
562
563 /* Restore the register variables */
564 F_RestoreRegVars (CurrentFunc);
565
566 /* Generate the exit code */
567 g_leave ();
568
569 /* Emit references to imports/exports */
570 EmitExternals ();
571
572 /* Emit function debug info */
573 F_EmitDebugInfo ();
574 EmitDebugInfo ();
575
576 /* Leave the lexical level */
577 LeaveFunctionLevel ();
578
579 /* Eat the closing brace */
580 ConsumeRCurly ();
581
582 /* Restore the old literal pool, remembering the one for the function */
583 Func->V.F.LitPool = PopLiteralPool ();
584
585 /* Switch back to the old segments */
586 PopSegments ();
587
588 /* Reset the current function pointer */
589 FreeFunction (CurrentFunc);
590 CurrentFunc = 0;
591}
592