1 /*****************************************************************************/
5 /* Parse function entry/body/exit */
9 /* (C) 2000-2003 Ullrich von Bassewitz */
10 /* Römerstrasse 52 */
11 /* D-70794 Filderstadt */
12 /* EMail: uz@cc65.org */
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. */
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: */
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 */
32 /*****************************************************************************/
57 /*****************************************************************************/
59 /*****************************************************************************/
63 /* Structure that holds all data needed for function activation */
65 struct SymEntry* FuncEntry; /* Symbol table entry */
66 type* ReturnType; /* Function return type */
67 struct FuncDesc* Desc; /* Function descriptor */
68 int Reserved; /* Reserved local space */
69 unsigned RetLab; /* Return code label */
70 int TopLevelSP; /* SP at function top level */
71 unsigned RegOffs; /* Register variable space offset */
74 /* Pointer to current function */
75 Function* CurrentFunc = 0;
79 /*****************************************************************************/
80 /* Subroutines working with struct Function */
81 /*****************************************************************************/
85 static Function* NewFunction (struct SymEntry* Sym)
86 /* Create a new function activation structure and return it */
88 /* Allocate a new structure */
89 Function* F = (Function*) xmalloc (sizeof (Function));
91 /* Initialize the fields */
93 F->ReturnType = GetFuncReturn (Sym->Type);
94 F->Desc = (FuncDesc*) DecodePtr (Sym->Type + 1);
96 F->RetLab = GetLocalLabel ();
98 F->RegOffs = RegisterSpace;
100 /* Return the new structure */
106 static void FreeFunction (Function* F)
107 /* Free a function activation structure */
114 const char* F_GetFuncName (const Function* F)
115 /* Return the name of the current function */
117 return F->FuncEntry->Name;
122 unsigned F_GetParamCount (const Function* F)
123 /* Return the parameter count for the current function */
125 return F->Desc->ParamCount;
130 unsigned F_GetParamSize (const Function* F)
131 /* Return the parameter size for the current function */
133 return F->Desc->ParamSize;
138 type* F_GetReturnType (Function* F)
139 /* Get the return type for the function */
141 return F->ReturnType;
146 int F_HasVoidReturn (const Function* F)
147 /* Return true if the function does not have a return value */
149 return IsTypeVoid (F->ReturnType);
154 int F_IsVariadic (const Function* F)
155 /* Return true if this is a variadic function */
157 return (F->Desc->Flags & FD_VARIADIC) != 0;
162 int F_IsOldStyle (const Function* F)
163 /* Return true if this is an old style (K&R) function */
165 return (F->Desc->Flags & FD_OLDSTYLE) != 0;
170 int F_HasOldStyleIntRet (const Function* F)
171 /* Return true if this is an old style (K&R) function with an implicit int return */
173 return (F->Desc->Flags & FD_OLDSTYLE_INTRET) != 0;
178 unsigned F_GetRetLab (const Function* F)
179 /* Return the return jump label */
186 int F_GetTopLevelSP (const Function* F)
187 /* Get the value of the stack pointer on function top level */
189 return F->TopLevelSP;
194 int F_ReserveLocalSpace (Function* F, unsigned Size)
195 /* Reserve (but don't allocate) the given local space and return the stack
200 return oursp - F->Reserved;
205 void F_AllocLocalSpace (Function* F)
206 /* Allocate any local space previously reserved. The function will do
207 * nothing if there is no reserved local space.
210 if (F->Reserved > 0) {
212 /* Create space on the stack */
213 g_space (F->Reserved);
215 /* Correct the stack pointer */
216 oursp -= F->Reserved;
218 /* Nothing more reserved */
225 int F_AllocRegVar (Function* F, const type* Type)
226 /* Allocate a register variable for the given variable type. If the allocation
227 * was successful, return the offset of the register variable in the register
228 * bank (zero page storage). If there is no register space left, return -1.
231 /* Allow register variables only on top level and if enabled */
232 if (EnableRegVars && GetLexicalLevel () == LEX_LEVEL_FUNCTION) {
234 /* Get the size of the variable */
235 unsigned Size = CheckedSizeOf (Type);
237 /* Do we have space left? */
238 if (F->RegOffs >= Size) {
239 /* Space left. We allocate the variables from high to low addresses,
240 * so the adressing is compatible with the saved values on stack.
241 * This allows shorter code when saving/restoring the variables.
248 /* No space left or no allocation */
254 static void F_RestoreRegVars (Function* F)
255 /* Restore the register variables for the local function if there are any. */
259 /* If we don't have register variables in this function, bail out early */
260 if (F->RegOffs == RegisterSpace) {
264 /* Save the accumulator if needed */
265 if (!F_HasVoidReturn (F)) {
266 g_save (CF_CHAR | CF_FORCECHAR);
269 /* Get the first symbol from the function symbol table */
270 Sym = F->FuncEntry->V.F.Func->SymTab->SymHead;
272 /* Walk through all symbols checking for register variables */
274 if (SymIsRegVar (Sym)) {
276 /* Check for more than one variable */
277 int Offs = Sym->V.R.SaveOffs;
278 unsigned Bytes = CheckedSizeOf (Sym->Type);
282 /* Find next register variable */
283 const SymEntry* NextSym = Sym->NextSym;
284 while (NextSym && !SymIsRegVar (NextSym)) {
285 NextSym = NextSym->NextSym;
288 /* If we have a next one, compare the stack offsets */
291 /* We have a following register variable. Get the size */
292 int Size = CheckedSizeOf (NextSym->Type);
294 /* Adjacent variable? */
295 if (NextSym->V.R.SaveOffs + Size != Offs) {
300 /* Adjacent variable */
310 /* Restore the memory range */
311 g_restore_regvars (Offs, Sym->V.R.RegOffs, Bytes);
315 /* Check next symbol */
319 /* Restore the accumulator if needed */
320 if (!F_HasVoidReturn (F)) {
321 g_restore (CF_CHAR | CF_FORCECHAR);
327 /*****************************************************************************/
329 /*****************************************************************************/
333 void NewFunc (SymEntry* Func)
334 /* Parse argument declarations and function body. */
339 /* Get the function descriptor from the function entry */
340 FuncDesc* D = Func->V.F.Func;
342 /* Allocate the function activation record for the function */
343 CurrentFunc = NewFunction (Func);
345 /* Reenter the lexical level */
346 ReenterFunctionLevel (D);
348 /* Declare two special functions symbols: __fixargs__ and __argsize__.
349 * The latter is different depending on the type of the function (variadic
352 AddConstSym ("__fixargs__", type_uint, SC_DEF | SC_CONST, D->ParamSize);
353 if (D->Flags & FD_VARIADIC) {
354 /* Variadic function. The variable must be const. */
355 static const type T [] = { T_UCHAR | T_QUAL_CONST, T_END };
356 AddLocalSym ("__argsize__", T, SC_DEF | SC_REF | SC_AUTO, 0);
359 AddConstSym ("__argsize__", type_uchar, SC_DEF | SC_CONST, D->ParamSize);
362 /* Function body now defined */
363 Func->Flags |= SC_DEF;
365 /* Allocate code and data segments for this function */
366 Func->V.F.Seg = PushSegments (Func);
368 /* Special handling for main() */
369 if (strcmp (Func->Name, "main") == 0) {
370 /* Main cannot be a fastcall function */
371 if (IsFastCallFunc (Func->Type)) {
372 Error ("`main' cannot be declared as __fastcall__");
375 /* If main() takes parameters, generate a forced import to a function
376 * that will setup these parameters. This way, programs that do not
377 * need the additional code will not get it.
379 if (D->ParamCount > 0 || (D->Flags & FD_VARIADIC) != 0) {
384 /* If this is a fastcall function, push the last parameter onto the stack */
385 if (IsFastCallFunc (Func->Type) && D->ParamCount > 0) {
389 /* Fastcall functions may never have an ellipsis or the compiler is buggy */
390 CHECK ((D->Flags & FD_VARIADIC) == 0);
392 /* Generate the push */
393 if (IsTypeFunc (D->LastParam->Type)) {
394 /* Pointer to function */
397 Flags = TypeOf (D->LastParam->Type) | CF_FORCECHAR;
402 /* Generate function entry code if needed */
403 g_enter (TypeOf (Func->Type), F_GetParamSize (CurrentFunc));
405 /* If stack checking code is requested, emit a call to the helper routine */
410 /* Setup the stack */
413 /* Walk through the parameter list and allocate register variable space
414 * for parameters declared as register. Generate code to swap the contents
415 * of the register bank with the save area on the stack.
417 Param = D->SymTab->SymHead;
418 while (Param && (Param->Flags & SC_PARAM) != 0) {
420 /* Check for a register variable */
421 if (SymIsRegVar (Param)) {
424 int Reg = F_AllocRegVar (CurrentFunc, Param->Type);
426 /* Could we allocate a register? */
428 /* No register available: Convert parameter to auto */
429 CvtRegVarToAuto (Param);
431 /* Remember the register offset */
432 Param->V.R.RegOffs = Reg;
434 /* Generate swap code */
435 g_swap_regvars (Param->V.R.SaveOffs, Reg, CheckedSizeOf (Param->Type));
441 Param = Param->NextSym;
444 /* Need a starting curly brace */
447 /* Parse local variable declarations if any */
450 /* Remember the current stack pointer. All variables allocated elsewhere
451 * must be dropped when doing a return from an inner block.
453 CurrentFunc->TopLevelSP = oursp;
455 /* Now process statements in this block */
457 while (CurTok.Tok != TOK_RCURLY) {
458 if (CurTok.Tok != TOK_CEOF) {
459 HadReturn = Statement (0);
465 /* Output the function exit code label */
466 g_defcodelabel (F_GetRetLab (CurrentFunc));
468 /* Restore the register variables */
469 F_RestoreRegVars (CurrentFunc);
471 /* Generate the exit code */
474 /* Eat the closing brace */
477 /* Emit references to imports/exports */
480 /* Leave the lexical level */
481 LeaveFunctionLevel ();
483 /* Switch back to the old segments */
486 /* Reset the current function pointer */
487 FreeFunction (CurrentFunc);