1 /*****************************************************************************/
5 /* Parse function entry/body/exit */
9 /* (C) 2000-2002 Ullrich von Bassewitz */
11 /* D-70597 Stuttgart */
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 /* Maximum register variable size */
64 #define MAX_REG_SPACE 6
66 /* Structure that holds all data needed for function activation */
68 struct SymEntry* FuncEntry; /* Symbol table entry */
69 type* ReturnType; /* Function return type */
70 struct FuncDesc* Desc; /* Function descriptor */
71 int Reserved; /* Reserved local space */
72 unsigned RetLab; /* Return code label */
73 int TopLevelSP; /* SP at function top level */
74 unsigned RegOffs; /* Register variable space offset */
77 /* Pointer to current function */
78 Function* CurrentFunc = 0;
82 /*****************************************************************************/
83 /* Subroutines working with struct Function */
84 /*****************************************************************************/
88 static Function* NewFunction (struct SymEntry* Sym)
89 /* Create a new function activation structure and return it */
91 /* Allocate a new structure */
92 Function* F = (Function*) xmalloc (sizeof (Function));
94 /* Initialize the fields */
96 F->ReturnType = GetFuncReturn (Sym->Type);
97 F->Desc = (FuncDesc*) DecodePtr (Sym->Type + 1);
99 F->RetLab = GetLocalLabel ();
101 F->RegOffs = MAX_REG_SPACE;
103 /* Return the new structure */
109 static void FreeFunction (Function* F)
110 /* Free a function activation structure */
117 const char* F_GetFuncName (const Function* F)
118 /* Return the name of the current function */
120 return F->FuncEntry->Name;
125 unsigned F_GetParamCount (const Function* F)
126 /* Return the parameter count for the current function */
128 return F->Desc->ParamCount;
133 unsigned F_GetParamSize (const Function* F)
134 /* Return the parameter size for the current function */
136 return F->Desc->ParamSize;
141 type* F_GetReturnType (Function* F)
142 /* Get the return type for the function */
144 return F->ReturnType;
149 int F_HasVoidReturn (const Function* F)
150 /* Return true if the function does not have a return value */
152 return IsTypeVoid (F->ReturnType);
157 int F_IsVariadic (const Function* F)
158 /* Return true if this is a variadic function */
160 return (F->Desc->Flags & FD_VARIADIC) != 0;
165 int F_IsOldStyle (const Function* F)
166 /* Return true if this is an old style (K&R) function */
168 return (F->Desc->Flags & FD_OLDSTYLE) != 0;
173 int F_HasOldStyleIntRet (const Function* F)
174 /* Return true if this is an old style (K&R) function with an implicit int return */
176 return (F->Desc->Flags & FD_OLDSTYLE_INTRET) != 0;
181 unsigned F_GetRetLab (const Function* F)
182 /* Return the return jump label */
189 int F_GetTopLevelSP (const Function* F)
190 /* Get the value of the stack pointer on function top level */
192 return F->TopLevelSP;
197 int F_ReserveLocalSpace (Function* F, unsigned Size)
198 /* Reserve (but don't allocate) the given local space and return the stack
203 return oursp - F->Reserved;
208 void F_AllocLocalSpace (Function* F)
209 /* Allocate any local space previously reserved. The function will do
210 * nothing if there is no reserved local space.
213 if (F->Reserved > 0) {
215 /* Create space on the stack */
216 g_space (F->Reserved);
218 /* Correct the stack pointer */
219 oursp -= F->Reserved;
221 /* Nothing more reserved */
228 int F_AllocRegVar (Function* F, const type* Type)
229 /* Allocate a register variable for the given variable type. If the allocation
230 * was successful, return the offset of the register variable in the register
231 * bank (zero page storage). If there is no register space left, return -1.
234 /* Allow register variables only on top level and if enabled */
235 if (EnableRegVars && GetLexicalLevel () == LEX_LEVEL_FUNCTION) {
237 /* Get the size of the variable */
238 unsigned Size = CheckedSizeOf (Type);
240 /* Do we have space left? */
241 if (F->RegOffs >= Size) {
242 /* Space left. We allocate the variables from high to low addresses,
243 * so the adressing is compatible with the saved values on stack.
244 * This allows shorter code when saving/restoring the variables.
251 /* No space left or no allocation */
257 static void F_RestoreRegVars (Function* F)
258 /* Restore the register variables for the local function if there are any. */
262 /* If we don't have register variables in this function, bail out early */
263 if (F->RegOffs == MAX_REG_SPACE) {
267 /* Save the accumulator if needed */
268 if (!F_HasVoidReturn (F)) {
269 g_save (CF_CHAR | CF_FORCECHAR);
272 /* Get the first symbol from the function symbol table */
273 Sym = F->FuncEntry->V.F.Func->SymTab->SymHead;
275 /* Walk through all symbols checking for register variables */
277 if (SymIsRegVar (Sym)) {
279 /* Check for more than one variable */
280 int Offs = Sym->V.R.SaveOffs;
281 unsigned Bytes = CheckedSizeOf (Sym->Type);
285 /* Find next register variable */
286 const SymEntry* NextSym = Sym->NextSym;
287 while (NextSym && !SymIsRegVar (NextSym)) {
288 NextSym = NextSym->NextSym;
291 /* If we have a next one, compare the stack offsets */
294 /* We have a following register variable. Get the size */
295 int Size = CheckedSizeOf (NextSym->Type);
297 /* Adjacent variable? */
298 if (NextSym->V.R.SaveOffs + Size != Offs) {
303 /* Adjacent variable */
313 /* Restore the memory range */
314 g_restore_regvars (Offs, Sym->V.R.RegOffs, Bytes);
318 /* Check next symbol */
322 /* Restore the accumulator if needed */
323 if (!F_HasVoidReturn (F)) {
324 g_restore (CF_CHAR | CF_FORCECHAR);
330 /*****************************************************************************/
332 /*****************************************************************************/
336 void NewFunc (SymEntry* Func)
337 /* Parse argument declarations and function body. */
343 /* Get the function descriptor from the function entry */
344 FuncDesc* D = Func->V.F.Func;
346 /* Allocate the function activation record for the function */
347 CurrentFunc = NewFunction (Func);
349 /* Reenter the lexical level */
350 ReenterFunctionLevel (D);
352 /* Before adding more symbols, remember the last parameter for later */
353 LastParam = D->SymTab->SymTail;
355 /* Declare two special functions symbols: __fixargs__ and __argsize__.
356 * The latter is different depending on the type of the function (variadic
359 AddConstSym ("__fixargs__", type_uint, SC_DEF | SC_CONST, D->ParamSize);
360 if (D->Flags & FD_VARIADIC) {
361 /* Variadic function. The variable must be const. */
362 static const type T [] = { T_UCHAR | T_QUAL_CONST, T_END };
363 AddLocalSym ("__argsize__", T, SC_DEF | SC_REF | SC_AUTO, 0);
366 AddConstSym ("__argsize__", type_uchar, SC_DEF | SC_CONST, D->ParamSize);
369 /* Function body now defined */
370 Func->Flags |= SC_DEF;
372 /* Allocate code and data segments for this function */
373 Func->V.F.Seg = PushSegments (Func);
375 /* If this is a fastcall function, push the last parameter onto the stack */
376 if (IsFastCallFunc (Func->Type) && D->ParamCount > 0) {
380 /* Fastcall functions may never have an ellipsis or the compiler is buggy */
381 CHECK ((D->Flags & FD_VARIADIC) == 0);
383 /* Generate the push */
384 if (IsTypeFunc (LastParam->Type)) {
385 /* Pointer to function */
388 Flags = TypeOf (LastParam->Type) | CF_FORCECHAR;
393 /* Generate function entry code if needed */
394 g_enter (TypeOf (Func->Type), F_GetParamSize (CurrentFunc));
396 /* If stack checking code is requested, emit a call to the helper routine */
401 /* Walk through the parameter list and allocate register variable space
402 * for parameters declared as register. Generate code to swap the contents
403 * of the register bank with the save area on the stack.
405 Param = D->SymTab->SymHead;
406 while (Param && (Param->Flags & SC_PARAM) != 0) {
408 /* Check for a register variable */
409 if (SymIsRegVar (Param)) {
412 int Reg = F_AllocRegVar (CurrentFunc, Param->Type);
414 /* Could we allocate a register? */
416 /* No register available: Convert parameter to auto */
417 CvtRegVarToAuto (Param);
419 /* Remember the register offset */
420 Param->V.R.RegOffs = Reg;
422 /* Generate swap code */
423 g_swap_regvars (Param->V.R.SaveOffs, Reg, CheckedSizeOf (Param->Type));
429 Param = Param->NextSym;
432 /* Setup the stack */
435 /* Need a starting curly brace */
438 /* Parse local variable declarations if any */
441 /* Remember the current stack pointer. All variables allocated elsewhere
442 * must be dropped when doing a return from an inner block.
444 CurrentFunc->TopLevelSP = oursp;
446 /* Now process statements in this block */
448 while (CurTok.Tok != TOK_RCURLY) {
449 if (CurTok.Tok != TOK_CEOF) {
450 HadReturn = Statement (0);
456 /* Output the function exit code label */
457 g_defcodelabel (F_GetRetLab (CurrentFunc));
459 /* Restore the register variables */
460 F_RestoreRegVars (CurrentFunc);
462 /* Generate the exit code */
465 /* Eat the closing brace */
468 /* Emit references to imports/exports */
471 /* Leave the lexical level */
472 LeaveFunctionLevel ();
474 /* Switch back to the old segments */
477 /* Reset the current function pointer */
478 FreeFunction (CurrentFunc);