lib/va_list.c

   1 /* va_list.c - tinycc support for va_list on X86_64 */
   2
   3 #if defined __x86_64__
   4
   5 /* Avoid include files, they may not be available when cross compiling */
   6 extern void abort(void);
   7
   8 /* This should be in sync with our include/stdarg.h */
   9 enum __va_arg_type {
  10     __va_gen_reg, __va_float_reg, __va_stack
  11 };
  12
  13 /* GCC compatible definition of va_list. */
  14 /*predefined by TCC (tcc_predefs.h):
  15 typedef struct {
  16     unsigned int gp_offset;
  17     unsigned int fp_offset;
  18     union {
  19         unsigned int overflow_offset;
  20         char *overflow_arg_area;
  21     };
  22     char *reg_save_area;
  23 } __builtin_va_list[1];
  24 */
  25
  26 void *__va_arg(__builtin_va_list ap,
  27                int arg_type,
  28                int size, int align)
  29 {
  30     size = (size + 7) & ~7;
  31     align = (align + 7) & ~7;
  32     switch ((enum __va_arg_type)arg_type) {
  33     case __va_gen_reg:
  34         if (ap->gp_offset + size <= 48) {
  35             ap->gp_offset += size;
  36             return ap->reg_save_area + ap->gp_offset - size;
  37         }
  38         goto use_overflow_area;
  39
  40     case __va_float_reg:
  41         if (ap->fp_offset < 128 + 48) {
  42             ap->fp_offset += 16;
  43             return ap->reg_save_area + ap->fp_offset - 16;
  44         }
  45         size = 8;
  46         goto use_overflow_area;
  47
  48     case __va_stack:
  49     use_overflow_area:
  50         ap->overflow_arg_area += size;
  51         ap->overflow_arg_area = (char*)((long long)(ap->overflow_arg_area + align - 1) & -align);
  52         return ap->overflow_arg_area - size;
  53
  54     default: /* should never happen */
  55         abort();
  56         return 0;
  57     }
  58 }
  59 #endif