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 *memset(void *s, int c, __SIZE_TYPE__ n);
   7 extern void abort(void);
   8
   9 /* This should be in sync with our include/stdarg.h */
  10 enum __va_arg_type {
  11     __va_gen_reg, __va_float_reg, __va_stack
  12 };
  13
  14 /* GCC compatible definition of va_list. */
  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 } __va_list_struct;
  24
  25 void __va_start(__va_list_struct *ap, void *fp)
  26 {
  27     memset(ap, 0, sizeof(__va_list_struct));
  28     *ap = *(__va_list_struct *)((char *)fp - 16);
  29     ap->overflow_arg_area = (char *)fp + ap->overflow_offset;
  30     ap->reg_save_area = (char *)fp - 176 - 16;
  31 }
  32
  33 void *__va_arg(__va_list_struct *ap,
  34                enum __va_arg_type arg_type,
  35                int size, int align)
  36 {
  37     size = (size + 7) & ~7;
  38     align = (align + 7) & ~7;
  39     switch (arg_type) {
  40     case __va_gen_reg:
  41         if (ap->gp_offset + size <= 48) {
  42             ap->gp_offset += size;
  43             return ap->reg_save_area + ap->gp_offset - size;
  44         }
  45         goto use_overflow_area;
  46
  47     case __va_float_reg:
  48         if (ap->fp_offset < 128 + 48) {
  49             ap->fp_offset += 16;
  50             return ap->reg_save_area + ap->fp_offset - 16;
  51         }
  52         size = 8;
  53         goto use_overflow_area;
  54
  55     case __va_stack:
  56     use_overflow_area:
  57         ap->overflow_arg_area += size;
  58         ap->overflow_arg_area = (char*)((long long)(ap->overflow_arg_area + align - 1) & -align);
  59         return ap->overflow_arg_area - size;
  60
  61     default: /* should never happen */
  62         abort();
  63     }
  64 }
  65 #endif