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Annotation of gcc/va-pyr.h, revision 1.1.1.2

1.1       root        1: /**
                      2:  *
                      3:  *     Varargs for PYR/GNU CC
                      4:  *
                      5:  * WARNING -- WARNING -- DANGER
                      6:  *
                      7:  * The code in this file implements varargs for gcc on a pyr in
                      8:  * a way that is compatible with code compiled by the Pyramid Technology
                      9:  * C compiler.
                     10:  * As such, it depends strongly on the Pyramid conventions for
                     11:  * parameter passing.ct and indepenent implementation. 
1.1.1.2 ! root       12:  * These (somewhat bizarre) parameter-passing conventions are described
1.1       root       13:  * in the ``OSx Operating System Porting Guide''.
                     14:  * 
                     15:  * A quick summary is useful:
                     16:  * 12 of the 48 register-windowed regs available for
                     17:  * parameter passing.  Parameters of a function call that are eligible
                     18:  * to be passed in registers are assigned registers from TR0/PR0 onwards;
                     19:  * all other arguments are passed on the stack.
                     20:  * Structure and union parameters are *never* passed in registers,
                     21:  * even if they are small enough to fit.  They are always passed on
                     22:  * the stack.
                     23:  *
                     24:  * Double-sized parameters cannot be passed in TR11, because
                     25:  * TR12 is not used for passing parameters.  If, in the absence of this
                     26:  * rule, a double-sized param would have been passed in TR11,
                     27:  * that parameter is passed on the stack and no parameters are
                     28:  * passed in TR11.
                     29:  * 
                     30:  * It is only known to work for passing 32-bit integer quantities
                     31:  * (ie chars, shorts, ints/enums, longs), doubles, or pointers. 
                     32:  * Passing structures on a Pyramid via varargs is a loser.
                     33:  * Passing an object larger than 8 bytes on a pyramid via varargs may
                     34:  * also be a loser.
                     35:  * 
                     36:  */
                     37: 
                     38: 
                     39: /*
                     40:  *  pointer to next stack parameter in __va_buf[0]
                     41:  *  pointer to next parameter register in __va_buf[1]
                     42:  *  Count of registers seen at __va_buf[2]
                     43:  *  saved pr0..pr11 in __va_buf[3..14]
                     44:  *  # of calls to va_arg (debugging) at __va_buf[15]
                     45:  */
                     46: 
                     47: typedef void *__voidptr;
                     48: #if 1
                     49: 
                     50: typedef struct __va_regs {
                     51:       __voidptr __stackp,__regp,__count;
                     52:       __voidptr __pr0,__pr1,__pr2,__pr3,__pr4,__pr5,__pr6,__pr7,__pr8,__pr9,__pr10,__pr11;
                     53:   } __va_regs;
                     54: 
                     55: typedef __va_regs __va_buf;
                     56: #else
                     57: 
                     58: /* __va_buf[0] = address of next arg passed on the stack
                     59:    __va_buf[1] = address of next arg passed in a register
                     60:    __va_buf[2] = register-# of next arg passed in a register
                     61:  */
                     62: typedef __voidptr(*__va_buf);
                     63: 
                     64: #endif
                     65: 
                     66: /* In GCC version 2, we want an ellipsis at the end of the declaration
                     67:    of the argument list.  GCC version 1 can't parse it.  */
                     68: 
                     69: #if __GNUC__ > 1
                     70: #define __va_ellipsis ...
                     71: #else
                     72: #define __va_ellipsis
                     73: #endif
                     74: 
                     75: #define va_alist \
                     76:   __va0,__va1,__va2,__va3,__va4,__va5,__va6,__va7,__va8,__va9,__va10,__va11, \
                     77:  __builtin_va_alist
                     78: 
                     79: /* The ... causes current_function_varargs to be set in cc1.  */
                     80: #define va_dcl __voidptr va_alist; __va_ellipsis
                     81: 
                     82: typedef __va_buf va_list;
                     83: 
                     84: 
                     85: /* __asm ("rcsp %0" : "=r" ( _AP [0]));*/
                     86: 
                     87: #define va_start(_AP)  \
                     88:   _AP =  ((struct __va_regs) {                                         \
                     89:    &(_AP.__pr0), (void*)&__builtin_va_alist, (void*)0,                 \
                     90:         __va0,__va1,__va2,__va3,__va4,__va5,                           \
                     91:        __va6,__va7,__va8,__va9,__va10,__va11})
                     92: 
                     93: 
                     94: /* Avoid errors if compiling GCC v2 with GCC v1.  */
                     95: #if __GNUC__ == 1
                     96: #define __extension__
                     97: #endif
                     98: 
                     99: #define va_arg(_AP, _MODE)     \
                    100: __extension__                                                          \
                    101: ({__voidptr *__ap = (__voidptr*)&_AP;                                  \
                    102:   register int __size = sizeof (_MODE);                                        \
                    103:   register int __onstack =                                             \
                    104:          (__size > 8 || ( (int)(__ap[2]) > 11) ||                      \
                    105:            (__size==8 && (int)(__ap[2])==11));                         \
                    106:   register int* __param_addr =  ((int*)((__ap) [__onstack]));          \
                    107:                                                                        \
                    108:   ((void *)__ap[__onstack])+=__size;                                   \
                    109:     if (__onstack==0 || (int)(__ap[2])==11)                            \
                    110:       __ap[2]+= (__size >> 2);                                         \
                    111:   *(( _MODE *)__param_addr);                                           \
                    112: })
                    113: 
                    114: #define va_end(_X)

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