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Annotation of gcc/va-pyr.h, revision 1.1

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. 
        !            12:  * These (somewhat bizarre) paramter-passing conventions are described
        !            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: #define va_alist \
        !            67:   _va0,_va1,_va2,_va3,_va4,_va5,_va6,_va7,_va8,_va9,_va10,_va11, \
        !            68:  __builtin_va_alist
        !            69: 
        !            70: #define va_dcl _voidptr va_alist;
        !            71: 
        !            72: #define va_list _va_buf
        !            73: 
        !            74: 
        !            75: /* __asm ("rcsp %0" : "=r" ( _AP [0]));*/
        !            76: 
        !            77: #define va_start(_AP)  \
        !            78: { _AP =  ((struct _va_regs) {                                          \
        !            79:    &(_AP._pr0), (void*)&__builtin_va_alist, (void*)0,                  \
        !            80:         _va0,_va1,_va2,_va3,_va4,_va5,                                 \
        !            81:                _va6,_va7,_va8,_va9,_va10,_va11})
        !            82:  
        !            83:   
        !            84:         
        !            85: 
        !            86: #define va_arg(_AP, _MODE)     \
        !            87: ({_voidptr *_ap = (_voidptr*)&_AP;                                     \
        !            88:   register int _size = sizeof (_MODE);                                 \
        !            89:   register int _onstack =                                              \
        !            90:          (_size > 8 || ( (int)(_ap[2]) > 11) ||                        \
        !            91:            (_size==8 && (int)(_ap[2])==11));                           \
        !            92:   register int* _param_addr =  ((int*)((_ap) [_onstack]));             \
        !            93:                                                                        \
        !            94:   ((void *)_ap[_onstack])+=_size;                                      \
        !            95:     if (_onstack==0 || (int)(_ap[2])==11)                              \
        !            96:       _ap[2]+= (_size >> 2);                                           \
        !            97:   *(( _MODE *)_param_addr);                                            \
        !            98: })
        !            99: 
        !           100: #define va_end(_X)     }

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