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      1 /* -----------------------------------------------------------------------
      2    sysv.S - Copyright (c) 2012  Alexandre K. I. de Mendonca <alexandre.keunecke (at) gmail.com>,
      3                                 Paulo Pizarro <paulo.pizarro (at) gmail.com>
      4 
      5    Blackfin Foreign Function Interface
      6 
      7    Permission is hereby granted, free of charge, to any person obtaining
      8    a copy of this software and associated documentation files (the
      9    ``Software''), to deal in the Software without restriction, including
     10    without limitation the rights to use, copy, modify, merge, publish,
     11    distribute, sublicense, and/or sell copies of the Software, and to
     12    permit persons to whom the Software is furnished to do so, subject to
     13    the following conditions:
     14 
     15    The above copyright notice and this permission notice shall be included
     16    in all copies or substantial portions of the Software.
     17 
     18    THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF ANY KIND,
     19    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
     20    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
     21    NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
     22    HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
     23    WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
     24    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
     25    DEALINGS IN THE SOFTWARE.
     26    ----------------------------------------------------------------------- */
     27 
     28 #define LIBFFI_ASM
     29 #include <fficonfig.h>
     30 #include <ffi.h>
     31 
     32 .text
     33 .align 4
     34 
     35 	/*
     36 	 There is a "feature" in the bfin toolchain that it puts a _ before function names
     37 	 that's why the function here it's called _ffi_call_SYSV and not ffi_call_SYSV
     38 	 */
     39 	.global _ffi_call_SYSV;
     40 	.type _ffi_call_SYSV, STT_FUNC;
     41 	.func ffi_call_SYSV
     42 
     43 	/*
     44          cif->bytes    = R0    (fp+8)
     45          &ecif         = R1    (fp+12)
     46          ffi_prep_args = R2    (fp+16)
     47          ret_type      = stack (fp+20)
     48          ecif.rvalue   = stack (fp+24)
     49          fn            = stack (fp+28)
     50                            got (fp+32)
     51 
     52         There is room for improvement here (we can use temporary registers
     53         instead of saving the values in the memory)
     54         REGS:
     55         P5 => Stack pointer (function arguments)
     56         R5 => cif->bytes
     57         R4 => ret->type
     58 
     59         FP-20 = P3
     60         FP-16 = SP (parameters area)
     61         FP-12 = SP (temp)
     62         FP-08 = function return part 1 [R0]
     63         FP-04 = function return part 2 [R1]
     64 	*/
     65 
     66 _ffi_call_SYSV:
     67 .prologue:
     68 	LINK 20;
     69 	[FP-20] = P3;
     70 	[FP+8] = R0;
     71 	[FP+12] = R1;
     72 	[FP+16] = R2;
     73 
     74 .allocate_stack:
     75 	//alocate cif->bytes into the stack
     76 	R1 = [FP+8];
     77 	R0 = SP;
     78 	R0 = R0 - R1;
     79 	R1 = 4;
     80 	R0 = R0 - R1;
     81 	[FP-12] = SP;
     82 	SP = R0;
     83 	[FP-16] = SP;
     84 
     85 .call_prep_args:
     86 	//get the addr of prep_args
     87 	P0 = [P3 + _ffi_prep_args@FUNCDESC_GOT17M4];
     88 	P1 = [P0];
     89 	P3 = [P0+4];
     90 	R0 = [FP-16];//SP (parameter area)
     91 	R1 = [FP+12];//ecif
     92 	call (P1);
     93 
     94 .call_user_function:
     95 	//ajust SP so as to allow the user function access the parameters on the stack
     96 	SP = [FP-16]; //point to function parameters
     97 	R0 = [SP];
     98 	R1 = [SP+4];
     99 	R2 = [SP+8];
    100 	//load user function address
    101 	P0 = FP;
    102 	P0 +=28;
    103 	P1 = [P0];
    104 	P1 = [P1];
    105 	P3 = [P0+4];
    106 	/*
    107 		For functions returning aggregate values (struct) occupying more than 8 bytes,
    108 		the caller allocates the return value object on the stack and the address
    109 		of this object is passed to the callee as a hidden argument in register P0.
    110 	*/
    111 	P0 = [FP+24];
    112 
    113 	call (P1);
    114 	SP = [FP-12];
    115 .compute_return:
    116 	P2 = [FP-20];
    117 	[FP-8] = R0;
    118 	[FP-4] = R1;
    119 
    120 	R0 = [FP+20];
    121 	R1 = R0 << 2;
    122 
    123 	R0 = [P2+.rettable@GOT17M4];
    124 	R0 = R1 + R0;
    125 	P2 = R0;
    126 	R1 = [P2];
    127 
    128 	P2 = [FP+-20];
    129 	R0 = [P2+.rettable@GOT17M4];
    130 	R0 = R1 + R0;
    131 	P2 = R0;
    132 	R0 = [FP-8];
    133 	R1 = [FP-4];
    134 	jump (P2);
    135 
    136 /*
    137 #define FFIBFIN_RET_VOID 0
    138 #define FFIBFIN_RET_BYTE 1
    139 #define FFIBFIN_RET_HALFWORD 2
    140 #define FFIBFIN_RET_INT64 3
    141 #define FFIBFIN_RET_INT32 4
    142 */
    143 .align 4
    144 .align 4
    145 .rettable:
    146 	.dd .epilogue - .rettable
    147 	.dd	.rbyte - .rettable;
    148 	.dd	.rhalfword - .rettable;
    149 	.dd	.rint64 - .rettable;
    150 	.dd	.rint32 - .rettable;
    151 
    152 .rbyte:
    153 	P0 = [FP+24];
    154 	R0 = R0.B (Z);
    155 	[P0] = R0;
    156 	JUMP .epilogue
    157 .rhalfword:
    158 	P0 = [FP+24];
    159 	R0 = R0.L;
    160 	[P0] = R0;
    161 	JUMP .epilogue
    162 .rint64:
    163 	P0 = [FP+24];// &rvalue
    164 	[P0] = R0;
    165 	[P0+4] = R1;
    166 	JUMP .epilogue
    167 .rint32:
    168 	P0 = [FP+24];
    169 	[P0] = R0;
    170 .epilogue:
    171 	R0 = [FP+8];
    172 	R1 = [FP+12];
    173 	R2 = [FP+16];
    174 	P3 = [FP-20];
    175 	UNLINK;
    176 	RTS;
    177 
    178 .size _ffi_call_SYSV,.-_ffi_call_SYSV;
    179 .endfunc
    180