Annotation of gforth/engine/threaded.h, revision 1.22

1.1       anton       1: /* This file defines a number of threading schemes.
                      2: 
1.22    ! anton       3:   Copyright (C) 1995, 1996,1997,1999,2003 Free Software Foundation, Inc.
1.1       anton       4: 
                      5:   This file is part of Gforth.
                      6: 
                      7:   Gforth is free software; you can redistribute it and/or
                      8:   modify it under the terms of the GNU General Public License
                      9:   as published by the Free Software Foundation; either version 2
                     10:   of the License, or (at your option) any later version.
                     11: 
                     12:   This program is distributed in the hope that it will be useful,
                     13:   but WITHOUT ANY WARRANTY; without even the implied warranty of
                     14:   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
                     15:   GNU General Public License for more details.
                     16: 
                     17:   You should have received a copy of the GNU General Public License
                     18:   along with this program; if not, write to the Free Software
1.7       anton      19:   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
1.1       anton      20: 
                     21: 
                     22:   This files defines macros for threading. Many sets of macros are
                     23:   defined. Functionally they have only one difference: Some implement
                     24:   direct threading, some indirect threading. The other differences are
                     25:   just variations to help GCC generate faster code for various
                     26:   machines.
                     27: 
                     28:   (Well, to tell the truth, there actually is another functional
                     29:   difference in some pathological cases: e.g., a '!' stores into the
                     30:   cell where the next executed word comes from; or, the next word
                     31:   executed comes from the top-of-stack. These differences are one of
                     32:   the reasons why GCC cannot produce the right variation by itself. We
                     33:   chose disallowing such practices and using the added implementation
                     34:   freedom to achieve a significant speedup, because these practices
                     35:   are not common in Forth (I have never heard of or seen anyone using
                     36:   them), and it is easy to circumvent problems: A control flow change
                     37:   will flush any prefetched words; you may want to do a "0
                     38:   drop" before that to write back the top-of-stack cache.)
                     39: 
                     40:   These macro sets are used in the following ways: After translation
                     41:   to C a typical primitive looks like
                     42: 
                     43:   ...
                     44:   {
                     45:   DEF_CA
                     46:   other declarations
                     47:   NEXT_P0;
                     48:   main part of the primitive
                     49:   NEXT_P1;
                     50:   store results to stack
                     51:   NEXT_P2;
                     52:   }
                     53: 
                     54:   DEF_CA and all the NEXT_P* together must implement NEXT; In the main
                     55:   part the instruction pointer can be read with IP, changed with
                     56:   INC_IP(const_inc), and the cell right behind the presently executing
                     57:   word (i.e. the value of *IP) is accessed with NEXT_INST.
                     58: 
                     59:   If a primitive does not fall through the main part, it has to do the
                     60:   rest by itself. If it changes ip, it has to redo NEXT_P0 (perhaps we
                     61:   should define a macro SET_IP).
                     62: 
                     63:   Some primitives (execute, dodefer) do not end with NEXT, but with
                     64:   EXEC(.). If NEXT_P0 has been called earlier, it has to perform
                     65:   "ip=IP;" to ensure that ip has the right value (NEXT_P0 may change
                     66:   it).
                     67: 
                     68:   Finally, there is NEXT1_P1 and NEXT1_P2, which are parts of EXEC
                     69:   (EXEC(XT) could be defined as "cfa=XT; NEXT1_P1; NEXT1_P2;" (is this
                     70:   true?)) and are used for making docol faster.
                     71: 
                     72:   We can define the ways in which these macros are used with a regular
                     73:   expression:
                     74: 
                     75:   For a primitive
                     76: 
                     77:   DEF_CA NEXT_P0 ( IP | INC_IP | NEXT_INST | ip=...; NEXT_P0 ) * ( NEXT_P1 NEXT_P2 | EXEC(...) )
                     78: 
                     79:   For a run-time routine, e.g., docol:
                     80:   PFA1(cfa) ( NEXT_P0 NEXT | cfa=...; NEXT1_P1; NEXT1_P2 | EXEC(...) )
                     81: 
                     82:   This comment does not yet describe all the dependences that the
                     83:   macros have to satisfy.
                     84: 
                     85:   To organize the former ifdef chaos, each path is separated
                     86:   This gives a quite impressive number of paths, but you clearly
                     87:   find things that go together.
                     88: 
                     89:   It should be possible to organize the whole thing in a way that
                     90:   contains less redundancy and allows a simpler description.
                     91: 
                     92: */
                     93: 
                     94: #ifdef DOUBLY_INDIRECT
1.19      pazsan     95: # ifndef DEBUG_DITC
                     96: #  define DEBUG_DITC 0
                     97: # endif
                     98: /* define to 1 if you want to check consistency */
1.1       anton      99: #  define NEXT_P0      ({cfa=*ip;})
                    100: #  define IP           (ip)
1.3       anton     101: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     102: #  define NEXT_INST    (cfa)
                    103: #  define INC_IP(const_inc)    ({cfa=IP[const_inc]; ip+=(const_inc);})
                    104: #  define DEF_CA       Label ca;
1.13      anton     105: #  define NEXT_P1      ({\
1.19      pazsan    106:   if (DEBUG_DITC && (cfa<=vm_prims+DOESJUMP || cfa>=vm_prims+npriminfos)) \
                    107:     fprintf(stderr,"NEXT encountered prim %p at ip=%p\n", cfa, ip); \
1.21      anton     108:   ip++;})
                    109: #  define NEXT_P2      ({ca=**cfa; goto *ca;})
1.13      anton     110: #  define EXEC(XT)     ({DEF_CA cfa=(XT);\
1.19      pazsan    111:   if (DEBUG_DITC && (cfa>vm_prims+DOESJUMP && cfa<vm_prims+npriminfos)) \
1.14      anton     112:     fprintf(stderr,"EXEC encountered xt %p at ip=%p, vm_prims=%p, xts=%p\n", cfa, ip, vm_prims, xts); \
1.13      anton     113:  ca=**cfa; goto *ca;})
1.1       anton     114: 
1.16      anton     115: #elif defined(NO_IP)
                    116: 
                    117: #define NEXT_P0
                    118: #define SET_IP(target) assert(0)
                    119: #define INC_IP(n)      ((void)0)
                    120: #define DEF_CA
                    121: #define NEXT_P1
                    122: #define NEXT_P2                ({goto *next_code;})
                    123: /* set next_code to the return address before performing EXEC */
                    124: #define EXEC(XT)       ({cfa=(XT); goto **cfa;})
                    125: 
                    126: #else  /* !defined(DOUBLY_INDIRECT) && !defined(NO_IP) */
1.1       anton     127: 
1.3       anton     128: #if defined(DIRECT_THREADED)
                    129: 
1.17      anton     130: /* This lets the compiler know that cfa is dead before; we place it at
                    131:    "goto *"s that perform direct threaded dispatch (i.e., not EXECUTE
                    132:    etc.), and thus do not reach doers, which would use cfa; the only
                    133:    way to a doer is through EXECUTE etc., which set the cfa
                    134:    themselves.
                    135: 
                    136:    Some of these direct threaded schemes use "cfa" to hold the code
                    137:    address in normal direct threaded code.  Of course we cannot use
                    138:    KILLS there.
                    139: 
                    140:    KILLS works by having an empty asm instruction, and claiming to the
                    141:    compiler that it writes to cfa.
                    142: 
                    143:    KILLS is optional.  You can write
                    144: 
                    145: #define KILLS
                    146: 
                    147:    and lose just a little performance.
                    148: */
                    149: #define KILLS asm("":"=X"(cfa));
                    150: 
1.20      anton     151: #ifndef THREADING_SCHEME
                    152: #define THREADING_SCHEME 6
                    153: #endif
                    154: 
1.3       anton     155: #if THREADING_SCHEME==1
                    156: #warning direct threading scheme 1: autoinc, long latency, cfa live
1.1       anton     157: #  define NEXT_P0      ({cfa=*ip++;})
                    158: #  define IP           (ip-1)
1.3       anton     159: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     160: #  define NEXT_INST    (cfa)
                    161: #  define INC_IP(const_inc)    ({cfa=IP[const_inc]; ip+=(const_inc);})
                    162: #  define DEF_CA
                    163: #  define NEXT_P1
                    164: #  define NEXT_P2      ({goto *cfa;})
1.15      anton     165: #  define EXEC(XT)     ({cfa=(XT); goto **cfa;})
1.1       anton     166: #endif
                    167: 
1.3       anton     168: #if THREADING_SCHEME==2
                    169: #warning direct threading scheme 2: autoinc, long latency, cfa dead
1.1       anton     170: #  define NEXT_P0      (ip++)
                    171: #  define IP           (ip-1)
1.3       anton     172: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     173: #  define NEXT_INST    (*(ip-1))
                    174: #  define INC_IP(const_inc)    ({ ip+=(const_inc);})
                    175: #  define DEF_CA
                    176: #  define NEXT_P1
1.17      anton     177: #  define NEXT_P2      ({KILLS goto **(ip-1);})
1.15      anton     178: #  define EXEC(XT)     ({cfa=(XT); goto **cfa;})
1.1       anton     179: #endif
                    180: 
                    181: 
1.3       anton     182: #if THREADING_SCHEME==3
                    183: #warning direct threading scheme 3: autoinc, low latency, cfa live
1.1       anton     184: #  define NEXT_P0
                    185: #  define IP           (ip)
1.3       anton     186: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     187: #  define NEXT_INST    (*ip)
                    188: #  define INC_IP(const_inc)    ({ip+=(const_inc);})
                    189: #  define DEF_CA
                    190: #  define NEXT_P1      ({cfa=*ip++;})
                    191: #  define NEXT_P2      ({goto *cfa;})
1.15      anton     192: #  define EXEC(XT)     ({cfa=(XT); goto **cfa;})
1.1       anton     193: #endif
                    194: 
1.3       anton     195: #if THREADING_SCHEME==4
                    196: #warning direct threading scheme 4: autoinc, low latency, cfa dead
1.1       anton     197: #  define NEXT_P0
                    198: #  define IP           (ip)
1.3       anton     199: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     200: #  define NEXT_INST    (*ip)
                    201: #  define INC_IP(const_inc)    ({ ip+=(const_inc);})
                    202: #  define DEF_CA
                    203: #  define NEXT_P1
1.17      anton     204: #  define NEXT_P2      ({KILLS goto **(ip++);})
1.15      anton     205: #  define EXEC(XT)     ({cfa=(XT); goto **cfa;})
1.1       anton     206: #endif
                    207: 
1.3       anton     208: #if THREADING_SCHEME==5
                    209: #warning direct threading scheme 5: long latency, cfa live
1.1       anton     210: #  define NEXT_P0      ({cfa=*ip;})
                    211: #  define IP           (ip)
1.3       anton     212: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     213: #  define NEXT_INST    (cfa)
                    214: #  define INC_IP(const_inc)    ({cfa=IP[const_inc]; ip+=(const_inc);})
                    215: #  define DEF_CA
                    216: #  define NEXT_P1      (ip++)
                    217: #  define NEXT_P2      ({goto *cfa;})
1.15      anton     218: #  define EXEC(XT)     ({cfa=(XT); goto **cfa;})
1.1       anton     219: #endif
                    220: 
1.3       anton     221: #if THREADING_SCHEME==6
                    222: #warning direct threading scheme 6: long latency, cfa dead
1.1       anton     223: #  define NEXT_P0
                    224: #  define IP           (ip)
1.3       anton     225: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     226: #  define NEXT_INST    (*ip)
                    227: #  define INC_IP(const_inc)    ({ip+=(const_inc);})
                    228: #  define DEF_CA
                    229: #  define NEXT_P1      (ip++)
1.17      anton     230: #  define NEXT_P2      ({KILLS goto **(ip-1);})
1.15      anton     231: #  define EXEC(XT)     ({cfa=(XT); goto **cfa;})
1.1       anton     232: #endif
                    233: 
                    234: 
1.3       anton     235: #if THREADING_SCHEME==7
                    236: #warning direct threading scheme 7: low latency, cfa live
1.1       anton     237: #  define NEXT_P0
                    238: #  define IP           (ip)
1.3       anton     239: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     240: #  define NEXT_INST    (*ip)
                    241: #  define INC_IP(const_inc)    ({ip+=(const_inc);})
                    242: #  define DEF_CA
                    243: #  define NEXT_P1      ({cfa=*ip++;})
                    244: #  define NEXT_P2      ({goto *cfa;})
1.15      anton     245: #  define EXEC(XT)     ({cfa=(XT); goto **cfa;})
1.1       anton     246: #endif
                    247: 
1.3       anton     248: #if THREADING_SCHEME==8
                    249: #warning direct threading scheme 8: cfa dead, i386 hack
1.1       anton     250: #  define NEXT_P0
                    251: #  define IP           (ip)
1.3       anton     252: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     253: #  define NEXT_INST    (*IP)
                    254: #  define INC_IP(const_inc)    ({ ip+=(const_inc);})
                    255: #  define DEF_CA
                    256: #  define NEXT_P1      (ip++)
1.17      anton     257: #  define NEXT_P2      ({KILLS goto **(ip-1);})
1.15      anton     258: #  define EXEC(XT)     ({cfa=(XT); goto **cfa;})
1.1       anton     259: #endif
                    260: 
1.3       anton     261: #if THREADING_SCHEME==9
                    262: #warning direct threading scheme 9: Power/PPC hack, long latency
                    263: /* Power uses a prepare-to-branch instruction, and the latency between
                    264:    this inst and the branch is 5 cycles on a PPC604; so we utilize this
                    265:    to do some prefetching in between */
                    266: #  define NEXT_P0
                    267: #  define IP           ip
                    268: #  define SET_IP(p)    ({ip=(p); next_cfa=*ip; NEXT_P0;})
                    269: #  define NEXT_INST    (next_cfa)
                    270: #  define INC_IP(const_inc)    ({next_cfa=IP[const_inc]; ip+=(const_inc);})
1.8       anton     271: #  define DEF_CA       
                    272: #  define NEXT_P1      ({cfa=next_cfa; ip++; next_cfa=*ip;})
                    273: #  define NEXT_P2      ({goto *cfa;})
1.15      anton     274: #  define EXEC(XT)     ({cfa=(XT); goto **cfa;})
1.3       anton     275: #  define MORE_VARS    Xt next_cfa;
                    276: #endif
1.1       anton     277: 
1.3       anton     278: #if THREADING_SCHEME==10
                    279: #warning direct threading scheme 10: plain (no attempt at scheduling)
                    280: #  define NEXT_P0
                    281: #  define IP           (ip)
                    282: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
                    283: #  define NEXT_INST    (*ip)
                    284: #  define INC_IP(const_inc)    ({ip+=(const_inc);})
                    285: #  define DEF_CA
                    286: #  define NEXT_P1
                    287: #  define NEXT_P2      ({cfa=*ip++; goto *cfa;})
1.15      anton     288: #  define EXEC(XT)     ({cfa=(XT); goto **cfa;})
1.3       anton     289: #endif
1.1       anton     290: 
1.3       anton     291: /* direct threaded */
                    292: #else
1.1       anton     293: /* indirect THREADED  */
1.20      anton     294: 
                    295: #ifndef THREADING_SCHEME
                    296: #define THREADING_SCHEME 6
                    297: #endif
1.1       anton     298: 
1.3       anton     299: #if THREADING_SCHEME==1
                    300: #warning indirect threading scheme 1: autoinc, long latency, cisc
1.1       anton     301: #  define NEXT_P0      ({cfa=*ip++;})
                    302: #  define IP           (ip-1)
1.3       anton     303: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     304: #  define NEXT_INST    (cfa)
                    305: #  define INC_IP(const_inc)    ({cfa=IP[const_inc]; ip+=(const_inc);})
                    306: #  define DEF_CA
                    307: #  define NEXT_P1
                    308: #  define NEXT_P2      ({goto **cfa;})
                    309: #  define EXEC(XT)     ({cfa=(XT); goto **cfa;})
                    310: #endif
                    311: 
1.3       anton     312: #if THREADING_SCHEME==2
                    313: #warning indirect threading scheme 2: autoinc, long latency
1.1       anton     314: #  define NEXT_P0      ({cfa=*ip++;})
                    315: #  define IP           (ip-1)
1.3       anton     316: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     317: #  define NEXT_INST    (cfa)
                    318: #  define INC_IP(const_inc)    ({cfa=IP[const_inc]; ip+=(const_inc);})
                    319: #  define DEF_CA       Label ca;
                    320: #  define NEXT_P1      ({ca=*cfa;})
                    321: #  define NEXT_P2      ({goto *ca;})
                    322: #  define EXEC(XT)     ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
                    323: #endif
                    324: 
                    325: 
1.3       anton     326: #if THREADING_SCHEME==3
                    327: #warning indirect threading scheme 3: autoinc, low latency, cisc
1.1       anton     328: #  define NEXT_P0
                    329: #  define IP           (ip)
1.3       anton     330: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     331: #  define NEXT_INST    (*ip)
                    332: #  define INC_IP(const_inc)    ({ip+=(const_inc);})
                    333: #  define DEF_CA
                    334: #  define NEXT_P1
                    335: #  define NEXT_P2      ({cfa=*ip++; goto **cfa;})
                    336: #  define EXEC(XT)     ({cfa=(XT); goto **cfa;})
                    337: #endif
                    338: 
1.3       anton     339: #if THREADING_SCHEME==4
                    340: #warning indirect threading scheme 4: autoinc, low latency
1.1       anton     341: #  define NEXT_P0      ({cfa=*ip++;})
                    342: #  define IP           (ip-1)
1.3       anton     343: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     344: #  define NEXT_INST    (cfa)
                    345: #  define INC_IP(const_inc)    ({cfa=IP[const_inc]; ip+=(const_inc);})
                    346: #  define DEF_CA       Label ca;
                    347: #  define NEXT_P1      ({ca=*cfa;})
                    348: #  define NEXT_P2      ({goto *ca;})
                    349: #  define EXEC(XT)     ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
                    350: #endif
                    351: 
                    352: 
1.3       anton     353: #if THREADING_SCHEME==5
                    354: #warning indirect threading scheme 5: long latency, cisc
1.1       anton     355: #  define NEXT_P0      ({cfa=*ip;})
                    356: #  define IP           (ip)
1.3       anton     357: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     358: #  define NEXT_INST    (cfa)
                    359: #  define INC_IP(const_inc)    ({cfa=IP[const_inc]; ip+=(const_inc);})
                    360: #  define DEF_CA
                    361: #  define NEXT_P1      (ip++)
                    362: #  define NEXT_P2      ({goto **cfa;})
                    363: #  define EXEC(XT)     ({cfa=(XT); goto **cfa;})
                    364: #endif
                    365: 
1.3       anton     366: #if THREADING_SCHEME==6
                    367: #warning indirect threading scheme 6: long latency
1.1       anton     368: #  define NEXT_P0      ({cfa=*ip;})
                    369: #  define IP           (ip)
1.3       anton     370: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     371: #  define NEXT_INST    (cfa)
                    372: #  define INC_IP(const_inc)    ({cfa=IP[const_inc]; ip+=(const_inc);})
                    373: #  define DEF_CA       Label ca;
                    374: #  define NEXT_P1      ({ip++; ca=*cfa;})
                    375: #  define NEXT_P2      ({goto *ca;})
                    376: #  define EXEC(XT)     ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
                    377: #endif
                    378: 
1.3       anton     379: #if THREADING_SCHEME==7
                    380: #warning indirect threading scheme 7: low latency
                    381: #  define NEXT_P0      ({cfa=*ip;})
                    382: #  define IP           (ip)
                    383: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
                    384: #  define NEXT_INST    (cfa)
                    385: #  define INC_IP(const_inc)    ({cfa=IP[const_inc]; ip+=(const_inc);})
                    386: #  define DEF_CA       Label ca;
                    387: #  define NEXT_P1      ({ip++; ca=*cfa;})
                    388: #  define NEXT_P2      ({goto *ca;})
                    389: #  define EXEC(XT)     ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
                    390: #endif
1.1       anton     391: 
1.3       anton     392: #if THREADING_SCHEME==8
                    393: #warning indirect threading scheme 8: low latency,cisc
1.1       anton     394: #  define NEXT_P0
                    395: #  define IP           (ip)
1.3       anton     396: #  define SET_IP(p)    ({ip=(p); NEXT_P0;})
1.1       anton     397: #  define NEXT_INST    (*ip)
                    398: #  define INC_IP(const_inc)    ({ip+=(const_inc);})
                    399: #  define DEF_CA
                    400: #  define NEXT_P1
                    401: #  define NEXT_P2      ({cfa=*ip++; goto **cfa;})
                    402: #  define EXEC(XT)     ({cfa=(XT); goto **cfa;})
                    403: #endif
                    404: 
1.3       anton     405: /* indirect threaded */
1.1       anton     406: #endif
                    407: 
1.16      anton     408: #endif /* !defined(DOUBLY_INDIRECT) && !defined(NO_IP) */
1.1       anton     409: 
                    410: #define NEXT ({DEF_CA NEXT_P1; NEXT_P2;})
1.10      anton     411: #define IPTOS NEXT_INST

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