1: /* This file defines a number of threading schemes.
2:
3: Copyright (C) 1995, 1996,1997,1999 Free Software Foundation, Inc.
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
19: Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
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
95: # ifndef DEBUG_DITC
96: # define DEBUG_DITC 0
97: # endif
98: /* define to 1 if you want to check consistency */
99: # define NEXT_P0 ({cfa=*ip;})
100: # define IP (ip)
101: # define SET_IP(p) ({ip=(p); NEXT_P0;})
102: # define NEXT_INST (cfa)
103: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
104: # define DEF_CA Label ca;
105: # define NEXT_P1 ({\
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); \
108: ip++; ca=**cfa;})
109: # define NEXT_P2 ({goto *ca;})
110: # define EXEC(XT) ({DEF_CA cfa=(XT);\
111: if (DEBUG_DITC && (cfa>vm_prims+DOESJUMP && cfa<vm_prims+npriminfos)) \
112: fprintf(stderr,"EXEC encountered xt %p at ip=%p, vm_prims=%p, xts=%p\n", cfa, ip, vm_prims, xts); \
113: ca=**cfa; goto *ca;})
114:
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) */
127:
128: #if defined(DIRECT_THREADED)
129:
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:
151: #if THREADING_SCHEME==1
152: #warning direct threading scheme 1: autoinc, long latency, cfa live
153: # define NEXT_P0 ({cfa=*ip++;})
154: # define IP (ip-1)
155: # define SET_IP(p) ({ip=(p); NEXT_P0;})
156: # define NEXT_INST (cfa)
157: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
158: # define DEF_CA
159: # define NEXT_P1
160: # define NEXT_P2 ({goto *cfa;})
161: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
162: #endif
163:
164: #if THREADING_SCHEME==2
165: #warning direct threading scheme 2: autoinc, long latency, cfa dead
166: # define NEXT_P0 (ip++)
167: # define IP (ip-1)
168: # define SET_IP(p) ({ip=(p); NEXT_P0;})
169: # define NEXT_INST (*(ip-1))
170: # define INC_IP(const_inc) ({ ip+=(const_inc);})
171: # define DEF_CA
172: # define NEXT_P1
173: # define NEXT_P2 ({KILLS goto **(ip-1);})
174: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
175: #endif
176:
177:
178: #if THREADING_SCHEME==3
179: #warning direct threading scheme 3: autoinc, low latency, cfa live
180: # define NEXT_P0
181: # define IP (ip)
182: # define SET_IP(p) ({ip=(p); NEXT_P0;})
183: # define NEXT_INST (*ip)
184: # define INC_IP(const_inc) ({ip+=(const_inc);})
185: # define DEF_CA
186: # define NEXT_P1 ({cfa=*ip++;})
187: # define NEXT_P2 ({goto *cfa;})
188: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
189: #endif
190:
191: #if THREADING_SCHEME==4
192: #warning direct threading scheme 4: autoinc, low latency, cfa dead
193: # define NEXT_P0
194: # define IP (ip)
195: # define SET_IP(p) ({ip=(p); NEXT_P0;})
196: # define NEXT_INST (*ip)
197: # define INC_IP(const_inc) ({ ip+=(const_inc);})
198: # define DEF_CA
199: # define NEXT_P1
200: # define NEXT_P2 ({KILLS goto **(ip++);})
201: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
202: #endif
203:
204: #if THREADING_SCHEME==5
205: #warning direct threading scheme 5: long latency, cfa live
206: # define NEXT_P0 ({cfa=*ip;})
207: # define IP (ip)
208: # define SET_IP(p) ({ip=(p); NEXT_P0;})
209: # define NEXT_INST (cfa)
210: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
211: # define DEF_CA
212: # define NEXT_P1 (ip++)
213: # define NEXT_P2 ({goto *cfa;})
214: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
215: #endif
216:
217: #if THREADING_SCHEME==6
218: #warning direct threading scheme 6: long latency, cfa dead
219: # define NEXT_P0
220: # define IP (ip)
221: # define SET_IP(p) ({ip=(p); NEXT_P0;})
222: # define NEXT_INST (*ip)
223: # define INC_IP(const_inc) ({ip+=(const_inc);})
224: # define DEF_CA
225: # define NEXT_P1 (ip++)
226: # define NEXT_P2 ({KILLS goto **(ip-1);})
227: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
228: #endif
229:
230:
231: #if THREADING_SCHEME==7
232: #warning direct threading scheme 7: low latency, cfa live
233: # define NEXT_P0
234: # define IP (ip)
235: # define SET_IP(p) ({ip=(p); NEXT_P0;})
236: # define NEXT_INST (*ip)
237: # define INC_IP(const_inc) ({ip+=(const_inc);})
238: # define DEF_CA
239: # define NEXT_P1 ({cfa=*ip++;})
240: # define NEXT_P2 ({goto *cfa;})
241: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
242: #endif
243:
244: #if THREADING_SCHEME==8
245: #warning direct threading scheme 8: cfa dead, i386 hack
246: # define NEXT_P0
247: # define IP (ip)
248: # define SET_IP(p) ({ip=(p); NEXT_P0;})
249: # define NEXT_INST (*IP)
250: # define INC_IP(const_inc) ({ ip+=(const_inc);})
251: # define DEF_CA
252: # define NEXT_P1 (ip++)
253: # define NEXT_P2 ({KILLS goto **(ip-1);})
254: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
255: #endif
256:
257: #if THREADING_SCHEME==9
258: #warning direct threading scheme 9: Power/PPC hack, long latency
259: /* Power uses a prepare-to-branch instruction, and the latency between
260: this inst and the branch is 5 cycles on a PPC604; so we utilize this
261: to do some prefetching in between */
262: # define NEXT_P0
263: # define IP ip
264: # define SET_IP(p) ({ip=(p); next_cfa=*ip; NEXT_P0;})
265: # define NEXT_INST (next_cfa)
266: # define INC_IP(const_inc) ({next_cfa=IP[const_inc]; ip+=(const_inc);})
267: # define DEF_CA
268: # define NEXT_P1 ({cfa=next_cfa; ip++; next_cfa=*ip;})
269: # define NEXT_P2 ({goto *cfa;})
270: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
271: # define MORE_VARS Xt next_cfa;
272: #endif
273:
274: #if THREADING_SCHEME==10
275: #warning direct threading scheme 10: plain (no attempt at scheduling)
276: # define NEXT_P0
277: # define IP (ip)
278: # define SET_IP(p) ({ip=(p); NEXT_P0;})
279: # define NEXT_INST (*ip)
280: # define INC_IP(const_inc) ({ip+=(const_inc);})
281: # define DEF_CA
282: # define NEXT_P1
283: # define NEXT_P2 ({cfa=*ip++; goto *cfa;})
284: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
285: #endif
286:
287: /* direct threaded */
288: #else
289: /* indirect THREADED */
290:
291: #if THREADING_SCHEME==1
292: #warning indirect threading scheme 1: autoinc, long latency, cisc
293: # define NEXT_P0 ({cfa=*ip++;})
294: # define IP (ip-1)
295: # define SET_IP(p) ({ip=(p); NEXT_P0;})
296: # define NEXT_INST (cfa)
297: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
298: # define DEF_CA
299: # define NEXT_P1
300: # define NEXT_P2 ({goto **cfa;})
301: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
302: #endif
303:
304: #if THREADING_SCHEME==2
305: #warning indirect threading scheme 2: autoinc, long latency
306: # define NEXT_P0 ({cfa=*ip++;})
307: # define IP (ip-1)
308: # define SET_IP(p) ({ip=(p); NEXT_P0;})
309: # define NEXT_INST (cfa)
310: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
311: # define DEF_CA Label ca;
312: # define NEXT_P1 ({ca=*cfa;})
313: # define NEXT_P2 ({goto *ca;})
314: # define EXEC(XT) ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
315: #endif
316:
317:
318: #if THREADING_SCHEME==3
319: #warning indirect threading scheme 3: autoinc, low latency, cisc
320: # define NEXT_P0
321: # define IP (ip)
322: # define SET_IP(p) ({ip=(p); NEXT_P0;})
323: # define NEXT_INST (*ip)
324: # define INC_IP(const_inc) ({ip+=(const_inc);})
325: # define DEF_CA
326: # define NEXT_P1
327: # define NEXT_P2 ({cfa=*ip++; goto **cfa;})
328: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
329: #endif
330:
331: #if THREADING_SCHEME==4
332: #warning indirect threading scheme 4: autoinc, low latency
333: # define NEXT_P0 ({cfa=*ip++;})
334: # define IP (ip-1)
335: # define SET_IP(p) ({ip=(p); NEXT_P0;})
336: # define NEXT_INST (cfa)
337: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
338: # define DEF_CA Label ca;
339: # define NEXT_P1 ({ca=*cfa;})
340: # define NEXT_P2 ({goto *ca;})
341: # define EXEC(XT) ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
342: #endif
343:
344:
345: #if THREADING_SCHEME==5
346: #warning indirect threading scheme 5: long latency, cisc
347: # define NEXT_P0 ({cfa=*ip;})
348: # define IP (ip)
349: # define SET_IP(p) ({ip=(p); NEXT_P0;})
350: # define NEXT_INST (cfa)
351: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
352: # define DEF_CA
353: # define NEXT_P1 (ip++)
354: # define NEXT_P2 ({goto **cfa;})
355: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
356: #endif
357:
358: #if THREADING_SCHEME==6
359: #warning indirect threading scheme 6: long latency
360: # define NEXT_P0 ({cfa=*ip;})
361: # define IP (ip)
362: # define SET_IP(p) ({ip=(p); NEXT_P0;})
363: # define NEXT_INST (cfa)
364: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
365: # define DEF_CA Label ca;
366: # define NEXT_P1 ({ip++; ca=*cfa;})
367: # define NEXT_P2 ({goto *ca;})
368: # define EXEC(XT) ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
369: #endif
370:
371: #if THREADING_SCHEME==7
372: #warning indirect threading scheme 7: low latency
373: # define NEXT_P0 ({cfa=*ip;})
374: # define IP (ip)
375: # define SET_IP(p) ({ip=(p); NEXT_P0;})
376: # define NEXT_INST (cfa)
377: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
378: # define DEF_CA Label ca;
379: # define NEXT_P1 ({ip++; ca=*cfa;})
380: # define NEXT_P2 ({goto *ca;})
381: # define EXEC(XT) ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
382: #endif
383:
384: #if THREADING_SCHEME==8
385: #warning indirect threading scheme 8: low latency,cisc
386: # define NEXT_P0
387: # define IP (ip)
388: # define SET_IP(p) ({ip=(p); NEXT_P0;})
389: # define NEXT_INST (*ip)
390: # define INC_IP(const_inc) ({ip+=(const_inc);})
391: # define DEF_CA
392: # define NEXT_P1
393: # define NEXT_P2 ({cfa=*ip++; goto **cfa;})
394: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
395: #endif
396:
397: /* indirect threaded */
398: #endif
399:
400: #endif /* !defined(DOUBLY_INDIRECT) && !defined(NO_IP) */
401:
402: #define NEXT ({DEF_CA NEXT_P1; NEXT_P2;})
403: #define IPTOS NEXT_INST
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