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: # define NEXT_P0 ({cfa=*ip;})
96: # define IP (ip)
97: # define SET_IP(p) ({ip=(p); NEXT_P0;})
98: # define NEXT_INST (cfa)
99: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
100: # define DEF_CA Label ca;
101: # define NEXT_P1 ({\
102: if (cfa<=vm_prims+DOESJUMP || cfa>=vm_prims+npriminfos) \
103: fprintf(stderr,"NEXT encountered prim %p at ip=%p\n", cfa, ip); \
104: ip++; ca=**cfa;})
105: # define NEXT_P2 ({goto *ca;})
106: # define EXEC(XT) ({DEF_CA cfa=(XT);\
107: if (cfa>vm_prims+DOESJUMP && cfa<vm_prims+npriminfos) \
108: fprintf(stderr,"EXEC encountered xt %p at ip=%p, vm_prims=%p, xts=%p\n", cfa, ip, vm_prims, xts); \
109: ca=**cfa; goto *ca;})
110:
111: #elif defined(NO_IP)
112:
113: #define NEXT_P0
114: #define SET_IP(target) assert(0)
115: #define INC_IP(n) ((void)0)
116: #define DEF_CA
117: #define NEXT_P1
118: #define NEXT_P2 ({goto *next_code;})
119: /* set next_code to the return address before performing EXEC */
120: #define EXEC(XT) ({cfa=(XT); goto **cfa;})
121:
122: #else /* !defined(DOUBLY_INDIRECT) && !defined(NO_IP) */
123:
124: #if defined(DIRECT_THREADED)
125:
126: /* This lets the compiler know that cfa is dead before; we place it at
127: "goto *"s that perform direct threaded dispatch (i.e., not EXECUTE
128: etc.), and thus do not reach doers, which would use cfa; the only
129: way to a doer is through EXECUTE etc., which set the cfa
130: themselves.
131:
132: Some of these direct threaded schemes use "cfa" to hold the code
133: address in normal direct threaded code. Of course we cannot use
134: KILLS there.
135:
136: KILLS works by having an empty asm instruction, and claiming to the
137: compiler that it writes to cfa.
138:
139: KILLS is optional. You can write
140:
141: #define KILLS
142:
143: and lose just a little performance.
144: */
145: #define KILLS asm("":"=X"(cfa));
146:
147: #if THREADING_SCHEME==1
148: #warning direct threading scheme 1: autoinc, long latency, cfa live
149: # define NEXT_P0 ({cfa=*ip++;})
150: # define IP (ip-1)
151: # define SET_IP(p) ({ip=(p); NEXT_P0;})
152: # define NEXT_INST (cfa)
153: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
154: # define DEF_CA
155: # define NEXT_P1
156: # define NEXT_P2 ({goto *cfa;})
157: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
158: #endif
159:
160: #if THREADING_SCHEME==2
161: #warning direct threading scheme 2: autoinc, long latency, cfa dead
162: # define NEXT_P0 (ip++)
163: # define IP (ip-1)
164: # define SET_IP(p) ({ip=(p); NEXT_P0;})
165: # define NEXT_INST (*(ip-1))
166: # define INC_IP(const_inc) ({ ip+=(const_inc);})
167: # define DEF_CA
168: # define NEXT_P1
169: # define NEXT_P2 ({KILLS goto **(ip-1);})
170: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
171: #endif
172:
173:
174: #if THREADING_SCHEME==3
175: #warning direct threading scheme 3: autoinc, low latency, cfa live
176: # define NEXT_P0
177: # define IP (ip)
178: # define SET_IP(p) ({ip=(p); NEXT_P0;})
179: # define NEXT_INST (*ip)
180: # define INC_IP(const_inc) ({ip+=(const_inc);})
181: # define DEF_CA
182: # define NEXT_P1 ({cfa=*ip++;})
183: # define NEXT_P2 ({goto *cfa;})
184: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
185: #endif
186:
187: #if THREADING_SCHEME==4
188: #warning direct threading scheme 4: autoinc, low latency, cfa dead
189: # define NEXT_P0
190: # define IP (ip)
191: # define SET_IP(p) ({ip=(p); NEXT_P0;})
192: # define NEXT_INST (*ip)
193: # define INC_IP(const_inc) ({ ip+=(const_inc);})
194: # define DEF_CA
195: # define NEXT_P1
196: # define NEXT_P2 ({KILLS goto **(ip++);})
197: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
198: #endif
199:
200: #if THREADING_SCHEME==5
201: #warning direct threading scheme 5: long latency, cfa live
202: # define NEXT_P0 ({cfa=*ip;})
203: # define IP (ip)
204: # define SET_IP(p) ({ip=(p); NEXT_P0;})
205: # define NEXT_INST (cfa)
206: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
207: # define DEF_CA
208: # define NEXT_P1 (ip++)
209: # define NEXT_P2 ({goto *cfa;})
210: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
211: #endif
212:
213: #if THREADING_SCHEME==6
214: #warning direct threading scheme 6: long latency, cfa dead
215: # define NEXT_P0
216: # define IP (ip)
217: # define SET_IP(p) ({ip=(p); NEXT_P0;})
218: # define NEXT_INST (*ip)
219: # define INC_IP(const_inc) ({ip+=(const_inc);})
220: # define DEF_CA
221: # define NEXT_P1 (ip++)
222: # define NEXT_P2 ({KILLS goto **(ip-1);})
223: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
224: #endif
225:
226:
227: #if THREADING_SCHEME==7
228: #warning direct threading scheme 7: low latency, cfa live
229: # define NEXT_P0
230: # define IP (ip)
231: # define SET_IP(p) ({ip=(p); NEXT_P0;})
232: # define NEXT_INST (*ip)
233: # define INC_IP(const_inc) ({ip+=(const_inc);})
234: # define DEF_CA
235: # define NEXT_P1 ({cfa=*ip++;})
236: # define NEXT_P2 ({goto *cfa;})
237: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
238: #endif
239:
240: #if THREADING_SCHEME==8
241: #warning direct threading scheme 8: cfa dead, i386 hack
242: # define NEXT_P0
243: # define IP (ip)
244: # define SET_IP(p) ({ip=(p); NEXT_P0;})
245: # define NEXT_INST (*IP)
246: # define INC_IP(const_inc) ({ ip+=(const_inc);})
247: # define DEF_CA
248: # define NEXT_P1 (ip++)
249: # define NEXT_P2 ({KILLS goto **(ip-1);})
250: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
251: #endif
252:
253: #if THREADING_SCHEME==9
254: #warning direct threading scheme 9: Power/PPC hack, long latency
255: /* Power uses a prepare-to-branch instruction, and the latency between
256: this inst and the branch is 5 cycles on a PPC604; so we utilize this
257: to do some prefetching in between */
258: # define NEXT_P0
259: # define IP ip
260: # define SET_IP(p) ({ip=(p); next_cfa=*ip; NEXT_P0;})
261: # define NEXT_INST (next_cfa)
262: # define INC_IP(const_inc) ({next_cfa=IP[const_inc]; ip+=(const_inc);})
263: # define DEF_CA
264: # define NEXT_P1 ({cfa=next_cfa; ip++; next_cfa=*ip;})
265: # define NEXT_P2 ({goto *cfa;})
266: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
267: # define MORE_VARS Xt next_cfa;
268: #endif
269:
270: #if THREADING_SCHEME==10
271: #warning direct threading scheme 10: plain (no attempt at scheduling)
272: # define NEXT_P0
273: # define IP (ip)
274: # define SET_IP(p) ({ip=(p); NEXT_P0;})
275: # define NEXT_INST (*ip)
276: # define INC_IP(const_inc) ({ip+=(const_inc);})
277: # define DEF_CA
278: # define NEXT_P1
279: # define NEXT_P2 ({cfa=*ip++; goto *cfa;})
280: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
281: #endif
282:
283: /* direct threaded */
284: #else
285: /* indirect THREADED */
286:
287: #if THREADING_SCHEME==1
288: #warning indirect threading scheme 1: autoinc, long latency, cisc
289: # define NEXT_P0 ({cfa=*ip++;})
290: # define IP (ip-1)
291: # define SET_IP(p) ({ip=(p); NEXT_P0;})
292: # define NEXT_INST (cfa)
293: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
294: # define DEF_CA
295: # define NEXT_P1
296: # define NEXT_P2 ({goto **cfa;})
297: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
298: #endif
299:
300: #if THREADING_SCHEME==2
301: #warning indirect threading scheme 2: autoinc, long latency
302: # define NEXT_P0 ({cfa=*ip++;})
303: # define IP (ip-1)
304: # define SET_IP(p) ({ip=(p); NEXT_P0;})
305: # define NEXT_INST (cfa)
306: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
307: # define DEF_CA Label ca;
308: # define NEXT_P1 ({ca=*cfa;})
309: # define NEXT_P2 ({goto *ca;})
310: # define EXEC(XT) ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
311: #endif
312:
313:
314: #if THREADING_SCHEME==3
315: #warning indirect threading scheme 3: autoinc, low latency, cisc
316: # define NEXT_P0
317: # define IP (ip)
318: # define SET_IP(p) ({ip=(p); NEXT_P0;})
319: # define NEXT_INST (*ip)
320: # define INC_IP(const_inc) ({ip+=(const_inc);})
321: # define DEF_CA
322: # define NEXT_P1
323: # define NEXT_P2 ({cfa=*ip++; goto **cfa;})
324: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
325: #endif
326:
327: #if THREADING_SCHEME==4
328: #warning indirect threading scheme 4: autoinc, low latency
329: # define NEXT_P0 ({cfa=*ip++;})
330: # define IP (ip-1)
331: # define SET_IP(p) ({ip=(p); NEXT_P0;})
332: # define NEXT_INST (cfa)
333: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
334: # define DEF_CA Label ca;
335: # define NEXT_P1 ({ca=*cfa;})
336: # define NEXT_P2 ({goto *ca;})
337: # define EXEC(XT) ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
338: #endif
339:
340:
341: #if THREADING_SCHEME==5
342: #warning indirect threading scheme 5: long latency, cisc
343: # define NEXT_P0 ({cfa=*ip;})
344: # define IP (ip)
345: # define SET_IP(p) ({ip=(p); NEXT_P0;})
346: # define NEXT_INST (cfa)
347: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
348: # define DEF_CA
349: # define NEXT_P1 (ip++)
350: # define NEXT_P2 ({goto **cfa;})
351: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
352: #endif
353:
354: #if THREADING_SCHEME==6
355: #warning indirect threading scheme 6: long latency
356: # define NEXT_P0 ({cfa=*ip;})
357: # define IP (ip)
358: # define SET_IP(p) ({ip=(p); NEXT_P0;})
359: # define NEXT_INST (cfa)
360: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
361: # define DEF_CA Label ca;
362: # define NEXT_P1 ({ip++; ca=*cfa;})
363: # define NEXT_P2 ({goto *ca;})
364: # define EXEC(XT) ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
365: #endif
366:
367: #if THREADING_SCHEME==7
368: #warning indirect threading scheme 7: low latency
369: # define NEXT_P0 ({cfa=*ip;})
370: # define IP (ip)
371: # define SET_IP(p) ({ip=(p); NEXT_P0;})
372: # define NEXT_INST (cfa)
373: # define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
374: # define DEF_CA Label ca;
375: # define NEXT_P1 ({ip++; ca=*cfa;})
376: # define NEXT_P2 ({goto *ca;})
377: # define EXEC(XT) ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
378: #endif
379:
380: #if THREADING_SCHEME==8
381: #warning indirect threading scheme 8: low latency,cisc
382: # define NEXT_P0
383: # define IP (ip)
384: # define SET_IP(p) ({ip=(p); NEXT_P0;})
385: # define NEXT_INST (*ip)
386: # define INC_IP(const_inc) ({ip+=(const_inc);})
387: # define DEF_CA
388: # define NEXT_P1
389: # define NEXT_P2 ({cfa=*ip++; goto **cfa;})
390: # define EXEC(XT) ({cfa=(XT); goto **cfa;})
391: #endif
392:
393: /* indirect threaded */
394: #endif
395:
396: #endif /* !defined(DOUBLY_INDIRECT) && !defined(NO_IP) */
397:
398: #define NEXT ({DEF_CA NEXT_P1; NEXT_P2;})
399: #define IPTOS NEXT_INST
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