/* This file defines a number of threading schemes.
Copyright (C) 1995, 1996,1997,1999 Free Software Foundation, Inc.
This file is part of Gforth.
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This files defines macros for threading. Many sets of macros are
defined. Functionally they have only one difference: Some implement
direct threading, some indirect threading. The other differences are
just variations to help GCC generate faster code for various
machines.
(Well, to tell the truth, there actually is another functional
difference in some pathological cases: e.g., a '!' stores into the
cell where the next executed word comes from; or, the next word
executed comes from the top-of-stack. These differences are one of
the reasons why GCC cannot produce the right variation by itself. We
chose disallowing such practices and using the added implementation
freedom to achieve a significant speedup, because these practices
are not common in Forth (I have never heard of or seen anyone using
them), and it is easy to circumvent problems: A control flow change
will flush any prefetched words; you may want to do a "0
drop" before that to write back the top-of-stack cache.)
These macro sets are used in the following ways: After translation
to C a typical primitive looks like
...
{
DEF_CA
other declarations
NEXT_P0;
main part of the primitive
NEXT_P1;
store results to stack
NEXT_P2;
}
DEF_CA and all the NEXT_P* together must implement NEXT; In the main
part the instruction pointer can be read with IP, changed with
INC_IP(const_inc), and the cell right behind the presently executing
word (i.e. the value of *IP) is accessed with NEXT_INST.
If a primitive does not fall through the main part, it has to do the
rest by itself. If it changes ip, it has to redo NEXT_P0 (perhaps we
should define a macro SET_IP).
Some primitives (execute, dodefer) do not end with NEXT, but with
EXEC(.). If NEXT_P0 has been called earlier, it has to perform
"ip=IP;" to ensure that ip has the right value (NEXT_P0 may change
it).
Finally, there is NEXT1_P1 and NEXT1_P2, which are parts of EXEC
(EXEC(XT) could be defined as "cfa=XT; NEXT1_P1; NEXT1_P2;" (is this
true?)) and are used for making docol faster.
We can define the ways in which these macros are used with a regular
expression:
For a primitive
DEF_CA NEXT_P0 ( IP | INC_IP | NEXT_INST | ip=...; NEXT_P0 ) * ( NEXT_P1 NEXT_P2 | EXEC(...) )
For a run-time routine, e.g., docol:
PFA1(cfa) ( NEXT_P0 NEXT | cfa=...; NEXT1_P1; NEXT1_P2 | EXEC(...) )
This comment does not yet describe all the dependences that the
macros have to satisfy.
To organize the former ifdef chaos, each path is separated
This gives a quite impressive number of paths, but you clearly
find things that go together.
It should be possible to organize the whole thing in a way that
contains less redundancy and allows a simpler description.
*/
/* CFA_NEXT: if NEXT uses cfa, you have to #define CFA_NEXT, to get
* cfa declared in engine.
*/
#ifdef DOUBLY_INDIRECT
# define CFA_NEXT
# define NEXT_P0 ({cfa=*ip;})
# define IP (ip)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (cfa)
# define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
# define DEF_CA Label ca;
# define NEXT_P1 ({ip++; ca=**cfa;})
# define NEXT_P2 ({goto *ca;})
# define EXEC(XT) ({DEF_CA cfa=(XT); ca=**cfa; goto *ca;})
# define NEXT1_P1 ({ca = **cfa;})
# define NEXT1_P2 ({goto *ca;})
#else /* !defined(DOUBLY_INDIRECT) */
#if defined(DIRECT_THREADED)
/* note that the "cfa dead" versions only work if GETCFA exists and works */
#if THREADING_SCHEME==1
#warning direct threading scheme 1: autoinc, long latency, cfa live
# define CFA_NEXT
# define NEXT_P0 ({cfa=*ip++;})
# define IP (ip-1)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (cfa)
# define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
# define DEF_CA
# define NEXT_P1
# define NEXT_P2 ({goto *cfa;})
# define EXEC(XT) ({cfa=(XT); goto *cfa;})
#endif
#if THREADING_SCHEME==2
#warning direct threading scheme 2: autoinc, long latency, cfa dead
#ifndef GETCFA
#error GETCFA must be defined for cfa dead threading
#endif
# define NEXT_P0 (ip++)
# define IP (ip-1)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (*(ip-1))
# define INC_IP(const_inc) ({ ip+=(const_inc);})
# define DEF_CA
# define NEXT_P1
# define NEXT_P2 ({goto **(ip-1);})
# define EXEC(XT) ({goto *(XT);})
#endif
#if THREADING_SCHEME==3
#warning direct threading scheme 3: autoinc, low latency, cfa live
# define CFA_NEXT
# define NEXT_P0
# define IP (ip)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (*ip)
# define INC_IP(const_inc) ({ip+=(const_inc);})
# define DEF_CA
# define NEXT_P1 ({cfa=*ip++;})
# define NEXT_P2 ({goto *cfa;})
# define EXEC(XT) ({cfa=(XT); goto *cfa;})
#endif
#if THREADING_SCHEME==4
#warning direct threading scheme 4: autoinc, low latency, cfa dead
#ifndef GETCFA
#error GETCFA must be defined for cfa dead threading
#endif
# define NEXT_P0
# define IP (ip)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (*ip)
# define INC_IP(const_inc) ({ ip+=(const_inc);})
# define DEF_CA
# define NEXT_P1
# define NEXT_P2 ({goto **(ip++);})
# define EXEC(XT) ({goto *(XT);})
#endif
#if THREADING_SCHEME==5
#warning direct threading scheme 5: long latency, cfa live
# define CFA_NEXT
# define NEXT_P0 ({cfa=*ip;})
# define IP (ip)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (cfa)
# define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
# define DEF_CA
# define NEXT_P1 (ip++)
# define NEXT_P2 ({goto *cfa;})
# define EXEC(XT) ({cfa=(XT); goto *cfa;})
#endif
#if THREADING_SCHEME==6
#warning direct threading scheme 6: long latency, cfa dead
#ifndef GETCFA
#error GETCFA must be defined for cfa dead threading
#endif
# define NEXT_P0
# define IP (ip)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (*ip)
# define INC_IP(const_inc) ({ip+=(const_inc);})
# define DEF_CA
# define NEXT_P1 (ip++)
# define NEXT_P2 ({goto **(ip-1);})
# define EXEC(XT) ({goto *(XT);})
#endif
#if THREADING_SCHEME==7
#warning direct threading scheme 7: low latency, cfa live
# define CFA_NEXT
# define NEXT_P0
# define IP (ip)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (*ip)
# define INC_IP(const_inc) ({ip+=(const_inc);})
# define DEF_CA
# define NEXT_P1 ({cfa=*ip++;})
# define NEXT_P2 ({goto *cfa;})
# define EXEC(XT) ({cfa=(XT); goto *cfa;})
#endif
#if THREADING_SCHEME==8
#warning direct threading scheme 8: cfa dead, i386 hack
#ifndef GETCFA
#error GETCFA must be defined for cfa dead threading
#endif
# define NEXT_P0
# define IP (ip)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (*IP)
# define INC_IP(const_inc) ({ ip+=(const_inc);})
# define DEF_CA
# define NEXT_P1 (ip++)
# define NEXT_P2 ({goto **(ip-1);})
# define EXEC(XT) ({goto *(XT);})
#endif
#if THREADING_SCHEME==9
#warning direct threading scheme 9: Power/PPC hack, long latency
/* Power uses a prepare-to-branch instruction, and the latency between
this inst and the branch is 5 cycles on a PPC604; so we utilize this
to do some prefetching in between */
# define CFA_NEXT
# define NEXT_P0
# define IP ip
# define SET_IP(p) ({ip=(p); next_cfa=*ip; NEXT_P0;})
# define NEXT_INST (next_cfa)
# define INC_IP(const_inc) ({next_cfa=IP[const_inc]; ip+=(const_inc);})
# define DEF_CA
# define NEXT_P1 ({cfa=next_cfa; ip++; next_cfa=*ip;})
# define NEXT_P2 ({goto *cfa;})
# define EXEC(XT) ({cfa=(XT); goto *cfa;})
# define MORE_VARS Xt next_cfa;
#endif
#if THREADING_SCHEME==10
#warning direct threading scheme 10: plain (no attempt at scheduling)
# define CFA_NEXT
# define NEXT_P0
# define IP (ip)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (*ip)
# define INC_IP(const_inc) ({ip+=(const_inc);})
# define DEF_CA
# define NEXT_P1
# define NEXT_P2 ({cfa=*ip++; goto *cfa;})
# define EXEC(XT) ({cfa=(XT); goto *cfa;})
#endif
/* direct threaded */
#else
/* indirect THREADED */
#if THREADING_SCHEME==1
#warning indirect threading scheme 1: autoinc, long latency, cisc
# define CFA_NEXT
# define NEXT_P0 ({cfa=*ip++;})
# define IP (ip-1)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (cfa)
# define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
# define DEF_CA
# define NEXT_P1
# define NEXT_P2 ({goto **cfa;})
# define EXEC(XT) ({cfa=(XT); goto **cfa;})
#endif
#if THREADING_SCHEME==2
#warning indirect threading scheme 2: autoinc, long latency
# define CFA_NEXT
# define NEXT_P0 ({cfa=*ip++;})
# define IP (ip-1)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (cfa)
# define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
# define DEF_CA Label ca;
# define NEXT_P1 ({ca=*cfa;})
# define NEXT_P2 ({goto *ca;})
# define EXEC(XT) ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
#endif
#if THREADING_SCHEME==3
#warning indirect threading scheme 3: autoinc, low latency, cisc
# define CFA_NEXT
# define NEXT_P0
# define IP (ip)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (*ip)
# define INC_IP(const_inc) ({ip+=(const_inc);})
# define DEF_CA
# define NEXT_P1
# define NEXT_P2 ({cfa=*ip++; goto **cfa;})
# define EXEC(XT) ({cfa=(XT); goto **cfa;})
#endif
#if THREADING_SCHEME==4
#warning indirect threading scheme 4: autoinc, low latency
# define CFA_NEXT
# define NEXT_P0 ({cfa=*ip++;})
# define IP (ip-1)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (cfa)
# define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
# define DEF_CA Label ca;
# define NEXT_P1 ({ca=*cfa;})
# define NEXT_P2 ({goto *ca;})
# define EXEC(XT) ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
#endif
#if THREADING_SCHEME==5
#warning indirect threading scheme 5: long latency, cisc
# define CFA_NEXT
# define NEXT_P0 ({cfa=*ip;})
# define IP (ip)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (cfa)
# define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
# define DEF_CA
# define NEXT_P1 (ip++)
# define NEXT_P2 ({goto **cfa;})
# define EXEC(XT) ({cfa=(XT); goto **cfa;})
#endif
#if THREADING_SCHEME==6
#warning indirect threading scheme 6: long latency
# define CFA_NEXT
# define NEXT_P0 ({cfa=*ip;})
# define IP (ip)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (cfa)
# define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
# define DEF_CA Label ca;
# define NEXT_P1 ({ip++; ca=*cfa;})
# define NEXT_P2 ({goto *ca;})
# define EXEC(XT) ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
#endif
#if THREADING_SCHEME==7
#warning indirect threading scheme 7: low latency
# define CFA_NEXT
# define NEXT_P0 ({cfa=*ip;})
# define IP (ip)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (cfa)
# define INC_IP(const_inc) ({cfa=IP[const_inc]; ip+=(const_inc);})
# define DEF_CA Label ca;
# define NEXT_P1 ({ip++; ca=*cfa;})
# define NEXT_P2 ({goto *ca;})
# define EXEC(XT) ({DEF_CA cfa=(XT); ca=*cfa; goto *ca;})
#endif
#if THREADING_SCHEME==8
#warning indirect threading scheme 8: low latency,cisc
# define CFA_NEXT
# define NEXT_P0
# define IP (ip)
# define SET_IP(p) ({ip=(p); NEXT_P0;})
# define NEXT_INST (*ip)
# define INC_IP(const_inc) ({ip+=(const_inc);})
# define DEF_CA
# define NEXT_P1
# define NEXT_P2 ({cfa=*ip++; goto **cfa;})
# define EXEC(XT) ({cfa=(XT); goto **cfa;})
#endif
/* indirect threaded */
#endif
#endif /* !defined(DOUBLY_INDIRECT) */
#define NEXT ({DEF_CA NEXT_P1; NEXT_P2;})
#define IPTOS NEXT_INST
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