ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/Faster/Faster.pm
Revision: 1.34
Committed: Wed Mar 15 02:32:27 2006 UTC (18 years, 3 months ago) by root
Branch: MAIN
Changes since 1.33: +48 -21 lines
Log Message:
*** empty log message ***

File Contents

# Content
1 =head1 NAME
2
3 Faster - do some things faster
4
5 =head1 SYNOPSIS
6
7 use Faster;
8
9 perl -MFaster ...
10
11 =head1 DESCRIPTION
12
13 This module implements a very simple-minded "JIT" (or actually AIT, ahead
14 of time compiler). It works by more or less translating every function it
15 sees into a C program, compiling it and then replacing the function by the
16 compiled code.
17
18 As a result, startup times are immense, as every function might lead to a
19 full-blown compilation.
20
21 The speed improvements are also not great, you can expect 20% or so on
22 average, for code that runs very often. The reason for this is that data
23 handling is mostly being done by the same old code, it just gets called
24 a bit faster. Regexes and string operations won't get faster. Airhtmetic
25 doresn't become any faster. Just the operands and other stuff is put on
26 the stack faster, and the opcodes themselves have a bit less overhead.
27
28 Faster is in the early stages of development. Due to its design its
29 relatively safe to use (it will either work or simply slowdown the program
30 immensely, but rarely cause bugs).
31
32 More intelligent algorithms (loop optimisation, type inference) could
33 improve that easily, but requires a much more elaborate presentation and
34 optimiser than what is in place. There are no plans to improve Faster in
35 this way, yet, but it would provide a reasonably good place to start.
36
37 Usage is very easy, just C<use Faster> and every function called from then
38 on will be compiled.
39
40 Right now, Faster can leave lots of F<*.c> and F<*.so> files in your
41 F<$FASTER_CACHEDIR> (by default F<$HOME/.perl-faster-cache>), and it will
42 even create those temporary files in an insecure manner, so watch out.
43
44 =over 4
45
46 =cut
47
48 package Faster;
49
50 no warnings;
51
52 use strict;
53 use Config;
54 use B ();
55 use DynaLoader ();
56 use Digest::MD5 ();
57 use Storable ();
58 use Fcntl ();
59
60 BEGIN {
61 our $VERSION = '0.01';
62
63 require XSLoader;
64 XSLoader::load __PACKAGE__, $VERSION;
65 }
66
67 my $CACHEDIR =
68 $ENV{FASTER_CACHE}
69 || (exists $ENV{HOME} && "$ENV{HOME}/.perl-faster-cache")
70 || do {
71 require File::Temp;
72 File::Temp::tempdir (CLEANUP => 1)
73 };
74
75 my $COMPILE = "$Config{cc} -c -I$Config{archlibexp}/CORE $Config{optimize} $Config{ccflags} $Config{cccdlflags}";
76 my $LINK = "$Config{ld} $Config{ldflags} $Config{lddlflags} $Config{ccdlflags}";
77 my $LIBS = "";
78 my $_o = $Config{_o};
79 my $_so = ".so";
80
81 # we don't need no steenking PIC on x86
82 $COMPILE =~ s/-f(?:PIC|pic)//g
83 if $Config{archname} =~ /^(i[3456]86)-/;
84
85 my $opt_assert = $ENV{FASTER_DEBUG} & 2;
86 my $verbose = $ENV{FASTER_VERBOSE}+0;
87
88 warn "Faster: CACHEDIR is $CACHEDIR\n" if $verbose > 2;
89
90 our $source;
91
92 our @ops;
93 our $insn;
94 our $op;
95 our $op_name;
96 our %op_regcomp;
97
98 # ops that cause immediate return to the interpreter
99 my %f_unsafe = map +($_ => undef), qw(
100 leavesub leavesublv return
101 goto last redo next
102 eval flip leaveeval entertry
103 formline grepstart mapstart
104 substcont entereval require
105 );
106
107 # ops with known stack extend behaviour
108 # the values given are maximum values
109 my %extend = (
110 pushmark => 0,
111 nextstate => 0, # might reduce the stack
112 unstack => 0,
113 enter => 0,
114
115 stringify => 0,
116 not => 0,
117 and => 0,
118 or => 0,
119 gvsv => 0,
120 rv2gv => 0,
121 preinc => 0,
122 predec => 0,
123 postinc => 0,
124 postdec => 0,
125 aelem => 0,
126 helem => 0,
127 qr => 1, #???
128 pushre => 1,
129 gv => 1,
130 aelemfast => 1,
131 aelem => 0,
132 padsv => 1,
133 const => 1,
134 pop => 1,
135 shift => 1,
136 eq => -1,
137 ne => -1,
138 gt => -1,
139 lt => -1,
140 ge => -1,
141 lt => -1,
142 cond_expr => -1,
143 add => -1,
144 subtract => -1,
145 multiply => -1,
146 divide => -1,
147 aassign => 0,
148 sassign => -2,
149 method => 0,
150 method_named => 1,
151 );
152
153 # ops that do not need an ASYNC_CHECK
154 my %f_noasync = map +($_ => undef), qw(
155 mapstart grepstart match entereval
156 enteriter entersub leaveloop
157
158 pushmark nextstate caller
159
160 const stub unstack
161 last next redo goto seq
162 padsv padav padhv padany
163 aassign sassign orassign
164 rv2av rv2cv rv2gv rv2hv refgen
165 gv gvsv
166 add subtract multiply divide
167 complement cond_expr and or not
168 bit_and bit_or bit_xor
169 defined
170 method method_named bless
171 preinc postinc predec postdec
172 aelem aelemfast helem delete exists
173 pushre subst list lslice join split concat
174 length substr stringify ord
175 push pop shift unshift
176 eq ne gt lt ge le
177 regcomp regcreset regcmaybe
178 );
179
180 my %callop = (
181 entersub => "(PL_op->op_ppaddr) (aTHX)",
182 mapstart => "Perl_pp_grepstart (aTHX)",
183 );
184
185 sub callop {
186 $callop{$op_name} || "Perl_pp_$op_name (aTHX)"
187 }
188
189 sub assert {
190 return unless $opt_assert;
191 $source .= " assert ((\"$op_name\", ($_[0])));\n";
192 }
193
194 sub out_callop {
195 assert "nextop == (OP *)$$op";
196 $source .= " PL_op = nextop; nextop = " . (callop $op) . ";\n";
197 }
198
199 sub out_jump {
200 assert "nextop == (OP *)${$_[0]}L";
201 $source .= " goto op_${$_[0]};\n";
202 }
203
204 sub out_cond_jump {
205 $source .= " if (nextop == (OP *)${$_[0]}L) goto op_${$_[0]};\n";
206 }
207
208 sub out_jump_next {
209 out_cond_jump $op_regcomp{$$op}
210 if $op_regcomp{$$op};
211
212 assert "nextop == (OP *)${$op->next}";
213 $source .= " goto op_${$op->next};\n";
214 }
215
216 sub out_next {
217 $source .= " nextop = (OP *)${$op->next}L;\n";
218
219 out_jump_next;
220 }
221
222 sub out_linear {
223 out_callop;
224 out_jump_next;
225 }
226
227 sub op_entersub {
228 out_callop;
229 $source .= " RUNOPS_TILL ((OP *)${$op->next}L);\n";
230 out_jump_next;
231 }
232
233 *op_require = \&op_entersub;
234
235 sub op_nextstate {
236 $source .= " PL_curcop = (COP *)nextop;\n";
237 $source .= " PL_stack_sp = PL_stack_base + cxstack[cxstack_ix].blk_oldsp;\n";
238 $source .= " FREETMPS;\n";
239
240 out_next;
241 }
242
243 sub op_pushmark {
244 $source .= " faster_PUSHMARK (PL_stack_sp);\n";
245
246 out_next;
247 }
248
249 if ($Config{useithreads} ne "define") {
250 # disable optimisations on ithreads
251
252 *op_const = sub {
253 $source .= " { dSP; PUSHs ((SV *)${$op->sv}L); PUTBACK; }\n";
254
255 $ops[0]{follows_const}++ if @ops;#d#
256
257 out_next;
258 };
259
260 *op_gv = \&op_const;
261
262 *op_aelemfast = sub {
263 my $targ = $op->targ;
264 my $private = $op->private;
265
266 $source .= " {\n";
267
268 if ($op->flags & B::OPf_SPECIAL) {
269 $source .= " AV *av = (AV*)PAD_SV((PADOFFSET)$targ);\n";
270 } else {
271 $source .= " AV *av = GvAV ((GV *)${$op->sv}L);\n";
272 }
273
274 if ($op->flags & B::OPf_MOD) {
275 $source .= " SV *sv = *av_fetch (av, $private, 1);\n";
276 } else {
277 $source .= " SV **svp = av_fetch (av, $private, 0); SV *sv = svp ? *svp : &PL_sv_undef;\n";
278 }
279
280 if (!($op->flags & B::OPf_MOD)) {
281 $source .= " if (SvGMAGICAL (sv)) sv = sv_mortalcopy (sv);\n";
282 }
283
284 $source .= " dSP;\n";
285 $source .= " PUSHs (sv);\n";
286 $source .= " PUTBACK;\n";
287 $source .= " }\n";
288
289 out_next;
290 };
291
292 *op_gvsv = sub {
293 $source .= " {\n";
294 $source .= " dSP;\n";
295
296 if ($op->private & B::OPpLVAL_INTRO) {
297 $source .= " PUSHs (save_scalar ((GV *)${$op->sv}L));\n";
298 } else {
299 $source .= " PUSHs (GvSV ((GV *)${$op->sv}L));\n";
300 }
301
302 $source .= " PUTBACK;\n";
303 $source .= " }\n";
304
305 out_next;
306 };
307 }
308
309 # does kill Crossfire/res2pm
310 sub op_stringify {
311 my $targ = $op->targ;
312
313 $source .= <<EOF;
314 {
315 dSP;
316 SV *targ = PAD_SV ((PADOFFSET)$targ);
317 sv_copypv (TARG, TOPs);
318 SETTARG;
319 PUTBACK;
320 }
321 EOF
322
323 out_next;
324 }
325
326 sub op_and {
327 $source .= <<EOF;
328 {
329 dSP;
330
331 if (SvTRUE (TOPs))
332 {
333 --SP;
334 PUTBACK;
335 nextop = (OP *)${$op->other}L;
336 goto op_${$op->other};
337 }
338 }
339 EOF
340
341 out_next;
342 }
343
344 sub op_or {
345 $source .= <<EOF;
346 {
347 dSP;
348
349 if (!SvTRUE (TOPs))
350 {
351 --SP;
352 PUTBACK;
353 nextop = (OP *)${$op->other}L;
354 goto op_${$op->other};
355 }
356 }
357 EOF
358
359 out_next;
360 }
361
362 sub op_padsv {
363 my $flags = $op->flags;
364 my $padofs = "(PADOFFSET)" . $op->targ;
365
366 $source .= <<EOF;
367 {
368 dSP;
369 SV *sv = PAD_SVl ($padofs);
370 EOF
371
372 if (($flags & B::OPf_MOD) && ($op->private & B::OPpLVAL_INTRO)) {
373 $source .= " SAVECLEARSV (PAD_SVl ($padofs));\n";
374 $ops[0]{follows_padsv_lval_intro}++ if @ops;#d#
375 }
376
377 $source .= <<EOF;
378 PUSHs (sv);
379 PUTBACK;
380 EOF
381
382 if (($flags & B::OPf_MOD) && ($op->private & B::OPpDEREF)) {
383 $source .= " if (!SvROK (sv)) vivify_ref (sv, " . $op->private . " & OPpDEREF);\n";
384 }
385 $source .= " }\n";
386
387 out_next;
388 }
389
390 sub op_sassign {
391 $source .= <<EOF;
392 {
393 dSP;
394 dPOPTOPssrl;
395 EOF
396 $source .= " SV *temp = left; left = right; right = temp;\n"
397 if $op->private & B::OPpASSIGN_BACKWARDS;
398
399 if ($insn->{follows_padsv_lval_intro} && !($op->private & B::OPpASSIGN_BACKWARDS)) {
400 # simple assignment - the target exists, but is basically undef
401 $source .= " SvSetSV (right, left);\n";
402 } else {
403 $source .= " SvSetMagicSV (right, left);\n";
404 }
405
406 $source .= <<EOF;
407 SETs (right);
408 PUTBACK;
409 }
410 EOF
411
412 out_next;
413 }
414
415 # pattern const+ (or general push1)
416 # pattern pushmark gv rv2av pushmark padsv+o.รค. aassign
417
418 sub op_method_named {
419 if ($insn->{follows_const}) {
420 $source .= <<EOF;
421 {
422 dSP;
423 static SV *last_cv;
424 static U32 last_sub_generation;
425
426 /* simple "polymorphic" inline cache */
427 if (PL_sub_generation == last_sub_generation)
428 {
429 PUSHs (last_cv);
430 PUTBACK;
431 }
432 else
433 {
434 PL_op = nextop; nextop = Perl_pp_method_named (aTHX);
435
436 SPAGAIN;
437 last_sub_generation = PL_sub_generation;
438 last_cv = TOPs;
439 }
440 }
441 EOF
442 } else {
443 $source .= <<EOF;
444 {
445 static HV *last_stash;
446 static SV *last_cv;
447 static U32 last_sub_generation;
448
449 SV *obj = *(PL_stack_base + TOPMARK + 1);
450
451 if (!SvGMAGICAL (obj) && SvROK (obj) && SvOBJECT (SvRV (obj)))
452 {
453 dSP;
454 HV *stash = SvSTASH (SvRV (obj));
455
456 /* simple "polymorphic" inline cache */
457 if (stash == last_stash
458 && PL_sub_generation == last_sub_generation)
459 {
460 PUSHs (last_cv);
461 PUTBACK;
462 }
463 else
464 {
465 PL_op = nextop; nextop = Perl_pp_method_named (aTHX);
466
467 SPAGAIN;
468 last_sub_generation = PL_sub_generation;
469 last_stash = stash;
470 last_cv = TOPs;
471 }
472 }
473 else
474 {
475 /* error case usually */
476 PL_op = nextop; nextop = Perl_pp_method_named (aTHX);
477 }
478 }
479 EOF
480 }
481
482 out_next;
483 }
484
485 sub op_grepstart {
486 out_callop;
487 $op = $op->next;
488 out_cond_jump $op->other;
489 out_jump_next;
490 }
491
492 *op_mapstart = \&op_grepstart;
493
494 sub op_substcont {
495 out_callop;
496 out_cond_jump $op->other->pmreplstart;
497 assert "nextop == (OP *)${$op->other->next}L";
498 $source .= " goto op_${$op->other->next};\n";
499 }
500
501 sub out_break_op {
502 my ($idx) = @_;
503
504 if ($op->flags & B::OPf_SPECIAL && $insn->{loop}) {
505 # common case: no label, innermost loop only
506 my $next = $insn->{loop}{loop_targ}[$idx];
507 out_callop;
508 out_jump $next;
509 } elsif (my $loop = $insn->{loop}) {
510 # less common case: maybe break to some outer loop
511 $source .= " return nextop;\n";
512 # todo: walk stack up
513 } else {
514 $source .= " return nextop;\n";
515 }
516 }
517
518 sub op_next {
519 out_break_op 0;
520 }
521
522 sub op_last {
523 out_break_op 1;
524 }
525
526 sub xop_redo {
527 out_break_op 2;
528 }
529
530 sub cv2c {
531 my ($cv) = @_;
532
533 local @ops;
534 local %op_regcomp;
535
536 my $curloop;
537 my @todo = $cv->START;
538 my %op_target;
539 my $numpushmark;
540 my $scope;
541
542 my %op_seen;
543 while (my $op = shift @todo) {
544 my $next;
545 for (; $$op; $op = $next) {
546 last if $op_seen{$$op}++;
547
548 $next = $op->next;
549
550 my $name = $op->name;
551 my $class = B::class $op;
552
553 my $insn = { op => $op };
554
555 # end of loop reached?
556 $curloop = $curloop->{loop} if $curloop && $$op == ${$curloop->{loop_targ}[1]};
557
558 # remember enclosing loop
559 $insn->{loop} = $curloop if $curloop;
560
561 push @ops, $insn;
562
563 if (exists $extend{$name}) {
564 my $extend = $extend{$name};
565 $extend = $extend->($op) if ref $extend;
566 $insn->{extend} = $extend if defined $extend;
567 }
568
569 # TODO: mark scopes similar to loops, make them comparable
570 # static cxstack(?)
571 if ($class eq "LOGOP") {
572 push @todo, $op->other;
573 $op_target{${$op->other}}++;
574
575 # regcomp/o patches ops at runtime, lets expect that
576 if ($name eq "regcomp" && $op->other->pmflags & B::PMf_KEEP) {
577 $op_target{${$op->first}}++;
578 $op_regcomp{${$op->first}} = $op->next;
579 }
580
581 } elsif ($class eq "PMOP") {
582 if (${$op->pmreplstart}) {
583 unshift @todo, $op->pmreplstart;
584 $op_target{${$op->pmreplstart}}++;
585 }
586
587 } elsif ($class eq "LOOP") {
588 my @targ = ($op->nextop, $op->lastop->next, $op->redoop);
589
590 unshift @todo, $next, $op->redoop, $op->nextop, $op->lastop;
591 $next = $op->redoop;
592
593 $op_target{$$_}++ for @targ;
594
595 $insn->{loop_targ} = \@targ;
596 $curloop = $insn;
597
598 } elsif ($class eq "COP") {
599 if (defined $op->label) {
600 $insn->{bblock}++;
601 $curloop->{contains_label}{$op->label}++ if $curloop; #TODO: should be within loop
602 }
603
604 } else {
605 if ($name eq "pushmark") {
606 $numpushmark++;
607 }
608 }
609 }
610 }
611
612 $_->{bblock}++ for grep $op_target{${$_->{op}}}, @ops;
613
614 local $source = <<EOF;
615 OP *%%%FUNC%%% (pTHX)
616 {
617 register OP *nextop = (OP *)${$ops[0]->{op}}L;
618 EOF
619
620 $source .= " faster_PUSHMARK_PREALLOC ($numpushmark);\n"
621 if $numpushmark;
622
623 while (@ops) {
624 $insn = shift @ops;
625
626 $op = $insn->{op};
627 $op_name = $op->name;
628
629 my $class = B::class $op;
630
631 $source .= "\n/* start basic block */\n" if exists $insn->{bblock};#d#
632 $source .= "op_$$op: /* $op_name */\n";
633 #$source .= "fprintf (stderr, \"$$op in op $op_name\\n\");\n";#d#
634 #$source .= "{ dSP; sv_dump (TOPs); }\n";#d#
635
636 $source .= " PERL_ASYNC_CHECK ();\n"
637 unless exists $f_noasync{$op_name};
638
639 if (my $can = __PACKAGE__->can ("op_$op_name")) {
640 # handcrafted replacement
641
642 if ($insn->{extend} > 0) {
643 # coalesce EXTENDs
644 # TODO: properly take negative preceeding and following EXTENDs into account
645 for my $i (@ops) {
646 last if exists $i->{bblock};
647 last unless exists $i->{extend};
648 my $extend = delete $i->{extend};
649 $insn->{extend} += $extend if $extend > 0;
650 }
651
652 $source .= " { dSP; EXTEND (SP, $insn->{extend}); PUTBACK; }\n"
653 if $insn->{extend} > 0;
654 }
655
656 $can->($op);
657
658 } elsif (exists $f_unsafe{$op_name}) {
659 # unsafe, return to interpreter
660 assert "nextop == (OP *)$$op";
661 $source .= " return nextop;\n";
662
663 } elsif ("LOGOP" eq $class) {
664 # logical operation with optional branch
665 out_callop;
666 out_cond_jump $op->other;
667 out_jump_next;
668
669 } elsif ("PMOP" eq $class) {
670 # regex-thingy
671 out_callop;
672 out_cond_jump $op->pmreplroot if $op_name ne "pushre" && ${$op->pmreplroot};
673 out_jump_next;
674
675 } else {
676 # normal operator, linear execution
677 out_linear;
678 }
679 }
680
681 $op_name = "func exit"; assert (0);
682
683 $source .= <<EOF;
684 op_0:
685 return 0;
686 }
687 EOF
688 #warn $source;
689
690 $source
691 }
692
693 my $uid = "aaaaaaa0";
694 my %so;
695
696 sub func2ptr {
697 my (@func) = @_;
698
699 #LOCK
700 mkdir $CACHEDIR, 0777;
701 sysopen my $meta_fh, "$CACHEDIR/meta", &Fcntl::O_RDWR | &Fcntl::O_CREAT, 0666
702 or die "$$CACHEDIR/meta: $!";
703 binmode $meta_fh, ":raw:perlio";
704 fcntl_lock fileno $meta_fh
705 or die "$CACHEDIR/meta: $!";
706
707 my $meta = eval { Storable::fd_retrieve $meta_fh } || { version => 1 };
708
709 for my $f (@func) {
710 $f->{func} = "F" . Digest::MD5::md5_hex ($f->{source});
711 $f->{so} = $meta->{$f->{func}};
712 }
713
714 if (grep !$_->{so}, @func) {
715 my $stem;
716
717 do {
718 $stem = "$CACHEDIR/$$-" . $uid++;
719 } while -e "$stem$_so";
720
721 open my $fh, ">:raw", "$stem.c";
722 print $fh <<EOF;
723 #define PERL_NO_GET_CONTEXT
724 #define PERL_CORE
725
726 #include <assert.h>
727
728 #include "EXTERN.h"
729 #include "perl.h"
730 #include "XSUB.h"
731
732 #if 1
733 # define faster_PUSHMARK_PREALLOC(count) while (PL_markstack_ptr + (count) >= PL_markstack_max) markstack_grow ()
734 # define faster_PUSHMARK(p) *++PL_markstack_ptr = (p) - PL_stack_base
735 #else
736 # define faster_PUSHMARK_PREALLOC(count) 1
737 # define faster_PUSHMARK(p) PUSHMARK(p)
738 #endif
739
740 #define RUNOPS_TILL(op) \\
741 while (nextop != (op)) \\
742 { \\
743 PERL_ASYNC_CHECK (); \\
744 PL_op = nextop; nextop = (PL_op->op_ppaddr)(aTHX); \\
745 }
746
747 EOF
748 for my $f (grep !$_->{so}, @func) {
749 next if $f->{so} = $meta->{$f->{func}}; # some cv's alias others
750
751 warn "compiling $f->{name} to $stem$_so:$f->{func}\n" if $verbose > 1;
752 my $source = $f->{source};
753 $source =~ s/%%%FUNC%%%/$f->{func}/g;
754 print $fh $source;
755 $meta->{$f->{func}} = $f->{so} = $stem;
756 }
757
758 close $fh;
759 system "$COMPILE -o $stem$_o $stem.c";
760 unlink "$stem.c" unless $ENV{FASTER_DEBUG} & 1;
761 system "$LINK -o $stem$_so $stem$_o $LIBS";
762 unlink "$stem$_o";
763 }
764
765 for my $f (@func) {
766 my $stem = $f->{so};
767
768 my $so = ($so{$stem} ||= DynaLoader::dl_load_file "$stem$_so")
769 or die "$stem$_so: $!";
770
771 #unlink "$stem$_so";
772
773 $f->{ptr} = DynaLoader::dl_find_symbol $so, $f->{func}
774 or die "$f->{func} not found in $stem$_so: $!";
775 }
776
777 seek $meta_fh, 0, 0 or die "$CACHEDIR/meta: $!";
778 Storable::nstore_fd $meta, $meta_fh;
779 truncate $meta_fh, tell $meta_fh;
780
781 # UNLOCK (by closing $meta_fh)
782 }
783
784 my %ignore;
785
786 sub entersub {
787 my ($cv) = @_;
788
789 my $pkg = $cv->STASH->NAME;
790
791 return if $ignore{$pkg};
792
793 warn "optimising ", $cv->STASH->NAME, "\n"
794 if $verbose;
795
796 eval {
797 my @func;
798
799 push @func, {
800 cv => $cv,
801 name => "<>",
802 source => cv2c $cv,
803 };
804
805 # always compile the whole stash
806 my %stash = $cv->STASH->ARRAY;
807 while (my ($k, $v) = each %stash) {
808 $v->isa (B::GV::)
809 or next;
810
811 my $cv = $v->CV;
812
813 if ($cv->isa (B::CV::)
814 && ${$cv->START}
815 && $cv->START->name ne "null") {
816
817 push @func, {
818 cv => $cv,
819 name => $k,
820 source => cv2c $cv,
821 };
822 }
823 }
824
825 func2ptr @func;
826
827 for my $f (@func) {
828 patch_cv $f->{cv}, $f->{ptr};
829 }
830 };
831
832 if ($@) {
833 $ignore{$pkg}++;
834 warn $@;
835 }
836 }
837
838 hook_entersub;
839
840 1;
841
842 =back
843
844 =head1 ENVIRONMENT VARIABLES
845
846 The following environment variables influence the behaviour of Faster:
847
848 =over 4
849
850 =item FASTER_VERBOSE
851
852 Faster will output more informational messages when set to values higher
853 than C<0>. Currently, C<1> outputs which packages are being compiled, C<3>
854 outputs the cache directory and C<10> outputs information on which perl
855 function is compiled into which shared object.
856
857 =item FASTER_DEBUG
858
859 Add debugging code when set to values higher than C<0>. Currently, this
860 adds 1-3 C<assert>'s per perl op (FASTER_DEBUG > 1), to ensure that opcode
861 order and C execution order are compatible.
862
863 =item FASTER_CACHE
864
865 Set a persistent cache directory that caches compiled code fragments. The
866 default is C<$HOME/.perl-faster-cache> if C<HOME> is set and a temporary
867 directory otherwise.
868
869 This directory will always grow in size, so you might need to erase it
870 from time to time.
871
872 =back
873
874 =head1 BUGS/LIMITATIONS
875
876 Perl will check much less often for asynchronous signals in
877 Faster-compiled code. It tries to check on every function call, loop
878 iteration and every I/O operator, though.
879
880 The following things will disable Faster. If you manage to enable them at
881 runtime, bad things will happen. Enabling them at startup will be fine,
882 though.
883
884 enabled tainting
885 enabled debugging
886
887 Thread-enabled builds of perl will dramatically reduce Faster's
888 performance, but you don't care about speed if you enable threads anyway.
889
890 These constructs will force the use of the interpreter for the currently
891 executed function as soon as they are being encountered during execution.
892
893 goto
894 next, redo (but not well-behaved last's)
895 labels, if used
896 eval
897 require
898 any use of formats
899 .., ... (flipflop operators)
900
901 =head1 AUTHOR
902
903 Marc Lehmann <schmorp@schmorp.de>
904 http://home.schmorp.de/
905
906 =cut
907