Annotation of gforth/glocals.fs, revision 1.64

1.15      anton       1: \ A powerful locals implementation
                      2: 
1.63      anton       3: \ Copyright (C) 1995,1996,1997,1998,2000,2003,2004,2005,2007,2011 Free Software Foundation, Inc.
1.15      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
1.60      anton       9: \ as published by the Free Software Foundation, either version 3
1.15      anton      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
1.60      anton      18: \ along with this program. If not, see http://www.gnu.org/licenses/.
1.15      anton      19: 
                     20: 
1.16      anton      21: \ More documentation can be found in the manual and in
                     22: \ http://www.complang.tuwien.ac.at/papers/ertl94l.ps.gz
                     23: 
1.1       anton      24: \ Local variables are quite important for writing readable programs, but
                     25: \ IMO (anton) they are the worst part of the standard. There they are very
                     26: \ restricted and have an ugly interface.
                     27: 
                     28: \ So, we implement the locals wordset, but do not recommend using
                     29: \ locals-ext (which is a really bad user interface for locals).
                     30: 
                     31: \ We also have a nice and powerful user-interface for locals: locals are
                     32: \ defined with
                     33: 
                     34: \ { local1 local2 ... }
                     35: \ or
                     36: \ { local1 local2 ... -- ... }
                     37: \ (anything after the -- is just a comment)
                     38: 
                     39: \ Every local in this list consists of an optional type specification
                     40: \ and a name. If there is only the name, it stands for a cell-sized
                     41: \ value (i.e., you get the value of the local variable, not it's
                     42: \ address). The following type specifiers stand before the name:
                     43: 
                     44: \ Specifier    Type    Access
                     45: \ W:           Cell    value
                     46: \ W^           Cell    address
                     47: \ D:           Double  value
                     48: \ D^           Double  address
                     49: \ F:           Float   value
                     50: \ F^           Float   address
                     51: \ C:           Char    value
                     52: \ C^           Char    address
                     53: 
                     54: \ The local variables are initialized with values from the appropriate
                     55: \ stack. In contrast to the examples in the standard document our locals
                     56: \ take the arguments in the expected way: The last local gets the top of
                     57: \ stack, the second last gets the second stack item etc. An example:
                     58: 
                     59: \ : CX* { F: Ar  F: Ai  F: Br  F: Bi -- Cr Ci }
                     60: \ \ complex multiplication
                     61: \  Ar Br f* Ai Bi f* f-
                     62: \  Ar Bi f* Ai Br f* f+ ;
                     63: 
                     64: \ There will also be a way to add user types, but it is not yet decided,
                     65: \ how. Ideas are welcome.
                     66: 
                     67: \ Locals defined in this manner live until (!! see below). 
                     68: \ Their names can be used during this time to get
                     69: \ their value or address; The addresses produced in this way become
                     70: \ invalid at the end of the lifetime.
                     71: 
                     72: \ Values can be changed with TO, but this is not recomended (TO is a
                     73: \ kludge and words lose the single-assignment property, which makes them
                     74: \ harder to analyse).
                     75: 
                     76: \ As for the internals, we use a special locals stack. This eliminates
                     77: \ the problems and restrictions of reusing the return stack and allows
                     78: \ to store floats as locals: the return stack is not guaranteed to be
                     79: \ aligned correctly, but our locals stack must be float-aligned between
                     80: \ words.
                     81: 
                     82: \ Other things about the internals are pretty unclear now.
                     83: 
                     84: \ Currently locals may only be
                     85: \ defined at the outer level and TO is not supported.
                     86: 
1.33      anton      87: require search.fs
1.14      anton      88: require float.fs
1.47      jwilke     89: require extend.fs \ for case
1.1       anton      90: 
1.62      anton      91: : save-mem-dict ( addr1 u -- addr2 u )
                     92:     here swap dup allot ( addr1 addr2 u )
                     93:     2dup 2>r move 2r> ;
                     94: 
1.14      anton      95: : compile-@local ( n -- ) \ gforth compile-fetch-local
1.3       anton      96:  case
1.7       pazsan     97:     0       of postpone @local0 endof
                     98:     1 cells of postpone @local1 endof
                     99:     2 cells of postpone @local2 endof
                    100:     3 cells of postpone @local3 endof
1.3       anton     101:    ( otherwise ) dup postpone @local# ,
                    102:  endcase ;
                    103: 
1.14      anton     104: : compile-f@local ( n -- ) \ gforth compile-f-fetch-local
1.3       anton     105:  case
1.7       pazsan    106:     0        of postpone f@local0 endof
                    107:     1 floats of postpone f@local1 endof
1.3       anton     108:    ( otherwise ) dup postpone f@local# ,
                    109:  endcase ;
                    110: 
1.27      pazsan    111: \ locals stuff needed for control structures
                    112: 
                    113: : compile-lp+! ( n -- ) \ gforth       compile-l-p-plus-store
                    114:     dup negate locals-size +!
                    115:     0 over = if
                    116:     else -1 cells  over = if postpone lp-
                    117:     else  1 floats over = if postpone lp+
                    118:     else  2 floats over = if postpone lp+2
                    119:     else postpone lp+!# dup ,
                    120:     then then then then drop ;
                    121: 
                    122: : adjust-locals-size ( n -- ) \ gforth
                    123:     \ sets locals-size to n and generates an appropriate lp+!
                    124:     locals-size @ swap - compile-lp+! ;
                    125: 
1.1       anton     126: \ the locals stack grows downwards (see primitives)
                    127: \ of the local variables of a group (in braces) the leftmost is on top,
                    128: \ i.e. by going onto the locals stack the order is reversed.
                    129: \ there are alignment gaps if necessary.
                    130: \ lp must have the strictest alignment (usually float) across calls;
                    131: \ for simplicity we align it strictly for every group.
                    132: 
1.5       anton     133: slowvoc @
                    134: slowvoc on \ we want a linked list for the vocabulary locals
1.1       anton     135: vocabulary locals \ this contains the local variables
1.37      pazsan    136: ' locals >body wordlist-id ' locals-list >body !
1.5       anton     137: slowvoc !
1.1       anton     138: 
1.62      anton     139: variable locals-mem-list \ linked list of all locals name memory in
                    140: 0 locals-mem-list !      \ the current (outer-level) definition
1.1       anton     141: 
1.62      anton     142: : free-list ( addr -- )
                    143:     \ free all members of a linked list (link field is first)
                    144:     begin
                    145:        dup while
                    146:            dup @ swap free throw
                    147:     repeat
                    148:     drop ;
                    149: 
                    150: : prepend-list ( addr1 addr2 -- )
                    151:     \ addr1 is the address of a list element, addr2 is the address of
                    152:     \ the cell containing the address of the first list element
                    153:     2dup @ swap ! \ store link to next element
                    154:     ! ; \ store pointer to new first element
1.1       anton     155: 
                    156: : alignlp-w ( n1 -- n2 )
                    157:     \ cell-align size and generate the corresponding code for aligning lp
1.3       anton     158:     aligned dup adjust-locals-size ;
1.1       anton     159: 
                    160: : alignlp-f ( n1 -- n2 )
1.3       anton     161:     faligned dup adjust-locals-size ;
1.1       anton     162: 
                    163: \ a local declaration group (the braces stuff) is compiled by calling
                    164: \ the appropriate compile-pushlocal for the locals, starting with the
                    165: \ righmost local; the names are already created earlier, the
                    166: \ compile-pushlocal just inserts the offsets from the frame base.
                    167: 
                    168: : compile-pushlocal-w ( a-addr -- ) ( run-time: w -- )
                    169: \ compiles a push of a local variable, and adjusts locals-size
                    170: \ stores the offset of the local variable to a-addr
                    171:     locals-size @ alignlp-w cell+ dup locals-size !
                    172:     swap !
                    173:     postpone >l ;
                    174: 
1.27      pazsan    175: \ locals list operations
                    176: 
                    177: : common-list ( list1 list2 -- list3 ) \ gforth-internal
                    178: \ list1 and list2 are lists, where the heads are at higher addresses than
                    179: \ the tail. list3 is the largest sublist of both lists.
                    180:  begin
                    181:    2dup u<>
                    182:  while
                    183:    2dup u>
                    184:    if
                    185:      swap
                    186:    then
                    187:    @
                    188:  repeat
                    189:  drop ;
                    190: 
                    191: : sub-list? ( list1 list2 -- f ) \ gforth-internal
                    192: \ true iff list1 is a sublist of list2
                    193:  begin
                    194:    2dup u<
                    195:  while
                    196:    @
                    197:  repeat
                    198:  = ;
                    199: 
                    200: : list-size ( list -- u ) \ gforth-internal
1.36      pazsan    201:     \ size of the locals frame represented by list
                    202:     0 ( list n )
                    203:     begin
                    204:        over 0<>
                    205:     while
                    206:        over
                    207:        ((name>)) >body @ max
                    208:        swap @ swap ( get next )
                    209:     repeat
                    210:     faligned nip ;
1.27      pazsan    211: 
                    212: : set-locals-size-list ( list -- )
1.37      pazsan    213:     dup locals-list !
1.36      pazsan    214:     list-size locals-size ! ;
1.27      pazsan    215: 
                    216: : check-begin ( list -- )
                    217: \ warn if list is not a sublist of locals-list
1.37      pazsan    218:  locals-list @ sub-list? 0= if
1.27      pazsan    219:    \ !! print current position
1.64    ! pazsan    220:      >stderr ." compiler was overly optimistic about locals at a BEGIN" cr
1.27      pazsan    221:    \ !! print assumption and reality
                    222:  then ;
                    223: 
1.1       anton     224: : compile-pushlocal-f ( a-addr -- ) ( run-time: f -- )
                    225:     locals-size @ alignlp-f float+ dup locals-size !
                    226:     swap !
                    227:     postpone f>l ;
                    228: 
                    229: : compile-pushlocal-d ( a-addr -- ) ( run-time: w1 w2 -- )
                    230:     locals-size @ alignlp-w cell+ cell+ dup locals-size !
                    231:     swap !
                    232:     postpone swap postpone >l postpone >l ;
                    233: 
                    234: : compile-pushlocal-c ( a-addr -- ) ( run-time: w -- )
1.3       anton     235:     -1 chars compile-lp+!
1.1       anton     236:     locals-size @ swap !
                    237:     postpone lp@ postpone c! ;
                    238: 
1.62      anton     239: 7 cells 32 + constant locals-name-size \ 32-char name + fields + wiggle room
                    240: 
                    241: : create-local1 ( "name" -- a-addr )
                    242:     create
                    243:     immediate restrict
                    244:     here 0 , ( place for the offset ) ;
                    245: 
                    246: variable dict-execute-dp \ the special dp for DICT-EXECUTE
                    247: 
                    248: 0 value dict-execute-ude \ USABLE-DICTIONARY-END during DICT-EXECUTE
                    249: 
                    250: : dict-execute1 ( ... addr1 addr2 xt -- ... )
                    251:     \ execute xt with HERE set to addr1 and USABLE-DICTIONARY-END set to addr2
                    252:     dict-execute-dp @ dp 2>r
                    253:     dict-execute-ude ['] usable-dictionary-end defer@ 2>r
                    254:     swap to dict-execute-ude
                    255:     ['] dict-execute-ude is usable-dictionary-end
                    256:     swap to dict-execute-dp
                    257:     dict-execute-dp dpp !
                    258:     catch
                    259:     2r> is usable-dictionary-end to dict-execute-ude
                    260:     2r> dpp ! dict-execute-dp !
                    261:     throw ;
                    262: 
                    263: defer dict-execute ( ... addr1 addr2 xt -- ... )
                    264: 
                    265: :noname ( ... addr1 addr2 xt -- ... )
                    266:     \ first have a dummy routine, for SOME-CLOCAL etc. below
                    267:     nip nip execute ;
                    268: is dict-execute
                    269: 
1.1       anton     270: : create-local ( " name" -- a-addr )
1.9       anton     271:     \ defines the local "name"; the offset of the local shall be
                    272:     \ stored in a-addr
1.62      anton     273:     locals-name-size allocate throw
                    274:     dup locals-mem-list prepend-list
                    275:     locals-name-size cell /string over + ['] create-local1 dict-execute ;
                    276: 
                    277: variable locals-dp \ so here's the special dp for locals.
1.1       anton     278: 
1.3       anton     279: : lp-offset ( n1 -- n2 )
                    280: \ converts the offset from the frame start to an offset from lp and
                    281: \ i.e., the address of the local is lp+locals_size-offset
                    282:   locals-size @ swap - ;
                    283: 
1.1       anton     284: : lp-offset, ( n -- )
                    285: \ converts the offset from the frame start to an offset from lp and
                    286: \ adds it as inline argument to a preceding locals primitive
1.3       anton     287:   lp-offset , ;
1.1       anton     288: 
                    289: vocabulary locals-types \ this contains all the type specifyers, -- and }
                    290: locals-types definitions
                    291: 
1.14      anton     292: : W: ( "name" -- a-addr xt ) \ gforth w-colon
                    293:     create-local
1.1       anton     294:        \ xt produces the appropriate locals pushing code when executed
                    295:        ['] compile-pushlocal-w
                    296:     does> ( Compilation: -- ) ( Run-time: -- w )
                    297:         \ compiles a local variable access
1.3       anton     298:        @ lp-offset compile-@local ;
1.1       anton     299: 
1.14      anton     300: : W^ ( "name" -- a-addr xt ) \ gforth w-caret
                    301:     create-local
1.1       anton     302:        ['] compile-pushlocal-w
                    303:     does> ( Compilation: -- ) ( Run-time: -- w )
                    304:        postpone laddr# @ lp-offset, ;
                    305: 
1.14      anton     306: : F: ( "name" -- a-addr xt ) \ gforth f-colon
                    307:     create-local
1.1       anton     308:        ['] compile-pushlocal-f
                    309:     does> ( Compilation: -- ) ( Run-time: -- w )
1.3       anton     310:        @ lp-offset compile-f@local ;
1.1       anton     311: 
1.14      anton     312: : F^ ( "name" -- a-addr xt ) \ gforth f-caret
                    313:     create-local
1.1       anton     314:        ['] compile-pushlocal-f
                    315:     does> ( Compilation: -- ) ( Run-time: -- w )
                    316:        postpone laddr# @ lp-offset, ;
                    317: 
1.14      anton     318: : D: ( "name" -- a-addr xt ) \ gforth d-colon
                    319:     create-local
1.1       anton     320:        ['] compile-pushlocal-d
                    321:     does> ( Compilation: -- ) ( Run-time: -- w )
                    322:        postpone laddr# @ lp-offset, postpone 2@ ;
                    323: 
1.14      anton     324: : D^ ( "name" -- a-addr xt ) \ gforth d-caret
                    325:     create-local
1.1       anton     326:        ['] compile-pushlocal-d
                    327:     does> ( Compilation: -- ) ( Run-time: -- w )
                    328:        postpone laddr# @ lp-offset, ;
                    329: 
1.14      anton     330: : C: ( "name" -- a-addr xt ) \ gforth c-colon
                    331:     create-local
1.1       anton     332:        ['] compile-pushlocal-c
                    333:     does> ( Compilation: -- ) ( Run-time: -- w )
                    334:        postpone laddr# @ lp-offset, postpone c@ ;
                    335: 
1.14      anton     336: : C^ ( "name" -- a-addr xt ) \ gforth c-caret
                    337:     create-local
1.1       anton     338:        ['] compile-pushlocal-c
                    339:     does> ( Compilation: -- ) ( Run-time: -- w )
                    340:        postpone laddr# @ lp-offset, ;
                    341: 
                    342: \ you may want to make comments in a locals definitions group:
1.44      anton     343: ' \ alias \ ( compilation 'ccc<newline>' -- ; run-time -- ) \ core-ext,block-ext backslash
1.42      anton     344: \G Comment till the end of the line if @code{BLK} contains 0 (i.e.,
                    345: \G while not loading a block), parse and discard the remainder of the
                    346: \G parse area. Otherwise, parse and discard all subsequent characters
                    347: \G in the parse area corresponding to the current line.
                    348: immediate
1.39      crook     349: 
                    350: ' ( alias ( ( compilation 'ccc<close-paren>' -- ; run-time -- ) \ core,file    paren
1.42      anton     351: \G Comment, usually till the next @code{)}: parse and discard all
                    352: \G subsequent characters in the parse area until ")" is
                    353: \G encountered. During interactive input, an end-of-line also acts as
                    354: \G a comment terminator. For file input, it does not; if the
                    355: \G end-of-file is encountered whilst parsing for the ")" delimiter,
                    356: \G Gforth will generate a warning.
1.39      crook     357: immediate
1.1       anton     358: 
                    359: forth definitions
1.54      anton     360: also locals-types
                    361:     
                    362: \ these "locals" are used for comparison in TO
                    363: c: some-clocal 2drop
                    364: d: some-dlocal 2drop
                    365: f: some-flocal 2drop
                    366: w: some-wlocal 2drop
1.62      anton     367: 
                    368: ' dict-execute1 is dict-execute \ now the real thing
1.54      anton     369:     
1.1       anton     370: \ the following gymnastics are for declaring locals without type specifier.
                    371: \ we exploit a feature of our dictionary: every wordlist
                    372: \ has it's own methods for finding words etc.
                    373: \ So we create a vocabulary new-locals, that creates a 'w:' local named x
                    374: \ when it is asked if it contains x.
                    375: 
                    376: : new-locals-find ( caddr u w -- nfa )
                    377: \ this is the find method of the new-locals vocabulary
                    378: \ make a new local with name caddr u; w is ignored
                    379: \ the returned nfa denotes a word that produces what W: produces
                    380: \ !! do the whole thing without nextname
1.3       anton     381:     drop nextname
1.43      anton     382:     ['] W: >head-noprim ;
1.1       anton     383: 
                    384: previous
                    385: 
                    386: : new-locals-reveal ( -- )
                    387:   true abort" this should not happen: new-locals-reveal" ;
                    388: 
1.22      anton     389: create new-locals-map ( -- wordlist-map )
1.29      anton     390: ' new-locals-find A,
                    391: ' new-locals-reveal A,
                    392: ' drop A, \ rehash method
1.34      jwilke    393: ' drop A,
1.1       anton     394: 
1.41      jwilke    395: new-locals-map mappedwordlist Constant new-locals-wl
                    396: 
                    397: \ slowvoc @
                    398: \ slowvoc on
                    399: \ vocabulary new-locals
                    400: \ slowvoc !
                    401: \ new-locals-map ' new-locals >body wordlist-map A! \ !! use special access words
1.1       anton     402: 
                    403: \ and now, finally, the user interface words
1.53      anton     404: : { ( -- latestxt wid 0 ) \ gforth open-brace
                    405:     latestxt get-current
1.41      jwilke    406:     get-order new-locals-wl swap 1+ set-order
1.32      anton     407:     also locals definitions locals-types
1.1       anton     408:     0 TO locals-wordlist
                    409:     0 postpone [ ; immediate
                    410: 
                    411: locals-types definitions
                    412: 
1.53      anton     413: : } ( latestxt wid 0 a-addr1 xt1 ... -- ) \ gforth close-brace
1.1       anton     414:     \ ends locals definitions
1.61      anton     415:     ]
1.1       anton     416:     begin
                    417:        dup
                    418:     while
                    419:        execute
                    420:     repeat
                    421:     drop
                    422:     locals-size @ alignlp-f locals-size ! \ the strictest alignment
                    423:     previous previous
1.32      anton     424:     set-current lastcfa !
1.37      pazsan    425:     locals-list 0 wordlist-id - TO locals-wordlist ;
1.1       anton     426: 
1.14      anton     427: : -- ( addr wid 0 ... -- ) \ gforth dash-dash
1.1       anton     428:     }
1.9       anton     429:     [char] } parse 2drop ;
1.1       anton     430: 
                    431: forth definitions
                    432: 
                    433: \ A few thoughts on automatic scopes for locals and how they can be
                    434: \ implemented:
                    435: 
                    436: \ We have to combine locals with the control structures. My basic idea
                    437: \ was to start the life of a local at the declaration point. The life
                    438: \ would end at any control flow join (THEN, BEGIN etc.) where the local
                    439: \ is lot live on both input flows (note that the local can still live in
                    440: \ other, later parts of the control flow). This would make a local live
                    441: \ as long as you expected and sometimes longer (e.g. a local declared in
                    442: \ a BEGIN..UNTIL loop would still live after the UNTIL).
                    443: 
                    444: \ The following example illustrates the problems of this approach:
                    445: 
                    446: \ { z }
                    447: \ if
                    448: \   { x }
                    449: \ begin
                    450: \   { y }
                    451: \ [ 1 cs-roll ] then
                    452: \   ...
                    453: \ until
                    454: 
                    455: \ x lives only until the BEGIN, but the compiler does not know this
                    456: \ until it compiles the UNTIL (it can deduce it at the THEN, because at
                    457: \ that point x lives in no thread, but that does not help much). This is
                    458: \ solved by optimistically assuming at the BEGIN that x lives, but
                    459: \ warning at the UNTIL that it does not. The user is then responsible
                    460: \ for checking that x is only used where it lives.
                    461: 
                    462: \ The produced code might look like this (leaving out alignment code):
                    463: 
                    464: \ >l ( z )
                    465: \ ?branch <then>
                    466: \ >l ( x )
                    467: \ <begin>:
                    468: \ >l ( y )
                    469: \ lp+!# 8 ( RIP: x,y )
                    470: \ <then>:
                    471: \ ...
                    472: \ lp+!# -4 ( adjust lp to <begin> state )
                    473: \ ?branch <begin>
                    474: \ lp+!# 4 ( undo adjust )
                    475: 
                    476: \ The BEGIN problem also has another incarnation:
                    477: 
                    478: \ AHEAD
                    479: \ BEGIN
                    480: \   x
                    481: \ [ 1 CS-ROLL ] THEN
                    482: \   { x }
                    483: \   ...
                    484: \ UNTIL
                    485: 
                    486: \ should be legal: The BEGIN is not a control flow join in this case,
                    487: \ since it cannot be entered from the top; therefore the definition of x
                    488: \ dominates the use. But the compiler processes the use first, and since
                    489: \ it does not look ahead to notice the definition, it will complain
                    490: \ about it. Here's another variation of this problem:
                    491: 
                    492: \ IF
                    493: \   { x }
                    494: \ ELSE
                    495: \   ...
                    496: \ AHEAD
                    497: \ BEGIN
                    498: \   x
                    499: \ [ 2 CS-ROLL ] THEN
                    500: \   ...
                    501: \ UNTIL
                    502: 
                    503: \ In this case x is defined before the use, and the definition dominates
                    504: \ the use, but the compiler does not know this until it processes the
                    505: \ UNTIL. So what should the compiler assume does live at the BEGIN, if
                    506: \ the BEGIN is not a control flow join? The safest assumption would be
                    507: \ the intersection of all locals lists on the control flow
                    508: \ stack. However, our compiler assumes that the same variables are live
                    509: \ as on the top of the control flow stack. This covers the following case:
                    510: 
                    511: \ { x }
                    512: \ AHEAD
                    513: \ BEGIN
                    514: \   x
                    515: \ [ 1 CS-ROLL ] THEN
                    516: \   ...
                    517: \ UNTIL
                    518: 
                    519: \ If this assumption is too optimistic, the compiler will warn the user.
                    520: 
1.28      anton     521: \ Implementation:
1.1       anton     522: 
1.3       anton     523: \ explicit scoping
1.1       anton     524: 
1.14      anton     525: : scope ( compilation  -- scope ; run-time  -- ) \ gforth
1.36      pazsan    526:     cs-push-part scopestart ; immediate
                    527: 
                    528: : adjust-locals-list ( wid -- )
1.37      pazsan    529:     locals-list @ common-list
1.36      pazsan    530:     dup list-size adjust-locals-size
1.37      pazsan    531:     locals-list ! ;
1.3       anton     532: 
1.14      anton     533: : endscope ( compilation scope -- ; run-time  -- ) \ gforth
1.36      pazsan    534:     scope?
                    535:     drop  adjust-locals-list ; immediate
1.1       anton     536: 
1.3       anton     537: \ adapt the hooks
1.1       anton     538: 
1.3       anton     539: : locals-:-hook ( sys -- sys addr xt n )
                    540:     \ addr is the nfa of the defined word, xt its xt
1.1       anton     541:     DEFERS :-hook
1.53      anton     542:     latest latestxt
1.1       anton     543:     clear-leave-stack
                    544:     0 locals-size !
1.62      anton     545:     locals-mem-list @ free-list
                    546:     0 locals-mem-list !
1.37      pazsan    547:     0 locals-list !
1.3       anton     548:     dead-code off
                    549:     defstart ;
1.1       anton     550: 
1.3       anton     551: : locals-;-hook ( sys addr xt sys -- sys )
                    552:     def?
1.1       anton     553:     0 TO locals-wordlist
1.3       anton     554:     0 adjust-locals-size ( not every def ends with an exit )
1.1       anton     555:     lastcfa ! last !
                    556:     DEFERS ;-hook ;
                    557: 
1.28      anton     558: \ THEN (another control flow from before joins the current one):
                    559: \ The new locals-list is the intersection of the current locals-list and
                    560: \ the orig-local-list. The new locals-size is the (alignment-adjusted)
                    561: \ size of the new locals-list. The following code is generated:
                    562: \ lp+!# (current-locals-size - orig-locals-size)
                    563: \ <then>:
                    564: \ lp+!# (orig-locals-size - new-locals-size)
                    565: 
                    566: \ Of course "lp+!# 0" is not generated. Still this is admittedly a bit
                    567: \ inefficient, e.g. if there is a locals declaration between IF and
                    568: \ ELSE. However, if ELSE generates an appropriate "lp+!#" before the
                    569: \ branch, there will be none after the target <then>.
                    570: 
1.30      anton     571: : (then-like) ( orig -- )
                    572:     dead-orig =
1.27      pazsan    573:     if
1.30      anton     574:        >resolve drop
1.27      pazsan    575:     else
                    576:         dead-code @
                    577:         if
1.30      anton     578:            >resolve set-locals-size-list dead-code off
1.27      pazsan    579:        else \ both live
1.30      anton     580:            over list-size adjust-locals-size
                    581:            >resolve
1.36      pazsan    582:            adjust-locals-list
1.27      pazsan    583:        then
                    584:     then ;
                    585: 
                    586: : (begin-like) ( -- )
                    587:     dead-code @ if
                    588:        \ set up an assumption of the locals visible here.  if the
                    589:        \ users want something to be visible, they have to declare
                    590:        \ that using ASSUME-LIVE
                    591:        backedge-locals @ set-locals-size-list
                    592:     then
                    593:     dead-code off ;
                    594: 
                    595: \ AGAIN (the current control flow joins another, earlier one):
                    596: \ If the dest-locals-list is not a subset of the current locals-list,
                    597: \ issue a warning (see below). The following code is generated:
                    598: \ lp+!# (current-local-size - dest-locals-size)
                    599: \ branch <begin>
                    600: 
                    601: : (again-like) ( dest -- addr )
                    602:     over list-size adjust-locals-size
                    603:     swap check-begin  POSTPONE unreachable ;
                    604: 
                    605: \ UNTIL (the current control flow may join an earlier one or continue):
                    606: \ Similar to AGAIN. The new locals-list and locals-size are the current
                    607: \ ones. The following code is generated:
                    608: \ ?branch-lp+!# <begin> (current-local-size - dest-locals-size)
                    609: 
                    610: : (until-like) ( list addr xt1 xt2 -- )
                    611:     \ list and addr are a fragment of a cs-item
                    612:     \ xt1 is the conditional branch without lp adjustment, xt2 is with
                    613:     >r >r
                    614:     locals-size @ 2 pick list-size - dup if ( list dest-addr adjustment )
                    615:        r> drop r> compile,
                    616:        swap <resolve ( list adjustment ) ,
                    617:     else ( list dest-addr adjustment )
                    618:        drop
                    619:        r> compile, <resolve
                    620:        r> drop
                    621:     then ( list )
                    622:     check-begin ;
                    623: 
                    624: : (exit-like) ( -- )
                    625:     0 adjust-locals-size ;
                    626: 
1.1       anton     627: ' locals-:-hook IS :-hook
                    628: ' locals-;-hook IS ;-hook
1.27      pazsan    629: 
                    630: ' (then-like)  IS then-like
                    631: ' (begin-like) IS begin-like
                    632: ' (again-like) IS again-like
                    633: ' (until-like) IS until-like
                    634: ' (exit-like)  IS exit-like
1.1       anton     635: 
                    636: \ The words in the locals dictionary space are not deleted until the end
                    637: \ of the current word. This is a bit too conservative, but very simple.
                    638: 
                    639: \ There are a few cases to consider: (see above)
                    640: 
                    641: \ after AGAIN, AHEAD, EXIT (the current control flow is dead):
                    642: \ We have to special-case the above cases against that. In this case the
                    643: \ things above are not control flow joins. Everything should be taken
                    644: \ over from the live flow. No lp+!# is generated.
                    645: 
                    646: \ About warning against uses of dead locals. There are several options:
                    647: 
                    648: \ 1) Do not complain (After all, this is Forth;-)
                    649: 
                    650: \ 2) Additional restrictions can be imposed so that the situation cannot
                    651: \ arise; the programmer would have to introduce explicit scoping
                    652: \ declarations in cases like the above one. I.e., complain if there are
                    653: \ locals that are live before the BEGIN but not before the corresponding
                    654: \ AGAIN (replace DO etc. for BEGIN and UNTIL etc. for AGAIN).
                    655: 
                    656: \ 3) The real thing: i.e. complain, iff a local lives at a BEGIN, is
                    657: \ used on a path starting at the BEGIN, and does not live at the
                    658: \ corresponding AGAIN. This is somewhat hard to implement. a) How does
                    659: \ the compiler know when it is working on a path starting at a BEGIN
                    660: \ (consider "{ x } if begin [ 1 cs-roll ] else x endif again")? b) How
                    661: \ is the usage info stored?
                    662: 
                    663: \ For now I'll resort to alternative 2. When it produces warnings they
                    664: \ will often be spurious, but warnings should be rare. And better
                    665: \ spurious warnings now and then than days of bug-searching.
                    666: 
                    667: \ Explicit scoping of locals is implemented by cs-pushing the current
                    668: \ locals-list and -size (and an unused cell, to make the size equal to
                    669: \ the other entries) at the start of the scope, and restoring them at
                    670: \ the end of the scope to the intersection, like THEN does.
                    671: 
                    672: 
                    673: \ And here's finally the ANS standard stuff
                    674: 
1.14      anton     675: : (local) ( addr u -- ) \ local paren-local-paren
1.3       anton     676:     \ a little space-inefficient, but well deserved ;-)
                    677:     \ In exchange, there are no restrictions whatsoever on using (local)
1.4       anton     678:     \ as long as you use it in a definition
1.3       anton     679:     dup
                    680:     if
                    681:        nextname POSTPONE { [ also locals-types ] W: } [ previous ]
                    682:     else
                    683:        2drop
                    684:     endif ;
1.1       anton     685: 
1.56      anton     686: : >definer ( xt -- definer ) \ gforth
1.48      anton     687:     \G @var{Definer} is a unique identifier for the way the @var{xt}
                    688:     \G was defined.  Words defined with different @code{does>}-codes
                    689:     \G have different definers.  The definer can be used for
                    690:     \G comparison and in @code{definer!}.
1.30      anton     691:     dup >does-code
                    692:     ?dup-if
                    693:        nip 1 or
1.4       anton     694:     else
                    695:        >code-address
                    696:     then ;
                    697: 
1.56      anton     698: : definer! ( definer xt -- ) \ gforth
1.48      anton     699:     \G The word represented by @var{xt} changes its behaviour to the
                    700:     \G behaviour associated with @var{definer}.
1.4       anton     701:     over 1 and if
1.13      anton     702:        swap [ 1 invert ] literal and does-code!
1.4       anton     703:     else
                    704:        code-address!
                    705:     then ;
                    706: 
1.23      pazsan    707: :noname
1.31      anton     708:     ' dup >definer [ ' locals-wordlist ] literal >definer =
1.23      pazsan    709:     if
                    710:        >body !
                    711:     else
                    712:        -&32 throw
                    713:     endif ;
                    714: :noname
1.28      anton     715:     comp' drop dup >definer
1.21      anton     716:     case
1.30      anton     717:        [ ' locals-wordlist ] literal >definer \ value
1.21      anton     718:        OF >body POSTPONE Aliteral POSTPONE ! ENDOF
1.35      anton     719:        \ !! dependent on c: etc. being does>-defining words
                    720:        \ this works, because >definer uses >does-code in this case,
                    721:        \ which produces a relocatable address
1.54      anton     722:        [ comp' some-clocal drop ] literal >definer
1.21      anton     723:        OF POSTPONE laddr# >body @ lp-offset, POSTPONE c! ENDOF
1.54      anton     724:        [ comp' some-wlocal drop ] literal >definer
1.21      anton     725:        OF POSTPONE laddr# >body @ lp-offset, POSTPONE ! ENDOF
1.54      anton     726:        [ comp' some-dlocal drop ] literal >definer
1.21      anton     727:        OF POSTPONE laddr# >body @ lp-offset, POSTPONE 2! ENDOF
1.54      anton     728:        [ comp' some-flocal drop ] literal >definer
1.21      anton     729:        OF POSTPONE laddr# >body @ lp-offset, POSTPONE f! ENDOF
                    730:        -&32 throw
1.23      pazsan    731:     endcase ;
1.24      anton     732: interpret/compile: TO ( c|w|d|r "name" -- ) \ core-ext,local
1.1       anton     733: 
1.58      anton     734: : locals| ( ... "name ..." -- ) \ local-ext locals-bar
1.14      anton     735:     \ don't use 'locals|'! use '{'! A portable and free '{'
1.21      anton     736:     \ implementation is compat/anslocals.fs
1.8       anton     737:     BEGIN
1.49      anton     738:        name 2dup s" |" str= 0=
1.8       anton     739:     WHILE
                    740:        (local)
                    741:     REPEAT
1.14      anton     742:     drop 0 (local) ; immediate restrict

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