--- gforth/glocals.fs 1996/08/26 10:07:18 1.25 +++ gforth/glocals.fs 1997/01/01 16:26:02 1.29 @@ -104,6 +104,21 @@ require float.fs ( otherwise ) dup postpone f@local# , endcase ; +\ locals stuff needed for control structures + +: compile-lp+! ( n -- ) \ gforth compile-l-p-plus-store + dup negate locals-size +! + 0 over = if + else -1 cells over = if postpone lp- + else 1 floats over = if postpone lp+ + else 2 floats over = if postpone lp+2 + else postpone lp+!# dup , + then then then then drop ; + +: adjust-locals-size ( n -- ) \ gforth + \ sets locals-size to n and generates an appropriate lp+! + locals-size @ swap - compile-lp+! ; + \ the locals stack grows downwards (see primitives) \ of the local variables of a group (in braces) the leftmost is on top, \ i.e. by going onto the locals stack the order is reversed. @@ -142,6 +157,55 @@ variable locals-dp \ so here's the speci swap ! postpone >l ; +\ locals list operations + +: common-list ( list1 list2 -- list3 ) \ gforth-internal +\ list1 and list2 are lists, where the heads are at higher addresses than +\ the tail. list3 is the largest sublist of both lists. + begin + 2dup u<> + while + 2dup u> + if + swap + then + @ + repeat + drop ; + +: sub-list? ( list1 list2 -- f ) \ gforth-internal +\ true iff list1 is a sublist of list2 + begin + 2dup u< + while + @ + repeat + = ; + +: list-size ( list -- u ) \ gforth-internal +\ size of the locals frame represented by list + 0 ( list n ) + begin + over 0<> + while + over + ((name>)) >body @ max + swap @ swap ( get next ) + repeat + faligned nip ; + +: set-locals-size-list ( list -- ) + dup locals-list ! + list-size locals-size ! ; + +: check-begin ( list -- ) +\ warn if list is not a sublist of locals-list + locals-list @ sub-list? 0= if + \ !! print current position + ." compiler was overly optimistic about locals at a BEGIN" cr + \ !! print assumption and reality + then ; + : compile-pushlocal-f ( a-addr -- ) ( run-time: f -- ) locals-size @ alignlp-f float+ dup locals-size ! swap ! @@ -255,9 +319,14 @@ previous true abort" this should not happen: new-locals-reveal" ; create new-locals-map ( -- wordlist-map ) -' new-locals-find A, ' new-locals-reveal A, +' new-locals-find A, +' new-locals-reveal A, +' drop A, \ rehash method +slowvoc @ +slowvoc on vocabulary new-locals +slowvoc ! new-locals-map ' new-locals >body cell+ A! \ !! use special access words variable old-dpp @@ -381,20 +450,7 @@ forth definitions \ If this assumption is too optimistic, the compiler will warn the user. -\ Implementation: migrated to kernal.fs - -\ THEN (another control flow from before joins the current one): -\ The new locals-list is the intersection of the current locals-list and -\ the orig-local-list. The new locals-size is the (alignment-adjusted) -\ size of the new locals-list. The following code is generated: -\ lp+!# (current-locals-size - orig-locals-size) -\ : -\ lp+!# (orig-locals-size - new-locals-size) - -\ Of course "lp+!# 0" is not generated. Still this is admittedly a bit -\ inefficient, e.g. if there is a locals declaration between IF and -\ ELSE. However, if ELSE generates an appropriate "lp+!#" before the -\ branch, there will be none after the target . +\ Implementation: \ explicit scoping @@ -428,9 +484,84 @@ forth definitions lastcfa ! last ! DEFERS ;-hook ; +\ THEN (another control flow from before joins the current one): +\ The new locals-list is the intersection of the current locals-list and +\ the orig-local-list. The new locals-size is the (alignment-adjusted) +\ size of the new locals-list. The following code is generated: +\ lp+!# (current-locals-size - orig-locals-size) +\ : +\ lp+!# (orig-locals-size - new-locals-size) + +\ Of course "lp+!# 0" is not generated. Still this is admittedly a bit +\ inefficient, e.g. if there is a locals declaration between IF and +\ ELSE. However, if ELSE generates an appropriate "lp+!#" before the +\ branch, there will be none after the target . + +: (then-like) ( orig -- addr ) + swap -rot dead-orig = + if + drop + else + dead-code @ + if + set-locals-size-list dead-code off + else \ both live + dup list-size adjust-locals-size + locals-list @ common-list dup list-size adjust-locals-size + locals-list ! + then + then ; + +: (begin-like) ( -- ) + dead-code @ if + \ set up an assumption of the locals visible here. if the + \ users want something to be visible, they have to declare + \ that using ASSUME-LIVE + backedge-locals @ set-locals-size-list + then + dead-code off ; + +\ AGAIN (the current control flow joins another, earlier one): +\ If the dest-locals-list is not a subset of the current locals-list, +\ issue a warning (see below). The following code is generated: +\ lp+!# (current-local-size - dest-locals-size) +\ branch + +: (again-like) ( dest -- addr ) + over list-size adjust-locals-size + swap check-begin POSTPONE unreachable ; + +\ UNTIL (the current control flow may join an earlier one or continue): +\ Similar to AGAIN. The new locals-list and locals-size are the current +\ ones. The following code is generated: +\ ?branch-lp+!# (current-local-size - dest-locals-size) + +: (until-like) ( list addr xt1 xt2 -- ) + \ list and addr are a fragment of a cs-item + \ xt1 is the conditional branch without lp adjustment, xt2 is with + >r >r + locals-size @ 2 pick list-size - dup if ( list dest-addr adjustment ) + r> drop r> compile, + swap compile, drop + then ( list ) + check-begin ; + +: (exit-like) ( -- ) + 0 adjust-locals-size ; + ' locals-:-hook IS :-hook ' locals-;-hook IS ;-hook +' (then-like) IS then-like +' (begin-like) IS begin-like +' (again-like) IS again-like +' (until-like) IS until-like +' (exit-like) IS exit-like + \ The words in the locals dictionary space are not deleted until the end \ of the current word. This is a bit too conservative, but very simple. @@ -441,10 +572,6 @@ forth definitions \ things above are not control flow joins. Everything should be taken \ over from the live flow. No lp+!# is generated. -\ !! The lp gymnastics for UNTIL are also a real problem: locals cannot be -\ used in signal handlers (or anything else that may be called while -\ locals live beyond the lp) without changing the locals stack. - \ About warning against uses of dead locals. There are several options: \ 1) Do not complain (After all, this is Forth;-) @@ -514,7 +641,7 @@ forth definitions endif ; :noname 0 0 0. 0.0e0 { c: clocal w: wlocal d: dlocal f: flocal } - ' dup >definer + comp' drop dup >definer case [ ' locals-wordlist >definer ] literal \ value OF >body POSTPONE Aliteral POSTPONE ! ENDOF