Annotation of /sml/branches/SMLNJ/src/compiler/FLINT/opt/loopify.sml

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1 :	monnier	191	(* copyright 1998 YALE FLINT PROJECT *)
2 :			(* monnier@cs.yale.edu *)
3 :
4 :			signature LOOPIFY =
5 :			sig
6 :			val loopify : FLINT.prog -> FLINT.prog
7 :			end
8 :
9 :
10 :			structure Loopify =
11 :			struct
12 :			local
13 :			structure F = FLINT
14 :			structure C = Collect
15 :			structure O = Option
16 :			structure M = IntmapF
17 :			structure LK = LtyKernel
18 :			in
19 :
20 :			fun bug msg = ErrorMsg.impossible ("Loopify: "^msg)
21 :			val cplv = LambdaVar.dupLvar
22 :
23 :			fun loopify (prog as (progkind,progname,progargs,progbody)) = let
24 :
25 :			(* m: int intmap renaming for function calls
26 :			* tf:(int,int) option the current function (if any) and its tail version
27 :			* le: you get the idea *)
28 :			fun lexp m tf le = let
29 :			val loop = lexp m tf
30 :			in case le
31 :			of F.RET _ => le
32 :			| F.LET(lvs,body,le) => F.LET(lvs, lexp m NONE body, loop le)
33 :			| F.FIX(fdecs,le) =>
34 :			let fun cfun (fk:F.fkind as {isrec=SOME(ltys,F.LK_UNKNOWN),cconv,...},
35 :			f,args,body) =
36 :			let val fi = C.get f
37 :			val icallnb = C.icallnb fi
38 :			(* cpsopt uses the following condition:
39 :			* escape = 0 andalso !unroll_call > 0
40 :			* andalso (!call - !unroll_call > 1
41 :			* orelse List.exists (fn t=>t) inv)
42 :			* `escape = 0': I don't quite see the need for it, though it
43 :			* probably won't change much since etasplit should have
44 :			* made "everything" known already.
45 :			* `!call - !unroll_call > 1 orelse List.exists (fn t=>t) inv)':
46 :			* loopification is only useful if there is more than one
47 :			* external call or if there are loop invariants.
48 :			* Note that we deal with invariants elsewhere, so it's
49 :			* not a good reason to loopify here. *)
50 :			(*** rationale behind the restrictions: ***
51 :			* `icallnb = 0': loopification is pointless and will be
52 :			* undone by fcontract.
53 :			* `C.callnb fi <= icallnb + 1': if there's only one external
54 :			* call, loopification will probably (?) not be of much use
55 :			* and the same benefit would be had by just moving f *)
56 :			in if icallnb = 0 (* orelse (C.callnb fi <= icallnb + 1) *)
57 :			(* not a good loop candidate *)
58 :			then (fk, f, args, loop body)
59 :			else
60 :			let val fl = cplv f
61 :			val ft = cplv f
62 :			val largs = map (fn(v,t) => (cplv v, t)) args
63 :			val args' = map (fn(v,t) => (cplv v, t)) args
64 :			val cconv' =
65 :			case cconv
66 :			of (F.CC_FCT | F.CC_FUN(LK.FF_FIXED)) => cconv
67 :			| F.CC_FUN(LK.FF_VAR(f1,f2)) =>
68 :			F.CC_FUN(LK.FF_VAR(true,f2))
69 :			val nm = M.add(m, f, fl)
70 :			val tailloop =
71 :			F.FIX([({isrec=SOME(ltys, F.LK_WHILE),
72 :			known=true, inline=F.IH_SAFE,
73 :			cconv=cconv'}, ft, args,
74 :			lexp nm (SOME(f,ft)) body)],
75 :			F.APP(F.VAR ft, map (F.VAR o #1) largs))
76 :			in (fk, f, args',
77 :			F.FIX([({isrec=SOME(ltys, F.LK_LOOP),
78 :			known=true, inline=F.IH_SAFE,
79 :			cconv=cconv'}, fl, largs,
80 :			tailloop)],
81 :			F.APP(F.VAR fl, map (F.VAR o #1) args')))
82 :			end
83 :			end
84 :			| cfun (fk,f,args,body) = (fk, f, args, lexp m NONE body)
85 :			in F.FIX(map cfun fdecs, loop le)
86 :			end
87 :			| F.APP(F.VAR f,vs) =>
88 :			(let val fl = M.lookup m f
89 :			in case tf
90 :			of SOME(f',ft) => if f' = f then F.APP(F.VAR ft, vs)
91 :			else F.APP(F.VAR fl, vs)
92 :			| NONE => F.APP(F.VAR fl, vs)
93 :			end handle M.IntmapF => le)
94 :			| F.TFN((f,args,body),le) => F.TFN((f, args, loop body), loop le)
95 :			| F.TAPP(f,tycs) => le
96 :			| F.SWITCH(v,ac,arms,def) =>
97 :			let fun carm (con,le) = (con, loop le)
98 :			in F.SWITCH(v, ac, map carm arms, O.map loop def)
99 :			end
100 :			| F.CON(dc,tycs,v,lv,le) => F.CON(dc, tycs, v, lv, loop le)
101 :			| F.RECORD(rk,vs,lv,le) => F.RECORD(rk, vs, lv, loop le)
102 :			| F.SELECT(v,i,lv,le) => F.SELECT(v, i, lv, loop le)
103 :			| F.RAISE(v,ltys) => le
104 :			| F.HANDLE(le,v) => F.HANDLE(loop le, v)
105 :			| F.BRANCH(po,vs,le1,le2) => F.BRANCH(po, vs, loop le1, loop le2)
106 :			| F.PRIMOP(po,vs,lv,le) => F.PRIMOP(po, vs, lv, loop le)
107 :
108 :			| F.APP _ => bug "unexpected APP"
109 :			end
110 :
111 :			in
112 :			C.collect prog; (* Collect is way overkill here *)
113 :			(progkind, progname, progargs, lexp M.empty NONE progbody)
114 :			end
115 :
116 :			end
117 :			end
118 :

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