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[diderot] Annotation of /branches/pure-cfg/src/compiler/high-il/high-opt.sml
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Annotation of /branches/pure-cfg/src/compiler/high-il/high-opt.sml

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1 : jhr 287 (* high-opt.sml
2 :     *
3 : jhr 435 * COPYRIGHT (c) 2010 The Diderot Project (http://diderot-language.cs.uchicago.edu)
4 : jhr 287 * All rights reserved.
5 :     *
6 :     * Optimization of the HighIL representation of Diderot terms. The main
7 :     * task of this phase is to statically resolve field definitions.
8 :     *)
9 :    
10 :     structure HighOptimizer : sig
11 :    
12 :     val optimize : HighIL.program -> HighIL.program
13 :    
14 :     end = struct
15 :    
16 :     structure IL = HighIL
17 : jhr 338 structure Op = HighOps
18 : jhr 287 structure V = IL.Var
19 : jhr 320 structure ST = Stats
20 : jhr 338 structure F = FieldDef
21 : jhr 287
22 : jhr 320 (********** Counters for statistics **********)
23 : jhr 649 val cntProbeAdd = ST.newCounter "high-opt:probe-add"
24 :     val cntProbeScale = ST.newCounter "high-opt:probe-scale"
25 :     val cntProbeNeg = ST.newCounter "high-opt:probe-neg"
26 :     val cntDiffField = ST.newCounter "high-opt:diff-field"
27 :     val cntDiffAdd = ST.newCounter "high-opt:diff-add"
28 :     val cntDiffScale = ST.newCounter "high-opt:diff-scale"
29 :     val cntDiffNeg = ST.newCounter "high-opt:diff-neg"
30 : jhr 320 val cntUnused = ST.newCounter "high-opt:unused"
31 : jhr 649 val firstCounter = cntProbeAdd
32 : jhr 338 val lastCounter = cntUnused
33 : jhr 320
34 :     fun useCount (IL.V{useCnt, ...}) = !useCnt
35 :    
36 : jhr 649 (* adjust a variable's use count *)
37 :     fun incUse (IL.V{useCnt, ...}) = (useCnt := !useCnt + 1)
38 : jhr 287 fun decUse (IL.V{useCnt, ...}) = (useCnt := !useCnt - 1)
39 :    
40 : jhr 372 fun getRHS x = (case V.binding x
41 :     of IL.VB_RHS(IL.OP arg) => SOME arg
42 :     | _ => NONE
43 :     (* end case *))
44 : jhr 287
45 :     (* optimize the rhs of an assignment, returning NONE if there is no change *)
46 : jhr 649 fun doRHS (lhs, IL.OP rhs) = (case rhs
47 :     of (Op.Probe(domTy, rngTy), [f, pos]) => (case getRHS f
48 :     of SOME(Op.Field _, _) => NONE (* direct probe does not need rewrite *)
49 :     | SOME(Op.AddField, [f, g]) => raise Fail "Probe(f+g)"
50 :     | SOME(Op.ScaleField, [s, f]) => raise Fail "Probe(s*f)"
51 :     | SOME(Op.NegField, [f]) => raise Fail "Probe(-f)"
52 :     | _ => raise Fail(concat[
53 :     "bogus field binding ", V.toString f, " = ", IL.vbToString(V.binding f)
54 :     ])
55 :     (* end case *))
56 :     | (Op.DiffField, [f]) => (case (getRHS f)
57 :     of SOME(Op.Field dim, [v, h]) => (case getRHS h
58 :     of SOME(Op.Kernel(kernel, k), []) => let
59 :     val h' = IL.Var.copy h
60 :     in
61 :     ST.tick cntDiffField;
62 :     decUse f;
63 :     incUse h'; incUse v;
64 :     SOME[
65 :     (h', IL.OP(Op.Kernel(kernel, k+1), [])),
66 :     (lhs, IL.OP(Op.Field dim, [v, h']))
67 :     ]
68 :     end
69 :     | _ => raise Fail(concat[
70 :     "bogus kernel binding ", V.toString h, " = ", IL.vbToString(V.binding h)
71 :     ])
72 : jhr 516 (* end case *))
73 : jhr 649 | SOME(Op.AddField, [f, g]) => raise Fail "Diff(f+g)"
74 :     | SOME(Op.ScaleField, [s, f]) => raise Fail "Diff(s*f)"
75 :     | SOME(Op.NegField, [f]) => raise Fail "Diff(-f)"
76 :     | _ => NONE
77 : jhr 287 (* end case *))
78 :     | _ => NONE
79 :     (* end case *))
80 : jhr 649 | doRHS _ = NONE
81 : jhr 287
82 : jhr 320 (* simplify expressions *)
83 : jhr 649 fun simplify (nd as IL.ND{kind=IL.ASSIGN{stm=(y, rhs), ...}, ...}) =
84 :     if (useCount y = 0)
85 :     then () (* skip unused assignments *)
86 :     else (case doRHS(y, rhs)
87 :     of SOME[] => IL.CFG.deleteNode nd
88 :     | SOME assigns => (
89 :     List.app (fn (y, rhs) => V.setBinding(y, IL.VB_RHS rhs)) assigns;
90 :     IL.CFG.splice (nd, IL.CFG.mkBlock assigns))
91 :     | NONE => ()
92 :     (* end case *))
93 : jhr 508 | simplify _ = ()
94 : jhr 320
95 :     (* reduce the code by removing variables with use counts of 0 *)
96 : jhr 508 local
97 :     fun checkVar (y, _) = (useCount y > 0) orelse (ST.tick cntUnused; false)
98 :     in
99 :     fun reduce (nd as IL.ND{kind, ...}) = (case kind
100 :     of IL.JOIN{phis, ...} => let
101 :     fun doVar (y, xs) = if (useCount y = 0)
102 :     then (
103 :     ST.tick cntUnused;
104 :     List.app decUse xs;
105 :     false)
106 :     else true
107 :     in
108 :     phis := List.filter doVar (!phis)
109 :     end
110 :     | IL.ASSIGN{stm=(y, rhs), ...} =>
111 :     if (useCount y = 0)
112 :     then (
113 :     ST.tick cntUnused;
114 :     case rhs
115 :     of IL.VAR x => decUse x
116 :     | IL.LIT _ => ()
117 :     | IL.OP(_, xs) => List.app decUse xs
118 :     | IL.CONS xs => List.app decUse xs
119 :     (* end case *);
120 :     IL.CFG.deleteNode nd)
121 :     else ()
122 :     | _ => ()
123 :     (* end case *))
124 :     end (* local *)
125 : jhr 320
126 : jhr 508 fun loopToFixPt f cfg = let
127 :     fun loop n = let
128 :     val () = IL.CFG.apply f cfg
129 : jhr 338 val n' = Stats.sum{from=firstCounter, to=lastCounter}
130 : jhr 320 in
131 : jhr 508 if (n = n') then () else loop n'
132 : jhr 320 end
133 :     in
134 : jhr 508 loop (Stats.sum{from=firstCounter, to=lastCounter})
135 : jhr 320 end
136 :    
137 : jhr 613 fun optimize (prog as IL.Program{globals, globalInit, initially, strands}) = let
138 : jhr 508 fun doCFG cfg = (
139 :     loopToFixPt simplify cfg;
140 :     loopToFixPt reduce cfg)
141 : jhr 491 val globInitNodes = doCFG globalInit
142 : jhr 508 fun doMethod (IL.Method{body, ...}) = doCFG body
143 :     fun doStrand (IL.Strand{stateInit, methods, ...}) = (
144 :     doCFG stateInit;
145 :     List.app doMethod methods)
146 : jhr 499 val _ = List.app doStrand strands
147 : jhr 320 in
148 :     IL.Program{
149 :     globals = globals,
150 :     globalInit = globalInit,
151 : jhr 613 initially = initially, (* FIXME: we should optimize this code *)
152 : jhr 499 strands = strands
153 : jhr 320 }
154 :     end
155 :    
156 : jhr 287 end

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