HCoop / hcoop / debian / mlton.git / blame
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|---|---|---|
| 7f918cf1 CE |
1 | (* Copyright (C) 1999-2005, 2008 Henry Cejtin, Matthew Fluet, Suresh |
| 2 | * Jagannathan, and Stephen Weeks. | |
| 3 | * Copyright (C) 1997-2000 NEC Research Institute. | |
| 4 | * | |
| 5 | * MLton is released under a BSD-style license. | |
| 6 | * See the file MLton-LICENSE for details. | |
| 7 | *) | |
| 8 | ||
| 9 | (* | |
| 10 | * Remove loop invariant args to local loops. | |
| 11 | * fun loop (x, y) = ... loop (x, z) ... | |
| 12 | * | |
| 13 | * becomes | |
| 14 | * | |
| 15 | * fun loop (x, y') = | |
| 16 | * let fun loop' (y) = ... loop' (z) ... | |
| 17 | * in loop' (y') | |
| 18 | * end | |
| 19 | *) | |
| 20 | ||
| 21 | functor LoopInvariant (S: SSA_TRANSFORM_STRUCTS): SSA_TRANSFORM = | |
| 22 | struct | |
| 23 | ||
| 24 | open S | |
| 25 | open Exp Transfer | |
| 26 | ||
| 27 | fun transform (Program.T {globals, datatypes, functions, main}) = | |
| 28 | let | |
| 29 | val shrink = shrinkFunction {globals = globals} | |
| 30 | ||
| 31 | fun simplifyFunction f = | |
| 32 | let | |
| 33 | val {args, blocks, mayInline, name, raises, returns, start} = | |
| 34 | Function.dest f | |
| 35 | val {get = labelInfo: Label.t -> {callsSelf: bool ref, | |
| 36 | visited: bool ref, | |
| 37 | invariant: (Var.t * bool ref) vector, | |
| 38 | newLabel: Label.t option ref}, | |
| 39 | set = setLabelInfo, ...} = | |
| 40 | Property.getSetOnce | |
| 41 | (Label.plist, | |
| 42 | Property.initRaise ("LoopInvariant.labelInfo", Label.layout)) | |
| 43 | ||
| 44 | val _ = | |
| 45 | Vector.foreach | |
| 46 | (blocks, fn Block.T {label, args, ...} => | |
| 47 | setLabelInfo (label, | |
| 48 | {callsSelf = ref false, | |
| 49 | visited = ref false, | |
| 50 | invariant = Vector.map (args, fn (x, _) => | |
| 51 | (x, ref true)), | |
| 52 | newLabel = ref NONE})) | |
| 53 | ||
| 54 | fun visit (Block.T {label, transfer, ...}): unit -> unit = | |
| 55 | let | |
| 56 | val {visited, ...} = labelInfo label | |
| 57 | val _ = visited := true | |
| 58 | val _ = | |
| 59 | case transfer of | |
| 60 | Goto {dst, args} => | |
| 61 | let | |
| 62 | val {callsSelf, visited, invariant, ...} = labelInfo dst | |
| 63 | in | |
| 64 | if !visited | |
| 65 | then (callsSelf := true | |
| 66 | ; Vector.foreach2 | |
| 67 | (args, invariant, fn (x, (y, b)) => | |
| 68 | if !b andalso not (Var.equals (x, y)) | |
| 69 | then b := false | |
| 70 | else ())) | |
| 71 | else () | |
| 72 | end | |
| 73 | | _ => () | |
| 74 | in | |
| 75 | fn () => visited := false | |
| 76 | end | |
| 77 | val _ = Function.dfs (f, visit) | |
| 78 | fun remove (xs: 'a vector, invariant: ('b * bool ref) vector) | |
| 79 | : 'a vector = | |
| 80 | Vector.keepAllMap2 (xs, invariant, fn (x, (_, b)) => | |
| 81 | if !b then NONE else SOME x) | |
| 82 | ||
| 83 | val newBlocks = ref [] | |
| 84 | fun visit (Block.T {label, args, statements, transfer}) | |
| 85 | : unit -> unit = | |
| 86 | let | |
| 87 | val {callsSelf, invariant, newLabel, ...} = labelInfo label | |
| 88 | val _ = | |
| 89 | if !callsSelf | |
| 90 | andalso Vector.exists (invariant, ! o #2) | |
| 91 | then newLabel := SOME (Label.new label) | |
| 92 | else () | |
| 93 | val transfer = | |
| 94 | case transfer of | |
| 95 | Goto {dst, args} => | |
| 96 | let | |
| 97 | val {invariant, newLabel, ...} = labelInfo dst | |
| 98 | in | |
| 99 | case !newLabel of | |
| 100 | NONE => transfer | |
| 101 | | SOME dst' => | |
| 102 | Goto {dst = dst', | |
| 103 | args = remove (args, invariant)} | |
| 104 | end | |
| 105 | | _ => transfer | |
| 106 | val (args, statements, transfer) = | |
| 107 | case !newLabel of | |
| 108 | NONE => (args, statements, transfer) | |
| 109 | | SOME label' => | |
| 110 | let | |
| 111 | val _ = | |
| 112 | Control.diagnostic | |
| 113 | (fn () => | |
| 114 | let open Layout | |
| 115 | in seq [Label.layout label, | |
| 116 | str " -> ", | |
| 117 | Label.layout label'] | |
| 118 | end) | |
| 119 | val (outerFormals, | |
| 120 | innerFormals, | |
| 121 | innerActuals) = | |
| 122 | Vector.foldr2 | |
| 123 | (args, invariant, ([], [], []), | |
| 124 | fn ((x, t), (_, b), (ofs, ifs, ias)) => | |
| 125 | if !b | |
| 126 | then ((x, t) :: ofs, ifs, ias) | |
| 127 | else let val x' = Var.new x | |
| 128 | in ((x', t) :: ofs, | |
| 129 | (x, t) :: ifs, | |
| 130 | x' :: ias) | |
| 131 | end) | |
| 132 | in | |
| 133 | List.push | |
| 134 | (newBlocks, | |
| 135 | Block.T {label = label', | |
| 136 | args = Vector.fromList innerFormals, | |
| 137 | statements = statements, | |
| 138 | transfer = transfer}) | |
| 139 | ; (Vector.fromList outerFormals, | |
| 140 | Vector.new0 (), | |
| 141 | Goto {dst = label', | |
| 142 | args = Vector.fromList innerActuals}) | |
| 143 | end | |
| 144 | val _ = List.push | |
| 145 | (newBlocks, | |
| 146 | Block.T {label = label, | |
| 147 | args = args, | |
| 148 | statements = statements, | |
| 149 | transfer = transfer}) | |
| 150 | in | |
| 151 | fn () => newLabel := NONE | |
| 152 | end | |
| 153 | val _ = Function.dfs (f, visit) | |
| 154 | val blocks = Vector.fromList (!newBlocks) | |
| 155 | in | |
| 156 | shrink (Function.new {args = args, | |
| 157 | blocks = blocks, | |
| 158 | mayInline = mayInline, | |
| 159 | name = name, | |
| 160 | raises = raises, | |
| 161 | returns = returns, | |
| 162 | start = start}) | |
| 163 | end | |
| 164 | val program = | |
| 165 | Program.T {datatypes = datatypes, | |
| 166 | globals = globals, | |
| 167 | functions = List.revMap (functions, simplifyFunction), | |
| 168 | main = main} | |
| 169 | val _ = Program.clearTop program | |
| 170 | in | |
| 171 | program | |
| 172 | end | |
| 173 | end |