2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
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6 ***************************
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8 ***************************
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10 1. We attach binding levels to Core bindings, in preparation for floating
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11 outwards (@FloatOut@).
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13 2. We also let-ify many expressions (notably case scrutinees), so they
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14 will have a fighting chance of being floated sensible.
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16 3. We clone the binders of any floatable let-binding, so that when it is
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17 floated out it will be unique. (This used to be done by the simplifier
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18 but the latter now only ensures that there's no shadowing; indeed, even
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19 that may not be true.)
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21 NOTE: this can't be done using the uniqAway idea, because the variable
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22 must be unique in the whole program, not just its current scope,
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23 because two variables in different scopes may float out to the
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24 same top level place
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26 NOTE: Very tiresomely, we must apply this substitution to
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27 the rules stored inside a variable too.
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29 We do *not* clone top-level bindings, because some of them must not change,
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30 but we *do* clone bindings that are heading for the top level
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32 4. In the expression
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33 case x of wild { p -> ...wild... }
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34 we substitute x for wild in the RHS of the case alternatives:
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35 case x of wild { p -> ...x... }
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36 This means that a sub-expression involving x is not "trapped" inside the RHS.
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37 And it's not inconvenient because we already have a substitution.
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39 Note that this is EXACTLY BACKWARDS from the what the simplifier does.
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40 The simplifier tries to get rid of occurrences of x, in favour of wild,
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41 in the hope that there will only be one remaining occurrence of x, namely
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42 the scrutinee of the case, and we can inline it.
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48 Level(..), tOP_LEVEL,
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50 incMinorLvl, ltMajLvl, ltLvl, isTopLvl
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53 #include "HsVersions.h"
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57 import CoreUtils ( exprType, exprIsTrivial, exprIsBottom, mkPiType )
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58 import CoreFVs -- all of it
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60 import Id ( Id, idType, mkSysLocal, isOneShotLambda, zapDemandIdInfo,
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61 idSpecialisation, idWorkerInfo, setIdInfo
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63 import IdInfo ( workerExists, vanillaIdInfo, )
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67 import Name ( getOccName )
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68 import OccName ( occNameUserString )
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69 import Type ( isUnLiftedType, Type )
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70 import BasicTypes ( TopLevelFlag(..) )
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72 import Util ( sortLt, isSingleton, count )
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76 %************************************************************************
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78 \subsection{Level numbers}
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80 %************************************************************************
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83 data Level = Level Int -- Level number of enclosing lambdas
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84 Int -- Number of big-lambda and/or case expressions between
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85 -- here and the nearest enclosing lambda
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88 The {\em level number} on a (type-)lambda-bound variable is the
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89 nesting depth of the (type-)lambda which binds it. The outermost lambda
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90 has level 1, so (Level 0 0) means that the variable is bound outside any lambda.
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92 On an expression, it's the maximum level number of its free
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93 (type-)variables. On a let(rec)-bound variable, it's the level of its
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94 RHS. On a case-bound variable, it's the number of enclosing lambdas.
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96 Top-level variables: level~0. Those bound on the RHS of a top-level
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97 definition but ``before'' a lambda; e.g., the \tr{x} in (levels shown
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98 as ``subscripts'')...
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100 a_0 = let b_? = ... in
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101 x_1 = ... b ... in ...
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104 The main function @lvlExpr@ carries a ``context level'' (@ctxt_lvl@).
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105 That's meant to be the level number of the enclosing binder in the
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106 final (floated) program. If the level number of a sub-expression is
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107 less than that of the context, then it might be worth let-binding the
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108 sub-expression so that it will indeed float. This context level starts
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112 type LevelledExpr = TaggedExpr Level
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113 type LevelledBind = TaggedBind Level
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115 tOP_LEVEL = Level 0 0
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117 incMajorLvl :: Level -> Level
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118 incMajorLvl (Level major minor) = Level (major+1) 0
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120 incMinorLvl :: Level -> Level
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121 incMinorLvl (Level major minor) = Level major (minor+1)
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123 maxLvl :: Level -> Level -> Level
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124 maxLvl l1@(Level maj1 min1) l2@(Level maj2 min2)
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125 | (maj1 > maj2) || (maj1 == maj2 && min1 > min2) = l1
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128 ltLvl :: Level -> Level -> Bool
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129 ltLvl (Level maj1 min1) (Level maj2 min2)
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130 = (maj1 < maj2) || (maj1 == maj2 && min1 < min2)
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132 ltMajLvl :: Level -> Level -> Bool
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133 -- Tells if one level belongs to a difft *lambda* level to another
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134 ltMajLvl (Level maj1 _) (Level maj2 _) = maj1 < maj2
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136 isTopLvl :: Level -> Bool
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137 isTopLvl (Level 0 0) = True
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138 isTopLvl other = False
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140 instance Outputable Level where
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141 ppr (Level maj min) = hcat [ char '<', int maj, char ',', int min, char '>' ]
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143 instance Eq Level where
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144 (Level maj1 min1) == (Level maj2 min2) = maj1==maj2 && min1==min2
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147 %************************************************************************
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149 \subsection{Main level-setting code}
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151 %************************************************************************
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154 setLevels :: Bool -- True <=> float lambdas to top level
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159 setLevels float_lams binds us
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160 = initLvl us (do_them binds)
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162 -- "do_them"'s main business is to thread the monad along
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163 -- It gives each top binding the same empty envt, because
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164 -- things unbound in the envt have level number zero implicitly
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165 do_them :: [CoreBind] -> LvlM [LevelledBind]
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167 do_them [] = returnLvl []
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169 = lvlTopBind init_env b `thenLvl` \ (lvld_bind, _) ->
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170 do_them bs `thenLvl` \ lvld_binds ->
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171 returnLvl (lvld_bind : lvld_binds)
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173 init_env = initialEnv float_lams
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175 lvlTopBind env (NonRec binder rhs)
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176 = lvlBind TopLevel tOP_LEVEL env (AnnNonRec binder (freeVars rhs))
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177 -- Rhs can have no free vars!
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179 lvlTopBind env (Rec pairs)
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180 = lvlBind TopLevel tOP_LEVEL env (AnnRec [(b,freeVars rhs) | (b,rhs) <- pairs])
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183 %************************************************************************
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185 \subsection{Setting expression levels}
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187 %************************************************************************
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190 lvlExpr :: Level -- ctxt_lvl: Level of enclosing expression
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191 -> LevelEnv -- Level of in-scope names/tyvars
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192 -> CoreExprWithFVs -- input expression
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193 -> LvlM LevelledExpr -- Result expression
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196 The @ctxt_lvl@ is, roughly, the level of the innermost enclosing
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197 binder. Here's an example
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199 v = \x -> ...\y -> let r = case (..x..) of
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203 When looking at the rhs of @r@, @ctxt_lvl@ will be 1 because that's
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204 the level of @r@, even though it's inside a level-2 @\y@. It's
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205 important that @ctxt_lvl@ is 1 and not 2 in @r@'s rhs, because we
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206 don't want @lvlExpr@ to turn the scrutinee of the @case@ into an MFE
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207 --- because it isn't a *maximal* free expression.
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209 If there were another lambda in @r@'s rhs, it would get level-2 as well.
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212 lvlExpr _ _ (_, AnnType ty) = returnLvl (Type ty)
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213 lvlExpr _ env (_, AnnVar v) = returnLvl (lookupVar env v)
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214 lvlExpr _ env (_, AnnLit lit) = returnLvl (Lit lit)
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216 lvlExpr ctxt_lvl env (_, AnnApp fun arg)
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217 = lvl_fun fun `thenLvl` \ fun' ->
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218 lvlMFE False ctxt_lvl env arg `thenLvl` \ arg' ->
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219 returnLvl (App fun' arg')
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221 lvl_fun (_, AnnCase _ _ _) = lvlMFE True ctxt_lvl env fun
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222 lvl_fun other = lvlExpr ctxt_lvl env fun
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223 -- We don't do MFE on partial applications generally,
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224 -- but we do if the function is big and hairy, like a case
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226 lvlExpr ctxt_lvl env (_, AnnNote InlineMe expr)
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227 -- Don't float anything out of an InlineMe; hence the tOP_LEVEL
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228 = lvlExpr tOP_LEVEL env expr `thenLvl` \ expr' ->
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229 returnLvl (Note InlineMe expr')
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231 lvlExpr ctxt_lvl env (_, AnnNote note expr)
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232 = lvlExpr ctxt_lvl env expr `thenLvl` \ expr' ->
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233 returnLvl (Note note expr')
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235 -- We don't split adjacent lambdas. That is, given
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237 -- we don't float to give
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238 -- \x -> let v = x+y in \y -> (v,y)
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239 -- Why not? Because partial applications are fairly rare, and splitting
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240 -- lambdas makes them more expensive.
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242 lvlExpr ctxt_lvl env expr@(_, AnnLam bndr rhs)
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243 = lvlMFE True new_lvl new_env body `thenLvl` \ new_body ->
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244 returnLvl (glue_binders new_bndrs expr new_body)
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246 (bndrs, body) = collect_binders expr
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247 (new_lvl, new_bndrs) = lvlLamBndrs ctxt_lvl bndrs
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248 new_env = extendLvlEnv env new_bndrs
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250 lvlExpr ctxt_lvl env (_, AnnLet bind body)
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251 = lvlBind NotTopLevel ctxt_lvl env bind `thenLvl` \ (bind', new_env) ->
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252 lvlExpr ctxt_lvl new_env body `thenLvl` \ body' ->
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253 returnLvl (Let bind' body')
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255 lvlExpr ctxt_lvl env (_, AnnCase expr case_bndr alts)
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256 = lvlMFE True ctxt_lvl env expr `thenLvl` \ expr' ->
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258 alts_env = extendCaseBndrLvlEnv env expr' case_bndr incd_lvl
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260 mapLvl (lvl_alt alts_env) alts `thenLvl` \ alts' ->
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261 returnLvl (Case expr' (case_bndr, incd_lvl) alts')
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263 incd_lvl = incMinorLvl ctxt_lvl
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265 lvl_alt alts_env (con, bs, rhs)
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266 = lvlMFE True incd_lvl new_env rhs `thenLvl` \ rhs' ->
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267 returnLvl (con, bs', rhs')
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269 bs' = [ (b, incd_lvl) | b <- bs ]
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270 new_env = extendLvlEnv alts_env bs'
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272 collect_binders lam
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275 go rev_bndrs (_, AnnLam b e) = go (b:rev_bndrs) e
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276 go rev_bndrs (_, AnnNote n e) = go rev_bndrs e
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277 go rev_bndrs rhs = (reverse rev_bndrs, rhs)
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278 -- Ignore notes, because we don't want to split
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279 -- a lambda like this (\x -> coerce t (\s -> ...))
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280 -- This happens quite a bit in state-transformer programs
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282 -- glue_binders puts the lambda back together
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283 glue_binders (b:bs) (_, AnnLam _ e) body = Lam b (glue_binders bs e body)
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284 glue_binders bs (_, AnnNote n e) body = Note n (glue_binders bs e body)
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285 glue_binders [] e body = body
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288 @lvlMFE@ is just like @lvlExpr@, except that it might let-bind
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289 the expression, so that it can itself be floated.
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292 lvlMFE :: Bool -- True <=> strict context [body of case or let]
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293 -> Level -- Level of innermost enclosing lambda/tylam
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294 -> LevelEnv -- Level of in-scope names/tyvars
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295 -> CoreExprWithFVs -- input expression
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296 -> LvlM LevelledExpr -- Result expression
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298 lvlMFE strict_ctxt ctxt_lvl env (_, AnnType ty)
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299 = returnLvl (Type ty)
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301 lvlMFE strict_ctxt ctxt_lvl env ann_expr@(fvs, _)
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302 | isUnLiftedType ty -- Can't let-bind it
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303 || not good_destination
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304 || exprIsTrivial expr -- Is trivial
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305 || (strict_ctxt && exprIsBottom expr) -- Strict context and is bottom
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306 -- e.g. \x -> error "foo"
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307 -- No gain from floating this
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308 = -- Don't float it out
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309 lvlExpr ctxt_lvl env ann_expr
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311 | otherwise -- Float it out!
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312 = lvlFloatRhs abs_vars dest_lvl env ann_expr `thenLvl` \ expr' ->
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313 newLvlVar "lvl" abs_vars ty `thenLvl` \ var ->
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314 returnLvl (Let (NonRec (var,dest_lvl) expr')
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315 (mkVarApps (Var var) abs_vars))
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317 expr = deAnnotate ann_expr
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319 dest_lvl = destLevel env fvs (isFunction ann_expr)
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320 abs_vars = abstractVars dest_lvl env fvs
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322 good_destination = dest_lvl `ltMajLvl` ctxt_lvl -- Escapes a value lambda
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323 || (isTopLvl dest_lvl && not strict_ctxt) -- Goes to the top
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324 -- A decision to float entails let-binding this thing, and we only do
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325 -- that if we'll escape a value lambda, or will go to the top level.
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327 -- concat = /\ a -> foldr ..a.. (++) []
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328 -- was getting turned into
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329 -- concat = /\ a -> lvl a
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330 -- lvl = /\ a -> foldr ..a.. (++) []
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331 -- which is pretty stupid. Hence the strict_ctxt test
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335 %************************************************************************
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337 \subsection{Bindings}
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339 %************************************************************************
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341 The binding stuff works for top level too.
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344 lvlBind :: TopLevelFlag -- Used solely to decide whether to clone
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345 -> Level -- Context level; might be Top even for bindings nested in the RHS
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346 -- of a top level binding
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349 -> LvlM (LevelledBind, LevelEnv)
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351 lvlBind top_lvl ctxt_lvl env (AnnNonRec bndr rhs@(rhs_fvs,_))
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353 = -- No type abstraction; clone existing binder
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354 lvlExpr dest_lvl env rhs `thenLvl` \ rhs' ->
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355 cloneVar top_lvl env bndr ctxt_lvl dest_lvl `thenLvl` \ (env', bndr') ->
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356 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
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359 = -- Yes, type abstraction; create a new binder, extend substitution, etc
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360 lvlFloatRhs abs_vars dest_lvl env rhs `thenLvl` \ rhs' ->
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361 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (env', [bndr']) ->
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362 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
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365 bind_fvs = rhs_fvs `unionVarSet` idFreeVars bndr
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366 abs_vars = abstractVars dest_lvl env bind_fvs
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368 dest_lvl | isUnLiftedType (idType bndr) = destLevel env bind_fvs False `maxLvl` Level 1 0
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369 | otherwise = destLevel env bind_fvs (isFunction rhs)
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370 -- Hack alert! We do have some unlifted bindings, for cheap primops, and
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371 -- it is ok to float them out; but not to the top level. If they would otherwise
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372 -- go to the top level, we pin them inside the topmost lambda
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377 lvlBind top_lvl ctxt_lvl env (AnnRec pairs)
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379 = cloneRecVars top_lvl env bndrs ctxt_lvl dest_lvl `thenLvl` \ (new_env, new_bndrs) ->
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380 mapLvl (lvlExpr ctxt_lvl new_env) rhss `thenLvl` \ new_rhss ->
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381 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
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383 | isSingleton pairs && count isId abs_vars > 1
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384 = -- Special case for self recursion where there are
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385 -- several variables carried around: build a local loop:
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386 -- poly_f = \abs_vars. \lam_vars . letrec f = \lam_vars. rhs in f lam_vars
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387 -- This just makes the closures a bit smaller. If we don't do
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388 -- this, allocation rises significantly on some programs
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390 -- We could elaborate it for the case where there are several
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391 -- mutually functions, but it's quite a bit more complicated
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393 -- This all seems a bit ad hoc -- sigh
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395 (bndr,rhs) = head pairs
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396 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
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397 rhs_env = extendLvlEnv env abs_vars_w_lvls
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399 cloneVar NotTopLevel rhs_env bndr rhs_lvl rhs_lvl `thenLvl` \ (rhs_env', new_bndr) ->
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401 (lam_bndrs, rhs_body) = collect_binders rhs
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402 (body_lvl, new_lam_bndrs) = lvlLamBndrs rhs_lvl lam_bndrs
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403 body_env = extendLvlEnv rhs_env' new_lam_bndrs
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405 lvlExpr body_lvl body_env rhs_body `thenLvl` \ new_rhs_body ->
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406 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (poly_env, [poly_bndr]) ->
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407 returnLvl (Rec [((poly_bndr,dest_lvl), mkLams abs_vars_w_lvls $
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408 glue_binders new_lam_bndrs rhs $
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409 Let (Rec [((new_bndr,rhs_lvl), mkLams new_lam_bndrs new_rhs_body)])
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410 (mkVarApps (Var new_bndr) lam_bndrs))],
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414 = newPolyBndrs dest_lvl env abs_vars bndrs `thenLvl` \ (new_env, new_bndrs) ->
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415 mapLvl (lvlFloatRhs abs_vars dest_lvl new_env) rhss `thenLvl` \ new_rhss ->
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416 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
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419 (bndrs,rhss) = unzip pairs
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421 -- Finding the free vars of the binding group is annoying
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422 bind_fvs = (unionVarSets [ idFreeVars bndr `unionVarSet` rhs_fvs
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423 | (bndr, (rhs_fvs,_)) <- pairs])
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427 dest_lvl = destLevel env bind_fvs (all isFunction rhss)
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428 abs_vars = abstractVars dest_lvl env bind_fvs
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430 ----------------------------------------------------
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431 -- Three help functons for the type-abstraction case
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433 lvlFloatRhs abs_vars dest_lvl env rhs
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434 = lvlExpr rhs_lvl rhs_env rhs `thenLvl` \ rhs' ->
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435 returnLvl (mkLams abs_vars_w_lvls rhs')
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437 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
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438 rhs_env = extendLvlEnv env abs_vars_w_lvls
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442 %************************************************************************
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444 \subsection{Deciding floatability}
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446 %************************************************************************
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449 lvlLamBndrs :: Level -> [CoreBndr] -> (Level, [(CoreBndr, Level)])
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450 -- Compute the levels for the binders of a lambda group
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451 -- The binders returned are exactly the same as the ones passed,
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452 -- but they are now paired with a level
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453 lvlLamBndrs lvl []
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456 lvlLamBndrs lvl bndrs
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457 = go (incMinorLvl lvl)
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458 False -- Havn't bumped major level in this group
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461 go old_lvl bumped_major rev_lvld_bndrs (bndr:bndrs)
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462 | isId bndr && -- Go to the next major level if this is a value binder,
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463 not bumped_major && -- and we havn't already gone to the next level (one jump per group)
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464 not (isOneShotLambda bndr) -- and it isn't a one-shot lambda
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465 = go new_lvl True ((bndr,new_lvl) : rev_lvld_bndrs) bndrs
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468 = go old_lvl bumped_major ((bndr,old_lvl) : rev_lvld_bndrs) bndrs
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471 new_lvl = incMajorLvl old_lvl
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473 go old_lvl _ rev_lvld_bndrs []
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474 = (old_lvl, reverse rev_lvld_bndrs)
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475 -- a lambda like this (\x -> coerce t (\s -> ...))
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476 -- This happens quite a bit in state-transformer programs
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480 abstractVars :: Level -> LevelEnv -> VarSet -> [Var]
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481 -- Find the variables in fvs, free vars of the target expresion,
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482 -- whose level is less than than the supplied level
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483 -- These are the ones we are going to abstract out
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484 abstractVars dest_lvl env fvs
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485 = uniq (sortLt lt [var | fv <- varSetElems fvs, var <- absVarsOf dest_lvl env fv])
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487 -- Sort the variables so we don't get
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488 -- mixed-up tyvars and Ids; it's just messy
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489 v1 `lt` v2 = case (isId v1, isId v2) of
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490 (True, False) -> False
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491 (False, True) -> True
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492 other -> v1 < v2 -- Same family
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493 uniq :: [Var] -> [Var]
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494 -- Remove adjacent duplicates; the sort will have brought them together
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495 uniq (v1:v2:vs) | v1 == v2 = uniq (v2:vs)
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496 | otherwise = v1 : uniq (v2:vs)
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499 -- Destintion level is the max Id level of the expression
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500 -- (We'll abstract the type variables, if any.)
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501 destLevel :: LevelEnv -> VarSet -> Bool -> Level
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502 destLevel env fvs is_function
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504 && is_function = tOP_LEVEL -- Send functions to top level; see
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505 -- the comments with isFunction
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506 | otherwise = maxIdLevel env fvs
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508 isFunction :: CoreExprWithFVs -> Bool
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509 -- The idea here is that we want to float *functions* to
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510 -- the top level. This saves no work, but
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511 -- (a) it can make the host function body a lot smaller,
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512 -- and hence inlinable.
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513 -- (b) it can also save allocation when the function is recursive:
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514 -- h = \x -> letrec f = \y -> ...f...y...x...
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517 -- f = \x y -> ...(f x)...y...x...
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519 -- No allocation for f now.
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520 -- We may only want to do this if there are sufficiently few free
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521 -- variables. We certainly only want to do it for values, and not for
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522 -- constructors. So the simple thing is just to look for lambdas
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523 isFunction (_, AnnLam b e) | isId b = True
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524 | otherwise = isFunction e
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525 isFunction (_, AnnNote n e) = isFunction e
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526 isFunction other = False
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530 %************************************************************************
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532 \subsection{Free-To-Level Monad}
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534 %************************************************************************
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537 type LevelEnv = (Bool, -- True <=> Float lambdas too
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538 VarEnv Level, -- Domain is *post-cloned* TyVars and Ids
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539 Subst, -- Domain is pre-cloned Ids; tracks the in-scope set
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540 -- so that subtitution is capture-avoiding
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541 IdEnv ([Var], LevelledExpr)) -- Domain is pre-cloned Ids
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542 -- We clone let-bound variables so that they are still
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543 -- distinct when floated out; hence the SubstEnv/IdEnv.
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544 -- (see point 3 of the module overview comment).
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545 -- We also use these envs when making a variable polymorphic
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546 -- because we want to float it out past a big lambda.
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548 -- The SubstEnv and IdEnv always implement the same mapping, but the
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549 -- SubstEnv maps to CoreExpr and the IdEnv to LevelledExpr
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550 -- Since the range is always a variable or type application,
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551 -- there is never any difference between the two, but sadly
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552 -- the types differ. The SubstEnv is used when substituting in
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553 -- a variable's IdInfo; the IdEnv when we find a Var.
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555 -- In addition the IdEnv records a list of tyvars free in the
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556 -- type application, just so we don't have to call freeVars on
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557 -- the type application repeatedly.
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559 -- The domain of the both envs is *pre-cloned* Ids, though
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561 -- The domain of the VarEnv Level is the *post-cloned* Ids
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563 initialEnv :: Bool -> LevelEnv
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564 initialEnv float_lams = (float_lams, emptyVarEnv, emptySubst, emptyVarEnv)
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566 floatLams :: LevelEnv -> Bool
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567 floatLams (float_lams, _, _, _) = float_lams
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569 extendLvlEnv :: LevelEnv -> [(Var,Level)] -> LevelEnv
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570 -- Used when *not* cloning
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571 extendLvlEnv (float_lams, lvl_env, subst, id_env) prs
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573 foldl add_lvl lvl_env prs,
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574 foldl del_subst subst prs,
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575 foldl del_id id_env prs)
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577 add_lvl env (v,l) = extendVarEnv env v l
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578 del_subst env (v,_) = extendInScope env v
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579 del_id env (v,_) = delVarEnv env v
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580 -- We must remove any clone for this variable name in case of
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581 -- shadowing. This bit me in the following case
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582 -- (in nofib/real/gg/Spark.hs):
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584 -- case ds of wild {
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585 -- ... -> case e of wild {
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586 -- ... -> ... wild ...
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590 -- The inside occurrence of @wild@ was being replaced with @ds@,
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591 -- incorrectly, because the SubstEnv was still lying around. Ouch!
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594 -- extendCaseBndrLvlEnv adds the mapping case-bndr->scrut-var if it can
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595 -- (see point 4 of the module overview comment)
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596 extendCaseBndrLvlEnv (float_lams, lvl_env, subst, id_env) (Var scrut_var) case_bndr lvl
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598 extendVarEnv lvl_env case_bndr lvl,
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599 extendSubst subst case_bndr (DoneEx (Var scrut_var)),
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600 extendVarEnv id_env case_bndr ([scrut_var], Var scrut_var))
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602 extendCaseBndrLvlEnv env scrut case_bndr lvl
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603 = extendLvlEnv env [(case_bndr,lvl)]
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605 extendPolyLvlEnv dest_lvl (float_lams, lvl_env, subst, id_env) abs_vars bndr_pairs
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607 foldl add_lvl lvl_env bndr_pairs,
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608 foldl add_subst subst bndr_pairs,
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609 foldl add_id id_env bndr_pairs)
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611 add_lvl env (v,v') = extendVarEnv env v' dest_lvl
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612 add_subst env (v,v') = extendSubst env v (DoneEx (mkVarApps (Var v') abs_vars))
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613 add_id env (v,v') = extendVarEnv env v ((v':abs_vars), mkVarApps (Var v') abs_vars)
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615 extendCloneLvlEnv lvl (float_lams, lvl_env, _, id_env) new_subst bndr_pairs
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617 foldl add_lvl lvl_env bndr_pairs,
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619 foldl add_id id_env bndr_pairs)
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621 add_lvl env (v,v') = extendVarEnv env v' lvl
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622 add_id env (v,v') = extendVarEnv env v ([v'], Var v')
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625 maxIdLevel :: LevelEnv -> VarSet -> Level
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626 maxIdLevel (_, lvl_env,_,id_env) var_set
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627 = foldVarSet max_in tOP_LEVEL var_set
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629 max_in in_var lvl = foldr max_out lvl (case lookupVarEnv id_env in_var of
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630 Just (abs_vars, _) -> abs_vars
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631 Nothing -> [in_var])
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633 max_out out_var lvl
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634 | isId out_var = case lookupVarEnv lvl_env out_var of
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635 Just lvl' -> maxLvl lvl' lvl
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637 | otherwise = lvl -- Ignore tyvars in *maxIdLevel*
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639 lookupVar :: LevelEnv -> Id -> LevelledExpr
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640 lookupVar (_, _, _, id_env) v = case lookupVarEnv id_env v of
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641 Just (_, expr) -> expr
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644 absVarsOf :: Level -> LevelEnv -> Var -> [Var]
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645 -- If f is free in the exression, and f maps to poly_f a b c in the
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646 -- current substitution, then we must report a b c as candidate type
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648 absVarsOf dest_lvl (_, lvl_env, _, id_env) v
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650 = [final_av | av <- lookup_avs v, abstract_me av, final_av <- add_tyvars av]
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653 = if abstract_me v then [v] else []
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656 abstract_me v = case lookupVarEnv lvl_env v of
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657 Just lvl -> dest_lvl `ltLvl` lvl
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660 lookup_avs v = case lookupVarEnv id_env v of
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661 Just (abs_vars, _) -> abs_vars
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664 -- We are going to lambda-abstract, so nuke any IdInfo,
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665 -- and add the tyvars of the Id
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666 add_tyvars v | isId v = zap v : varSetElems (idFreeTyVars v)
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669 zap v = WARN( workerExists (idWorkerInfo v)
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670 || not (isEmptyCoreRules (idSpecialisation v)),
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671 text "absVarsOf: discarding info on" <+> ppr v )
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672 setIdInfo v vanillaIdInfo
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676 type LvlM result = UniqSM result
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680 returnLvl = returnUs
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685 newPolyBndrs dest_lvl env abs_vars bndrs
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686 = getUniquesUs (length bndrs) `thenLvl` \ uniqs ->
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688 new_bndrs = zipWith mk_poly_bndr bndrs uniqs
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690 returnLvl (extendPolyLvlEnv dest_lvl env abs_vars (bndrs `zip` new_bndrs), new_bndrs)
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692 mk_poly_bndr bndr uniq = mkSysLocal (_PK_ str) uniq poly_ty
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694 str = "poly_" ++ occNameUserString (getOccName bndr)
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695 poly_ty = foldr mkPiType (idType bndr) abs_vars
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698 newLvlVar :: String
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699 -> [CoreBndr] -> Type -- Abstract wrt these bndrs
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701 newLvlVar str vars body_ty
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702 = getUniqueUs `thenLvl` \ uniq ->
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703 returnUs (mkSysLocal (_PK_ str) uniq (foldr mkPiType body_ty vars))
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705 -- The deeply tiresome thing is that we have to apply the substitution
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706 -- to the rules inside each Id. Grr. But it matters.
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708 cloneVar :: TopLevelFlag -> LevelEnv -> Id -> Level -> Level -> LvlM (LevelEnv, Id)
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709 cloneVar TopLevel env v ctxt_lvl dest_lvl
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710 = returnUs (env, v) -- Don't clone top level things
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711 cloneVar NotTopLevel env@(_,_,subst,_) v ctxt_lvl dest_lvl
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713 getUs `thenLvl` \ us ->
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715 (subst', v1) = substAndCloneId subst us v
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716 v2 = zap_demand ctxt_lvl dest_lvl v1
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717 env' = extendCloneLvlEnv dest_lvl env subst' [(v,v2)]
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719 returnUs (env', v2)
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721 cloneRecVars :: TopLevelFlag -> LevelEnv -> [Id] -> Level -> Level -> LvlM (LevelEnv, [Id])
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722 cloneRecVars TopLevel env vs ctxt_lvl dest_lvl
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723 = returnUs (env, vs) -- Don't clone top level things
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724 cloneRecVars NotTopLevel env@(_,_,subst,_) vs ctxt_lvl dest_lvl
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725 = ASSERT( all isId vs )
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726 getUs `thenLvl` \ us ->
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728 (subst', vs1) = substAndCloneRecIds subst us vs
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729 vs2 = map (zap_demand ctxt_lvl dest_lvl) vs1
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730 env' = extendCloneLvlEnv dest_lvl env subst' (vs `zip` vs2)
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732 returnUs (env', vs2)
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734 -- VERY IMPORTANT: we must zap the demand info
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735 -- if the thing is going to float out past a lambda
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736 zap_demand dest_lvl ctxt_lvl id
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737 | ctxt_lvl == dest_lvl = id -- Stays put
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738 | otherwise = zapDemandIdInfo id -- Floats out
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