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(* lift.sml * * COPYRIGHT (c) 2010 The Diderot Project (http://diderot.cs.uchicago.edu) * All rights reserved. * * Lift field operations to global scope and split global initialization to * pre and post image loading phases. * * NOTE: this process can be streamlined as follows: * 1) identify the static variables * 2) evaluate eagerly, with the proviso that if the lhs is not static, then * only evaluate if the rhs is static and the operation is supported * 3) reduce code * This evaluation process could be extended to the body of the actors too. *) structure Lift : sig val transform : Simple.program -> Simple.program end = struct structure BV = BasisVars structure S = Simple structure VSet = Var.Set structure VMap = Var.Map (* the kinds of things a variable in Simple AST can be bound to *) datatype var_binding = RHS of S.exp | Param (* identify the image load operations and lift them and their antecedents; in terms of BTA, * this phase is essentially determining what must be static in order to get the image * info needed for the rest of the compile. *) fun liftLoads block = let (* analysis to compute the set of static variables *) fun mkStatic (env, statics, x) = if VSet.member(statics, x) then statics else let val statics = VSet.add(statics, x) in case VMap.find(env, x) of SOME(S.E_Var y) => mkStatic (env, statics, y) | SOME(S.E_Tuple ys) => mkStatics (env, statics, ys) | SOME(S.E_Apply(_, _, ys, _)) => mkStatics (env, statics, ys) | SOME(S.E_Cons ys) => mkStatics (env, statics, ys) | SOME(S.E_Input(_, _, SOME y)) => mkStatic (env, statics, y) | SOME _ => statics | NONE => raise Fail(concat["variable ", Var.uniqueNameOf x, " has no binding"]) (* end case *) end and mkStatics (env, statics, xs) = List.foldl (fn (x, statics) => mkStatic(env, statics, x)) statics xs fun doBlock (env, statics, S.Block stms) = let fun doStmts (env, statics, []) = statics | doStmts (env, statics, stm::stms) = let val (env, statics) = doStmt (env, statics, stm) in doStmts (env, statics, stms) end in doStmts (env, statics, stms) end and doStmt (env, statics, stm) = (case stm of S.S_Assign(x, e) => let val env = VMap.insert(env, x, e) in case e of S.E_Apply(f, _, xs, _) => if Var.same(f, BV.fn_load) then (env, mkStatic(env, statics, x)) else (env, statics) | _ => (env, statics) (* end case *) end | S.S_IfThenElse(x, b1, b2) => let val statics1 = doBlock (env, statics, b1) val statics2 = doBlock (env, statics, b2) val n = VSet.numItems statics in if ((n <> VSet.numItems statics1) orelse (n <> VSet.numItems statics2)) then (env, mkStatic(env, statics, x)) else (env, statics) end | _ => (env, statics) (* end case *)) val statics = doBlock (VMap.empty, VSet.empty, block) (* lift out the static code *) fun doBlock (S.Block stms) = let fun doStmts ([], staticStms) = S.Block(List.rev staticStms) | doStmts (stm::stms, staticStms) = (case doStmt stm of SOME stm => doStmts (stms, stm::staticStms) | NONE => doStmts (stms, staticStms) (* end case *)) in doStmts (stms, []) end and doStmt stm = (case stm of S.S_Assign(x, e) => if VSet.member(statics, x) then SOME stm else NONE | S.S_IfThenElse(x, b1, b2) => if VSet.member(statics, x) then SOME(S.S_IfThenElse(x, doBlock b1, doBlock b2)) else NONE | _ => NONE (* end case *)) val staticBlock = doBlock block in Log.msg "**** static variables: "; VSet.app (fn x => Log.msg(" "^Var.uniqueNameOf x)) statics; Log.msg "\n"; staticBlock end (* given values for the static variables; reduce the static initialization code *) fun reduce (env, blk) = let fun doBlock (S.Block stms) = List.foldr (fn (stm, stms) => doStmt stm @ stms) [] stms and doStmt stm = (case stm of S.S_Assign(x, e) => (case Var.Map.find(env, x) of SOME v => let val rhs = (case v of (Eval.BV b) => S.E_Lit(Literal.Bool b) | (Eval.SV s) => S.E_Lit(Literal.String s) | (Eval.IV i) => S.E_Lit(Literal.Int i) | (Eval.TV _) => e | (Eval.FV fld) => S.E_Field fld | (Eval.Img info) => S.E_LoadImage info | (Eval.KV h) => e (* end case *)) in [S.S_Assign(x, rhs)] end | NONE => [stm] (* end case *)) | S.S_IfThenElse(x, b1, b2) => (case Var.Map.find(env, x) of SOME(Eval.BV b) => if b then doBlock b1 else doBlock b2 | NONE => [stm] (* end case *)) | _ => [stm] (* end case *)) in S.Block(doBlock blk) end fun transform (prog as S.Program{globals, globalInit, actors}) = let val staticInit = liftLoads globalInit val staticEnv = Eval.evalStatics staticInit val globalInit = reduce (staticEnv, globalInit) in S.Program{ globals = globals, globalInit = globalInit, actors = actors } end end

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