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makes dead code elimination less conservative #906

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merged 5 commits into from
Dec 11, 2018
Merged

makes dead code elimination less conservative #906

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df60d09
maked dead code elimination less conservative
ivg Dec 11, 2018
dfac2b2
makes it sound
ivg Dec 11, 2018
43e9d17
removes a dead function
ivg Dec 11, 2018
fb32307
drops debug info
ivg Dec 11, 2018
f808b39
drops a change that is irrelevant to the proposal
ivg Dec 11, 2018
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18 changes: 11 additions & 7 deletions plugins/optimization/optimization_main.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -42,13 +42,17 @@ let compute_dead can_touch protected sub =
let defs,uses = computed_def_use sub in
let dead = Set.diff defs uses in
let live v = not (Set.mem dead v) in
(object inherit [Tid.Set.t] Term.visitor
method! enter_def t dead =
let v = Def.lhs t in
if not (can_touch v) || Set.mem protected (Var.base v) || live v
then dead
else Set.add dead (Term.tid t)
end)#visit_sub sub Tid.Set.empty
Term.enum blk_t sub |>
Seq.fold ~init:Tid.Set.empty ~f:(fun dead blk ->
Term.enum ~rev:true def_t blk |>
Seq.fold ~init:(protected,dead) ~f:(fun (protected,dead) def ->
let v = Def.lhs def in
if not (can_touch v) || live v
then (protected,dead)
else if Set.mem protected (Var.base v)
then Set.remove protected (Var.base v), dead
else protected, Set.add dead (Term.tid def)) |>
snd)

let is_alive dead t = not (Set.mem dead (Term.tid t))
let live_phi dead blk = Term.filter phi_t ~f:(is_alive dead) blk
Expand Down