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Improve/fix handling of WordXVector constants in Useless pass #567

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merged 4 commits into from
May 16, 2024
Merged

Improve/fix handling of WordXVector constants in Useless pass #567

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4a06e6e
Refactor `Useless.Value.layout`
MatthewFluet May 15, 2024
5e84a24
Simplify `Useless.doit{Exp,Statement}`
MatthewFluet May 15, 2024
322205f
Improve/fix handling of `WordXVector` constants in `Useless` pass
MatthewFluet May 15, 2024
741732b
Improve `Useless.Value.layout`
MatthewFluet May 15, 2024
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82 changes: 44 additions & 38 deletions mlton/ssa/useless.fun
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
(* Copyright (C) 2009,2017-2021 Matthew Fluet.
(* Copyright (C) 2009,2017-2021,2024 Matthew Fluet.
* Copyright (C) 1999-2008 Henry Cejtin, Matthew Fluet, Suresh
* Jagannathan, and Stephen Weeks.
* Copyright (C) 1997-2000 NEC Research Institute.
Expand Down Expand Up @@ -128,22 +128,29 @@ structure Value =
let
val {value, ...} = Set.! s
in
case value of
Array {elt, length, ...} =>
seq [str "array", tuple [layout length, layoutSlot elt]]
| Ground g => seq [str "ground ", Useful.layout g]
| Ref {arg, useful, ...} =>
seq [str "ref ",
record [("useful", Useful.layout useful),
("slot", layoutSlot arg)]]
| Tuple vs => Vector.layout layoutSlot vs
| Vector {elt, length} =>
seq [str "vector", tuple [layout length, layoutSlot elt]]
| Weak {arg, useful} =>
seq [str "weak ",
record [("useful", Useful.layout useful),
("slot", layoutSlot arg)]]
layoutValue value
end
and layoutValue value =
case value of
Array {elt, length, useful} =>
seq [str "array ",
record [("useful", Useful.layout useful),
("length", layout length),
("elt", layoutSlot elt)]]
| Ground g => seq [str "ground ", Useful.layout g]
| Ref {arg, useful, ...} =>
seq [str "ref ",
record [("useful", Useful.layout useful),
("arg", layoutSlot arg)]]
| Tuple vs => Vector.layout layoutSlot vs
| Vector {elt, length} =>
seq [str "vector ",
record [("length", layout length),
("elt", layoutSlot elt)]]
| Weak {arg, useful} =>
seq [str "weak ",
record [("useful", Useful.layout useful),
("arg", layoutSlot arg)]]
and layoutSlot (v, e) =
tuple [Exists.layout e, layout v]
end
Expand Down Expand Up @@ -306,17 +313,7 @@ structure Value =
loop (t, [])
end

fun const (c: Const.t): t =
let
val v = fromType (Type.ofConst c)
(* allOrNothing v because constants are not transformed and their
* type cannot change. So they must either be completely eliminated
* or completely kept.
*)
val _ = allOrNothing v
in
v
end
fun const (c: Const.t): t = fromType (Type.ofConst c)

fun detupleSlots (v: t): slot vector =
case value v of
Expand Down Expand Up @@ -904,12 +901,21 @@ fun transform (program: Program.t): Program.t =
in loop (0, n, 0)
end

fun doitExp (e: Exp.t, resultType: Type.t, resultValue: Value.t option) =
fun doitExp (e: Exp.t, resultType: Type.t, resultValue: Value.t) =
case e of
ConApp {con, args} =>
ConApp {con = con,
args = keepUseful (args, conArgs con)}
| Const _ => e
| Const c =>
(case c of
Const.WordVector ws =>
if Type.isUnit (Type.deVector resultType)
then PrimApp
{prim = Prim.Vector_vector,
targs = Vector.new1 Type.unit,
args = WordXVector.toVectorMap (ws, fn _ => unitVar)}
else e
| _ => e)
| PrimApp {prim, args, ...} =>
let
fun arg i = Vector.sub (args, i)
Expand Down Expand Up @@ -995,7 +1001,7 @@ fun transform (program: Program.t): Program.t =
end
| Tuple xs =>
let
val slots = Value.detupleSlots (valOf resultValue)
val slots = Value.detupleSlots resultValue
val xs =
Vector.keepAllMap2
(xs, slots, fn (x, (v, e)) =>
Expand All @@ -1012,24 +1018,24 @@ fun transform (program: Program.t): Program.t =
| _ => e
val doitExp =
Trace.trace3 ("Useless.doitExp",
Exp.layout, Layout.ignore, Layout.ignore,
Exp.layout, Type.layout, Value.layout,
Exp.layout)
doitExp
fun doitStatement (Statement.T {var, exp, ty}) =
let
val v = Option.map (var, value)
val (ty, b) =
val (v, (ty, b)) =
case v of
NONE => (ty, false)
| SOME v => Value.getNew v
fun yes ty =
NONE => (Value.fromType ty, (ty, false))
| SOME v => (v, Value.getNew v)
fun yes () =
SOME (Statement.T
{var = var,
ty = ty,
exp = doitExp (exp, ty, v)})
in
if b
then yes ty
then yes ()
else
case exp of
PrimApp {prim, args, ...} =>
Expand All @@ -1051,9 +1057,9 @@ fun transform (program: Program.t): Program.t =
| Prim.WordArray_updateWord _ => array ()
| _ => true
end
then yes ty
then yes ()
else NONE
| Profile _ => yes ty
| Profile _ => yes ()
| _ => NONE
end
val doitStatement =
Expand Down
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