lean4-htt/library/init/lean/compiler/ir/elimdead.lean
Leonardo de Moura ea6eee516b chore(frontends/lean): use => instead of := in match-expressions
Motivation: use same separator used in lambda expressions as in
other programming languages.
2019-07-04 11:38:38 -07:00

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/-
Copyright (c) 2019 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Leonardo de Moura
-/
prelude
import init.lean.compiler.ir.basic
import init.lean.compiler.ir.freevars
namespace Lean
namespace IR
partial def reshapeWithoutDeadAux : Array FnBody → FnBody → IndexSet → FnBody
| bs b used :=
if bs.isEmpty then b
else
let curr := bs.back;
let bs := bs.pop;
let keep (_ : Unit) :=
let used := curr.collectFreeIndices used;
let b := curr.setBody b;
reshapeWithoutDeadAux bs b used;
let keepIfUsed (vidx : Index) :=
if used.contains vidx then keep ()
else reshapeWithoutDeadAux bs b used;
match curr with
| FnBody.vdecl x _ _ _ => keepIfUsed x.idx
| FnBody.jdecl j _ _ _ => keepIfUsed j.idx
| _ => keep ()
def reshapeWithoutDead (bs : Array FnBody) (term : FnBody) : FnBody :=
reshapeWithoutDeadAux bs term term.freeIndices
partial def FnBody.elimDead : FnBody → FnBody
| b :=
let (bs, term) := b.flatten;
let bs := modifyJPs bs FnBody.elimDead;
let term := match term with
| FnBody.case tid x alts =>
let alts := alts.map $ fun alt => alt.modifyBody FnBody.elimDead;
FnBody.case tid x alts
| other => other;
reshapeWithoutDead bs term
/-- Eliminate dead let-declarations and join points -/
def Decl.elimDead : Decl → Decl
| (Decl.fdecl f xs t b) := Decl.fdecl f xs t b.elimDead
| other := other
end IR
end Lean