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overhaul remove_redundant_temp_vars pass to remove more variables
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JeffBezanson committed Mar 8, 2017
1 parent 6d6218f commit c703c4d
Showing 1 changed file with 75 additions and 44 deletions.
119 changes: 75 additions & 44 deletions base/inference.jl
Original file line number Diff line number Diff line change
Expand Up @@ -4536,62 +4536,90 @@ function remove_unused_vars!(src::CodeInfo)
end
end

function delete_var!(src::CodeInfo, id, T)
var_matches(a::ANY, b::ANY) = false
var_matches(a::SSAValue, b::SSAValue) = a.id == b.id
var_matches(a::Slot, b::Slot) = a.id == b.id

function delete_var!(src::CodeInfo, v::Union{Slot,SSAValue})
filter!(x->!(isa(x,Expr) && (x.head === :(=) || x.head === :const) &&
isa(x.args[1],T) && x.args[1].id == id),
var_matches(x.args[1], v)),
src.code)
return src
end

function slot_replace!(src::CodeInfo, id::Int, rhs::ANY, T::ANY)
function slot_replace!(src::CodeInfo, v::Union{Slot,SSAValue}, rhs::ANY)
for i = 1:length(src.code)
src.code[i] = _slot_replace!(src.code[i], id, rhs, T)
src.code[i] = _slot_replace!(src.code[i], v, rhs)
end
return src
end

function _slot_replace!(e, id::Int, rhs::ANY, T::ANY)
if isa(e,T) && e.id == id
function _slot_replace!(e::ANY, v::Union{Slot,SSAValue}, rhs::ANY)
if var_matches(e, v)
return rhs
end
if isa(e,Expr)
for i = 1:length(e.args)
e.args[i] = _slot_replace!(e.args[i], id, rhs, T)
e.args[i] = _slot_replace!(e.args[i], v, rhs)
end
end
return e
end

occurs_undef(var::Int, expr, flags) =
flags[var] & Slot_UsedUndef != 0 && occurs_more(expr, e -> (isa(e, Slot) && slot_id(e) == var), 0) > 0

is_argument(nargs::Int, v::Slot) = slot_id(v) <= nargs

normslot(s::SlotNumber) = s
normslot(s::TypedSlot) = SlotNumber(slot_id(s))

# given a single-assigned var and its initializer `init`, return what we can
# replace `var` with, or `var` itself if we shouldn't replace it
function get_replacement(table, var::Union{SlotNumber, SSAValue}, init::ANY, nargs, slottypes, ssavaluetypes)
#if isa(init, QuoteNode) # this can cause slight code size increases
# return init
if isa(init, Expr) && init.head === :static_parameter
return init
elseif isa(init, Slot) && is_argument(nargs, init::Slot)
# the transformation is not ideal if the assignment
# is present for the auto-unbox functionality
# (from inlining improved type inference information)
# and this transformation would worsen the type information
# everywhere later in the function
ityp = isa(init, TypedSlot) ? init.typ : slottypes[(init::SlotNumber).id]
if ityp (isa(var,SSAValue) ? ssavaluetypes[var.id + 1] : slottypes[var.id])
return init
end
elseif isa(init, SSAValue)
if haskey(table, init)
return get_replacement(table, init, table[init], nargs, slottypes, ssavaluetypes)
end
return init
elseif isa(init, SlotNumber) && haskey(table, init)
return get_replacement(table, init, table[init], nargs, slottypes, ssavaluetypes)
elseif isa(init, TypedSlot)
sl = normslot(init)
if haskey(table, sl)
rep = get_replacement(table, sl, table[sl], nargs, slottypes, ssavaluetypes)
if isa(rep, SlotNumber)
rep = TypedSlot(rep.id, init.typ)
end
return rep
end
end
return var
end

# remove all single-assigned vars v in "v = x" where x is an argument.
# "sa" is the result of find_sa_vars
# T: Slot or SSAValue
function remove_redundant_temp_vars(src::CodeInfo, nargs::Int, sa, T)
function remove_redundant_temp_vars!(src::CodeInfo, nargs::Int, sa)
flags = src.slotflags
ssavalue_types = src.ssavaluetypes
bexpr = Expr(:block)
bexpr.args = src.code
slottypes = src.slottypes
ssavaluetypes = src.ssavaluetypes
for (v, init) in sa
if isa(init, Slot) && is_argument(nargs, init::Slot)
# this transformation is not valid for vars used before def.
# we need to preserve the point of assignment to know where to
# throw errors (issue #4645).
if T === SSAValue || !occurs_undef(v, bexpr, flags)
# the transformation is not ideal if the assignment
# is present for the auto-unbox functionality
# (from inlining improved type inference information)
# and this transformation would worsen the type information
# everywhere later in the function
ityp = isa(init, TypedSlot) ? init.typ : src.slottypes[(init::SlotNumber).id]
if ityp (T === SSAValue ? ssavalue_types[v + 1] : src.slottypes[v])
delete_var!(src, v, T)
slot_replace!(src, v, init, T)
end
end
repl = get_replacement(sa, v, init, nargs, slottypes, ssavaluetypes)
compare = isa(repl,TypedSlot) ? normslot(repl) : repl
if compare !== v
delete_var!(src, v)
slot_replace!(src, v, repl)
end
end
return src
Expand All @@ -4602,27 +4630,31 @@ function find_sa_vars(src::CodeInfo, nargs::Int)
body = src.code
av = ObjectIdDict()
av2 = ObjectIdDict()
gss = ObjectIdDict()
for i = 1:length(body)
e = body[i]
if isa(e,Expr) && e.head === :(=)
lhs = e.args[1]
if isa(lhs, SSAValue)
gss[lhs.id] = e.args[2]
av[lhs] = e.args[2]
elseif isa(lhs, Slot)
id = slot_id(lhs)
if id > nargs # exclude args
if !haskey(av, id)
av[id] = e.args[2]
lhs = normslot(lhs)
id = lhs.id
# exclude args and used undef vars
# this transformation is not valid for vars used before def.
# we need to preserve the point of assignment to know where to
# throw errors (issue #4645).
if id > nargs && (src.slotflags[id] & Slot_UsedUndef == 0)
if !haskey(av, lhs)
av[lhs] = e.args[2]
else
av2[id] = true
av2[lhs] = true
end
end
end
end
end
filter!((id, _) -> !haskey(av2, id), av)
return (av, gss)
filter!((v, _) -> !haskey(av2, v), av)
return av
end

symequal(x::SSAValue, y::SSAValue) = x.id === y.id
Expand Down Expand Up @@ -5066,9 +5098,8 @@ function alloc_elim_pass!(sv::InferenceState)
body = sv.src.code
bexpr = Expr(:block)
bexpr.args = body
vs, gs = find_sa_vars(sv.src, sv.nargs)
remove_redundant_temp_vars(sv.src, sv.nargs, vs, Slot)
remove_redundant_temp_vars(sv.src, sv.nargs, gs, SSAValue)
vs = find_sa_vars(sv.src, sv.nargs)
remove_redundant_temp_vars!(sv.src, sv.nargs, vs)
remove_unused_vars!(sv.src)
i = 1
while i < length(body)
Expand All @@ -5079,7 +5110,7 @@ function alloc_elim_pass!(sv::InferenceState)
end
e = e::Expr
if e.head === :(=) && (isa(e.args[1], SSAValue) ||
(isa(e.args[1], Slot) && haskey(vs, slot_id(e.args[1]))))
(isa(e.args[1], Slot) && haskey(vs, normslot(e.args[1]))))
var = e.args[1]
rhs = e.args[2]
# Need to make sure LLVM can recognize this as LLVM ssa value too
Expand Down

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