File 3751-Optimize-find_yregs-pass-from-beam_ssa_pre_codegen.patch of Package erlang
From c2185cde6f9f038250a522aee0938faa9789b251 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Valim?= <jose.valim@dashbit.co>
Date: Thu, 17 Sep 2020 12:58:36 +0200
Subject: [PATCH] Optimize find_yregs pass from beam_ssa_pre_codegen
The current pass gets very expensive the longer the
code block is. This commit address it. For example,
imagine this code:
-module(bar).
-export([bar/0]).
bar() ->
foo:bar(),
% repeat foo:bar() 999 times
ok.
Prior to this patch, it would take:
find_yregs : 0.212 s 73 %
After this patch, it takes:
find_yregs : 0.013 s 14 %
Another example is the code in this gist:
https://gist.github.com/josevalim/acac154996e1e61058f367a5b3a161aa
After the patch, find_yregs goes from 3.5s to 0.8s.
---
lib/compiler/src/beam_ssa_pre_codegen.erl | 62 ++++++++++++++++-------
1 file changed, 44 insertions(+), 18 deletions(-)
diff --git a/lib/compiler/src/beam_ssa_pre_codegen.erl b/lib/compiler/src/beam_ssa_pre_codegen.erl
index 9a52399b3b..274952b05e 100644
--- a/lib/compiler/src/beam_ssa_pre_codegen.erl
+++ b/lib/compiler/src/beam_ssa_pre_codegen.erl
@@ -1749,7 +1749,7 @@ find_rm_act([]) ->
%%%
-record(dk, {d :: ordsets:ordset(var_name()),
- k :: ordsets:ordset(var_name())
+ k :: cerl_sets:set(var_name())
}).
%% find_yregs(St0) -> St.
@@ -1772,10 +1772,10 @@ find_yregs(#st{frames=[_|_]=Frames,args=Args,ssa=Blocks0}=St) ->
St#st{ssa=Blocks}.
find_yregs_1([{F,Defs}|Fs], Blocks0) ->
- DK = #dk{d=Defs,k=[]},
+ DK = #dk{d=Defs,k=cerl_sets:new()},
D0 = #{F=>DK},
Ls = beam_ssa:rpo([F], Blocks0),
- Yregs0 = [],
+ Yregs0 = cerl_sets:new(),
Yregs = find_yregs_2(Ls, Blocks0, D0, Yregs0),
Blk0 = map_get(F, Blocks0),
Blk = beam_ssa:add_anno(yregs, Yregs, Blk0),
@@ -1830,7 +1830,7 @@ find_update_succ([S|Ss], #dk{d=Defs0,k=Killed0}=DK0, D0) ->
case D0 of
#{S:=#dk{d=Defs1,k=Killed1}} ->
Defs = ordsets:intersection(Defs0, Defs1),
- Killed = ordsets:union(Killed0, Killed1),
+ Killed = cerl_sets:union(Killed0, Killed1),
DK = #dk{d=Defs,k=Killed},
D = D0#{S:=DK},
find_update_succ(Ss, DK0, D);
@@ -1841,24 +1841,51 @@ find_update_succ([S|Ss], #dk{d=Defs0,k=Killed0}=DK0, D0) ->
find_update_succ([], _, D) -> D.
find_yregs_is([#b_set{dst=Dst}=I|Is], #dk{d=Defs0,k=Killed0}=Ys, Yregs0) ->
- Used = beam_ssa:used(I),
- Yregs1 = ordsets:intersection(Used, Killed0),
- Yregs = ordsets:union(Yregs0, Yregs1),
+ Yregs1 = intersect_used(I, Killed0),
+ Yregs = cerl_sets:union(Yregs0, Yregs1),
case beam_ssa:clobbers_xregs(I) of
false ->
Defs = ordsets:add_element(Dst, Defs0),
find_yregs_is(Is, Ys#dk{d=Defs}, Yregs);
true ->
- Killed = ordsets:union(Defs0, Killed0),
+ Killed = cerl_sets:union(cerl_sets:from_list(Defs0), Killed0),
Defs = [Dst],
find_yregs_is(Is, Ys#dk{d=Defs,k=Killed}, Yregs)
end;
find_yregs_is([], Ys, Yregs) -> {Yregs,Ys}.
find_yregs_terminator(Terminator, #dk{k=Killed}, Yregs0) ->
- Used = beam_ssa:used(Terminator),
- Yregs = ordsets:intersection(Used, Killed),
- ordsets:union(Yregs0, Yregs).
+ Yregs = intersect_used(Terminator, Killed),
+ cerl_sets:union(Yregs0, Yregs).
+
+intersect_used(#b_br{bool=#b_var{}=V}, Set) ->
+ intersect_used_keep_singleton(V, Set);
+intersect_used(#b_ret{arg=#b_var{}=V}, Set) ->
+ intersect_used_keep_singleton(V, Set);
+intersect_used(#b_set{op=phi,args=Args}, Set) ->
+ cerl_sets:from_list([V || {#b_var{}=V,_} <- Args, cerl_sets:is_element(V, Set)]);
+intersect_used(#b_set{args=Args}, Set) ->
+ cerl_sets:from_list(intersect_used_keep(used_args(Args), Set));
+intersect_used(#b_switch{arg=#b_var{}=V}, Set) ->
+ intersect_used_keep_singleton(V, Set);
+intersect_used(_, _) -> cerl_sets:new().
+
+intersect_used_keep_singleton(V, Set) ->
+ case cerl_sets:is_element(V, Set) of
+ true -> cerl_sets:from_list([V]);
+ false -> cerl_sets:new()
+ end.
+
+intersect_used_keep(Vs, Set) ->
+ [V || V <- Vs, cerl_sets:is_element(V, Set)].
+
+used_args([#b_var{}=V|As]) ->
+ [V|used_args(As)];
+used_args([#b_remote{mod=Mod,name=Name}|As]) ->
+ used_args([Mod,Name|As]);
+used_args([_|As]) ->
+ used_args(As);
+used_args([]) -> [].
%%%
%%% Try to reduce the size of the stack frame, by adding an explicit
@@ -1942,8 +1969,7 @@ copy_retval(#st{frames=Frames,ssa=Blocks0,cnt=Count0}=St) ->
copy_retval_1([F|Fs], Blocks0, Count0) ->
#b_blk{anno=#{yregs:=Yregs0},is=Is} = map_get(F, Blocks0),
- Yregs1 = gb_sets:from_list(Yregs0),
- Yregs = collect_yregs(Is, Yregs1),
+ Yregs = collect_yregs(Is, Yregs0),
Ls = beam_ssa:rpo([F], Blocks0),
{Blocks,Count} = copy_retval_2(Ls, Yregs, none, Blocks0, Count0),
copy_retval_1(Fs, Blocks, Count);
@@ -1952,8 +1978,8 @@ copy_retval_1([], Blocks, Count) ->
collect_yregs([#b_set{op=copy,dst=Y,args=[#b_var{}=X]}|Is],
Yregs0) ->
- true = gb_sets:is_member(X, Yregs0), %Assertion.
- Yregs = gb_sets:insert(Y, gb_sets:delete(X, Yregs0)),
+ true = cerl_sets:is_element(X, Yregs0), %Assertion.
+ Yregs = cerl_sets:add_element(Y, cerl_sets:del_element(X, Yregs0)),
collect_yregs(Is, Yregs);
collect_yregs([#b_set{}|Is], Yregs) ->
collect_yregs(Is, Yregs);
@@ -1998,7 +2024,7 @@ copy_retval_is([#b_set{},#b_set{op=succeeded}]=Is, false, _Yregs, Copy, Count, A
copy_retval_is([#b_set{op=Op,dst=#b_var{name=RetName}=Dst}=I0|Is], RC, Yregs,
Copy0, Count0, Acc0) when Op =:= call; Op =:= make_fun ->
{I1,Count1,Acc} = place_retval_copy(I0, Yregs, Copy0, Count0, Acc0),
- case gb_sets:is_member(Dst, Yregs) of
+ case cerl_sets:is_element(Dst, Yregs) of
true ->
{NewVar,Count} = new_var(RetName, Count1),
Copy = #b_set{op=copy,dst=Dst,args=[NewVar]},
@@ -2056,7 +2082,7 @@ place_retval_copy(#b_set{args=[F|Args0]}=I, Yregs, Copy, Count0, Acc0) ->
{I#b_set{args=[F|Args]},Count,Acc}.
copy_func_args([#b_var{name=AName}=A|As], Yregs, Avoid, CopyAcc, Acc, Count0) ->
- case gb_sets:is_member(A, Yregs) of
+ case cerl_sets:is_element(A, Yregs) of
true when A =/= Avoid ->
{NewVar,Count} = new_var(AName, Count0),
Copy = #b_set{op=copy,dst=NewVar,args=[A]},
@@ -2303,7 +2329,7 @@ reserve_yregs(#st{frames=Frames}=St0) ->
reserve_yregs_1(L, #st{ssa=Blocks0,cnt=Count0,res=Res0}=St) ->
Blk = map_get(L, Blocks0),
- Yregs = beam_ssa:get_anno(yregs, Blk),
+ Yregs = ordsets:from_list(cerl_sets:to_list(beam_ssa:get_anno(yregs, Blk))),
{Def,Unused} = beam_ssa:def_unused([L], Yregs, Blocks0),
UsedYregs = ordsets:subtract(Yregs, Unused),
DefBefore = ordsets:subtract(UsedYregs, Def),
--
2.26.2
