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File 2936-Slightly-optimize-union-of-a-short-list-and-a-set.patch of Package erlang (Revision b4f72044e1af8cfe32130ab849a401a1)

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From 6b78afccc9bf01584e1d8460c98e893190ada6b1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Sat, 20 Feb 2021 13:56:56 +0100
Subject: [PATCH 6/6] Slightly optimize union of a short list and a set

---
 lib/compiler/src/beam_ssa.erl      |  3 +++
 lib/compiler/src/beam_ssa_dead.erl | 15 +++++++++++----
 lib/compiler/src/beam_ssa_opt.erl  | 20 ++++++++++++--------
 3 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/lib/compiler/src/beam_ssa.erl b/lib/compiler/src/beam_ssa.erl
index 8ed508ef48..0163f59ae7 100644
--- a/lib/compiler/src/beam_ssa.erl
+++ b/lib/compiler/src/beam_ssa.erl
@@ -889,6 +889,9 @@ trim_unreachable_1([{L,Blk0}|Bs], Seen0) ->
             case successors(Blk) of
                 [] ->
                     [{L,Blk}|trim_unreachable_1(Bs, Seen0)];
+                [Next] ->
+                    Seen = sets:add_element(Next, Seen0),
+                    [{L,Blk}|trim_unreachable_1(Bs, Seen)];
                 [_|_]=Successors ->
                     Seen = sets:union(Seen0, sets:from_list(Successors, [{version, 2}])),
                     [{L,Blk}|trim_unreachable_1(Bs, Seen)]
diff --git a/lib/compiler/src/beam_ssa_dead.erl b/lib/compiler/src/beam_ssa_dead.erl
index 7af48c0860..037887529b 100644
--- a/lib/compiler/src/beam_ssa_dead.erl
+++ b/lib/compiler/src/beam_ssa_dead.erl
@@ -383,7 +383,7 @@ update_unset_vars(L, Is, Br, UnsetVars, #st{skippable=Skippable}) ->
             %% Some variables defined in this block are used by
             %% successors. We must update the set of unset variables.
             SetInThisBlock = [V || #b_set{dst=V} <- Is],
-            sets:union(UnsetVars, sets:from_list(SetInThisBlock, [{version, 2}]))
+            list_set_union(SetInThisBlock, UnsetVars)
     end.
 
 shortcut_two_way(#b_br{succ=Succ,fail=Fail}, From, Bs0, UnsetVars0, St0) ->
@@ -1108,7 +1108,7 @@ used_vars_phis(Is, L, Live0, UsedVars0) ->
             case [{P,V} || {#b_var{}=V,P} <- PhiArgs] of
                 [_|_]=PhiVars ->
                     PhiLive0 = rel2fam(PhiVars),
-                    PhiLive = [{{L,P},sets:union(sets:from_list(Vs, [{version, 2}]), Live0)} ||
+                    PhiLive = [{{L,P},list_set_union(Vs, Live0)} ||
                                   {P,Vs} <- PhiLive0],
                     maps:merge(UsedVars, maps:from_list(PhiLive));
                 [] ->
@@ -1118,13 +1118,13 @@ used_vars_phis(Is, L, Live0, UsedVars0) ->
     end.
 
 used_vars_blk(#b_blk{is=Is,last=Last}, Used0) ->
-    Used = sets:union(Used0, sets:from_list(beam_ssa:used(Last), [{version, 2}])),
+    Used = list_set_union(beam_ssa:used(Last), Used0),
     used_vars_is(reverse(Is), Used).
 
 used_vars_is([#b_set{op=phi}|Is], Used) ->
     used_vars_is(Is, Used);
 used_vars_is([#b_set{dst=Dst}=I|Is], Used0) ->
-    Used1 = sets:union(Used0, sets:from_list(beam_ssa:used(I), [{version, 2}])),
+    Used1 = list_set_union(beam_ssa:used(I), Used0),
     Used = sets:del_element(Dst, Used1),
     used_vars_is(Is, Used);
 used_vars_is([], Used) ->
@@ -1134,6 +1134,13 @@ used_vars_is([], Used) ->
 %%% Common utilities.
 %%%
 
+list_set_union([], Set) ->
+    Set;
+list_set_union([E], Set) ->
+    sets:add_element(E, Set);
+list_set_union(List, Set) ->
+    sets:union(sets:from_list(List, [{version, 2}]), Set).
+
 sub(#b_set{args=Args}=I, Sub) when map_size(Sub) =/= 0 ->
     I#b_set{args=[sub_arg(A, Sub) || A <- Args]};
 sub(I, _Sub) -> I.
diff --git a/lib/compiler/src/beam_ssa_opt.erl b/lib/compiler/src/beam_ssa_opt.erl
index 68445906fb..165330cfff 100644
--- a/lib/compiler/src/beam_ssa_opt.erl
+++ b/lib/compiler/src/beam_ssa_opt.erl
@@ -1299,7 +1299,7 @@ live_opt_phis(Is, L, Live0, LiveMap0) ->
             case [{P,V} || {#b_var{}=V,P} <- PhiArgs] of
                 [_|_]=PhiVars ->
                     PhiLive0 = rel2fam(PhiVars),
-                    PhiLive = [{{L,P},sets:union(sets:from_list(Vs, [{version, 2}]), Live0)} ||
+                    PhiLive = [{{L,P},list_set_union(Vs, Live0)} ||
                                   {P,Vs} <- PhiLive0],
                     maps:merge(LiveMap, maps:from_list(PhiLive));
                 [] ->
@@ -1309,7 +1309,7 @@ live_opt_phis(Is, L, Live0, LiveMap0) ->
     end.
 
 live_opt_blk(#b_blk{is=Is0,last=Last}=Blk, Live0) ->
-    Live1 = sets:union(Live0, sets:from_list(beam_ssa:used(Last), [{version, 2}])),
+    Live1 = list_set_union(beam_ssa:used(Last), Live0),
     {Is,Live} = live_opt_is(reverse(Is0), Live1, []),
     {Blk#b_blk{is=Is},Live}.
 
@@ -1359,8 +1359,7 @@ live_opt_is([#b_set{op={succeeded,guard},dst=SuccDst,args=[Dst]}=SuccI,
 live_opt_is([#b_set{dst=Dst}=I|Is], Live0, Acc) ->
     case sets:is_element(Dst, Live0) of
         true ->
-            LiveUsed = sets:from_list(beam_ssa:used(I), [{version, 2}]),
-            Live1 = sets:union(Live0, LiveUsed),
+            Live1 = list_set_union(beam_ssa:used(I), Live0),
             Live = sets:del_element(Dst, Live1),
             live_opt_is(Is, Live, [I|Acc]);
         false ->
@@ -1368,8 +1367,7 @@ live_opt_is([#b_set{dst=Dst}=I|Is], Live0, Acc) ->
                 true ->
                     live_opt_is(Is, Live0, Acc);
                 false ->
-                    LiveUsed = sets:from_list(beam_ssa:used(I), [{version, 2}]),
-                    Live = sets:union(Live0, LiveUsed),
+                    Live = list_set_union(beam_ssa:used(I), Live0),
                     live_opt_is(Is, Live, [I|Acc])
             end
     end;
@@ -1444,8 +1442,7 @@ do_reduce_try([{L, Blk} | Bs]=Bs0, Ws0) ->
                     %% This block does not execute any instructions
                     %% that would require a try. Analyze successors.
                     Successors = beam_ssa:successors(Blk),
-                    Ws = sets:union(sets:from_list(Successors, [{version, 2}]),
-                                         Ws1),
+                    Ws = list_set_union(Successors, Ws1),
                     [{L, Blk#b_blk{is=Is}} | do_reduce_try(Bs, Ws)];
                 unsafe ->
                     %% There is something unsafe in the block, for
@@ -3056,6 +3053,13 @@ is_tail_call_is([], _Bool, _Ret, _Acc) -> no.
 %%% Common utilities.
 %%%
 
+list_set_union([], Set) ->
+    Set;
+list_set_union([E], Set) ->
+    sets:add_element(E, Set);
+list_set_union(List, Set) ->
+    sets:union(sets:from_list(List, [{version, 2}]), Set).
+
 non_guards(Linear) ->
     gb_sets:from_list(non_guards_1(Linear)).
 
-- 
2.26.2

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File 2936-Slightly-optimize-union-of-a-short-list-and-a-set.patch of Package erlang (Revision b4f72044e1af8cfe32130ab849a401a1)

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