Merge pull request #10252 from bjorng/bjorn/compiler/fix-bottlenecks/OTP-19797

Fix two bottlenecks in the compiler

Author: bjorng

lib/compiler/src/beam_core_to_ssa.erl

@@ -2599,8 +2599,14 @@ select_val_cg(Type, R, Vls, Tf, Vf, Sis, St0) ->
             {TypeIs++[#b_switch{arg=R,fail=Vf,list=Vls}|Sis],St1}
     end.
 
-combine([{Is,Vs1},{Is,Vs2}|Vis]) -> combine([{Is,Vs1 ++ Vs2}|Vis]);
-combine([V|Vis]) -> [V|combine(Vis)];
+
+combine([V|Vis0]) ->
+    case {V, combine(Vis0)} of
+        {{Is,Vs1}, [{Is,Vs2}|Vis]} ->
+            [{Is,Vs1 ++ Vs2}|Vis];
+        {_,Vis} ->
+            [V|Vis]
+    end;
 combine([]) -> [].
 
 select_labels([{Is,Vs}|Vis], St0, Vls, Sis) ->

lib/stdlib/src/erl_lint.erl

@@ -3988,7 +3988,7 @@ icrt_export([{V,{{export,_},_,_}}|Vs0], [{V,{{export,_}=S0,_,As}}|Vt],
     %% V was an exported variable and has been used in an expression in at least
     %% one clause. Its state needs to be merged from all clauses to silence any
     %% exported var warning already emitted.
-    {VVs,Vs} = lists:partition(fun ({K,_}) -> K =:= V end, Vs0),
+    {VVs,Vs} = lists:splitwith(fun ({K,_}) -> K =:= V end, Vs0),
     S = foldl(fun ({_,{S1,_,_}}, AccS) -> merge_state(AccS, S1) end, S0, VVs),
     icrt_export(Vs, Vt, In, I, [{V,{S,used,As}}|Acc]);
 icrt_export([{V,_}|Vs0], [{V,{_,_,As}}|Vt], In, I, Acc) ->
@@ -4003,7 +4003,7 @@ icrt_export([{V1,_}|_]=Vs, [{V2,_}|Vt], In, I, Acc) when V1 > V2 ->
     icrt_export(Vs, Vt, In, I, Acc);
 icrt_export([{V,_}|_]=Vs0, Vt, In, I, Acc) ->
     %% V is a new variable.
-    {VVs,Vs} = lists:partition(fun ({K,_}) -> K =:= V end, Vs0),
+    {VVs,Vs} = lists:splitwith(fun ({K,_}) -> K =:= V end, Vs0),
     F = fun ({_,{S,U,As}}, {AccI,AccS0,AccAs0}) ->
                 AccS = case {S,AccS0} of
                            {{unsafe,_},{unsafe,_}} ->