File 2871-Speed-up-beam_ssa_type-using-a-metadata-ca... of Package erlang

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File 2871-Speed-up-beam_ssa_type-using-a-metadata-cache.patch of Package erlang

From 880eb62e69841938e00426c6c311fbc03f8fbded Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Mon, 6 Sep 2021 13:21:34 +0200
Subject: [PATCH 1/2] Speed up beam_ssa_type using a metadata cache

The `beam_ssa_type:opt_start/2` optimizing pass processes each
function at least twice. Each time it recalculates the same metadata
for the function.

Caching the metadata so that it only calculated once for each function
will speed up compilation. On my computer, the running time of the
`beam_ssa_opt` pass when compiling a version of Elixir's
`String.Unicode` module was reduced by about half a second, from
roughly 5 seconds down to 4.5 seconds.
---
 lib/compiler/src/beam_ssa_type.erl | 91 +++++++++++++++++++-----------
 1 file changed, 57 insertions(+), 34 deletions(-)

diff --git a/lib/compiler/src/beam_ssa_type.erl b/lib/compiler/src/beam_ssa_type.erl
index 6a04d11b37..d3bb6df878 100644
--- a/lib/compiler/src/beam_ssa_type.erl
+++ b/lib/compiler/src/beam_ssa_type.erl
@@ -60,35 +60,37 @@
         { func_id :: func_id(),
           limit_return :: boolean(),
           params :: [beam_ssa:b_var()],
-          used_once :: sets:set(beam_ssa:b_var()) }).
+          used_once :: #{beam_ssa:b_var() => _ } }).
 
+-type metadata() :: #metadata{}.
+-type meta_cache() :: #{ func_id() => metadata() }.
 -type type_db() :: #{ beam_ssa:var_name() := type() }.
 
 %%
 
 -spec opt_start(term(), term()) -> term().
 opt_start(StMap, FuncDb0) when FuncDb0 =/= #{} ->
-    {ArgDb, FuncDb} = signatures(StMap, FuncDb0),
+    {ArgDb, MetaCache, FuncDb} = signatures(StMap, FuncDb0),
 
-    opt_start_1(maps:keys(StMap), ArgDb, StMap, FuncDb);
+    opt_start_1(maps:keys(StMap), ArgDb, StMap, FuncDb, MetaCache);
 opt_start(StMap, FuncDb) ->
     %% Module-level analysis is disabled, likely because of a call to
     %% load_nif/2 or similar. opt_continue/4 will assume that all arguments and
     %% return types are 'any'.
     {StMap, FuncDb}.
 
-opt_start_1([Id | Ids], ArgDb, StMap0, FuncDb0) ->
+opt_start_1([Id | Ids], ArgDb, StMap0, FuncDb0, MetaCache) ->
     case ArgDb of
         #{ Id := ArgTypes } ->
             #opt_st{ssa=Linear0,args=Args} = St0 = map_get(Id, StMap0),
 
             Ts = maps:from_list(zip(Args, ArgTypes)),
-            {Linear, FuncDb} = opt_function(Linear0, Args, Id, Ts, FuncDb0),
+            {Linear, FuncDb} = opt_function(Linear0, Args, Id, Ts, FuncDb0, MetaCache),
 
             St = St0#opt_st{ssa=Linear},
             StMap = StMap0#{ Id := St },
 
-            opt_start_1(Ids, ArgDb, StMap, FuncDb);
+            opt_start_1(Ids, ArgDb, StMap, FuncDb, MetaCache);
         #{} ->
             %% Unreachable functions must be removed so that opt_continue/4
             %% won't process them and potentially taint the argument types of
@@ -96,9 +98,9 @@ opt_start_1([Id | Ids], ArgDb, StMap0, FuncDb0) ->
             StMap = maps:remove(Id, StMap0),
             FuncDb = maps:remove(Id, FuncDb0),
 
-            opt_start_1(Ids, ArgDb, StMap, FuncDb)
+            opt_start_1(Ids, ArgDb, StMap, FuncDb, MetaCache)
     end;
-opt_start_1([], _CommittedArgs, StMap, FuncDb) ->
+opt_start_1([], _CommittedArgs, StMap, FuncDb, _MetaCache) ->
     {StMap, FuncDb}.
 
 %%
@@ -124,12 +126,13 @@ opt_start_1([], _CommittedArgs, StMap, FuncDb) ->
 -record(sig_st,
         { wl = wl_new() :: worklist(),
           committed = #{} :: #{ func_id() => [type()] },
-          updates = #{} :: #{ func_id() => [type()] }}).
+          updates = #{} :: #{ func_id() => [type()] },
+          meta_cache = #{} :: meta_cache()}).
 
 signatures(StMap, FuncDb0) ->
     State0 = init_sig_st(StMap, FuncDb0),
     {State, FuncDb} = signatures_1(StMap, FuncDb0, State0),
-    {State#sig_st.committed, FuncDb}.
+    {State#sig_st.committed, State#sig_st.meta_cache, FuncDb}.
 
 signatures_1(StMap, FuncDb0, State0) ->
     case wl_next(State0#sig_st.wl) of
@@ -203,11 +206,11 @@ sig_function_1(Id, StMap, State0, FuncDb) ->
     Ls = #{ ?EXCEPTION_BLOCK => {incoming, Ts},
             0 => {incoming, Ts} },
 
-    Meta = init_metadata(Id, Linear, Args),
+    {Meta, State2} = sig_init_metadata(Id, Linear, Args, State1),
 
     Wl0 = State1#sig_st.wl,
 
-    {State, SuccTypes} = sig_bs(Linear, Ds, Ls, FuncDb, #{}, [], Meta, State1),
+    {State, SuccTypes} = sig_bs(Linear, Ds, Ls, FuncDb, #{}, [], Meta, State2),
 
     WlChanged = wl_changed(Wl0, State#sig_st.wl),
     #{ Id := #func_info{succ_types=SuccTypes0}=Entry0 } = FuncDb,
@@ -220,6 +223,17 @@ sig_function_1(Id, StMap, State0, FuncDb) ->
             {true, WlChanged, State, FuncDb#{ Id := Entry }}
     end.
 
+%% Get the metadata for a function. If this function has been analysed
+%% previously, retrieve the previously calculated metadata.
+sig_init_metadata(Id, Linear, Args, #sig_st{meta_cache=MetaCache} = State) ->
+    case MetaCache of
+        #{Id := Meta} ->
+            {Meta, State};
+        #{} ->
+            Meta = init_metadata(Id, Linear, Args),
+            {Meta, State#sig_st{meta_cache=MetaCache#{Id => Meta}}}
+    end.
+
 sig_bs([{L, #b_blk{is=Is,last=Last0}} | Bs],
        Ds0, Ls0, Fdb, Sub0, SuccTypes0, Meta, State0) ->
     case Ls0 of
@@ -413,23 +427,28 @@ join_arg_types([], [], Ts) ->
 
 %%
 %% Optimizes a function based on the type information inferred by signatures/2
-%% and earlier runs of opt_function/5.
+%% and earlier runs of opt_function/5,6.
 %%
 %% This is pretty straightforward as it only walks through each function once,
 %% and because it only makes types narrower it's safe to optimize the functions
 %% in any order or not at all.
 %%
 
--spec opt_function(Linear, Args, Id, Ts, FuncDb) -> Result when
+opt_function(Linear, Args, Id, Ts, FuncDb) ->
+    MetaCache = #{},
+    opt_function(Linear, Args, Id, Ts, FuncDb, MetaCache).
+
+-spec opt_function(Linear, Args, Id, Ts, FuncDb, MetaCache) -> Result when
       Linear :: [{non_neg_integer(), beam_ssa:b_blk()}],
       Args :: [beam_ssa:b_var()],
       Id :: func_id(),
       Ts :: type_db(),
       FuncDb :: func_info_db(),
-      Result :: {Linear, FuncDb}.
-opt_function(Linear, Args, Id, Ts, FuncDb) ->
+      Result :: {Linear, FuncDb},
+      MetaCache :: meta_cache().
+opt_function(Linear, Args, Id, Ts, FuncDb, MetaCache) ->
     try
-        do_opt_function(Linear, Args, Id, Ts, FuncDb)
+        do_opt_function(Linear, Args, Id, Ts, FuncDb, MetaCache)
     catch
         Class:Error:Stack ->
             #b_local{name=#b_literal{val=Name},arity=Arity} = Id,
@@ -437,7 +456,7 @@ opt_function(Linear, Args, Id, Ts, FuncDb) ->
             erlang:raise(Class, Error, Stack)
     end.
 
-do_opt_function(Linear0, Args, Id, Ts, FuncDb0) ->
+do_opt_function(Linear0, Args, Id, Ts, FuncDb0, MetaCache) ->
     FakeCall = #b_set{op=call,args=[#b_remote{mod=#b_literal{val=unknown},
                                               name=#b_literal{val=unknown},
                                               arity=0}]},
@@ -448,7 +467,12 @@ do_opt_function(Linear0, Args, Id, Ts, FuncDb0) ->
     Ls = #{ ?EXCEPTION_BLOCK => {incoming, Ts},
             0 => {incoming, Ts} },
 
-    Meta = init_metadata(Id, Linear0, Args),
+    Meta = case MetaCache of
+               #{Id := Meta0} ->
+                   Meta0;
+               #{} ->
+                   init_metadata(Id, Linear0, Args)
+           end,
 
     {Linear, FuncDb, SuccTypes} =
         opt_bs(Linear0, Ds, Ls, FuncDb0, #{}, [], Meta, []),
@@ -1621,7 +1645,7 @@ update_successors(#b_br{bool=#b_literal{val=true},succ=Succ}=Last,
     {Last, update_successor(Succ, Ts, Ls)};
 update_successors(#b_br{bool=#b_var{}=Bool,succ=Succ,fail=Fail}=Last0,
                   Ts, Ds, Ls0, UsedOnce) ->
-    IsTempVar = sets:is_element(Bool, UsedOnce),
+    IsTempVar = is_map_key(Bool, UsedOnce),
     case infer_types_br(Bool, Ts, IsTempVar, Ds) of
         {#{}=SuccTs, #{}=FailTs} ->
             Ls1 = update_successor(Succ, SuccTs, Ls0),
@@ -1636,7 +1660,7 @@ update_successors(#b_br{bool=#b_var{}=Bool,succ=Succ,fail=Fail}=Last0,
     end;
 update_successors(#b_switch{arg=#b_var{}=V,fail=Fail0,list=List0}=Last0,
                   Ts, Ds, Ls0, UsedOnce) ->
-    IsTempVar = sets:is_element(V, UsedOnce),
+    IsTempVar = is_map_key(V, UsedOnce),
 
     {List1, FailTs, Ls1} =
         update_switch(List0, V, raw_type(V, Ts), Ts, Ds, Ls0, IsTempVar, []),
@@ -2205,9 +2229,8 @@ gcd(A, B) ->
 %%%
 
 init_metadata(FuncId, Linear, Params) ->
-    {RetCounter, Map0} = init_metadata_1(reverse(Linear), 0, #{}),
-    Map = maps:without(Params, Map0),
-    UsedOnce = sets:from_list(maps:keys(Map), [{version, 2}]),
+    {RetCounter, UsedOnce0} = init_metadata_1(reverse(Linear), 0, #{}),
+    UsedOnce = maps:without(Params, UsedOnce0),
 
     #metadata{ func_id = FuncId,
                limit_return = (RetCounter >= ?RETURN_LIMIT),
@@ -2222,11 +2245,11 @@ init_metadata_1([{L,#b_blk{is=Is,last=Last}} | Bs], RetCounter0, Uses0) ->
                      _ -> RetCounter0
                  end,
 
-    %% Calculate the set of variables that are only used once in the terminator
-    %% of the block that defines them. That will allow us to discard type
-    %% information discard type information for variables that will never be
-    %% referenced by the successor blocks, potentially improving compilation
-    %% times.
+    %% Calculate the set of variables that are only used once in the
+    %% terminator of the block that defines them. That will allow us
+    %% to discard type information for variables that will never be
+    %% referenced by the successor blocks, potentially improving
+    %% compilation times.
 
     Uses1 = used_once_last_uses(beam_ssa:used(Last), L, Uses0),
     Uses = used_once_2(reverse(Is), L, Uses1),
@@ -2237,7 +2260,7 @@ init_metadata_1([], RetCounter, Uses) ->
 used_once_2([#b_set{dst=Dst}=I|Is], L, Uses0) ->
     Uses = used_once_uses(beam_ssa:used(I), L, Uses0),
     case Uses of
-        #{Dst:=[L]} ->
+        #{Dst:=L} ->
             used_once_2(Is, L, Uses);
         #{} ->
             %% Used more than once or used once in
@@ -2259,15 +2282,15 @@ used_once_uses([], _, Uses) -> Uses.
 
 used_once_last_uses([V|Vs], L, Uses) ->
     case Uses of
-        #{V:=[_]} ->
-            %% Second time this variable is used.
-            used_once_last_uses(Vs, L, Uses#{V:=more_than_once});
         #{V:=more_than_once} ->
             %% Used at least twice before.
             used_once_last_uses(Vs, L, Uses);
+        #{V:=_} ->
+            %% Second time this variable is used.
+            used_once_last_uses(Vs, L, Uses#{V:=more_than_once});
         #{} ->
             %% First time this variable is used.
-            used_once_last_uses(Vs, L, Uses#{V=>[L]})
+            used_once_last_uses(Vs, L, Uses#{V=>L})
     end;
 used_once_last_uses([], _, Uses) -> Uses.
 
-- 
2.31.1

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