From 9814a205a2cf9e1024261e2eee80e460e78600d0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Wed, 16 Jan 2019 19:31:22 +0100
Subject: beam_ssa_opt: Run the type optimization pass twice

The code will be significantly improved by running the
type optimization pass twice.

The ssa_opt_misc pass can be eliminated because everything it does
is also done by the type optimization pass.
---
 lib/compiler/src/beam_ssa_opt.erl | 102 ++++----------------------------------
 1 file changed, 9 insertions(+), 93 deletions(-)

(limited to 'lib/compiler/src')

diff --git a/lib/compiler/src/beam_ssa_opt.erl b/lib/compiler/src/beam_ssa_opt.erl
index e23e62b5ad..df40c918b2 100644
--- a/lib/compiler/src/beam_ssa_opt.erl
+++ b/lib/compiler/src/beam_ssa_opt.erl
@@ -22,7 +22,7 @@
 -export([module/2]).
 
 -include("beam_ssa.hrl").
--import(lists, [all/2,append/1,foldl/3,keyfind/3,member/2,
+-import(lists, [append/1,foldl/3,keyfind/3,member/2,
                 reverse/1,reverse/2,
                 splitwith/2,takewhile/2,unzip/1]).
 
@@ -55,9 +55,13 @@ passes(Opts0) ->
           ?PASS(ssa_opt_record),
 
           %% Run ssa_opt_cse twice, because it will help ssa_opt_dead,
-          %% and ssa_opt_dead will help ssa_opt_cse. Run ssa_opt_live
-          %% twice, because it will help ssa_opt_dead and ssa_opt_dead
-          %% will help ssa_opt_live.
+          %% and ssa_opt_dead will help ssa_opt_cse.
+          %%
+          %% Run ssa_opt_live twice, because it will help ssa_opt_dead
+          %% and ssa_opt_dead will help ssa_opt_live.
+          %%
+          %% Run beam_ssa_type twice, because there will be more
+          %% opportunities for optimizations after running beam_ssa_dead.
           ?PASS(ssa_opt_cse),
           ?PASS(ssa_opt_type),
           ?PASS(ssa_opt_live),
@@ -65,12 +69,12 @@ passes(Opts0) ->
           ?PASS(ssa_opt_dead),
           ?PASS(ssa_opt_cse),                   %Second time.
           ?PASS(ssa_opt_float),
+          ?PASS(ssa_opt_type),                  %Second time.
           ?PASS(ssa_opt_live),                  %Second time.
 
           ?PASS(ssa_opt_bsm),
           ?PASS(ssa_opt_bsm_units),
           ?PASS(ssa_opt_bsm_shortcut),
-          ?PASS(ssa_opt_misc),
           ?PASS(ssa_opt_tuple_size),
           ?PASS(ssa_opt_sw),
           ?PASS(ssa_opt_blockify),
@@ -1345,94 +1349,6 @@ opt_bs_put_split_int_1(Int, L, R) ->
             opt_bs_put_split_int_1(Int, Mid + 1, R)
     end.
 
-%%%
-%%% Miscellanous optimizations in execution order.
-%%%
-
-ssa_opt_misc(#st{ssa=Linear}=St) ->
-    St#st{ssa=misc_opt(Linear, #{})}.
-
-misc_opt([{L,#b_blk{is=Is0,last=Last0}=Blk0}|Bs], Sub0) ->
-    {Is,Sub} = misc_opt_is(Is0, Sub0, []),
-    Last = sub(Last0, Sub),
-    Blk = Blk0#b_blk{is=Is,last=Last},
-    [{L,Blk}|misc_opt(Bs, Sub)];
-misc_opt([], _) -> [].
-
-misc_opt_is([#b_set{op=phi}=I0|Is], Sub0, Acc) ->
-    #b_set{dst=Dst,args=Args} = I = sub(I0, Sub0),
-    case all_same(Args) of
-        true ->
-            %% Eliminate the phi node if there is just one source
-            %% value or if the values are identical.
-            [{Val,_}|_] = Args,
-            Sub = Sub0#{Dst=>Val},
-            misc_opt_is(Is, Sub, Acc);
-        false ->
-            misc_opt_is(Is, Sub0, [I|Acc])
-    end;
-misc_opt_is([#b_set{op={bif,'and'}}=I0], Sub, Acc) ->
-    #b_set{dst=Dst,args=Args} = I = sub(I0, Sub),
-    case eval_and(Args) of
-        error ->
-            misc_opt_is([], Sub, [I|Acc]);
-        Val ->
-            misc_opt_is([], Sub#{Dst=>Val}, Acc)
-    end;
-misc_opt_is([#b_set{op={bif,'or'}}=I0], Sub, Acc) ->
-    #b_set{dst=Dst,args=Args} = I = sub(I0, Sub),
-    case eval_or(Args) of
-        error ->
-            misc_opt_is([], Sub, [I|Acc]);
-        Val ->
-            misc_opt_is([], Sub#{Dst=>Val}, Acc)
-    end;
-misc_opt_is([#b_set{}=I0|Is], Sub, Acc) ->
-    #b_set{op=Op,dst=Dst,args=Args} = I = sub(I0, Sub),
-    case make_literal(Op, Args) of
-        #b_literal{}=Literal ->
-            misc_opt_is(Is, Sub#{Dst=>Literal}, Acc);
-        error ->
-            misc_opt_is(Is, Sub, [I|Acc])
-    end;
-misc_opt_is([], Sub, Acc) ->
-    {reverse(Acc),Sub}.
-
-all_same([{H,_}|T]) ->
-    all(fun({E,_}) -> E =:= H end, T).
-
-make_literal(put_tuple, Args) ->
-    case make_literal_list(Args, []) of
-        error ->
-            error;
-        List ->
-            #b_literal{val=list_to_tuple(List)}
-    end;
-make_literal(put_list, [#b_literal{val=H},#b_literal{val=T}]) ->
-    #b_literal{val=[H|T]};
-make_literal(_, _) -> error.
-
-make_literal_list([#b_literal{val=H}|T], Acc) ->
-    make_literal_list(T, [H|Acc]);
-make_literal_list([_|_], _) ->
-    error;
-make_literal_list([], Acc) ->
-    reverse(Acc).
-
-eval_and(Args) ->
-    case Args of
-        [_,#b_literal{val=false}=Res] -> Res;
-        [Res,#b_literal{val=true}] -> Res;
-        [_,_] -> error
-    end.
-
-eval_or(Args) ->
-    case Args of
-        [Res,#b_literal{val=false}] -> Res;
-        [_,#b_literal{val=true}=Res] -> Res;
-        [_,_] -> error
-    end.
-
 %%%
 %%% Optimize expressions such as "tuple_size(Var) =:= 2".
 %%%
-- 
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