From b66193afc3fe85072da4631c52c5ccec136caa05 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Wed, 23 Sep 2015 12:30:16 +0200
Subject: beam_type: Improve optimizations by keeping track of booleans

There is an optimization in beam_block to simplify a select_val
on a known boolean value. We can implement this optimization
in a cleaner way in beam_type and it will also be applicable
in more situations. (When I added the optimization to beam_type
without removing the optimization from beam_block, the optimization
was applied 66 times.)
---
 lib/compiler/src/beam_type.erl | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

(limited to 'lib/compiler/src/beam_type.erl')

diff --git a/lib/compiler/src/beam_type.erl b/lib/compiler/src/beam_type.erl
index 17ce7082f6..4b45c28623 100644
--- a/lib/compiler/src/beam_type.erl
+++ b/lib/compiler/src/beam_type.erl
@@ -95,6 +95,11 @@ simplify_basic_1([{set,[D],[TupleReg],{get_tuple_element,0}}=I|Is0], Ts0, Acc) -
     end;
 simplify_basic_1([{set,_,_,{try_catch,_,_}}=I|Is], _Ts, Acc) ->
     simplify_basic_1(Is, tdb_new(), [I|Acc]);
+simplify_basic_1([{test,is_atom,_,[R]}=I|Is], Ts, Acc) ->
+    case tdb_find(R, Ts) of
+	boolean -> simplify_basic_1(Is, Ts, Acc);
+	_ -> simplify_basic_1(Is, Ts, [I|Acc])
+    end;
 simplify_basic_1([{test,is_integer,_,[R]}=I|Is], Ts, Acc) ->
     case tdb_find(R, Ts) of
 	integer -> simplify_basic_1(Is, Ts, Acc);
@@ -148,6 +153,8 @@ simplify_basic_1([{select,select_val,Reg,_,_}=I0|Is], Ts, Acc) ->
     I = case tdb_find(Reg, Ts) of
 	    {integer,Range} ->
 		simplify_select_val_int(I0, Range);
+	    boolean ->
+		simplify_select_val_bool(I0);
 	    _ ->
 		I0
 	end,
@@ -166,6 +173,15 @@ simplify_select_val_int({select,select_val,R,_,L0}=I, {Min,Max}) ->
 	true -> simplify_select_val_1(L0, {integer,Max}, R, [])
     end.
 
+simplify_select_val_bool({select,select_val,R,_,L}=I) ->
+    Vs = sort([V || {atom,V} <- L]),
+    case Vs of
+	[false,true] ->
+	    simplify_select_val_1(L, {atom,false}, R, []);
+	_ ->
+	    I
+    end.
+
 simplify_select_val_1([Val,F|T], Val, R, Acc) ->
     L = reverse(Acc, T),
     {select,select_val,R,F,L};
@@ -414,6 +430,17 @@ update({set,[D],[{integer,I},Reg],{bif,element,_}}, Ts0) ->
     tdb_update([{Reg,{tuple,I,[]}},{D,kill}], Ts0);
 update({set,[D],[_Index,Reg],{bif,element,_}}, Ts0) ->
     tdb_update([{Reg,{tuple,0,[]}},{D,kill}], Ts0);
+update({set,[D],Args,{bif,N,_}}, Ts0) ->
+    Ar = length(Args),
+    BoolOp = erl_internal:new_type_test(N, Ar) orelse
+	erl_internal:comp_op(N, Ar) orelse
+	erl_internal:bool_op(N, Ar),
+    case BoolOp of
+	true ->
+	    tdb_update([{D,boolean}], Ts0);
+	false ->
+	    tdb_update([{D,kill}], Ts0)
+    end;
 update({set,[D],[S],{get_tuple_element,0}}, Ts) ->
     tdb_update([{D,{tuple_element,S,0}}], Ts);
 update({set,[D],[S],{alloc,_,{gc_bif,float,{f,0}}}}, Ts0) ->
@@ -828,6 +855,7 @@ merge_type_info(NewType, _) ->
     verify_type(NewType),
     NewType.
 
+verify_type(boolean) -> ok;
 verify_type(integer) -> ok;
 verify_type({integer,{Min,Max}})
   when is_integer(Min), is_integer(Max) -> ok;
-- 
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