From 456ba65161d9228a2562d32bd25b0a15c90011b8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Wed, 26 Oct 2016 12:58:38 +0200
Subject: sys_core_fold: Use less effort optimizing not in lets

There are two calls opt_not_in_let(). Since 05130e4855
introduced iteration to a fixpoint, only the first call
is needed. Removing the redundant call will slightly speed
up compilation.
---
 lib/compiler/src/sys_core_fold.erl | 23 +++++++----------------
 1 file changed, 7 insertions(+), 16 deletions(-)

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

diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index 7c233b323b..5d7fd37270 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -2151,7 +2151,7 @@ letify(Bs, Body) ->
 -spec opt_not_in_let(cerl:c_let()) -> cerl:cerl().
 
 opt_not_in_let(#c_let{vars=[_]=Vs0,arg=Arg0,body=Body0}=Let) ->
-    case opt_not_in_let(Vs0, Arg0, Body0) of
+    case opt_not_in_let_0(Vs0, Arg0, Body0) of
 	{[],#c_values{es=[]},Body} ->
 	    Body;
 	{Vs,Arg,Body} ->
@@ -2159,13 +2159,7 @@ opt_not_in_let(#c_let{vars=[_]=Vs0,arg=Arg0,body=Body0}=Let) ->
     end;
 opt_not_in_let(Let) -> Let.
 
-%% opt_not_in_let(Vs, Arg, Body) -> {Vs',Arg',Body'}
-%%  Try to optimize away a 'not' operator in a 'let'.
-
--spec opt_not_in_let([cerl:c_var()], cerl:cerl(), cerl:cerl()) ->
-			    {[cerl:c_var()],cerl:cerl(),cerl:cerl()}.
-
-opt_not_in_let([#c_var{name=V}]=Vs0, Arg0, Body0) ->
+opt_not_in_let_0([#c_var{name=V}]=Vs0, Arg0, Body0) ->
     case cerl:type(Body0) of
 	call ->
 	    %% let <V> = Expr in not V  ==>
@@ -2196,9 +2190,7 @@ opt_not_in_let([#c_var{name=V}]=Vs0, Arg0, Body0) ->
 	    end;
 	_ ->
 	    {Vs0,Arg0,Body0}
-    end;
-opt_not_in_let(Vs, Arg, Body) ->
-    {Vs,Arg,Body}.
+    end.
 
 opt_not_in_let_1(V, Call, Body) ->
     case Call of
@@ -2652,11 +2644,10 @@ opt_simple_let_0(#c_let{arg=Arg0}=Let, Ctxt, Sub) ->
 
 opt_simple_let_1(#c_let{vars=Vs0,body=B0}=Let, Arg0, Ctxt, Sub0) ->
     %% Optimise let and add new substitutions.
-    {Vs1,Args,Sub1} = let_substs(Vs0, Arg0, Sub0),
-    BodySub = update_let_types(Vs1, Args, Sub1),
-    B1 = body(B0, Ctxt, BodySub),
-    Arg1 = core_lib:make_values(Args),
-    {Vs,Arg,B} = opt_not_in_let(Vs1, Arg1, B1),
+    {Vs,Args,Sub1} = let_substs(Vs0, Arg0, Sub0),
+    BodySub = update_let_types(Vs, Args, Sub1),
+    B = body(B0, Ctxt, BodySub),
+    Arg = core_lib:make_values(Args),
     opt_simple_let_2(Let, Vs, Arg, B, B0, Ctxt, Sub1).
 
 opt_simple_let_2(Let0, Vs0, Arg0, Body, PrevBody, Ctxt, Sub) ->
-- 
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