sys_core_fold: Improve optimization of 'not'

Optimize away 'not' in sys_core_fold instead of in beam_block
and beam_dead, as we can do a better job in sys_core_fold.

I modified the test suite temporarily to never turn off Core Erlang
modifications and looked at the coverage. With the new optimizations
active in sys_core_fold, the code in beam_block and beam_dead did not
find a single 'not' that it could optimize.  That proves that the new
optimization is at least as good as the old one. Manually, I could
also verify that the new optimization would optimize some variations
of 'not' that the old one would not handle.

1 files changed, 2 insertions, 14 deletions

diff --git a/lib/compiler/src/beam_dead.erl b/lib/compiler/src/beam_dead.erl
index 7cd07dc3be..7f28575a65 100644
--- a/lib/compiler/src/beam_dead.erl
+++ b/lib/compiler/src/beam_dead.erl
@@ -234,10 +234,8 @@ backward([{select,select_val,Reg,{f,Fail0},List0}|Is], D, Acc) ->
     Fail = shortcut_bs_test(Fail1, Is, D),
     Sel = {select,select_val,Reg,{f,Fail},List},
     backward(Is, D, [Sel|Acc]);
-backward([{jump,{f,To0}},{move,Src0,Reg}|Is], D, Acc) ->
-    To1 = shortcut_select_label(To0, Reg, Src0, D),
-    {To,Src} = shortcut_boolean_label(To1, Reg, Src0, D),
-    Move = {move,Src,Reg},
+backward([{jump,{f,To0}},{move,Src,Reg}=Move|Is], D, Acc) ->
+    To = shortcut_select_label(To0, Reg, Src, D),
     Jump = {jump,{f,To}},
     case beam_utils:is_killed_at(Reg, To, D) of
 	false -> backward([Move|Is], D, [Jump|Acc]);
@@ -330,16 +328,6 @@ shortcut_label(To0, D) ->
 shortcut_select_label(To, Reg, Lit, D) ->
     shortcut_rel_op(To, is_ne_exact, [Reg,Lit], D).
 
-shortcut_boolean_label(To0, Reg, {atom,Bool0}=Lit, D) when is_boolean(Bool0) ->
-    case beam_utils:code_at(To0, D) of
-	[{line,_},{bif,'not',_,[Reg],Reg},{jump,{f,To}}|_] ->
-	    Bool = {atom,not Bool0},
-	    {shortcut_select_label(To, Reg, Bool, D),Bool};
-	_ ->
-	    {To0,Lit}
-    end;
-shortcut_boolean_label(To, _, Bool, _) -> {To,Bool}.
-
 %% Replace a comparison operator with a test instruction and a jump.
 %% For example, if we have this code:
 %%