From 4c76ea1116faa3efd797c39539131b9262b6fa36 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Sat, 12 Nov 2016 12:31:31 +0100 Subject: beam_dead: Remove redundant 'or' instruction In practice, this optimization will only apply to contrived guards that are almost never used in real applications. The only reason we add this optimization is to help approach the goal of zero tolerance for 'bif' instructions instead of 'test' instructions in guards. --- lib/compiler/src/beam_dead.erl | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/lib/compiler/src/beam_dead.erl b/lib/compiler/src/beam_dead.erl index 8ea949425e..9087586b58 100644 --- a/lib/compiler/src/beam_dead.erl +++ b/lib/compiler/src/beam_dead.erl @@ -379,6 +379,14 @@ backward([{kill,_}=I|Is], D, [{line,_},Exit|_]=Acc) -> false -> backward(Is, D, [I|Acc]); true -> backward(Is, D, Acc) end; +backward([{bif,'or',{f,To0},[Dst,{atom,false}],Dst}=I|Is], D, + [{test,is_eq_exact,{f,To},[Dst,{atom,true}]}|_]=Acc) -> + case shortcut_label(To0, D) of + To -> + backward(Is, D, Acc); + _ -> + backward(Is, D, [I|Acc]) + end; backward([I|Is], D, Acc) -> backward(Is, D, [I|Acc]); backward([], _D, Acc) -> Acc. @@ -397,6 +405,8 @@ shortcut_select_list([Lit,{f,To0}|T], Reg, D, Acc) -> shortcut_select_list(T, Reg, D, [{f,To},Lit|Acc]); shortcut_select_list([], _, _, Acc) -> reverse(Acc). +shortcut_label(0, _) -> + 0; shortcut_label(To0, D) -> case beam_utils:code_at(To0, D) of [{jump,{f,To}}|_] -> shortcut_label(To, D); -- cgit v1.2.3