From 105c5b0071056dc062797e58772e098d2a3a4627 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Tue, 22 Sep 2015 10:40:06 +0200 Subject: beam_dead: Improve optimization of literal binary matching When the bit syntax is used to match a single binary literal, the bit syntax instructions will be replaced with a comparison to a binary literal. The only problem is that the bs_context_to_binary instruction will not be eliminated. Example: f(<<"string">>) -> ok. This function would be translated to: {function, f, 1, 2}. {label,1}. {line,...}. {func_info,...}. {label,2}. {test,is_eq_exact,{f,3},[{x,0},{literal,<<"string">>}]}. {move,{atom,ok},{x,0}}. return. {label,3}. {bs_context_to_binary,{x,0}}. {jump,{f,1}}. The bs_context_to_binary instruction serves no useful purpose, since {x,0} can never be a match context. Eliminating the instruction, the resulting code will be: {function, f, 1, 2}. {label,1}. {line,...}. {func_info,...}. {label,2}. {test,is_eq_exact,{f,1},[{x,0},{literal,<<"string">>}]}. {move,{atom,ok},{x,0}}. return. --- lib/compiler/src/beam_dead.erl | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/lib/compiler/src/beam_dead.erl b/lib/compiler/src/beam_dead.erl index fcd108bd89..11129c39bc 100644 --- a/lib/compiler/src/beam_dead.erl +++ b/lib/compiler/src/beam_dead.erl @@ -272,14 +272,17 @@ backward([{jump,{f,To}}=J|[{bif,Op,_,Ops,Reg}|Is]=Is0], D, Acc) -> catch throw:not_possible -> backward(Is0, D, [J|Acc]) end; -backward([{test,bs_start_match2,F,_,[R,_],Ctxt}=I|Is], D, +backward([{test,bs_start_match2,F,Live,[R,_]=Args,Ctxt}|Is], D, [{test,bs_match_string,F,[Ctxt,Bs]}, {test,bs_test_tail2,F,[Ctxt,0]}|Acc0]=Acc) -> + {f,To0} = F, + To = shortcut_bs_start_match(To0, R, D), case beam_utils:is_killed(Ctxt, Acc0, D) of true -> - Eq = {test,is_eq_exact,F,[R,{literal,Bs}]}, + Eq = {test,is_eq_exact,{f,To},[R,{literal,Bs}]}, backward(Is, D, [Eq|Acc0]); false -> + I = {test,bs_start_match2,{f,To},Live,Args,Ctxt}, backward(Is, D, [I|Acc]) end; backward([{test,bs_start_match2,{f,To0},Live,[Src|_]=Info,Dst}|Is], D, Acc) -> -- cgit v1.2.3