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authorBjörn Gustavsson <[email protected]>2015-09-22 10:40:06 +0200
committerBjörn Gustavsson <[email protected]>2015-09-28 10:26:39 +0200
commit105c5b0071056dc062797e58772e098d2a3a4627 (patch)
tree4fee14610caff25589ea27bad9b4fc37991681d0
parent58a0c1c6c7efdb1f1250edec1b5fcd5eb72e99b9 (diff)
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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.
-rw-r--r--lib/compiler/src/beam_dead.erl7
1 files 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) ->