File 2062-Reinstate-optimization-of-binary-literal-m... of Package erlang

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File 2062-Reinstate-optimization-of-binary-literal-matching.patch of Package erlang

From a66a2e84ec4c6fb7c19affe43134570caabe8569 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Fri, 19 Aug 2016 14:07:38 +0200
Subject: [PATCH 2/2] Reinstate optimization of binary literal matching

105c5b0071 was reverted in dd1162846e because clauses that were
supposed to match would not match. (See 8b83bc0b.)

Reintroduce the optimization, but make sure that we only shortcut
bs_context_to_binary instructions and not bs_start_match2 instructions.
---
 lib/compiler/src/beam_dead.erl | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/lib/compiler/src/beam_dead.erl b/lib/compiler/src/beam_dead.erl
index 6f6d742..3606af9 100644
--- a/lib/compiler/src/beam_dead.erl
+++ b/lib/compiler/src/beam_dead.erl
@@ -272,14 +272,18 @@ 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,
     case beam_utils:is_killed(Ctxt, Acc0, D) of
 	true ->
-	    Eq = {test,is_eq_exact,F,[R,{literal,Bs}]},
+	    To = shortcut_bs_context_to_binary(To0, R, D),
+	    Eq = {test,is_eq_exact,{f,To},[R,{literal,Bs}]},
 	    backward(Is, D, [Eq|Acc0]);
 	false ->
+	    To = shortcut_bs_start_match(To0, R, D),
+	    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) ->
@@ -551,6 +555,21 @@ shortcut_bs_start_match_1([{test,bs_start_match2,{f,To},_,[Reg|_],_}|_],
 shortcut_bs_start_match_1(_, _, To, _) ->
     To.
 
+%% shortcut_bs_context_to_binary(TargetLabel, Reg) -> TargetLabel
+%%  If a bs_start_match2 instruction has been eliminated, the
+%%  bs_context_to_binary instruction can be eliminated too.
+
+shortcut_bs_context_to_binary(To, Reg, D) ->
+    shortcut_bs_ctb_1(beam_utils:code_at(To, D), Reg, To, D).
+
+shortcut_bs_ctb_1([{bs_context_to_binary,Reg}|Is], Reg, To, D) ->
+    shortcut_bs_ctb_1(Is, Reg, To, D);
+shortcut_bs_ctb_1([{jump,{f,To}}|_], Reg, _, D) ->
+    Code = beam_utils:code_at(To, D),
+    shortcut_bs_ctb_1(Code, Reg, To, D);
+shortcut_bs_ctb_1(_, _, To, _) ->
+    To.
+
 %% shortcut_rel_op(FailLabel, Operator, [Operand], D) -> FailLabel'
 %%  Try to shortcut the given test instruction. Example:
 %%
-- 
2.9.3

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File 2062-Reinstate-optimization-of-binary-literal-matching.patch of Package erlang

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