Merge branch 'bjorn/compiler/binary-literal-matching'

* bjorn/compiler/binary-literal-matching:
  Reinstate optimization of binary literal matching
  Strengthen test case added in 8b83bc0b

2 files changed, 30 insertions, 3 deletions

diff --git a/lib/compiler/src/beam_dead.erl b/lib/compiler/src/beam_dead.erl
index 6f6d742293..3606af9d75 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:
 %%
diff --git a/lib/compiler/test/match_SUITE.erl b/lib/compiler/test/match_SUITE.erl
index 127679ba69..52b2da05f7 100644
--- a/lib/compiler/test/match_SUITE.erl
+++ b/lib/compiler/test/match_SUITE.erl
@@ -576,7 +576,15 @@ grab_bag_remove_failure([{stretch,_,Mi}=Stretch | Specs], Unit, _MaxFailure) ->
 
 %% Regression in 19.0, reported by Alexei Sholik
 literal_binary(_Config) ->
-    3 = literal_binary_match(bar,<<"y">>),
+    3 = literal_binary_match(bar, <<"y">>),
+
+    %% While we are at it, also test the remaining code paths
+    %% in literal_binary_match/2.
+    1 = literal_binary_match(bar, <<"x">>),
+    2 = literal_binary_match(foo, <<"x">>),
+    3 = literal_binary_match(foo, <<"y">>),
+    fail = literal_binary_match(bar, <<"z">>),
+    fail = literal_binary_match(foo, <<"z">>),
     ok.
 
 literal_binary_match(bar, <<"x">>) -> 1;