beam_block: Optimize matching of binary literals

When matching a binary literal as in:

  <<"abc">> = Bin

the compiler will produce a sequence of three instructions
(some details in the instructions removed for simplicity):

  bs_start_match2 Fail BinReg CtxtReg
  bs_match_string Fail CtxtReg "abc"
  bs_test_tail2 Fail CtxtReg 0

The sequence can be replaced with:

  is_eq_exact Fail BinReg "abc"

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/compiler/src/beam_dead.erl b/lib/compiler/src/beam_dead.erl
index adc3cebc62..5932d8ce1d 100644
--- a/lib/compiler/src/beam_dead.erl
+++ b/lib/compiler/src/beam_dead.erl
@@ -255,6 +255,16 @@ 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,
+	 [{test,bs_match_string,F,[Ctxt,Bs]},
+	  {test,bs_test_tail2,F,[Ctxt,0]}|Acc0]=Acc) ->
+    case beam_utils:is_killed(Ctxt, Acc0, D) of
+	true ->
+	    Eq = {test,is_eq_exact,F,[R,{literal,Bs}]},
+	    backward(Is, D, [Eq|Acc0]);
+	false ->
+	    backward(Is, D, [I|Acc])
+    end;
 backward([{test,bs_start_match2,{f,To0},Live,[Src|_]=Info,Dst}|Is], D, Acc) ->
     To = shortcut_bs_start_match(To0, Src, D),
     I = {test,bs_start_match2,{f,To},Live,Info,Dst},