Move rewriting of bs_match from beam_clean to beam_z

The actual bs_match_string instruction has four operands:

   bs_match_string {f,Lbl} Ctxt NumBits {string,ListOfBytes}

However, v3_codegen emits a more compact representation where
the bits to match are packaged in a bitstring:

   bs_match_string {f,Lbl} Ctxt Bitstring

Currently, beam_clean:clean_labels/1 will rewrite the compact
representation to the final representation. That is unfortunate
since clean_labels/1 is called by beam_dead, which means that
the less compact representation will be introduced long before
it is actually needed by beam_asm. It will also complicate any
optimizations that we might want to do.

Move the rewriting of bs_match_string from beam_clean:clean_labels/1
to the beam_z pass, which is the last pass executed before
beam_validator and beam_asm.

1 files changed, 7 insertions, 0 deletions

diff --git a/lib/compiler/src/beam_z.erl b/lib/compiler/src/beam_z.erl
index 0c7bef9183..47e786034d 100644
--- a/lib/compiler/src/beam_z.erl
+++ b/lib/compiler/src/beam_z.erl
@@ -74,6 +74,13 @@ undo_rename({bs_init,F,{I,Extra,U,Flags},Live,[Sz,Src],Dst}) ->
     {I,F,Sz,Extra,Live,U,Src,Flags,Dst};
 undo_rename({bs_init,_,bs_init_writable=I,_,_,_}) ->
     I;
+undo_rename({test,bs_match_string=Op,F,[Ctx,Bin0]}) ->
+    Bits = bit_size(Bin0),
+    Bin = case Bits rem 8 of
+	      0 -> Bin0;
+	      Rem -> <<Bin0/bitstring,0:(8-Rem)>>
+	  end,
+    {test,Op,F,[Ctx,Bits,{string,binary_to_list(Bin)}]};
 undo_rename({put_map,Fail,assoc,S,D,R,L}) ->
     {put_map_assoc,Fail,S,D,R,L};
 undo_rename({put_map,Fail,exact,S,D,R,L}) ->