Refactor string operands

There are two instructions that take string operands:

     {bs_put_string,Fail,NumberOfBytes,{string,String}}
     {bs_match_string,Fail,Register,NumberOfBits,{string,String}}

In the canonical BEAM code that is passed to beam_asm, string String
is currently represented as a list. (The string in bs_match_string is
a bitstring before the beam_z compiler pass.) That is wasteful,
because there will be unnecessary conversions between lists and
binaries.

Change the representation of String to be a binary.

Furthermore, bs_put_string is an optimization of a bs_put_binary
instruction with a literal binary operand. Currently, the
bs_put_string instruction is introduced in beam_bs. Delay the
introduction of bs_put_string to the beam_z pass. That will simplify
optimizations and allow us to do the optimization currently done
in beam_bs in a SSA pass in a future commit.

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/compiler/src/beam_asm.erl b/lib/compiler/src/beam_asm.erl
index df0321e85a..bc1290f6fd 100644
--- a/lib/compiler/src/beam_asm.erl
+++ b/lib/compiler/src/beam_asm.erl
@@ -424,8 +424,8 @@ encode_arg({f, W}, Dict) ->
     {encode(?tag_f, W), Dict};
 %% encode_arg({'char', C}, Dict) ->
 %%     {encode(?tag_h, C), Dict};
-encode_arg({string, String}, Dict0) ->
-    {Offset, Dict} = beam_dict:string(String, Dict0),
+encode_arg({string, BinString}, Dict0) when is_binary(BinString) ->
+    {Offset, Dict} = beam_dict:string(BinString, Dict0),
     {encode(?tag_u, Offset), Dict};
 encode_arg({extfunc, M, F, A}, Dict0) ->
     {Index, Dict} = beam_dict:import(M, F, A, Dict0),