Support matching bitstrings that are in fact binaries (size divisible by 8)

[mat-hek]

In some cases, there's generic code that uses the bitstring modifier because it needs to work for both bitstrings and binaries, for example in erl_eval. Currently such code doesn't work even if no actual bitstrings are involved, and this PR attempts to fix it. In other words, this now works:

defmodule Foo do
  def pattern_match(x, s) do
    case x do
      <<a::bitstring-size(s), b::bitstring>> ->
        {a, b}

      _ ->
        :no_match
    end
  end
end

Foo.pattern_match(<<234, 123, 2>>, 16)
# => {<<234, 123>>, <<2>>}

TODO:

• add tests
• adjust jit.erl

[bettio]

I think there is still an issue.
build-and-test (arm-linux-gnueabihf-gcc, -mcpu=cortex-a7 -mfloat-abi=hard -O2 -mthumb -mthumb-int is failing and this tells me there is a problem with JIT implementation.
We have to fix this before merging this PR. Maybe @pguyot has some advice here.

[bettio]

Tests keep failing:

test_binary_to_term:
CRASH 
======
pid: <0.1.0>

Stacktrace:
[{test_binary_to_term,test_function,0,[{file,"/home/runner/work/AtomVM/AtomVM/tests/erlang_tests/test_binary_to_term.erl"},{line,316}]},{test_binary_to_term,start,0,[{file,"/home/runner/work/AtomVM/AtomVM/tests/erlang_tests/test_binary_to_term.erl"},{line,170}]}]

cp: #CP<module: 0, label: 52, offset: 2272>

x[0]: error
x[1]: {badmatch,<<1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,5,0,0,0,1,119,19,116,101,115,116,95,98,105,110,97,114,121,95,116,111,95,116,101,114,109,97,5,98,5,26,215,111,88,119,13,110,111,110,111,100,101,64,110,111,104,111,115,116,0,0,0,0,0,0,0,0,0,0,0,0,97,2>>}
x[2]: {2,2,74,1,[{0,8240},{0,27350}],error}

Stack 
-----

<<88,119,13,110,111,110,111,100,101,64,110,111,104,111,115,116,0,0,0,0,0,0,0,0,0,0,0,0>>
85645167
4
85
21
<<119,19,116,101,115,116,95,98,105,110,97,114,121,95,116,111,95,116,101,114,109>>
<<131,108,0,0,0,2,112,0,0,0,85,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,4,0,0,0,0,119,19,116,101,115,116,95,98,105,110,97,114,121,95,116,111,95,116,101,114,109,97,4,98,5,26,215,111,88,119,13,110,111,110,111,100,101,64,110,111,104,111,115,116,0,0,0,0,0,0,0,0,0,0,0,0,112,0,0,0,87,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,5,0,0,0,1,119,19,116,101,115,116,95,98,105,110,97,114,121,95,116,111,95,116,101,114,109,97,5,98,5,26,215,111,88,119,13,110,111,110,111,100,101,64,110,111,104,111,115,116,0,0,0,0,0,0,0,0,0,0,0,0,97,2,106>>
#CP<module: 0, label: 2, offset: 2760>
#CP<module: 0, label: 0, offset: 5424>


Mailbox
-------


Monitors
--------


**End Of Crash Report**
Expected 0 but result is not an integer
test_binary_to_term:FAILED

[mat-hek]

@bettio I'll try looking into it. There's also https://github.com/atomvm/AtomVM/actions/runs/20231091694/job/58073962162?pr=1978#step:18:596 failing, with disabled JIT 🤔 Instead of {<<123, 234>>, <<245>>}, {<<123, 234>>, <<234>>} is returned. Not sure if it's my changes or some other memory corruption

test_bs:
CRASH 
======
pid: <0.1.0>

Stacktrace:
[{test_bs,test_bs_match_bitstring_modifier,0,[{file,"/__w/AtomVM/AtomVM/tests/erlang_tests/test_bs.erl"},{line,688}]},{test_bs,start,0,[{file,"/__w/AtomVM/AtomVM/tests/erlang_tests/test_bs.erl"},{line,108}]}]

cp: #CP<module: 0, label: 399, offset: 42>

x[0]: error
x[1]: {badmatch,{<<123,234>>,<<234>>}}
x[2]: {2,2,49,1,[{0,902},{0,10758}],error}

[pguyot]

You still need to bsl 4 here as well.

[pguyot]

Actually it seems there is a bug in this opcode. Working on it.

[pguyot]

See #2113

You may want to rebase once it is merged.

[pguyot]

You still need to bsl 4 the (Size * Unit) div 8. You could write (Size * Unit) bsl 1.

Indeed, SizeReg contains the size in bytes as a term ((Imm bsl 4) bor 16#F).

We could add a comment here to clarify.

[pguyot]

(see above).