Wasm to x86 backend

[ubaidsk]

towards #1222

[ubaidsk]

This WASMDecoder class is being repeated (it is already defined in src/libasr/codegen/wasm_to_wat.cpp). We should extract it and place in a common file.

doubt: Where should we place this WASMDecoder class? Creating a new file (e.g. wasm_disassembler.cpp or wasm_decoder.cpp) seems possible, but I am unsure if this is the right way.

[ubaidsk]

I temporarily moved this class into a new file wasm_decoder.h.

[certik]

Awesome, thanks for this! Will review it tomorrow.

[ubaidsk]

I am an facing the following error.

Traceback (most recent call last):
  Binary file "/home/ubaid/OpenSource/lpython/src/bin/lpython", in _start()
  Binary file "/lib/x86_64-linux-gnu/libc.so.6", in __libc_start_main()
  File "/home/ubaid/OpenSource/lpython/src/bin/lpython.cpp", line 1555, in ??
    return compile_to_binary_wasm_to_x86(arg_file, outfile,
  File "/home/ubaid/OpenSource/lpython/src/bin/lpython.cpp", line 856, in ??
    LFortran::Result<int> res = LFortran::wasm_to_x86(r3.result, al,  outfile, time_report, diagnostics);
  File "/home/ubaid/OpenSource/lpython/src/libasr/codegen/wasm_to_x86.cpp", line 98, in LFortran::wasm_to_x86(LFortran::Vec<unsigned char>&, Allocator&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, bool, LFortran::diag::Diagnostics&)
    x86_generator.get_x86_bytes(m_a);
  File "/home/ubaid/OpenSource/lpython/src/libasr/codegen/wasm_to_x86.cpp", line 53, in LFortran::wasm::X86Generator::get_x86_bytes(LFortran::X86Assembler&)
    v.decode_instructions();
  File "/home/ubaid/OpenSource/lpython/src/libasr/../libasr/wasm_visitor.h", line 926, in LFortran::WASM_INSTS_VISITOR::BaseWASMVisitor<LFortran::WASM_INSTS_VISITOR::X86Visitor>::decode_instructions()
    self().visit_Call(funcidx);
  File "/home/ubaid/OpenSource/lpython/src/libasr/../libasr/codegen/wasm_to_x86.h", line 52, in LFortran::WASM_INSTS_VISITOR::X86Visitor::visit_Call(unsigned int)
    m_a.asm_call_label(exports[func_index].name);
  File "/home/ubaid/OpenSource/lpython/src/libasr/../libasr/codegen/x86_assembler.h", line 691, in LFortran::X86Assembler::asm_call_label(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)
    uint32_t imm32 = relative_symbol(label);
  File "/home/ubaid/OpenSource/lpython/src/libasr/../libasr/codegen/x86_assembler.h", line 365, in LFortran::X86Assembler::relative_symbol(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)
    return reference_symbol(name, 2).value-pos()-4;
  File "/home/ubaid/OpenSource/lpython/src/libasr/../libasr/codegen/x86_assembler.h", line 333, in LFortran::X86Assembler::reference_symbol(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, int)
    if (m_symbols.find(name) == m_symbols.end()) {
  File "/usr/include/c++/9/bits/stl_map.h", line 1169, in std::map<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, LFortran::Symbol, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, LFortran::Symbol> > >::find(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)
    { return _M_t.find(__x); }
  File "/usr/include/c++/9/bits/stl_tree.h", line 2562, in std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, LFortran::Symbol>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, LFortran::Symbol> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, LFortran::Symbol> > >::find(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)
    iterator __j = _M_lower_bound(_M_begin(), _M_end(), __k);
  File "/usr/include/c++/9/bits/stl_tree.h", line 1934, in std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, LFortran::Symbol>, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, LFortran::Symbol> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, LFortran::Symbol> > >::_M_lower_bound(std::_Rb_tree_node<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, LFortran::Symbol> >*, std::_Rb_tree_node_base*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)
    if (!_M_impl._M_key_compare(_S_key(__x), __k))
  File "/usr/include/c++/9/bits/stl_function.h", line 386, in std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >::operator()(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) const
    { return __x < __y; }
  File "/usr/include/c++/9/bits/basic_string.h", line 6232, in bool std::operator< <char, std::char_traits<char>, std::allocator<char> >(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)
    { return __lhs.compare(__rhs) < 0; }
  Binary file "/lib/x86_64-linux-gnu/libstdc++.so.6", in std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::compare(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) const
  Binary file "/lib/x86_64-linux-gnu/libc.so.6", in __nss_database_lookup()
  Binary file "/lib/x86_64-linux-gnu/libc.so.6", in killpg()
Segfault: Signal SIGSEGV (segmentation fault) received

Could someone possibly try this PR and help with the bug, please?

[ubaidsk]

The wasm to x86 backend can be used as lpython examples/expr2.py --backend wasm_x86.

[ubaidsk]

For #1223 (comment), the I am here flow that is being generated using the wasm to x86 backend is

(lp) ubaid@ubaid-Lenovo-ideapad-330-15ARR:~/OpenSource/lpython$ lpython examples/expr2.py --backend wasm_x86
I am here - 1
I am here - 2
I am here - 3
I am here - 4
I am here - 1
I am here - 2
I am here - 3
I am here - 4
I am here - 1
I am here - 2
I am here - 3
I am here - 4
I am here - 1
I am here - 2
I am here - 3
I am here - 4
I am here - 1
I am here - 2
I am here - 3
I am here - 4
I am here - 1
I am here - 4
I am here - 1
I am here - 2
I am here - 3
I am here - 4
I am here - 1
I am here - 4
I am here - 1
I am here - 2
I am here - 3
I am here - 4
I am here - 1
I am here - 4
I am here - 1
I am here - 4
Call to imported function with index 5 not yet supportedI am here - 1
I am here - 2
I am here - 3
I am here - 4
I am here - 1

[ubaidsk]

This #1223 (comment) seems to be solved now.

[ubaidsk]

The following example works with both the x86 backends.

def Main0():
    x: i32
    x = (2+3)*5
    y: i32
    z: i32
    y = 14
    z = 2
    print(x + y * z)

Main0()

# Not implemented yet in LPython:
#if __name__ == "__main__":
#    main()

(lp) ubaid@ubaid-Lenovo-ideapad-330-15ARR:~/OpenSource/lpython$ lpython examples/expr2.py --backend x86
(lp) ubaid@ubaid-Lenovo-ideapad-330-15ARR:~/OpenSource/lpython$ ./a.out 
53
(lp) ubaid@ubaid-Lenovo-ideapad-330-15ARR:~/OpenSource/lpython$ lpython examples/expr2.py --backend wasm_x86
(lp) ubaid@ubaid-Lenovo-ideapad-330-15ARR:~/OpenSource/lpython$ ./a.out 
53(lp) ubaid@ubaid-Lenovo-ideapad-330-15ARR:~/OpenSource/lpython$ 

[ubaidsk]

Notes:

• We are needing to name the main0 function as Main0 so that it gets defined before the _lpython_main_program() which calls it.
• Only Non-Negative integers are currently supported as it seems x86_assembler does not support negative integers fully. (It seems there is no printing support for negative integers).
• Functions are supported, but returning values from functions is not yet supported.

[ubaidsk]

This is ready. Please possibly review and please share feedback.

[certik]

At a high level this looks good. I need to review in more detail.

The changes in lpython.cpp seem long. We should try to figure out if there is an easier way to do this there, possibly in subsequent PRs.

[certik]

I will only have time next week to play with this --- in the meantime why don't you setup a CI to automatically test this? We'll need that anyway.

[ubaidsk]

in the meantime why don't you setup a CI to automatically test this? We'll need that anyway.

I was hoping to submit a PR for setting up the CI, but it seems the current wasm to x86 backend is very early and does/might not support even basic integration tests. I am working on supporting return values from function calls. It seems to work. I will be sending a PR soon.

For CI, it seems we might also need support for visit_Assert() as several integration tests seem to use assert in them.