Handle verify check in intrinsic_function pass

[HarshitaKalani]

Fixes: #3584

[HarshitaKalani]

This makes integration_tests/arrays_38.f90 fail
MRE for the same:

program arrays_38
integer :: res(5)
res = abc(5)
contains
    function abc(n) result(res)
    integer :: n
    integer :: res(max(n, 0))
    end function
end program

$ lfortran integration_tests/arrays_38.f90
ASR verify pass error: ASR verify: The symbol table was found, but the symbol `sym` is not in it

ASR verify pass error: FunctionCall::m_name `_lcompilers_max0_i323` cannot point outside of its symbol table
Internal Compiler Error: Unhandled exception
Traceback (most recent call last):
  Binary file "/home/harshita/Desktop/lfortran/src/bin/lfortran", in _start()
  File "./csu/../csu/libc-start.c", line 392, in __libc_start_main_impl()
  File "./csu/../sysdeps/nptl/libc_start_call_main.h", line 58, in __libc_start_call_main()
  File "/home/harshita/Desktop/lfortran/src/bin/lfortran.cpp", line 2389, in ??
    return main_app(argc, argv);
  File "/home/harshita/Desktop/lfortran/src/bin/lfortran.cpp", line 2350, in main_app(int, char**)
    err = compile_to_object_file(arg_file, tmp_o, false,
  File "/home/harshita/Desktop/lfortran/src/bin/lfortran.cpp", line 948, in ??
    res = fe.get_llvm3(*asr, lpm, diagnostics, infile);
  File "/home/harshita/Desktop/lfortran/src/lfortran/fortran_evaluator.cpp", line 359, in LCompilers::FortranEvaluator::get_llvm3(LCompilers::ASR::TranslationUnit_t&, LCompilers::PassManager&, LCompilers::diag::Diagnostics&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)
    compiler_options, run_fn, infile);
  File "/home/harshita/Desktop/lfortran/src/libasr/codegen/asr_to_llvm.cpp", line 9739, in LCompilers::asr_to_llvm(LCompilers::ASR::TranslationUnit_t&, LCompilers::diag::Diagnostics&, llvm::LLVMContext&, Allocator&, LCompilers::PassManager&, LCompilers::CompilerOptions&, 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&)
    pass_manager.apply_passes(al, &asr, co.po, diagnostics);
  File "/home/harshita/Desktop/lfortran/src/libasr/pass/pass_manager.h", line 303, in LCompilers::PassManager::apply_passes(Allocator&, LCompilers::ASR::TranslationUnit_t*, LCompilers::PassOptions&, LCompilers::diag::Diagnostics&)
    apply_passes(al, asr, _passes, pass_options, diagnostics);
LCompilersException: Verify failed in the pass: unused_functions

[Pranavchiku]

I think this is not relevant to this PR, can you do a clean build and check again?

[Pranavchiku]

If you apply following diff

--- a/src/libasr/asr_verify.cpp
+++ b/src/libasr/asr_verify.cpp
@@ -67,7 +67,7 @@ public:
     // case when the symtab is in a different module or if the `sym`'s symbol table
     // does not actually contain it.
     bool symtab_in_scope(const SymbolTable *symtab, const ASR::symbol_t *sym) {
-        unsigned int symtab_ID = symbol_parent_symtab(sym)->counter;
+        unsigned int symtab_ID = symbol_parent_symtab(sym)->counter; // 1
         char *sym_name = symbol_name(sym);
         const SymbolTable *s = symtab;
         while (s != nullptr) {
@@ -83,6 +83,8 @@ public:
                         return false;
                     }
                 } else {
+                    std::cout<<"sym_name: "<<sym_name<<std::endl;
+                    std::cout<<"symtab_ID: "<<symtab_ID<<std::endl;
                     diagnostics.message_label("ASR verify: The symbol table was found, but the symbol `sym` is not in it",
                         {sym->base.loc}, "failed here", diag::Level::Error, diag::Stage::ASRVerify);
                     return false;
@@ -1078,6 +1080,9 @@ public:
             }
         }
 
+        std::cout<<"visit_FunctionCall"<<std::endl;
+        std::cout<<"FunctionCall::m_name: "<<ASRUtils::symbol_name(x.m_name)<<std::endl;
+        std::cout<<"current_symtab->counter: "<<current_symtab->counter<<std::endl;
         require(symtab_in_scope(current_symtab, x.m_name),
             "FunctionCall::m_name `" + std::string(symbol_name(x.m_name)) +
             "` cannot point outside of its symbol table");

and then

% lfortran a.f90 
[.....]
visit_FunctionCall
FunctionCall::m_name: _lcompilers_max0_i322
current_symtab->counter: 3
sym_name: _lcompilers_max0_i322
symtab_ID: 1
ASR verify pass error: ASR verify: The symbol table was found, but the symbol `sym` is not in it

ASR verify pass error: FunctionCall::m_name `_lcompilers_max0_i322` cannot point outside of its symbol table
Internal Compiler Error: Unhandled exception
Traceback (most recent call last):
  File "/Users/pranavchiku/repos/lfortran/src/bin/lfortran.cpp", line 2386
    LCompilers::print_stack_on_segfault();
  File "/Users/pranavchiku/repos/lfortran/src/bin/lfortran.cpp", line 2350
    err = compile_to_object_file(arg_file, tmp_o, false,
  File "/Users/pranavchiku/repos/lfortran/src/bin/lfortran.cpp", line 948
    res = fe.get_llvm3(*asr, lpm, diagnostics, infile);
  File "/Users/pranavchiku/repos/lfortran/src/lfortran/fortran_evaluator.cpp", line 359
    compiler_options, run_fn, infile);
  File "/Users/pranavchiku/repos/lfortran/src/libasr/codegen/asr_to_llvm.cpp", line 9739
    pass_manager.apply_passes(al, &asr, co.po, diagnostics);
  File "/Users/pranavchiku/repos/lfortran/src/libasr/pass/pass_manager.h", line 303
    apply_passes(al, asr, _passes, pass_options, diagnostics);
  File "/Users/pranavchiku/repos/lfortran/src/libasr/pass/pass_manager.h", line 167
    throw LCompilersException("Verify failed in the pass: "
LCompilersException: Verify failed in the pass: unused_functions

Here you can see FunctionCall::m_name: _lcompilers_max0_i322 and current_symtab->counter: 3, now when we go to symtab_in_scope, we get symtab_ID = 1, and then we try to search _lcompilers_max0_i322 in that symtab, this is where code goes to else part and states _lcompilers_max0_i322 does not exisits ( sym2 == nullptr ).

This gives us an hypothesis that _lcompilers_max0_i322 is not even created.

We then check pass_12_intrinsic_function.clj, and we find definition of

_lcompilers_max0_i322:
                (Function .... )

Gives rise to new hypothesis that somehow compiler identified _lcompilers_max0_i322 as unused and removed it.

Thus we check, pass_24_inline_function_calls.clj to ensure _lcompilers_max0_i322 still exists in pass just before pass_25_unused_functions.clj, yes it does.

Hence somehow it got deleted in unused_functions pass.

_lcompilers_max0_i322 is being used in abc which is contained inside program arrays_38,

this means somehow abc is not visited, a new hypothesis

Applying the following diff makes it clear that abc is visited:

--- a/src/libasr/pass/unused_functions.cpp
+++ b/src/libasr/pass/unused_functions.cpp
@@ -24,6 +24,7 @@ public:
     std::map<uint64_t, std::string> fn_used;
 
     void visit_Function(const ASR::Function_t &x) {
+        std::cout<<"Function: "<<x.m_name<<std::endl;
         uint64_t h = get_hash((ASR::asr_t*)&x);
         if (ASRUtils::get_FunctionType(x)->m_abi != ASR::abiType::BindC
          && ASRUtils::get_FunctionType(x)->m_abi != ASR::abiType::BindPython) {

% lfortran a.f90
Function: _lcompilers_max0_i32
Function: _lcompilers_max0_i321
Function: _lcompilers_max0_i322
Function: abc
Function: _lcompilers_max0_i32
Function: _lcompilers_max0_i321
Function: abc
Function: _lcompilers_max0_i32
Function: _lcompilers_max0_i321
Function: abc
Function: _lcompilers_max0_i32
Function: _lcompilers_max0_i321
Function: abc
ASR verify pass error: ASR verify: The symbol table was found, but the symbol `sym` is not in it

Now we visit_FunctionCall with following diff:

     void visit_FunctionCall(const ASR::FunctionCall_t &x) {
+        std::cout<<"visit_FunctionCall: "<<ASRUtils::symbol_name(x.m_name)<<std::endl;
         visit_FuncSubCall(x);
         visit_ttype(*x.m_type);
         if (x.m_value)

and get:

% lfortran a.f90 
Function: _lcompilers_max0_i32
Function: _lcompilers_max0_i321
Function: _lcompilers_max0_i322
visit_FunctionCall: _lcompilers_max0_i32
Function: abc
visit_FunctionCall: _lcompilers_max0_i321
Function: _lcompilers_max0_i32
Function: _lcompilers_max0_i321
visit_FunctionCall: _lcompilers_max0_i32
Function: abc
visit_FunctionCall: _lcompilers_max0_i321
Function: _lcompilers_max0_i32
Function: _lcompilers_max0_i321
visit_FunctionCall: _lcompilers_max0_i32
Function: abc
visit_FunctionCall: _lcompilers_max0_i321
Function: _lcompilers_max0_i32
Function: _lcompilers_max0_i321
visit_FunctionCall: _lcompilers_max0_i32
Function: abc
visit_FunctionCall: _lcompilers_max0_i321
ASR verify pass error: ASR verify: The symbol table was found, but the symbol `sym` is not in it

This clearly states that there is no function call to _lcompilers_max0_i322, hence marked as unused, but why?

Because, this is called via FunctionType of abc which is not visited through visit_Function, hence we apply following diff

          && ASRUtils::get_FunctionType(x)->m_abi != ASR::abiType::BindPython) {
@@ -45,6 +46,8 @@ public:
         for (size_t i=0; i<x.n_body; i++) {
             visit_stmt(*x.m_body[i]);
         }
+
+        visit_ttype(*x.m_function_signature);
     }

and it works :))

[Pranavchiku]

program arrays_38
integer :: res(5)
res = abc(5)
print *, res
contains
    function abc(n) result(res)
    integer :: n
    integer :: res(max(n, 0))
    end function
end program

--- a/src/libasr/pass/unused_functions.cpp
+++ b/src/libasr/pass/unused_functions.cpp
@@ -45,6 +45,7 @@ public:
         for (size_t i=0; i<x.n_body; i++) {
             visit_stmt(*x.m_body[i]);
         }
+        visit_ttype(*x.m_function_signature);
     }
 
     void visit_GenericProcedure(const ASR::GenericProcedure_t &x) {

% lfortran a.f90 
0 0 0 0 0 

[HarshitaKalani]

Thanks @Pranavchiku for the detailed description of the solution. It was helpful.

[Pranavchiku]

Looks good to me, just improve test and this is ready to merge.

[certik]

The failure was due to #3663.

[certik]

I think this is fine.