[flang] Add semantic checks for threadprivate and declare target directives

[peixin]

Summary

This patch supports the following checks:

[5.1] 2.21.2 THREADPRIVATE Directive
The threadprivate directive must appear in the declaration section of
a scoping unit in which the common block or variable is declared.
[5.1] 2.14.7 Declare Target Directive
The directive must appear in the declaration section of a scoping unit
in which the common block or variable is declared.

[peixin]

@shraiysh We misunderstood this check before (https://reviews.llvm.org/D114941#inline-1099581). I confirmed this check with OpenMP committee. gfortran does not report semantic error, but it result in unspecified behaviors, and sometimes gets segmentation fault. Sent you the confirmation email.

[NimishMishra]

Thank you @peixin for the patch. LGTM with one small question.

flang/test/Semantics/omp-threadprivate05.f90

39

Does it make sense to include the particular offending Name here as well? Like in case i is the offending variable, maybe we can say so explicitly in the error. Please let me know what you think about this.

[peixin]

flang/test/Semantics/omp-threadprivate05.f90

39

Yes, the message should point to the "Name". The name->source in context_.Say(name->source above achieve this. The error message will be the following on terminal:

./omp-threadprivate05.f90:40:25: error: The THREADPRIVATE directive and the common block or variable in it must appear in the same declaration section of a scoping unit
      !$omp threadprivate(i, j)
                          ^

[peixin]

@kiranchandramohan Do you have further comments for this?

[shraiysh]

In D125767#3518679, @peixin wrote:

@shraiysh We misunderstood this check before (https://reviews.llvm.org/D114941#inline-1099581). I confirmed this check with OpenMP committee. gfortran does not report semantic error, but it result in unspecified behaviors, and sometimes gets segmentation fault. Sent you the confirmation email.

Yes, I checked the email. Sounds good to me. Thank you for driving this discussion!

[peixin]

In D125767#3540093, @peixin wrote:

@kiranchandramohan Do you have further comments for this?

ping @kiranchandramohan

[peixin]

@kiranchandramohan Is it OK to land this now?

[kiranchandramohan]

Thanks @peixin. You do not have to wait for me if I have not requested changes and others have approved.

[peixin]

In D125767#3550147, @kiranchandramohan wrote:

Thanks @peixin. You do not have to wait for me if I have not requested changes and others have approved.

OK. Thanks.

flang/lib/Semantics/check-omp-structure.cpp

 
 void OmpStructureChecker::CheckThreadprivateOrDeclareTargetVar(
     const parser::OmpObjectList &objList) {
   for (const auto &ompObject : objList.v) {
     common::visit(
         common::visitors{
             [&](const parser::Designator &) {
               if (const auto *name{parser::Unwrap<parser::Name>(ompObject)}) {
+                const auto &useScope{
+                    context_.FindScope(GetContext().directiveSource)};
                 const auto &declScope{
                     GetProgramUnitContaining(name->symbol->GetUltimate())};
                 const auto *sym =
                     declScope.parent().FindSymbol(name->symbol->name());
                 if (sym &&
                     (sym->has<MainProgramDetails>() ||
                         sym->has<ModuleDetails>())) {
                   context_.Say(name->source,
common::visit(
                 } else if (!IsSave(*name->symbol) &&
                     declScope.kind() != Scope::Kind::MainProgram &&
                     declScope.kind() != Scope::Kind::Module) {
                   context_.Say(name->source,
                       "A variable that appears in a %s directive must be "
                       "declared in the scope of a module or have the SAVE "
                       "attribute, either explicitly or implicitly"_err_en_US,
                       ContextDirectiveAsFortran());
+                } else if (useScope != declScope) {
+                  context_.Say(name->source,
+                      "The %s directive and the common block or variable in it "
+                      "must appear in the same declaration section of a "
+                      "scoping unit"_err_en_US,
+                      ContextDirectiveAsFortran());
                 } else if (FindEquivalenceSet(*name->symbol)) {
                   context_.Say(name->source,
                       "A variable in a %s directive cannot appear in an "
                       "EQUIVALENCE statement"_err_en_US,
                       ContextDirectiveAsFortran());
                 } else if (name->symbol->test(Symbol::Flag::OmpThreadprivate) &&
                     GetContext().directive ==
                         llvm::omp::Directive::OMPD_declare_target) {

flang/test/Semantics/omp-declare-target05.f90

+! RUN: %python %S/test_errors.py %s %flang_fc1 -fopenmp
+! OpenMP Version 5.1
+! Check OpenMP construct validity for the following directives:
+! 2.14.7 Declare Target Directive
+
+module mod0
+  integer :: mi
+
+contains
+  subroutine subm()
+    integer, save :: mmi
+
+    !ERROR: The DECLARE TARGET directive and the common block or variable in it must appear in the same declaration section of a scoping unit
+    !$omp declare target (mi)
+    mi = 1
+  contains
+    subroutine subsubm()
+      !ERROR: The DECLARE TARGET directive and the common block or variable in it must appear in the same declaration section of a scoping unit
+      !$omp declare target (mmi)
+    end
+  end
+end
+
+module mod1
+  integer :: mod_i
+end
+
+program main
+  use mod1
+  integer, save :: i
+  integer :: j
+
+  !ERROR: The DECLARE TARGET directive and the common block or variable in it must appear in the same declaration section of a scoping unit
+  !$omp declare target (mod_i)
+
+contains
+  subroutine sub()
+    !ERROR: The DECLARE TARGET directive and the common block or variable in it must appear in the same declaration section of a scoping unit
+    !ERROR: The DECLARE TARGET directive and the common block or variable in it must appear in the same declaration section of a scoping unit
+    !$omp declare target (i, j)
+    i = 1
+    j = 1
+  end
+end

flang/test/Semantics/omp-threadprivate05.f90

+! RUN: %python %S/test_errors.py %s %flang_fc1 -fopenmp
+! OpenMP Version 5.1
+! Check OpenMP construct validity for the following directives:
+! 2.21.2 Threadprivate Directive
+
+module mod0
+  integer :: mi
+
+contains
+  subroutine subm()
+    integer, save :: mmi
+
+    !ERROR: The THREADPRIVATE directive and the common block or variable in it must appear in the same declaration section of a scoping unit
+    !$omp threadprivate(mi)
+    mi = 1
+  contains
+    subroutine subsubm()
+      !ERROR: The THREADPRIVATE directive and the common block or variable in it must appear in the same declaration section of a scoping unit
+      !$omp threadprivate(mmi)
+    end
+  end
+end
+
+module mod1
+  integer :: mod_i
+end
+
+program main
+  use mod1
+  integer, save :: i
+  integer :: j
+
+  !ERROR: The THREADPRIVATE directive and the common block or variable in it must appear in the same declaration section of a scoping unit
+  !$omp threadprivate(mod_i)
+
+contains
+  subroutine sub()
+    !ERROR: The THREADPRIVATE directive and the common block or variable in it must appear in the same declaration section of a scoping unit
+    !ERROR: The THREADPRIVATE directive and the common block or variable in it must appear in the same declaration section of a scoping unit
+    !$omp threadprivate(i, j)
+    i = 1
+    j = 1
+  end
+end