[flang][openacc] Warn only when the same variable is in the same declare

[clementval]

A var may appear at most once in all the clauses of declare directives for a function, subroutine, program, or module.
We raise an error when a var appears in two different clauses. If it is in the same clauses, we just issue a warning.

[llvmbot]

@llvm/pr-subscribers-flang-semantics

@llvm/pr-subscribers-openacc

Author: Valentin Clement (バレンタイン クレメン) (clementval)

Changes

A var may appear at most once in all the clauses of declare directives for a function, subroutine, program, or module.
We raise an error when a var appears in two different clauses. If it is in the same clauses, we just issue a warning.

---

Full diff: https://github.com/llvm/llvm-project/pull/70698.diff

3 Files Affected:

• (modified) flang/lib/Semantics/check-acc-structure.cpp (+16-7)
• (modified) flang/lib/Semantics/check-acc-structure.h (+2-2)
• (modified) flang/test/Semantics/OpenACC/acc-declare-validity.f90 (+1-1)

diff --git a/flang/lib/Semantics/check-acc-structure.cpp b/flang/lib/Semantics/check-acc-structure.cpp
index 763418ede24d5a7..d14098e09a8f0e8 100644
--- a/flang/lib/Semantics/check-acc-structure.cpp
+++ b/flang/lib/Semantics/check-acc-structure.cpp
@@ -401,14 +401,23 @@ void AccStructureChecker::CheckMultipleOccurrenceInDeclare(
             [&](const Fortran::parser::Designator &designator) {
               if (const auto *name = getDesignatorNameIfDataRef(designator)) {
                 if (declareSymbols.contains(&name->symbol->GetUltimate())) {
-                  context_.Say(GetContext().clauseSource,
-                      "'%s' in the %s clause is already present in another "
-                      "clause in this module"_err_en_US,
-                      name->symbol->name(),
-                      parser::ToUpperCaseLetters(
-                          llvm::acc::getOpenACCClauseName(clause).str()));
+                  if (declareSymbols[&name->symbol->GetUltimate()] == clause) {
+                    context_.Say(GetContext().clauseSource,
+                        "'%s' in the %s clause is already present in the same "
+                        "clause in this module"_warn_en_US,
+                        name->symbol->name(),
+                        parser::ToUpperCaseLetters(
+                            llvm::acc::getOpenACCClauseName(clause).str()));
+                  } else {
+                    context_.Say(GetContext().clauseSource,
+                        "'%s' in the %s clause is already present in another "
+                        "clause in this module"_err_en_US,
+                        name->symbol->name(),
+                        parser::ToUpperCaseLetters(
+                            llvm::acc::getOpenACCClauseName(clause).str()));
+                  }
                 }
-                declareSymbols.insert(&name->symbol->GetUltimate());
+                declareSymbols.insert({&name->symbol->GetUltimate(), clause});
               }
             },
             [&](const Fortran::parser::Name &name) {
diff --git a/flang/lib/Semantics/check-acc-structure.h b/flang/lib/Semantics/check-acc-structure.h
index 2a09b7a39395d16..6a9aa01a9bb1333 100644
--- a/flang/lib/Semantics/check-acc-structure.h
+++ b/flang/lib/Semantics/check-acc-structure.h
@@ -18,7 +18,7 @@
 #include "flang/Common/enum-set.h"
 #include "flang/Parser/parse-tree.h"
 #include "flang/Semantics/semantics.h"
-#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/Frontend/OpenACC/ACC.h.inc"
 
 using AccDirectiveSet = Fortran::common::EnumSet<llvm::acc::Directive,
@@ -91,7 +91,7 @@ class AccStructureChecker
   llvm::StringRef getClauseName(llvm::acc::Clause clause) override;
   llvm::StringRef getDirectiveName(llvm::acc::Directive directive) override;
 
-  llvm::SmallDenseSet<Symbol *> declareSymbols;
+  llvm::SmallDenseMap<Symbol *, llvm::acc::Clause> declareSymbols;
   unsigned loopNestLevel = 0;
 };
 
diff --git a/flang/test/Semantics/OpenACC/acc-declare-validity.f90 b/flang/test/Semantics/OpenACC/acc-declare-validity.f90
index c0333d78dd9f78b..6907e17919c93e3 100644
--- a/flang/test/Semantics/OpenACC/acc-declare-validity.f90
+++ b/flang/test/Semantics/OpenACC/acc-declare-validity.f90
@@ -14,7 +14,7 @@ module openacc_declare_validity
 
   !$acc declare create(aa, bb)
 
-  !ERROR: 'aa' in the CREATE clause is already present in another clause in this module
+  !WARNING: 'aa' in the CREATE clause is already present in the same clause in this module
   !$acc declare create(aa)
 
   !$acc declare link(ab)

[razvanlupusoru]

Can you also add an error check for case when it is in conflicting declare clause again?

[clementval]

There was on in the function but I added one back in the module declaration.

[razvanlupusoru]

Looks good - just a small suggestion.

[razvanlupusoru]

Thank you!