[flang][OpenMP] Move check of ALIGN clause to visitor function (#164261)

This replaces CheckAlignValue with an Enter function, and adds a check
that the alignment is a power of 2.

Author: kparzysz

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

@@ -1562,20 +1562,11 @@ void OmpStructureChecker::Leave(const parser::OpenMPRequiresConstruct &) {
   dirContext_.pop_back();
 }
 
-void OmpStructureChecker::CheckAlignValue(const parser::OmpClause &clause) {
-  if (auto *align{std::get_if<parser::OmpClause::Align>(&clause.u)}) {
-    if (const auto &v{GetIntValue(align->v)}; v && *v <= 0) {
-      context_.Say(clause.source, "The alignment should be positive"_err_en_US);
-    }
-  }
-}
-
 void OmpStructureChecker::Enter(const parser::OpenMPDeclarativeAllocate &x) {
   isPredefinedAllocator = true;
   const auto &dir{std::get<parser::Verbatim>(x.t)};
   const auto &objectList{std::get<parser::OmpObjectList>(x.t)};
   PushContextAndClauseSets(dir.source, llvm::omp::Directive::OMPD_allocate);
-  const auto &clauseList{std::get<parser::OmpClauseList>(x.t)};
   SymbolSourceMap currSymbols;
   GetSymbolsInObjectList(objectList, currSymbols);
   for (auto &[symbol, source] : currSymbols) {
@@ -1598,9 +1589,6 @@ void OmpStructureChecker::Enter(const parser::OpenMPDeclarativeAllocate &x) {
           source.ToString());
     }
   }
-  for (const auto &clause : clauseList.v) {
-    CheckAlignValue(clause);
-  }
   CheckVarIsNotPartOfAnotherVar(dir.source, objectList);
 }
 
@@ -2007,9 +1995,6 @@ void OmpStructureChecker::Enter(const parser::OpenMPExecutableAllocate &x) {
 
   isPredefinedAllocator = true;
   const auto &objectList{std::get<std::optional<parser::OmpObjectList>>(x.t)};
-  for (const auto &clause : clauseList.v) {
-    CheckAlignValue(clause);
-  }
   if (objectList) {
     CheckVarIsNotPartOfAnotherVar(dir.source, *objectList);
   }
@@ -3234,7 +3219,6 @@ CHECK_SIMPLE_CLAUSE(AdjustArgs, OMPC_adjust_args)
 CHECK_SIMPLE_CLAUSE(AppendArgs, OMPC_append_args)
 CHECK_SIMPLE_CLAUSE(MemoryOrder, OMPC_memory_order)
 CHECK_SIMPLE_CLAUSE(Bind, OMPC_bind)
-CHECK_SIMPLE_CLAUSE(Align, OMPC_align)
 CHECK_SIMPLE_CLAUSE(Compare, OMPC_compare)
 CHECK_SIMPLE_CLAUSE(OmpxAttribute, OMPC_ompx_attribute)
 CHECK_SIMPLE_CLAUSE(Weak, OMPC_weak)
@@ -3898,6 +3882,19 @@ void OmpStructureChecker::CheckIsLoopIvPartOfClause(
   }
 }
 
+void OmpStructureChecker::Enter(const parser::OmpClause::Align &x) {
+  CheckAllowedClause(llvm::omp::Clause::OMPC_align);
+  if (const auto &v{GetIntValue(x.v.v)}) {
+    if (*v <= 0) {
+      context_.Say(GetContext().clauseSource,
+          "The alignment should be positive"_err_en_US);
+    } else if (!llvm::isPowerOf2_64(*v)) {
+      context_.Say(GetContext().clauseSource,
+          "The alignment should be a power of 2"_err_en_US);
+    }
+  }
+}
+
 // Restrictions specific to each clause are implemented apart from the
 // generalized restrictions.
 void OmpStructureChecker::Enter(const parser::OmpClause::Aligned &x) {

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

@@ -347,8 +347,6 @@ class OmpStructureChecker
   void CheckAllowedRequiresClause(llvmOmpClause clause);
   bool deviceConstructFound_{false};
 
-  void CheckAlignValue(const parser::OmpClause &);
-
   void AddEndDirectiveClauses(const parser::OmpClauseList &clauses);
 
   void EnterDirectiveNest(const int index) { directiveNest_[index]++; }

flang/test/Semantics/OpenMP/align-clause.f90

@@ -0,0 +1,20 @@
+!RUN: %python %S/../test_errors.py %s %flang -fopenmp -fopenmp-version=51
+
+subroutine f00(y)
+  integer :: x(10), y
+  !ERROR: Must be a constant value
+  !$omp allocate(x) align(y)
+end
+
+subroutine f01()
+  integer :: x(10)
+  !ERROR: The alignment should be a power of 2
+  !$omp allocate(x) align(7)
+end
+
+subroutine f02()
+  integer :: x(10)
+  !ERROR: The alignment should be positive
+  !$omp allocate(x) align(-8)
+end
+