[clang] Prune 'IsOMPStructuredBlock' Stmt bit

As discussed in https://reviews.llvm.org/D59214#1916596
and in some other reviews dealing with FPenv,
bits in Stmt are scarce, and i got so burnout with D59214
and https://bugs.llvm.org/show_bug.cgi?id=40563 specifically
that i never actually followed up with the usages for this bit.

So let's unhoard it, at least for now?

Author: LebedevRI

clang/docs/LibASTMatchersReference.html

@@ -4181,19 +4181,6 @@ <h2 id="narrowing-matchers">Narrowing Matchers</h2>
 </pre></td></tr>
 
 
-<tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1Stmt.html">Stmt</a>&gt;</td><td class="name" onclick="toggle('isOMPStructuredBlock0')"><a name="isOMPStructuredBlock0Anchor">isOMPStructuredBlock</a></td><td></td></tr>
-<tr><td colspan="4" class="doc" id="isOMPStructuredBlock0"><pre>Matches the Stmt AST node that is marked as being the structured-block
-of an OpenMP executable directive.
-
-Given
-
-   #pragma omp parallel
-   {}
-
-``stmt(isOMPStructuredBlock()))`` matches ``{}``.
-</pre></td></tr>
-
-
 <tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1StringLiteral.html">StringLiteral</a>&gt;</td><td class="name" onclick="toggle('hasSize1')"><a name="hasSize1Anchor">hasSize</a></td><td>unsigned N</td></tr>
 <tr><td colspan="4" class="doc" id="hasSize1"><pre>Matches nodes that have the specified size.
 

clang/include/clang/AST/Stmt.h

@@ -99,14 +99,8 @@ class alignas(void *) Stmt {
 
     /// The statement class.
     unsigned sClass : 8;
-
-    /// This bit is set only for the Stmts that are the structured-block of
-    /// OpenMP executable directives. Directives that have a structured block
-    /// are called "non-standalone" directives.
-    /// I.e. those returned by OMPExecutableDirective::getStructuredBlock().
-    unsigned IsOMPStructuredBlock : 1;
   };
-  enum { NumStmtBits = 9 };
+  enum { NumStmtBits = 8 };
 
   class NullStmtBitfields {
     friend class ASTStmtReader;
@@ -1118,7 +1112,6 @@ class alignas(void *) Stmt {
     static_assert(sizeof(*this) % alignof(void *) == 0,
                   "Insufficient alignment!");
     StmtBits.sClass = SC;
-    StmtBits.IsOMPStructuredBlock = false;
     if (StatisticsEnabled) Stmt::addStmtClass(SC);
   }
 
@@ -1128,11 +1121,6 @@ class alignas(void *) Stmt {
 
   const char *getStmtClassName() const;
 
-  bool isOMPStructuredBlock() const { return StmtBits.IsOMPStructuredBlock; }
-  void setIsOMPStructuredBlock(bool IsOMPStructuredBlock) {
-    StmtBits.IsOMPStructuredBlock = IsOMPStructuredBlock;
-  }
-
   /// SourceLocation tokens are not useful in isolation - they are low level
   /// value objects created/interpreted by SourceManager. We assume AST
   /// clients will have a pointer to the respective SourceManager.

clang/include/clang/ASTMatchers/ASTMatchers.h

@@ -7016,19 +7016,6 @@ AST_MATCHER(OMPExecutableDirective, isStandaloneDirective) {
   return Node.isStandaloneDirective();
 }
 
-/// Matches the Stmt AST node that is marked as being the structured-block
-/// of an OpenMP executable directive.
-///
-/// Given
-///
-/// \code
-///    #pragma omp parallel
-///    {}
-/// \endcode
-///
-/// ``stmt(isOMPStructuredBlock()))`` matches ``{}``.
-AST_MATCHER(Stmt, isOMPStructuredBlock) { return Node.isOMPStructuredBlock(); }
-
 /// Matches the structured-block of the OpenMP executable directive
 ///
 /// Prerequisite: the executable directive must not be standalone directive.

clang/lib/AST/TextNodeDumper.cpp

@@ -123,9 +123,6 @@ void TextNodeDumper::Visit(const Stmt *Node) {
   dumpPointer(Node);
   dumpSourceRange(Node->getSourceRange());
 
-  if (Node->isOMPStructuredBlock())
-    OS << " openmp_structured_block";
-
   if (const auto *E = dyn_cast<Expr>(Node)) {
     dumpType(E->getType());
 

clang/lib/ASTMatchers/Dynamic/Registry.cpp

@@ -398,7 +398,6 @@ RegistryMaps::RegistryMaps() {
   REGISTER_MATCHER(isNoReturn);
   REGISTER_MATCHER(isNoThrow);
   REGISTER_MATCHER(isNoneKind);
-  REGISTER_MATCHER(isOMPStructuredBlock);
   REGISTER_MATCHER(isOverride);
   REGISTER_MATCHER(isPrivate);
   REGISTER_MATCHER(isProtected);

clang/lib/Sema/SemaOpenMP.cpp

@@ -5091,12 +5091,6 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
   if (ErrorFound)
     return StmtError();
 
-  if (!(Res.getAs<OMPExecutableDirective>()->isStandaloneDirective())) {
-    Res.getAs<OMPExecutableDirective>()
-        ->getStructuredBlock()
-        ->setIsOMPStructuredBlock(true);
-  }
-
   if (!CurContext->isDependentContext() &&
       isOpenMPTargetExecutionDirective(Kind) &&
       !(DSAStack->hasRequiresDeclWithClause<OMPUnifiedSharedMemoryClause>() ||

clang/lib/Serialization/ASTReaderStmt.cpp

@@ -102,7 +102,7 @@ namespace clang {
 
     /// The number of record fields required for the Stmt class
     /// itself.
-    static const unsigned NumStmtFields = 1;
+    static const unsigned NumStmtFields = 0;
 
     /// The number of record fields required for the Expr class
     /// itself.
@@ -138,7 +138,6 @@ void ASTStmtReader::ReadTemplateKWAndArgsInfo(ASTTemplateKWAndArgsInfo &Args,
 }
 
 void ASTStmtReader::VisitStmt(Stmt *S) {
-  S->setIsOMPStructuredBlock(Record.readInt());
   assert(Record.getIdx() == NumStmtFields && "Incorrect statement field count");
 }
 

clang/lib/Serialization/ASTWriterDecl.cpp

@@ -2274,7 +2274,6 @@ void ASTWriter::WriteDeclAbbrevs() {
   Abv = std::make_shared<BitCodeAbbrev>();
   Abv->Add(BitCodeAbbrevOp(serialization::EXPR_DECL_REF));
   //Stmt
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // IsOMPStructuredBlock
   // Expr
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); //TypeDependent
@@ -2298,7 +2297,6 @@ void ASTWriter::WriteDeclAbbrevs() {
   Abv = std::make_shared<BitCodeAbbrev>();
   Abv->Add(BitCodeAbbrevOp(serialization::EXPR_INTEGER_LITERAL));
   //Stmt
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // IsOMPStructuredBlock
   // Expr
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); //TypeDependent
@@ -2317,7 +2315,6 @@ void ASTWriter::WriteDeclAbbrevs() {
   Abv = std::make_shared<BitCodeAbbrev>();
   Abv->Add(BitCodeAbbrevOp(serialization::EXPR_CHARACTER_LITERAL));
   //Stmt
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // IsOMPStructuredBlock
   // Expr
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); //TypeDependent
@@ -2336,7 +2333,6 @@ void ASTWriter::WriteDeclAbbrevs() {
   Abv = std::make_shared<BitCodeAbbrev>();
   Abv->Add(BitCodeAbbrevOp(serialization::EXPR_IMPLICIT_CAST));
   // Stmt
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // IsOMPStructuredBlock
   // Expr
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); //TypeDependent

clang/lib/Serialization/ASTWriterStmt.cpp

@@ -68,7 +68,6 @@ void ASTStmtWriter::AddTemplateKWAndArgsInfo(
 }
 
 void ASTStmtWriter::VisitStmt(Stmt *S) {
-  Record.push_back(S->StmtBits.IsOMPStructuredBlock);
 }
 
 void ASTStmtWriter::VisitNullStmt(NullStmt *S) {

clang/test/AST/ast-dump-openmp-atomic.c

@@ -12,7 +12,7 @@ void test(int i) {
 // CHECK-NEXT:     `-OMPAtomicDirective {{.*}} <line:4:1, col:19>
 // CHECK-NEXT:       `-CapturedStmt {{.*}} <line:5:3, col:5>
 // CHECK-NEXT:         |-CapturedDecl {{.*}} <<invalid sloc>> <invalid sloc>
-// CHECK-NEXT:         | |-UnaryOperator {{.*}} <col:3, col:5> openmp_structured_block 'int' prefix '++'
+// CHECK-NEXT:         | |-UnaryOperator {{.*}} <col:3, col:5> 'int' prefix '++'
 // CHECK-NEXT:         | | `-DeclRefExpr {{.*}} <col:5> 'int' lvalue ParmVar {{.*}} 'i' 'int'
 // CHECK-NEXT:         | `-ImplicitParamDecl {{.*}} <line:4:1> col:1 implicit __context 'struct (anonymous at {{.*}}ast-dump-openmp-atomic.c:4:1) *const restrict'
 // CHECK-NEXT:         `-DeclRefExpr {{.*}} <line:5:5> 'int' lvalue ParmVar {{.*}} 'i' 'int'