[clang] [clang][OpenMP] Add 'align' modifier for 'allocate' clause (PR #121814)

[Alexey Bataev via cfe-commits]

================
@@ -4530,32 +4530,89 @@ static bool parseStepSize(Parser &P, SemaOpenMP::OpenMPVarListDataTy &Data,
 }
 
 /// Parse 'allocate' clause modifiers.
-///   If allocator-modifier exists, return an expression for it and set
-///   Data field noting modifier was specified.
-///
+///   If allocator-modifier exists, return an expression for it. For both
+///   allocator and align modifiers, set Data fields as appropriate.
 static ExprResult
 parseOpenMPAllocateClauseModifiers(Parser &P, OpenMPClauseKind Kind,
                                    SemaOpenMP::OpenMPVarListDataTy &Data) {
   const Token &Tok = P.getCurToken();
   Preprocessor &PP = P.getPreprocessor();
   ExprResult Tail;
-  auto Modifier = static_cast<OpenMPAllocateClauseModifier>(
+  ExprResult Val;
+  SourceLocation RLoc;
+  bool AllocatorSeen = false;
+  bool AlignSeen = false;
+  SourceLocation CurrentModifierLoc = Tok.getLocation();
+  auto CurrentModifier = static_cast<OpenMPAllocateClauseModifier>(
       getOpenMPSimpleClauseType(Kind, PP.getSpelling(Tok), P.getLangOpts()));
-  if (Modifier == OMPC_ALLOCATE_allocator) {
-    Data.AllocClauseModifier = Modifier;
+
+  // Modifiers did not exist before 5.1
+  if (P.getLangOpts().OpenMP < 51)
+    return P.ParseAssignmentExpression();
+
+  // An allocator-simple-modifier is exclusive and must appear alone. See
+  // OpenMP6.0 spec, pg. 313, L1 on Modifiers, as well as Table 5.1, pg. 50,
+  // description of "exclusive" property. If we don't recognized an explicit
+  // simple-/complex- modifier, assume we're looking at expression
+  // representing allocator and consider ourselves done.
+  if (CurrentModifier == OMPC_ALLOCATE_unknown)
+    return P.ParseAssignmentExpression();
+
+  do {
     P.ConsumeToken();
-    BalancedDelimiterTracker AllocateT(P, tok::l_paren,
-                                       tok::annot_pragma_openmp_end);
     if (Tok.is(tok::l_paren)) {
-      AllocateT.consumeOpen();
-      Tail = P.ParseAssignmentExpression();
-      AllocateT.consumeClose();
+      switch (CurrentModifier) {
+      case OMPC_ALLOCATE_allocator: {
+        if (AllocatorSeen) {
+          P.Diag(Tok, diag::err_omp_duplicate_modifier)
+              << getOpenMPSimpleClauseTypeName(OMPC_allocate, CurrentModifier)
+              << getOpenMPClauseName(Kind);
+        } else {
+          Data.AllocClauseModifiers.push_back(CurrentModifier);
+          Data.AllocClauseModifiersLoc.push_back(CurrentModifierLoc);
+        }
+        BalancedDelimiterTracker AllocateT(P, tok::l_paren,
+                                           tok::annot_pragma_openmp_end);
+        AllocateT.consumeOpen();
+        Tail = P.ParseAssignmentExpression();
+        AllocateT.consumeClose();
+        AllocatorSeen = true;
+        break;
+      }
+      case OMPC_ALLOCATE_align: {
+        if (AlignSeen) {
+          P.Diag(Tok, diag::err_omp_duplicate_modifier)
+              << getOpenMPSimpleClauseTypeName(OMPC_allocate, CurrentModifier)
+              << getOpenMPClauseName(Kind);
+        } else {
+          Data.AllocClauseModifiers.push_back(CurrentModifier);
+          Data.AllocClauseModifiersLoc.push_back(CurrentModifierLoc);
+        }
+        Val = P.ParseOpenMPParensExpr(getOpenMPClauseName(Kind), RLoc);
+        if (Val.isUsable())
+          Data.AllocateAlignment = Val.get();
+        AlignSeen = true;
+        break;
+      }
+      default:
+        assert(false && "Unexpected allocate modifier");
----------------
alexey-bataev wrote:

```suggestion
        lvm_unreachable("Unexpected allocate modifier");
```


https://github.com/llvm/llvm-project/pull/121814