[clang] [OpenACC] Implement 'if' clause for Compute Constructs (PR #88411)

[Alexey Bataev via cfe-commits]

================
@@ -55,12 +55,49 @@ bool doesClauseApplyToDirective(OpenACCDirectiveKind DirectiveKind,
     default:
       return false;
     }
+  case OpenACCClauseKind::If:
+    switch (DirectiveKind) {
+    case OpenACCDirectiveKind::Parallel:
+    case OpenACCDirectiveKind::Serial:
+    case OpenACCDirectiveKind::Kernels:
+    case OpenACCDirectiveKind::Data:
+    case OpenACCDirectiveKind::EnterData:
+    case OpenACCDirectiveKind::ExitData:
+    case OpenACCDirectiveKind::HostData:
+    case OpenACCDirectiveKind::Init:
+    case OpenACCDirectiveKind::Shutdown:
+    case OpenACCDirectiveKind::Set:
+    case OpenACCDirectiveKind::Update:
+    case OpenACCDirectiveKind::Wait:
+    case OpenACCDirectiveKind::ParallelLoop:
+    case OpenACCDirectiveKind::SerialLoop:
+    case OpenACCDirectiveKind::KernelsLoop:
+      return true;
+    default:
+      return false;
+    }
   default:
     // Do nothing so we can go to the 'unimplemented' diagnostic instead.
     return true;
   }
   llvm_unreachable("Invalid clause kind");
 }
+
+bool checkAlreadyHasClauseOfKind(
+    SemaOpenACC &S, ArrayRef<const OpenACCClause *> ExistingClauses,
+    SemaOpenACC::OpenACCParsedClause &Clause) {
+  auto Itr = llvm::find_if(ExistingClauses, [&](const OpenACCClause *C) {
----------------
alexey-bataev wrote:

```suggestion
  const auto *Itr = llvm::find_if(ExistingClauses, [&](const OpenACCClause *C) {
```


https://github.com/llvm/llvm-project/pull/88411