[clang] [OpenMP][CodeGen] Improved codegen for combined loop directives (PR #87278)

[Mike Rice via cfe-commits]

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@@ -6135,6 +6137,79 @@ processImplicitMapsWithDefaultMappers(Sema &S, DSAStackTy *Stack,
   }
 }
 
+namespace {
+/// A 'teams loop' with a nested 'loop bind(parallel)' or generic function
+/// call in the associated loop-nest cannot be a 'parallel for'.
+class TeamsLoopChecker final : public ConstStmtVisitor<TeamsLoopChecker> {
+  Sema &SemaRef;
+
+public:
+  bool teamsLoopCanBeParallelFor() const { return TeamsLoopCanBeParallelFor; }
+
+  // Is there a nested OpenMP loop bind(parallel)
+  void VisitOMPExecutableDirective(const OMPExecutableDirective *D) {
+    if (D->getDirectiveKind() == llvm::omp::Directive::OMPD_loop) {
+      if (const auto *C = D->getSingleClause<OMPBindClause>())
+        if (C->getBindKind() == OMPC_BIND_parallel) {
+          TeamsLoopCanBeParallelFor = false;
+          // No need to continue visiting any more
+          return;
+        }
+    }
+    for (const Stmt *Child : D->children())
+      if (Child)
+        Visit(Child);
+  }
+
+  void VisitCallExpr(const CallExpr *C) {
+    // Function calls inhibit parallel loop translation of 'target teams loop'
+    // unless the assume-no-nested-parallelism flag has been specified.
+    // OpenMP API runtime library calls do not inhibit parallel loop
+    // translation, regardless of the assume-no-nested-parallelism.
+    if (C) {
+      bool IsOpenMPAPI = false;
+      auto *FD = dyn_cast_or_null<FunctionDecl>(C->getCalleeDecl());
+      if (FD) {
+        std::string Name = FD->getNameInfo().getAsString();
+        IsOpenMPAPI = Name.find("omp_") == 0;
+      }
+      TeamsLoopCanBeParallelFor =
+          IsOpenMPAPI || SemaRef.getLangOpts().OpenMPNoNestedParallelism;
+      if (!TeamsLoopCanBeParallelFor)
+        return;
+    }
+    for (const Stmt *Child : C->children())
+      if (Child)
+        Visit(Child);
+  }
----------------
mikerice1969 wrote:

Hi @ddpagan, the static verifier complains about this code since you check that 'C' is not a nullptr, but then do not check before the 'C->children() call. It seems 'C' won't be null since it is checked in ActOnOpenMPTargetTeamsGenericLoopDirective. Can we remove the if(C) check and use an assert instead if you think it helps? Or if 'C' really can be null somehow we need to ensure that for loop is excluded for that case.

https://github.com/llvm/llvm-project/pull/87278