[OpenMP] Avoid crash in preparation for diagnose of unsupported type

[jdoerfert]

Summary

This was reported as PR45231 but occurs even without cmath in C++17
mode if we have an expression involving unsupported types outside of a
function. For now we just avoid to create a diagnose builder in this
case as it might be valid anyway. A proper solution to handle
unsupported types has to be found. Discussion is ongoing in D74387.

[JonChesterfield]

Thanks!

[Fznamznon]

clang/lib/Sema/SemaOpenMP.cpp

1831

Please ignore my comment if it says nonsense. It actually can since I don't know a lot about OpenMP but,
looking into targetDiag, I would say that underlying function (diagIfOpenMPDeviceCode in case of OpenMP device mode) should check that we actually have current function because it does getCurFunctionDecl() call.
Otherwise any attempt to emit diagnostic in OpenMP device mode using targetDiag or diagIfOpenMPDeviceCode will fail outside of functions.

[jdoerfert]

clang/lib/Sema/SemaOpenMP.cpp

1831

It's not nonsense. I think the current system is not meant for non-function diagnostics. That said, I could probably bail later in the call chain, e.g. in diagIfOpenMPDeviceCode. Later we should rethink how this is done as we adopt to a more user-friendly model.

[jdoerfert]

I think this will be fixed by D74387, we should include the tests somewhere though.

[Fznamznon]

In D77918#2060446, @jdoerfert wrote:

I think this will be fixed by D74387, we should include the tests somewhere though.

D74387 includes a test case with expression involving unsupported types outside of a function (at the end of in nvptx_unsupported_type_messages.cpp).

[jdoerfert]

Great. I'll ask in the other patch to add these three lines just to be sure ;)

clang/lib/Sema/SemaOpenMP.cpp

Sema::DeviceDiagBuilder Sema::diagIfOpenMPHostCode(SourceLocation Loc,
   }
 
   return DeviceDiagBuilder(Kind, Loc, DiagID, getCurFunctionDecl(), *this);
 }
 
 void Sema::checkOpenMPDeviceExpr(const Expr *E) {
   assert(getLangOpts().OpenMP && getLangOpts().OpenMPIsDevice &&
          "OpenMP device compilation mode is expected.");
+  // TODO: Do not check outside of functions for now as the targetDiag below
+  //       requires one.
+  if (!getCurFunctionDecl())
+    return;
   QualType Ty = E->getType();
   if ((Ty->isFloat16Type() && !Context.getTargetInfo().hasFloat16Type()) ||
       ((Ty->isFloat128Type() ||
         (Ty->isRealFloatingType() && Context.getTypeSize(Ty) == 128)) &&
        !Context.getTargetInfo().hasFloat128Type()) ||
       (Ty->isIntegerType() && Context.getTypeSize(Ty) == 128 &&
        !Context.getTargetInfo().hasInt128Type()))
     targetDiag(E->getExprLoc(), diag::err_omp_unsupported_type)

clang/test/OpenMP/nvptx_unsupported_type_messages.cpp

 }
 T1 bar1() {
   return T1();
 }
 void baz1() {
   T1 t = bar1();
 }
 #pragma omp end declare target
+
+// Do not crash on these expressions during device compilation.
+long double qa, qb;
+decltype(qa + qb) qc;
+double qd[sizeof(-(-(qc * 2)))];