[clang] [OpenMP] Diagnose use of 'target_clones' in OpenMP variant declarations.

[tahonermann]

Summary

Previously, OpenMP variant declarations for a function declaration that included
the 'cpu_dispatch', 'cpu_specific', or 'target' attributes was diagnosed, but
one with the 'target_clones' attribute was not. Now fixed.

[jdoerfert]

LG

[tahonermann]

Rebase.

[tahonermann]

Rebase to acquire fixes from parent commits.

clang/lib/Sema/SemaOpenMP.cpp

Sema::checkOpenMPDeclareVariantFunction(Sema::DeclGroupPtrTy DG,
   auto *FD = dyn_cast<FunctionDecl>(ADecl);
   if (!FD) {
     Diag(ADecl->getLocation(), diag::err_omp_function_expected)
         << VariantId << SR;
     return None;
   }
 
   auto &&HasMultiVersionAttributes = [](const FunctionDecl *FD) {
-    return FD->hasAttrs() &&
-           (FD->hasAttr<CPUDispatchAttr>() || FD->hasAttr<CPUSpecificAttr>() ||
-            FD->hasAttr<TargetAttr>());
+    // The 'target' attribute needs to be separately checked because it does
+    // not always signify a multiversion function declaration.
+    return FD->isMultiVersion() || FD->hasAttr<TargetAttr>();
   };
-  // OpenMP is not compatible with CPU-specific attributes.
+  // OpenMP is not compatible with multiversion function attributes.
   if (HasMultiVersionAttributes(FD)) {
     Diag(FD->getLocation(), diag::err_omp_declare_variant_incompat_attributes)
         << SR;
     return None;
   }
 
   // Allow #pragma omp declare variant only if the function is not used.
   if (FD->isUsed(false))

clang/test/OpenMP/declare_variant_messages.c

 // This declaration makes it one.
 #pragma omp declare variant(incompat_attr_variant) match(implementation={vendor(llvm)})
 __attribute__((target("sse"))) void incompat_attr_target(void); // expected-error {{'#pragma omp declare variant' is not compatible with any target-specific attributes}}
 
 // 'incompat_attr_target_default' is always a multiversion function.
 #pragma omp declare variant(incompat_attr_variant) match(implementation={vendor(llvm)})
 __attribute__((target("default"))) void incompat_attr_target_default(void); // expected-error {{'#pragma omp declare variant' is not compatible with any target-specific attributes}}
 
-// FIXME: No diagnostics are produced for use of the 'target_clones' attribute in an OMP variant declaration.
 #pragma omp declare variant(incompat_attr_variant) match(implementation={vendor(llvm)})
-__attribute__((target_clones("sse,default"))) void incompat_attr_target_clones(void);
+__attribute__((target_clones("sse,default"))) void incompat_attr_target_clones(void); // expected-error {{'#pragma omp declare variant' is not compatible with any target-specific attributes}}
 
 void marked(void);
 void not_marked(void);
 
 #pragma omp declare variant(not_marked) match(implementation={vendor(unknown)}, device={kind(cpu)}) // expected-note {{marked as 'declare variant' here}}
 void marked_variant(void);
 
 #pragma omp declare variant(marked_variant) match(xxx={}) // expected-warning {{'xxx' is not a valid context set in a `declare variant`; set ignored}} expected-warning {{variant function in '#pragma omp declare variant' is itself marked as '#pragma omp declare variant'}} expected-note {{context set options are: 'construct' 'device' 'implementation' 'user'}} expected-note {{the ignored set spans until here}}