[Sema][OpenCL] Improve diagnostics for not viable overloadable functi…

…on candidates

Summary:
Allowed extension name (that ought to be disabled) printing in the note message.

This diagnostic was proposed here: https://reviews.llvm.org/D51341

Reviewers: Anastasia, yaxunl

Reviewed By: Anastasia

Subscribers: cfe-commits, asavonic, bader

Differential Revision: https://reviews.llvm.org/D52292

llvm-svn: 344246

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -3674,7 +3674,7 @@ def warn_diagnose_if_succeeded : Warning<"%0">, InGroup<UserDefinedWarnings>,
 def note_ovl_candidate_disabled_by_function_cond_attr : Note<
     "candidate disabled: %0">;
 def note_ovl_candidate_disabled_by_extension : Note<
-    "candidate disabled due to OpenCL extension">;
+    "candidate unavailable as it requires OpenCL extension '%0' to be disabled">;
 def err_addrof_function_disabled_by_enable_if_attr : Error<
     "cannot take address of function %0 because it has one or more "
     "non-tautological enable_if conditions">;

clang/include/clang/Sema/Sema.h

@@ -8576,6 +8576,21 @@ class Sema {
   llvm::StringRef getCurrentOpenCLExtension() const {
     return CurrOpenCLExtension;
   }
+
+  /// Check if a function declaration \p FD associates with any
+  /// extensions present in OpenCLDeclExtMap and if so return the
+  /// extension(s) name(s).
+  std::string getOpenCLExtensionsFromDeclExtMap(FunctionDecl *FD);
+
+  /// Check if a function type \p FT associates with any
+  /// extensions present in OpenCLTypeExtMap and if so return the
+  /// extension(s) name(s).
+  std::string getOpenCLExtensionsFromTypeExtMap(FunctionType *FT);
+
+  /// Find an extension in an appropriate extension map and return its name
+  template<typename T, typename MapT>
+  std::string getOpenCLExtensionsFromExtMap(T* FT, MapT &Map);
+
   void setCurrentOpenCLExtension(llvm::StringRef Ext) {
     CurrOpenCLExtension = Ext;
   }

clang/lib/Sema/Sema.cpp

@@ -1914,6 +1914,34 @@ void Sema::setCurrentOpenCLExtensionForDecl(Decl *D) {
   setOpenCLExtensionForDecl(D, CurrOpenCLExtension);
 }
 
+std::string Sema::getOpenCLExtensionsFromDeclExtMap(FunctionDecl *FD) {
+  if (!OpenCLDeclExtMap.empty())
+    return getOpenCLExtensionsFromExtMap(FD, OpenCLDeclExtMap);
+
+  return "";
+}
+
+std::string Sema::getOpenCLExtensionsFromTypeExtMap(FunctionType *FT) {
+  if (!OpenCLTypeExtMap.empty())
+    return getOpenCLExtensionsFromExtMap(FT, OpenCLTypeExtMap);
+
+  return "";
+}
+
+template <typename T, typename MapT>
+std::string Sema::getOpenCLExtensionsFromExtMap(T *FDT, MapT &Map) {
+  std::string ExtensionNames = "";
+  auto Loc = Map.find(FDT);
+
+  for (auto const& I : Loc->second) {
+    ExtensionNames += I;
+    ExtensionNames += " ";
+  }
+  ExtensionNames.pop_back();
+
+  return ExtensionNames;
+}
+
 bool Sema::isOpenCLDisabledDecl(Decl *FD) {
   auto Loc = OpenCLDeclExtMap.find(FD);
   if (Loc == OpenCLDeclExtMap.end())

clang/lib/Sema/SemaOverload.cpp

@@ -10242,7 +10242,8 @@ static void DiagnoseOpenCLExtensionDisabled(Sema &S, OverloadCandidate *Cand) {
   FunctionDecl *Callee = Cand->Function;
 
   S.Diag(Callee->getLocation(),
-         diag::note_ovl_candidate_disabled_by_extension);
+         diag::note_ovl_candidate_disabled_by_extension)
+    << S.getOpenCLExtensionsFromDeclExtMap(Callee);
 }
 
 /// Generates a 'note' diagnostic for an overload candidate.  We've

clang/test/SemaOpenCL/extension-begin.cl

@@ -48,7 +48,7 @@ void test_f2(void) {
   PointerOfA test_A_pointer; // expected-error {{use of type 'PointerOfA' (aka 'const struct A *') requires my_ext extension to be enabled}}
   f(); // expected-error {{use of declaration 'f' requires my_ext extension to be enabled}}
   g(0); // expected-error {{no matching function for call to 'g'}}
-        // expected-note@-26 {{candidate disabled due to OpenCL extension}}
+        // expected-note@-26 {{candidate unavailable as it requires OpenCL extension 'my_ext' to be disabled}}
         // expected-note@-22 {{candidate function not viable: requires 0 arguments, but 1 was provided}}
 }