[OpenCL] Add verbosity when checking support of read_write images

[azabaznov]

Summary

Parenthesis were fixed incorrectly by D105890

[thakis]

This is not NFC, is it? Before, this got evaluated as (!S.getLangOpts().OpenCLCPlusPlus && S.getLangOpts().OpenCLVersion < 200) || (S.getLangOpts().OpenCLVersion == 300 && !S.getOpenCLOptions().isSupported("__opencl_c_read_write_images", S.getLangOpts())). Now, it's evaluated as !S.getLangOpts().OpenCLCPlusPlus && (...rest...) -- that is, !S.getLangOpts().OpenCLCPlusPlus used to be anded with just one term and now it's anded with the whole thing.

Maybe it's worth to introduce some bool variables to make this less confusing instead of this one very long term?

[aaron.ballman]

Note: https://reviews.llvm.org/D105890 that was just landed to touch the same area.

FWIW, I agree that this should probably be using some local variables to make the conditions a bit more clear.

[azabaznov]

Add comment for C++ for OpenCL, add variable to check support for OpenCL C

[Anastasia]

LGTM! Thanks!

[Anastasia]

In D105892#2873951, @aaron.ballman wrote:

Note: https://reviews.llvm.org/D105890 that was just landed to touch the same area.

Yeah, I think it fixed the actual warning but we can still simplify the condition.

[thakis]

Thanks!

clang/lib/Sema/SemaDeclAttr.cpp

static void handleOpenCLAccessAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
 
   // OpenCL v2.0 s6.6 - read_write can be used for image types to specify that
   // an image object can be read and written. OpenCL v2.0 s6.13.6 - A kernel
   // cannot read from and write to the same pipe object. Using the read_write
   // (or __read_write) qualifier with the pipe qualifier is a compilation error.
   // OpenCL v3.0 s6.8 - For OpenCL C 2.0, or with the
   // __opencl_c_read_write_images feature, image objects specified as arguments
   // to a kernel can additionally be declared to be read-write.
+  // C++ for OpenCL inherits rule from OpenCL C v2.0.
   if (const auto *PDecl = dyn_cast<ParmVarDecl>(D)) {
     const Type *DeclTy = PDecl->getType().getCanonicalType().getTypePtr();
     if (AL.getAttrName()->getName().find("read_write") != StringRef::npos) {
-      if (((!S.getLangOpts().OpenCLCPlusPlus &&
-            (S.getLangOpts().OpenCLVersion < 200)) ||
-           (S.getLangOpts().OpenCLVersion == 300 &&
-            !S.getOpenCLOptions().isSupported("__opencl_c_read_write_images",
-                                              S.getLangOpts()))) ||
+      bool ReadWriteImagesUnsupportedForOCLC =
+          (S.getLangOpts().OpenCLVersion < 200) ||
+                                             S.getLangOpts()));
+      if ((!S.getLangOpts().OpenCLCPlusPlus &&
+           ReadWriteImagesUnsupportedForOCLC) ||
           DeclTy->isPipeType()) {
         S.Diag(AL.getLoc(), diag::err_opencl_invalid_read_write)
             << AL << PDecl->getType() << DeclTy->isImageType();
         D->setInvalidDecl(true);
         return;
       }
     }
   }