[PATCH] D89909: [SYCL] Implement SYCL address space attributes handling

[Alexey Bader via Phabricator via llvm-commits]

bader added inline comments.


================
Comment at: clang/lib/CodeGen/CGExpr.cpp:4554
+
+      // Language rules define if it is legal to cast from one address space
+      // to another, and which address space we should use as a "common
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asavonic wrote:
> sdmitriev wrote:
> > bader wrote:
> > > Anastasia wrote:
> > > > What language rules?
> > > I suppose it's a generic note and author didn't meant some particular language here. This change was contributed by @sdmitriev. 
> > > @sdmitriev, could you clarify, please?
> > This comment was originally added by @asavonic to clang/lib/CodeGen/CGExprScalar.cpp (lines 2962-2965 in this patch), and later I reused his code along with the comment in this file while fixing a very similar issue. So, I guess it would be more correct to ask Andrew to clarify. @asavonic, can you please comment on this?
> > This comment was originally added by @asavonic to clang/lib/CodeGen/CGExprScalar.cpp (lines 2962-2965 in this patch), and later I reused his code along with the comment in this file while fixing a very similar issue.
> 
> There is `if (Opts.SYCLIsDevice)` In CGExprScalar.cpp, so we handle SYCL language rules.
> In SYCL, (almost) all pointers have default address space in AST, but in CG some pointers become private/local/global, and some are lowered as generic pointers. We need to add an implicit addrspacecast in CG to emit an expression that expects the same type for its operands.
> 
> For example:
>     const char *str = ... ;
>     const char *phi_str = i > 2 ? str : "hello world!";
> 
> In AST types of `str` and `"hello world"` are the same (`const char *`). In CG we emit `str` as `i8 addrspace(4)*` and `"hello world"` as `i8*`. At this point we have to decide what type `phi_str` should have, and addrspacecast the operands accordingly.
Is it possible to avoid fixing address space mismatch at this point by adjusting AST as suggested by John in this comment: https://reviews.llvm.org/D89909#inline-837495?

I wonder if it can be done w/o impacting C++ template metaprogramming as noted in this thread: http://clang-developers.42468.n3.nabble.com/RFC-Re-use-OpenCL-address-space-attributes-for-SYCL-td4068754.html.


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  https://reviews.llvm.org/D89909/new/

https://reviews.llvm.org/D89909