[PATCH] D124866: [CUDA][HIP] support __noinline__ as keyword

[Yaxun Liu via Phabricator via cfe-commits]

yaxunl marked 4 inline comments as done.
yaxunl added inline comments.


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Comment at: clang/docs/ReleaseNotes.rst:344-345
 
-CUDA Language Changes in Clang
+CUDA/HIP Language Changes in Clang
 ------------------------------
 
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aaron.ballman wrote:
> 
will fix


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Comment at: clang/include/clang/Basic/AttrDocs.td:543
+avoid diagnostics due to usage of ``__attribute__((__noinline__))``
+with ``__noinline__`` defined as a macro as ``__attribute__((noinline))`.
+
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aaron.ballman wrote:
> 
will fix.


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Comment at: clang/lib/Parse/ParseDecl.cpp:902
+  while (Tok.is(tok::kw___noinline__)) {
+    IdentifierInfo *AttrName = Tok.getIdentifierInfo();
+    SourceLocation AttrNameLoc = ConsumeToken();
----------------
tra wrote:
> yaxunl wrote:
> > tra wrote:
> > > aaron.ballman wrote:
> > > > yaxunl wrote:
> > > > > aaron.ballman wrote:
> > > > > > I think we should we be issuing a pedantic "this is a clang extension" warning here, WDYT?
> > > > > will do
> > > > I'm questioning whether my advice here was good or not -- now that I see the CUDA spec already calls these function qualifiers... it's debatable whether this is a Clang extension or just the way in which Clang implements the CUDA function qualifiers. @tra -- do you have opinions?
> > > > 
> > > > I'm sort of leaning towards dropping the extension warning, but the only reason I can think of for keeping it is if Clang is the only CUDA compiler that doesn't require you to include a header before using the function qualifiers. If that's the case, there is a portability concern.
> > > I'm not sure if such a warning would be useful. 
> > > 
> > > > the only reason I can think of for keeping it is if Clang is the only CUDA compiler that doesn't require you to include a header before using the function qualifiers. If that's the case, there is a portability concern.
> > > 
> > > I don't think it's an issue.
> > > 
> > > We already have similar divergence between nvcc/clang. E.g. built-in variables like `threadIdx`. Clang implements them in a header, but NVCC provides them by compiler itself. 
> > > With both compilers the variables are available by the time we get to compile user code. Virtually all CUDA compilations are done with tons of CUDA headers pre-included by compiler. Those that do not do that are already on their own and have to provide many other 'standard' CUDA things like target attributes. I don't think we need to worry about that.
> > > 
> > I can remove the diagnostics since it seems unnecessary.
> > 
> > I tend to treat it as an extension since nvcc is the de facto standard implementation, which does not implement it as a keyword. Compared to that, this is like an extension.
> I'd argue that NVCC does implement it (as in "documents and makes it available"). Providing the documented functionality using a different implementation does not reach the point of being an extension, IMO. While there are observable differences between implementations, depending on them would be a portability error for the user.
> 
that makes sense. will change the extension to feature


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Comment at: clang/test/SemaCUDA/noinline.cu:8
+__attribute__((noinline)) void fun2() { }
+__attribute__((__noinline__)) void fun3() { }
----------------
aaron.ballman wrote:
> yaxunl wrote:
> > aaron.ballman wrote:
> > > yaxunl wrote:
> > > > aaron.ballman wrote:
> > > > > I think there should also be a test like:
> > > > > ```
> > > > > [[gnu::__noinline__]] void fun4() {}
> > > > > ```
> > > > > to verify that the double square bracket syntax also correctly handles this being a keyword now (I expect the test to pass).
> > > > will do
> > > Ah, I just noticed we also have no tests for the behavior of the keyword in the presence of the macro being defined. e.g.,
> > > ```
> > > #define __noinline__ __attribute__((__noinline__))
> > > __noinline__ void fun5() {}
> > > ```
> > will do
> I missed an important detail -- I think this is now going to generate a warning in `-pedantic` mode (through `-Wkeyword-macro`) when compiling for CUDA; is that going to be a problem for CUDA headers, or are those always included as a system header (and so the diagnostics will be suppressed)?
I could not find how clang driver adds CUDA include path

https://github.com/llvm/llvm-project/blob/main/clang/lib/Driver/ToolChains/Cuda.cpp#L284

@tra do you know how CUDA include path is added? is it done by CMake? 

For HIP the HIP include path is added as a system include path by clang driver.


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https://reviews.llvm.org/D124866