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<p class="MsoNormal">Language extensions/changes that need to be controlled on the command-line are generally controlled with “-f” options. I think we want to continue doing that.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">For the standard version, it isn’t clear to me how tightly SYCL and the C++ standard version are tied together. Are the SYCL features supported orthogonal to the C++ language features supported? Does the SYCL standard require some specific
version of C++? If it makes sense, then specifying the SYCL standard version in a separate flag is probably fine.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">“1.2.1-ext” doesn’t really make sense, I think; we don’t want the “standard version” to refer to some unspecified set of extensions. If there’s a revised standard under development, it could make sense to refer to that before it’s finalized,
though. For C++, for example, we have -std=c++2a to refer to the draft C++20 standard.<o:p></o:p></p>
<p class="MsoNormal"><o:p></o:p></p>
<p class="MsoNormal">We don’t want to enable extensions by default unless they’re extensions the standard allows (for C++, that generally means that it uses some identifier reserved for the compiler).<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">-Eli<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>From:</b> cfe-dev <cfe-dev-bounces@lists.llvm.org> <b>On Behalf Of
</b>Bader, Alexey via cfe-dev<br>
<b>Sent:</b> Monday, November 25, 2019 5:03 AM<br>
<b>To:</b> clang-dev developer list <cfe-dev@lists.llvm.org><br>
<b>Cc:</b> Toguchi, Michael D <michael.d.toguchi@intel.com><br>
<b>Subject:</b> [EXT] [cfe-dev] [RFC][SYCL] Driver options to control non-standard features.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’d like to clarify the guidelines regarding clang driver option names for Clang extensions. We developed a number of options to control SYCL standard version and extensions to the SYCL standard features and we would like to make sure that
these are aligned with the community expectations.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>Options to turn on/off an individual extension of SYCL standard functionality<o:p></o:p></b></p>
<p class="MsoNormal">Naming convention we use for these options is to prefix option with -fsycl- prefix (e.g. -fsycl-usm, -fsycl-unnamed-lambda).<o:p></o:p></p>
<p class="MsoNormal">SYCL runtime library or application can check extension status via __has_extension macro (e.g. __has_extension(sycl_usm), __has_extension(sycl_unnamed_lambda)).<o:p></o:p></p>
<p class="MsoNormal">Some of SYCL extensions can be enabled by default.<o:p></o:p></p>
<p class="MsoNormal"><b><o:p> </o:p></b></p>
<p class="MsoNormal"><b>Option to set SYCL standard version<o:p></o:p></b></p>
<p class="MsoNormal">Current implementation [1] supports -sycl-std=<value> option name with only one supported value: 1.2.1 (default).<o:p></o:p></p>
<p class="MsoNormal">We are considering a new value “1.2.1-ext”, which will enable SYCL 1.2.1 features + a set of default extensions and “1.2.1” will restrict usage of non-standard features. “1.2.1-ext” is going to be a new default value.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Does it sound like something that can be accepted into the clang tree?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>Open questions/alternatives<o:p></o:p></b></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l1 level1 lfo3">Should we extend/re-use existing options or add SYCL specific options? For instance, re-use -std to set SYCL standard version instead of adding -sycl-std. Or make -pedantic to warn
about using SYCL extensions enabled by default.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l1 level1 lfo3">Does it make sense to provide OpenCL-like single option to control individual extensions: -sycl-ext=”+<extension1>,-<extension2>,…” instead of adding -f[no-]sycl-<extension1>, -f[no-]sycl-<extension2>,...
options.<o:p></o:p></li></ul>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks,<o:p></o:p></p>
<p class="MsoNormal">Alexey<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">PS SYCL developers internal discussion can be found in this GitHub issue:
<a href="https://github.com/intel/llvm/issues/806">https://github.com/intel/llvm/issues/806</a>.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">[1] <a href="https://github.com/intel/llvm/tree/sycl">https://github.com/intel/llvm/tree/sycl</a><o:p></o:p></p>
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