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<p class="MsoNormal"><span style="color:#1F497D">Hi Sam,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Could you implement CL2.0 atomics by calling the C11 ones, i.e. doing something like:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> C atomic_exchange( volatile A* obj, C desired ){<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> return __c11_atomic_exchange(obj, desired);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">There is still one issue we have though with an absence of memory_scope in Clang/LLVM.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">So for the following declaration, we don’t have anything available in Clang to represent the last parameter:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">C atomic_exchange_explicit(volatile A *object, C desired, memory_order order, memory_scope scope);
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">We also don’t have anything in IR to map it to.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">One approach here could be to just ignore it and perhaps call a regular C11 atomic passing all other parameters except memory scope.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Alternatively we could extend the Clang atomic builtins with CL2.0 style builtins for those that require memory scope.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Btw @Alexey, we did add some CL builtins recently i.e for Pipes (see clang@r258782) and will probably need more – enqueue_kernel.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Cheers,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Anastasia<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Liu, Yaxun (Sam) [mailto:Yaxun.Liu@amd.com]
<br>
<b>Sent:</b> 04 March 2016 18:04<br>
<b>To:</b> Bader, Alexey; Anastasia Stulova; Pan, Xiuli; cfe-dev@lists.llvm.org<br>
<b>Cc:</b> Sumner, Brian; Stellard, Thomas; Zhang, Guansong<br>
<b>Subject:</b> RE: [OpenCL] RFC: let Clang generate llvm atomic instructions for OpenCL atomic builtin functions<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">Hi Alexey,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">To clarify, when I said OpenCL atomic builtin functions, the ‘builtin’ was in the sense of OpenCL spec. In Clang they are just treated as ordinary functions.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">Let’s take an example of OpenCL atomic builtin function:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">uint y;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">volatile __global atomic_uint *x;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">atomic_store(x, y);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">Currently we clang generates a function call<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"> call spir_func void @_Z12atomic_storePVU3AS1U7_Atomicjj(i32 addrspace(1)* %x, i32 %y)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">However, it can simply be represented as an LLVM instruction<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"> store atomic volatile i32 %y, i32 addrspace(1)* %x seq_cst, align 4<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">So I am wondering why not let Clang just generating the instruction directly, since Clang already did the same thing for some libm functions.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">Sam<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> Bader, Alexey [<a href="mailto:alexey.bader@intel.com">mailto:alexey.bader@intel.com</a>]
<br>
<b>Sent:</b> Friday, March 4, 2016 11:22 AM<br>
<b>To:</b> Liu, Yaxun (Sam) <<a href="mailto:Yaxun.Liu@amd.com">Yaxun.Liu@amd.com</a>>; 'anastasia.stulova@arm.com' <<a href="mailto:anastasia.stulova@arm.com">anastasia.stulova@arm.com</a>>; Pan, Xiuli <<a href="mailto:xiuli.pan@intel.com">xiuli.pan@intel.com</a>>;
<a href="mailto:cfe-dev@lists.llvm.org">cfe-dev@lists.llvm.org</a><br>
<b>Cc:</b> Sumner, Brian <<a href="mailto:Brian.Sumner@amd.com">Brian.Sumner@amd.com</a>><br>
<b>Subject:</b> RE: [OpenCL] RFC: let Clang generate llvm atomic instructions for OpenCL atomic builtin functions<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><a name="_MailEndCompose"><span lang="EN-US" style="color:#993366">Hi Sam,</span></a><span lang="EN-US" style="color:#993366"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#993366"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#993366">Could you clarify your idea?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#993366">At the moment clang doesn’t provide any OpenCL built-in functions – they are provided by OpenCL implementation.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#993366">Clang provides </span>
<span lang="RU"><a href="http://clang.llvm.org/docs/LanguageExtensions.html#c11-atomic-builtins"><span lang="EN-US">C11 atomic built-ins</span></a></span><span lang="EN-US" style="color:#993366"> which should produce desired llvm atomic instructions.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#993366">This should work for OpenCL v2.0 atomics since they are taken from C11.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#993366"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US" style="color:#993366">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#993366">Alexey<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><a name="_____replyseparator"></a><b><span lang="EN-US">From:</span></b><span lang="EN-US"> Liu, Yaxun (Sam) [<a href="mailto:Yaxun.Liu@amd.com">mailto:Yaxun.Liu@amd.com</a>]
<br>
<b>Sent:</b> Thursday, March 3, 2016 11:37 PM<br>
<b>To:</b> Bader, Alexey; 'anastasia.stulova@arm.com'; Pan, Xiuli; <a href="mailto:cfe-dev@lists.llvm.org">
cfe-dev@lists.llvm.org</a><br>
<b>Cc:</b> Sumner, Brian<br>
<b>Subject:</b> RE: [OpenCL] RFC: let Clang generate llvm atomic instructions for OpenCL atomic builtin functions<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="RU"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">OpenCL atomic builtin functions are similar to llvm atomic instructions. It seems natural to represent OpenCL atomic builtin functions by LLVM atomic instructions.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Doing this can simplify implementation of OpenCL builtin library and have a unified representation for OpenCL atomic builtin functions.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Any feedback? Thanks.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Sam<o:p></o:p></span></p>
<p><span lang="RU"><br>
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