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<p class="MsoNormal"><span style="color:#1F497D">I guess another option would be to mangle differently OpenCL and GCC vectors. Not sure what would be better though…<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""> cfe-dev [mailto:cfe-dev-bounces@lists.llvm.org]
<b>On Behalf Of </b>Yung, Douglas via cfe-dev<br>
<b>Sent:</b> 03 February 2016 03:33<br>
<b>To:</b> cfe-dev@lists.llvm.org<br>
<b>Subject:</b> [cfe-dev] Using both OpenCL and GCC vectors<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">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">In our testing, we discovered a regression in 3.8 when trying to use both OpenCL and GCC vectors in the same program. Consider the following code:<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" style="font-size:13.5pt;font-family:"Courier New";color:black">template <typename alpha><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:13.5pt;font-family:"Courier New";color:black">static void foo() {}<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:13.5pt;font-family:"Courier New";color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:13.5pt;font-family:"Courier New";color:black">void bar() {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:13.5pt;font-family:"Courier New";color:black"> foo<float __attribute__((__vector_size__(16)))>();<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:13.5pt;font-family:"Courier New";color:black"> foo<float __attribute__((ext_vector_type(4)))>();<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:13.5pt;font-family:"Courier New";color:black">}<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">In 3.7, the code compiled without any errors, but in 3.8 it fails to compile. The problem is that clang considers GCC and OpenCL vectors to be unique types, but since they mangle identically, the compiler instantiates
two versions of foo which are identical and emits an error:<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" style="font-family:Consolas">repro.cpp:2:13: error: definition with same mangled name as another definition<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:Consolas">static void foo() {}<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:Consolas"> ^<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:Consolas">repro4.cpp:2:13: note: previous definition is here<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:Consolas">1 error generated.</span><span lang="EN-US"><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">The error is unfortunately not very helpful and was filed as PR25343. However, we feel that the compiler could be smarter in these cases. For example, the compiler could recognize that it is generating the same function
when instantiating the second instance of foo and reuse the first one instead of creating another one. This would prevent the creation of two identically mangled names which caused the error seen above. Or perhaps the compiler could be smarter and when it
encounters the second instantiation of foo, it would issue an error at that point with a useful diagnostic.<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">Thoughts?<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">Douglas Yung<o:p></o:p></span></p>
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