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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Ok, thanks for pointing out the location in the spec. There are some good points here, especially in the rank of ‘size_t’ that the SPIR WG will have to decide.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">However, one thing to keep in mind, this code is by definition non-portable and so SPIR is not trying to make it more portable. This might be one of those cases
where implementation defined behavior of C does not allow the program to be portable.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><br>
Thanks.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> metafoo@gmail.com [mailto:metafoo@gmail.com]
<b>On Behalf Of </b>Richard Smith<br>
<b>Sent:</b> Wednesday, September 12, 2012 4:03 PM<br>
<b>To:</b> Villmow, Micah<br>
<b>Cc:</b> Eli Friedman; cfe-dev@cs.uiuc.edu; llvmdev@cs.uiuc.edu<br>
<b>Subject:</b> Re: [cfe-dev] [LLVMdev] SPIR Portability Discussion<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">On Wed, Sep 12, 2012 at 3:40 PM, Villmow, Micah <<a href="mailto:Micah.Villmow@amd.com" target="_blank">Micah.Villmow@amd.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">
<a href="mailto:metafoo@gmail.com" target="_blank">metafoo@gmail.com</a> [mailto:<a href="mailto:metafoo@gmail.com" target="_blank">metafoo@gmail.com</a>]
<b>On Behalf Of </b>Richard Smith<br>
<b>Sent:</b> Wednesday, September 12, 2012 3:30 PM<br>
<b>To:</b> Villmow, Micah<br>
<b>Cc:</b> Eli Friedman; <a href="mailto:cfe-dev@cs.uiuc.edu" target="_blank">cfe-dev@cs.uiuc.edu</a>;
<a href="mailto:llvmdev@cs.uiuc.edu" target="_blank">llvmdev@cs.uiuc.edu</a></span><o:p></o:p></p>
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<p class="MsoNormal"><br>
<b>Subject:</b> Re: [cfe-dev] [LLVMdev] SPIR Portability Discussion<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">On Wed, Sep 12, 2012 at 3:26 PM, Villmow, Micah <<a href="mailto:Micah.Villmow@amd.com" target="_blank">Micah.Villmow@amd.com</a>> wrote:<o:p></o:p></p>
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<br>
> -----Original Message-----<br>
> From: Eli Friedman [mailto:<a href="mailto:eli.friedman@gmail.com" target="_blank">eli.friedman@gmail.com</a>]<br>
> Sent: Wednesday, September 12, 2012 3:22 PM<br>
> To: Villmow, Micah<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">> Cc: Richard Smith;
<a href="mailto:cfe-dev@cs.uiuc.edu" target="_blank">cfe-dev@cs.uiuc.edu</a>; <a href="mailto:llvmdev@cs.uiuc.edu" target="_blank">
llvmdev@cs.uiuc.edu</a><br>
> Subject: Re: [cfe-dev] [LLVMdev] SPIR Portability Discussion<br>
><br>
> On Wed, Sep 12, 2012 at 2:58 PM, Villmow, Micah <<a href="mailto:Micah.Villmow@amd.com" target="_blank">Micah.Villmow@amd.com</a>><br>
> wrote:<br>
> > Another factor to consider, with size_t etc as defined in SPIR, is<br>
> the usual<br>
> > arithmetic conversions. For instance (assuming a 64-bit long long),<br>
> > sizeof(int) + 1LL would be signed if size_t is 32 bits wide, and<br>
> would be<br>
> > unsigned if size_t is 64 bits wide. How is this handled?<br>
> ><br>
> > [Villmow, Micah] OpenCL C defines 'int' to be 32bits irrespective of<br>
> the<br>
> > host/device bitness. So this would follow the normal integer<br>
> promotion<br>
> > rules.<br>
><br>
> I think you're misunderstanding the issue: the point is, is<br>
> "sizeof(int) + -8LL < 0" true or false?<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">[Villmow, Micah] Yep, I don't see why this is any different than "4 + -8LL < 0". OpenCL C, and in turn SPIR, defines sizeof(int) == 4. While this might be a problem in C, this
isn't an issue in OpenCL since there is no variance in the sizeof(int) across devices.<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I think you're still misunderstanding. If size_t is 32 bits, sizeof(int) + -8LL is -4LL, so the comparison produces true. If it's 64 bits, the -8LL promotes to an unsigned long
long, sizeof(int) + -8LL is 18446744073709551612ULL, the 0 promotes to 0ULL, and the comparison produces false.<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">[Villmow, Micah] I see now, I think you had a type-o in the previous email, “sizeof(sizeof(int))”
should have been size_t(sizeof(int)), which was throwing me off.</span></i></b><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">What I wrote was what I meant. The *value* of sizeof(int) is not relevant here, what matters is the precision of its type (or more specifically, its integer conversion rank).<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Though I’m curious where it states we have to promote -8LL to unsigned long and not signed
long, I would have thought it would be signed.\</span></i></b><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">C99 <a href="http://6.3.1.8/1">6.3.1.8/1</a>.<o:p></o:p></p>
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