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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>This idea seems to have good merits to me. It seems like any functionality related to pointer types could determined at load/store time without the overhead of specifying pointer types in IR only to cast it away right before usage.<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'>I often found myself doing the i8* trick any time what I was pointing to didn’t easy fit in to the type system since, as others pointed out, the frontend should know what the actual types are anyway.<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'>One migration issue I could see is any time a frontend depends on the LLVM type system for tracking types rather than doing it itself.<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><b><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>From:</span></b><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'> llvmdev-bounces@cs.uiuc.edu [mailto:llvmdev-bounces@cs.uiuc.edu] <b>On Behalf Of </b>David Blaikie<br><b>Sent:</b> Tuesday, February 17, 2015 11:34 AM<br><b>To:</b> Chris Lattner<br><b>Cc:</b> LLVM Developers Mailing List<br><b>Subject:</b> Re: [LLVMdev] Moving towards a singular pointer type<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>On Mon, Feb 16, 2015 at 3:53 PM, Chris Lattner <<a href="mailto:clattner@apple.com" target="_blank">clattner@apple.com</a>> wrote:<o:p></o:p></p><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><div><p class=MsoNormal><o:p> </o:p></p><div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal>On Feb 6, 2015, at 3:38 PM, David Blaikie <<a href="mailto:dblaikie@gmail.com" target="_blank">dblaikie@gmail.com</a>> wrote:<o:p></o:p></p></div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal>It's an idea been thrown around in a few different threads (including Rafael's recent <a href="http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20141201/247285.html" target="_blank">http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20141201/247285.html</a> and Chandler's <a href="http://llvm.org/viewvc/llvm-project?rev=226781&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=226781&view=rev</a> ) so I'm putting up my hand to volunteer to do the work & interested in getting a bit more feedback, thoughts on best approaches, timing, etc.<br><br>For some more detail: pointer types (i32*, %foo*, etc) complicate IR canonicalization. store + load should be the same instructions given the same number of bytes stored to memory, but instead we can have store float, store int, etc, etc. Another point Chandler made was that the bitcasts involved when a pointer isn't of the right type results in extra IR instructions we don't really need.<br><br>So the general idea is that all pointers would just be called "ptr" (pointer? void*?).<br><br>Is this something everyone feels is the right direction? Any reason why it wouldn't be?<o:p></o:p></p></div></div></blockquote></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Hi David,<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>You can emulate this by having clang always generate "i8*” as the general type, then bitcast to "%Foo*” before doing a GEP. Have you prototyped this change (with this approach, or any other one) to see what it does to the optimizers?<o:p></o:p></p></div></div></blockquote><div><p class=MsoNormal><br>No, I haven't tried prototyping it. It's a fair point, though I'm not sure how much of that work would be thrown out (some of it would be reusable - since it'll force the front end to track type information wehre it might've previously been relying on the IR types). Reckon it's worthwhile? (I can certainly see that side of it - throwing all this churn in when we don't quite know how it'll play out in the end seem risky, but it seemed like those who're invested in this stuff felt pretty certain it was the right way to go)<br><br>- David<br> <o:p></o:p></p></div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><div><div><p class=MsoNormal><span style='color:#888888'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='color:#888888'>-Chris<o:p></o:p></span></p></div></div></blockquote></div><p class=MsoNormal><o:p> </o:p></p></div></div></div></body></html>