<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Oct 31, 2016, at 10:53 AM, Hal Finkel via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">----- Original Message -----</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><blockquote type="cite" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class="">From: "Reid Kleckner" <<a href="mailto:rnk@google.com" class="">rnk@google.com</a>><br class="">To: "Hal Finkel" <<a href="mailto:hfinkel@anl.gov" class="">hfinkel@anl.gov</a>><br class="">Cc: "Chris Lattner" <<a href="mailto:clattner@apple.com" class="">clattner@apple.com</a>>, "llvm-dev" <<a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a>>, "ジョウェットジェームス"<br class=""><<a href="mailto:b3i4zz1gu1@docomo.ne.jp" class="">b3i4zz1gu1@docomo.ne.jp</a>><br class="">Sent: Monday, October 31, 2016 11:39:04 AM<br class="">Subject: Re: [llvm-dev] What was the IR made for precisely?<br class=""><br class=""><br class="">I think it would be possible to build a stripped-down<br class="">C-with-extensions-only type representation that represents only the<br class="">types that have interesting ABI implications. This includes several<br class="">things not present in LLVM IR types: _Complex, union, flexible array<br class="">members, alignment attributes, etc. We could either then use that<br class="">library to generate LLVM IR, or embed it in the IR for use at call<br class="">sites.<br class=""><br class=""></blockquote><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">I think this is certainly possible. The question is: Is Clang going to use this representation? If not, who will want to maintain this separately from Clang?</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">To a large extent, this seems like factoring out the logic in Clang's lib/CodeGen/TargetInfo* (as well as lib/Basic/Target* and a few other places) into a reusable form.</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""></div></blockquote><div><br class=""></div><div>I share this view, and I’d like a solution that would be used by clang by default! (Mostly for the reason hinted above in the question: “who will want to maintain this separately from Clang?”)</div><div><br class=""></div><div>— </div><div>Mehdi</div><div><br class=""></div><blockquote type="cite" class=""><div class=""><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><blockquote type="cite" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class=""><br class="">You can exclude C++ because, for the most part, C++ types are either<br class="">passed indirectly or as the analogous C struct would be passed. Some<br class="">work would be needed to support packing fields into base tail<br class="">padding, but that's not too bad.<br class=""><br class=""><br class="">On Fri, Oct 28, 2016 at 1:25 PM, Hal Finkel via llvm-dev <<br class=""><a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a> > wrote:<br class=""><br class=""><br class=""><br class=""><br class="">----- Original Message -----<br class=""><blockquote type="cite" class="">From: "Chris Lattner via llvm-dev" < <a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a> ><br class="">To: "David Chisnall" < <a href="mailto:David.Chisnall@cl.cam.ac.uk" class="">David.Chisnall@cl.cam.ac.uk</a> ><br class="">Cc: <a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a> , "ジョウェットジェームス" <<br class=""><a href="mailto:b3i4zz1gu1@docomo.ne.jp" class="">b3i4zz1gu1@docomo.ne.jp</a> ><br class="">Sent: Friday, October 28, 2016 2:13:06 PM<br class="">Subject: Re: [llvm-dev] What was the IR made for precisely?<br class=""><br class=""><br class=""><blockquote type="cite" class="">On Oct 28, 2016, at 1:21 AM, David Chisnall<br class="">< <a href="mailto:David.Chisnall@cl.cam.ac.uk" class="">David.Chisnall@cl.cam.ac.uk</a> > wrote:<br class=""><br class="">On 28 Oct 2016, at 02:43, ジョウェットジェームス < <a href="mailto:b3i4zz1gu1@docomo.ne.jp" class="">b3i4zz1gu1@docomo.ne.jp</a> ><br class="">wrote:<br class=""><blockquote type="cite" class=""><br class="">I would need to sum up all the rules and ABIs and sizes for all<br class="">the targets I need and generate different IR for each, am I<br class="">correct?<br class=""></blockquote><br class="">This is a long-known limitation of LLVM IR and there are a lot of<br class="">proposals to fix it. It would be great if the LLVM Foundation<br class="">would fund someone to do the work, as it isn’t a sufficiently<br class="">high<br class="">priority for any of the large LLVM consumers and would make a<br class="">huge<br class="">difference to the utility of LLVM for a lot of people.<br class=""></blockquote>…<br class=""><blockquote type="cite" class="">I think it would be difficult to do it within the timescale of<br class="">the<br class="">GSoC unless the student was already an experienced LLVM<br class="">developer.<br class="">It would likely involve designing some good APIs (difficult!),<br class="">refactoring a bunch of Clang code, and creating a new LLVM<br class="">library. I’ve not seen a GSoC project on this scale succeed in<br class="">any of the open source projects that I’ve been involved with. If<br class="">we had a good design doc and a couple of engaged mentors then it<br class="">might stand a chance.<br class=""></blockquote><br class="">Is there a specific design that you think would work? One of the<br class="">major problems with this sort of proposal is that you need the<br class="">entire clang type system to do this, which means it depends on a<br class="">huge chunk of the Clang AST. At that point, this isn’t a small<br class="">library that clang uses, this is a library layered on top of Clang<br class="">itself.<br class=""></blockquote><br class="">Given that ABIs are defined in terms of C (and sometimes now C++)<br class="">language constructs, I think that something like this is the best of<br class="">all bad options. Really, however, it depends only on the AST and<br class="">CodeGen, and maybe those (along with 'Basic', etc.) could be made<br class="">into a separately-compilable library. Along with an easy ASTBuilder<br class="">for C types and function declarations we should be able to satisfy<br class="">this use case.<br class=""><br class="">-Hal<br class=""><br class=""><blockquote type="cite" class=""><br class="">-Chris<br class="">_______________________________________________<br class="">LLVM Developers mailing list<br class=""><a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a><br class="">http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev<br class=""><br class=""></blockquote><br class="">--<br class="">Hal Finkel<br class="">Lead, Compiler Technology and Programming Languages<br class="">Leadership Computing Facility<br class="">Argonne National Laboratory<br class=""><br class=""><br class="">_______________________________________________<br class="">LLVM Developers mailing list<br class=""><a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a><br class="">http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev<br class=""><br class=""><br class=""></blockquote><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">--<span class="Apple-converted-space"> </span></span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">Hal Finkel</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">Lead, Compiler Technology and Programming Languages</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">Leadership Computing Facility</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; 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