<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 Jul 13, 2016, at 12:40 PM, Mehdi Amini <<a href="mailto:mehdi.amini@apple.com" class="">mehdi.amini@apple.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><blockquote type="cite" class="" 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;"><div class=""><br class="Apple-interchange-newline">On Jul 13, 2016, at 12:26 PM, Lawrence, Peter <<a href="mailto:c_plawre@qca.qualcomm.com" class="">c_plawre@qca.qualcomm.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="WordSection1" style="page: WordSection1; 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;"><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">Vivek,<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"> I apologize if you took my original email as a request for implementation,<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">I meant to be asking what is already available, I think the answer to that<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">is the ‘preserves_most’ and ‘preserves_all’ attributes, but I will also<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">Use ‘regmask’ if those prove to be too sub-optimal.<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"><o:p class=""> </o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">I am still interested in figuring out the necessary and sufficient conditions<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">For LLC to do optimal IPRA when given a “whole program”<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">(as per my previous definition of “whole program”),<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">As opposed to how to accomplish this with LTO,<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"></span></div></div></div></blockquote><div 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 class=""></div><div 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="">Easy: mark *all* of your function “static” (or “internal” in LLVM denomination). <span class="" style="color: rgb(31, 73, 125); font-family: Calibri, sans-serif; font-size: 11pt;"> </span></div><blockquote type="cite" class="" 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;"><div class="WordSection1" style="page: WordSection1; 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;"><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"></div></div></blockquote><br class="" 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;"><blockquote type="cite" class="" 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;"><div class=""><div class="WordSection1" style="page: WordSection1; 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;"><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">If you are open to having such discussions, even though your focus<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">IIUC is supposed to be LTO, then great. I think Mehdi is stuck trying<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">To convince me to use LTO, but given all the changes I’ve had to make<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">To CodeGen (IE outside of my Target sub-dir) for having separate Data and Address<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">register sets, I think using LTO is a long term solution that I can’t take<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">On just now (IE the svn branch merge problem)</span></div></div></div></blockquote><blockquote type="cite" class="" 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;"><div class=""><div class="WordSection1" style="page: WordSection1; 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;"><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"><o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"><o:p class=""> </o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">As one of my old math professors used to say “don’t use a sledge hammer<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">To crush a pea”, to wit I am only compiling a single source file as an entire whole<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">Program and I don’t do any linking, why should I have to use a linker.</span></div></div></div></blockquote><div 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 class=""></div><div 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="">Just semantic issue: you need to tell the optimizer what it can and can’t do. In general we can’t assume that the code being optimized or generated won’t be dlopen/dlsym for instance.</div><div 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="">Unfortunately I’d prefer everything to be hidden/private by default and the user having to explicitly export symbols, but that’s not the current model.</div><div 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 class=""></div><div 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="">The LTO API is here to circumvent this issue: by delaying the optimizations/codegen to the link time, we have more information about what function can / can’t be called from another module. </div><div 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="">One of the key point of LTO is the linker telling us “I don’t need to export this symbol” and we turn it into an “internal” one.</div></div></blockquote><div><br class=""></div><div>What I meant here is: you don’t *have to* use LTO (especially if you don’t use a linker right now), but it is an existing mechanism to achieve what you want. So somehow you need to accomplish the same thing (I.e. mark as many functions as possible “internal”).</div><div>The best way to implement it is very dependent on your workflow.</div><div><br class=""></div><div>— </div><div>Mehdi</div><div><br class=""></div><br class=""><blockquote type="cite" class=""><div class=""><div 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 class=""></div><div 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><div 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="">Mehdi</div><div 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 class=""></div><div 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 class=""></div><br class="" 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;"><blockquote type="cite" class="" 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;"><div class=""><div class="WordSection1" style="page: WordSection1; 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;"><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"><o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"><o:p class=""> </o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">--Peter Lawrence<o:p class=""></o:p></span></div><div class="" style="border-style: none none solid; border-bottom-color: windowtext; border-bottom-width: 1pt; padding: 0in 0in 1pt;"><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; border: none; padding: 0in;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"><o:p class=""> </o:p></span></div></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"><o:p class=""> </o:p></span></div><p class="MsoNormal" style="margin: 0in 0in 12pt; font-size: 12pt; font-family: 'Times New Roman', serif;">Vivek,<br class=""> I have an application where many of the leaf functions are<br class="">Hand-coded assembly language, because they use special IO instructions<br class="">That only the assembler knows about. These functions typically don't<br class="">Use any registers besides the incoming argument registers, IE they don't<br class="">Need to use any additional callee-save nor caller-save registers.<o:p class=""></o:p></p><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;">Perhaps using some form of __attribute__ ?<br class="">Maybe __attribute__ ((registermask = ....)) ?<br class=""><br class=""><br class="">--Peter Lawrence.<o:p class=""></o:p></div><div class="" style="border-style: none none solid; border-bottom-color: windowtext; border-bottom-width: 1pt; padding: 0in 0in 1pt;"><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; border: none; padding: 0in;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"><o:p class=""> </o:p></span></div></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"><o:p class=""> </o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"><o:p class=""> </o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"><o:p class=""> </o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"><o:p class=""> </o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><b class=""><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif;">From:</span></b><span class="" style="font-size: 11pt; font-family: Calibri, sans-serif;"><span class="Apple-converted-space"> </span>vivek pandya [<a href="mailto:vivekvpandya@gmail.com" class="">mailto:vivekvpandya@gmail.com</a>]<span class="Apple-converted-space"> </span><br class=""><b class="">Sent:</b><span class="Apple-converted-space"> </span>Wednesday, July 13, 2016 11:47 AM<br class=""><b class="">To:</b><span class="Apple-converted-space"> </span>Lawrence, Peter <<a href="mailto:c_plawre@qca.qualcomm.com" class="">c_plawre@qca.qualcomm.com</a>><br class=""><b class="">Cc:</b><span class="Apple-converted-space"> </span><a href="mailto:mehdi.amini@apple.com" class="">mehdi.amini@apple.com</a>; llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a>>;<span class="Apple-converted-space"> </span><a href="mailto:llvm-dev-request@lists.llvm.org" class="">llvm-dev-request@lists.llvm.org</a>; Hal Finkel <<a href="mailto:hfinkel@anl.gov" class="">hfinkel@anl.gov</a>><br class=""><b class="">Subject:</b><span class="Apple-converted-space"> </span>Re: [llvm-dev] IPRA, interprocedural register allocation, question<o:p class=""></o:p></span></div><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><o:p class=""> </o:p></div><div class=""><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;">Hello Peter,<o:p class=""></o:p></div><div class=""><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><o:p class=""> </o:p></div></div><div class=""><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;">Are you still interested in __attribute__(regmask) ? <o:p class=""></o:p></div></div><div class=""><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;">I have done some hack ( both clang+IPRA) to get it working if you want to play around it I can send a patch by tomorrow.<o:p class=""></o:p></div></div><div class=""><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><o:p class=""> </o:p></div></div><div class=""><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;">Sincerely,<o:p class=""></o:p></div></div><div class=""><div class="" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;">Vivek</div></div></div></div></div></blockquote></div></blockquote></div><br class=""></body></html>