<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="">I don’t believe we document anything on this aspect.<div class=""><br class=""></div><div class="">— </div><div class="">Mehdi</div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Aug 23, 2016, at 1:07 AM, Shixiong Xu <<a href="mailto:shixiong@cadence.com" class="">shixiong@cadence.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 style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);" class="">Thanks for your comments. I tried using the promotion to deal with operations on v32i8. It seems work well. As you mentioned “canonicalization”, I am wondering where I can find the document on canonicalized form of IR. When I saw truncate to minimal bitwidth in innerloop vectorization, I thought it was kind of optimization rather than canonicalization.<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);" class="">Shixiong<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div class=""><div style="border-style: solid none none; border-top-color: rgb(225, 225, 225); border-top-width: 1pt; padding: 3pt 0in 0in;" class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><b class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class="">From:</span></b><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class="Apple-converted-space"> </span>Hal Finkel [<a href="mailto:hfinkel@anl.gov" class="">mailto:hfinkel@anl.gov</a>]<span class="Apple-converted-space"> </span><br class=""><b class="">Sent:</b><span class="Apple-converted-space"> </span>Thursday, August 18, 2016 5:10 PM<br class=""><b class="">To:</b><span class="Apple-converted-space"> </span>Mehdi Amini<br class=""><b class="">Cc:</b><span class="Apple-converted-space"> </span><a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a>; Shixiong Xu<br class=""><b class="">Subject:</b><span class="Apple-converted-space"> </span>Re: [llvm-dev] Cost model is missing in InstCombiner<o:p class=""></o:p></span></div></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><o:p class=""> </o:p></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 10pt; font-family: Arial, sans-serif;" class=""><o:p class=""> </o:p></span></div><div class="MsoNormal" align="center" style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; text-align: center;"><span style="font-size: 10pt; font-family: Arial, sans-serif;" class=""><hr size="3" width="100%" align="center" id="zwchr" class=""></span></div><blockquote style="border-style: none none none solid; border-left-color: rgb(16, 16, 255); border-left-width: 1.5pt; padding: 0in 0in 0in 4pt; margin-left: 3.75pt; margin-top: 5pt; margin-bottom: 5pt;" class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><b class=""><span style="font-family: Helvetica, sans-serif;" class="">From:<span class="Apple-converted-space"> </span></span></b><span style="font-family: Helvetica, sans-serif;" class="">"Mehdi Amini via llvm-dev" <<a href="mailto:llvm-dev@lists.llvm.org" style="color: purple; text-decoration: underline;" class="">llvm-dev@lists.llvm.org</a>><br class=""><b class="">To:<span class="Apple-converted-space"> </span></b>"Shixiong Xu" <<a href="mailto:shixiong@cadence.com" style="color: purple; text-decoration: underline;" class="">shixiong@cadence.com</a>><br class=""><b class="">Cc:<span class="Apple-converted-space"> </span></b><a href="mailto:llvm-dev@lists.llvm.org" style="color: purple; text-decoration: underline;" class="">llvm-dev@lists.llvm.org</a><br class=""><b class="">Sent:<span class="Apple-converted-space"> </span></b>Thursday, August 18, 2016 11:05:35 AM<br class=""><b class="">Subject:<span class="Apple-converted-space"> </span></b>Re: [llvm-dev] Cost model is missing in InstCombiner<br class=""><br class="">+David M.<o:p class=""></o:p></span></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-family: Helvetica, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-family: Helvetica, sans-serif;" class=""><o:p class=""> </o:p></span></div><div class=""><blockquote style="margin-top: 5pt; margin-bottom: 5pt;" class=""><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-family: Helvetica, sans-serif;" class="">On Aug 17, 2016, at 3:48 AM, Shixiong Xu via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank" style="color: purple; text-decoration: underline;" class="">llvm-dev@lists.llvm.org</a>> wrote:<o:p class=""></o:p></span></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-family: Helvetica, sans-serif;" class=""><o:p class=""> </o:p></span></div><div class=""><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class="">Hi,<o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""> <o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class="">I think canEvaluateTruncated() in InstCombiner needs use cost model to decide whether perform optimization or not.<o:p class=""></o:p></span></div></div></div></blockquote><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-family: Helvetica, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div id="DWT1942" class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-family: Helvetica, sans-serif;" class="">I’ve always seen InstCombine as doing “canonicalization” of the IR and not “optimization”. So the output of InstCombine should be in a form that is the most suitable for further analyses and transformations.<o:p class=""></o:p></span></div></div></div></div></blockquote><p class="MsoNormal" style="margin: 0in 0in 12pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 10pt; font-family: Arial, sans-serif;" class="">This is exactly our traditional view. Why can the backend not be fixed to generate better code for mul <32 x i8>? It looks like the widening in the IR is something natural to get from legalization (if you set up the correct promotion preferences in *ISelLowering).<br class=""><br class=""> -Hal<o:p class=""></o:p></span></p><blockquote style="border-style: none none none solid; border-left-color: rgb(16, 16, 255); border-left-width: 1.5pt; padding: 0in 0in 0in 4pt; margin-left: 3.75pt; margin-top: 5pt; margin-bottom: 5pt;" class=""><div class=""><div class=""><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-family: Helvetica, sans-serif;" class="">I’m not sure how this view fits with TTI, I may not be incompatible if used within some limits I guess?<o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-family: Helvetica, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-family: Helvetica, sans-serif;" class="">— <o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-family: Helvetica, sans-serif;" class="">Mehdi<o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-family: Helvetica, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-family: Helvetica, sans-serif;" class=""><o:p class=""> </o:p></span></div><blockquote style="margin-top: 5pt; margin-bottom: 5pt;" class=""><div class=""><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""> Without cost model from TargetTransformInfo, aggressively optimizing IR in vector types according to the number of bits demanded may lead to scalarization of vector operations. For example, if the input IR is:<o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""> <o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""> %wide.load25 = load <32 x i8>, <32 x i8>* %231, align 1<o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""> %232 = zext <32 x i8> %wide.load25 to <32 x i16><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""> %233 = mul nuw nsw <32 x i16> %232, %164<o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""> …<o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""> %237 = trunc <32 x i16> %233 to <32 x i8><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""> store <32 x i8> %237, <32 x i8>* %236, align 1<o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""> <o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class="">ICE: EvaluateInDifferentType converting expression type to avoid cast: %9 = trunc <32 x i16> %6 to <32 x i8><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class="">IC: ADD: %6 = mul <32 x i8> %wide.load25, %wide.load<o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class="">IC: Replacing %10 = trunc <32 x i16> %7 to <32 x i8><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""> with %6 = mul <32 x i8> %wide.load25, %wide.load<o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""> <o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class="">If the target doesn’t have support for mul <32 x i8>, the inst combiner will yield less profitable code.<o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""> <o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span lang="EN-IE" style="font-size: 11pt; font-family: Calibri, sans-serif;" class="">Cheers,</span><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span lang="EN-IE" style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""> </span><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span lang="EN-IE" style="font-size: 11pt; font-family: Calibri, sans-serif;" class="">Shixiong (Jason) Xu</span><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""> <o:p class=""></o:p></span></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 9pt; font-family: Helvetica, sans-serif;" class="">_______________________________________________<br class="">LLVM Developers mailing list<br class=""></span><span style="font-family: Helvetica, sans-serif;" class=""><a href="mailto:llvm-dev@lists.llvm.org" target="_blank" style="color: purple; text-decoration: underline;" class=""><span style="font-size: 9pt; color: rgb(149, 79, 114);" class="">llvm-dev@lists.llvm.org</span></a></span><span style="font-size: 9pt; font-family: Helvetica, sans-serif;" class=""><br class=""></span><span style="font-family: Helvetica, sans-serif;" class=""><a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.llvm.org_cgi-2Dbin_mailman_listinfo_llvm-2Ddev&d=DQMFaQ&c=aUq983L2pue2FqKFoP6PGHMJQyoJ7kl3s3GZ-_haXqY&r=FZEW1cDCyCU3ZbRFatG9st_R0bbu9fLOaIEKyKAe7wg&m=ESfk7Z5IaUlWUQ0rjWLN1_jpMmkVJrhyBkDHZf16Vqg&s=EI-jBeC2luAByubh3z9LdCyYUtvkbZrO_SgtrJO5CJQ&e=" target="_blank" style="color: purple; text-decoration: underline;" class=""><span style="font-size: 9pt; color: rgb(149, 79, 114);" class="">http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</span></a><o:p class=""></o:p></span></div></div></blockquote></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-family: Helvetica, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-family: Helvetica, sans-serif;" class=""><br class="">_______________________________________________<br class="">LLVM Developers mailing list<br class=""><a href="mailto:llvm-dev@lists.llvm.org" style="color: purple; text-decoration: underline;" class="">llvm-dev@lists.llvm.org</a><br class=""><a href="http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev" style="color: purple; text-decoration: underline;" class="">http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a><o:p class=""></o:p></span></div></blockquote><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 10pt; font-family: Arial, sans-serif;" class=""><br class=""><br class=""><br class="">--<span class="Apple-converted-space"> </span><o:p class=""></o:p></span></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;" class=""><span style="font-size: 10pt; font-family: Arial, sans-serif;" class="">Hal Finkel<br class="">Assistant Computational Scientist<br class="">Leadership Computing Facility<br class="">Argonne National Laboratory</span></div></div></div></div></div></blockquote></div><br class=""></div></body></html>