<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=utf-8"><meta name=Generator content="Microsoft Word 15 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p.msonormal0, li.msonormal0, div.msonormal0
{mso-style-name:msonormal;
mso-margin-top-alt:auto;
margin-right:0in;
mso-margin-bottom-alt:auto;
margin-left:0in;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
span.apple-converted-space
{mso-style-name:apple-converted-space;}
span.EmailStyle20
{mso-style-type:personal-reply;
font-family:"Calibri",sans-serif;
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>I wouldn’t say the understanding of register classes is changed with this patch, I would say it increases how aggressively we take advantage of the hasExtraRegAlloc opcode properties to do post-RA register renaming. Not that that is necessarily less concerning.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>-- <o:p></o:p></p><p class=MsoNormal>Geoff Berry<o:p></o:p></p><p class=MsoNormal>Employee of Qualcomm Datacenter Technologies, Inc.<o:p></o:p></p><p class=MsoNormal> Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.<o:p></o:p></p></div><p class=MsoNormal><o:p> </o:p></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b>From:</b> fglaser@apple.com [mailto:fglaser@apple.com] <b>On Behalf Of </b>escha@apple.com<br><b>Sent:</b> Friday, February 2, 2018 4:38 PM<br><b>To:</b> gberry@codeaurora.org<br><b>Cc:</b> Quentin Colombet <qcolombet@apple.com>; reviews+D41835+public+9c1dec7fb6e75ce0@reviews.llvm.org; Geoff Berry via Phabricator <reviews@reviews.llvm.org>; javed.absar@arm.com; Matthias Braun <matze@braunis.de>; Jonas Paulsson <paulsson@linux.vnet.ibm.com>; tstellar@redhat.com; Matt Arsenault <Matthew.Arsenault@amd.com>; junbuml@codeaurora.org; marina.yatsina@intel.com; wei.ding2@amd.com; kannan.narayanan@amd.com; nhaehnle@gmail.com; Nemanja Ivanovic <nemanja.i.ibm@gmail.com>; llvm-commits <llvm-commits@lists.llvm.org>; tpr.llvm@botech.co.uk<br><b>Subject:</b> Re: [PATCH] D41835: [MachineCopyPropagation] Extend pass to do COPY source forwarding<o:p></o:p></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>this is probably a reasonable solution. mostly, at this point, i’m worried about the fact that upstream now apparently has a different understanding of register classes than we do (in terms of what is “safe”), which could lead to other future issues for us.<o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>—escha<o:p></o:p></p><div><p class=MsoNormal><br><br><o:p></o:p></p><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal>On Feb 2, 2018, at 1:36 PM, <a href="mailto:gberry@codeaurora.org">gberry@codeaurora.org</a> wrote:<o:p></o:p></p></div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal>Ah, okay. So I assume you’re okay with disabling the post-RA run of this pass for this particular target to fix this particular issue?<o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><div><p class=MsoNormal>--<span class=apple-converted-space> </span><o:p></o:p></p></div><div><p class=MsoNormal>Geoff Berry<o:p></o:p></p></div><div><p class=MsoNormal>Employee of Qualcomm Datacenter Technologies, Inc.<o:p></o:p></p></div><div><p class=MsoNormal>Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.<o:p></o:p></p></div></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><div><p class=MsoNormal><b>From:</b><span class=apple-converted-space> </span><a href="mailto:fglaser@apple.com">fglaser@apple.com</a> [<a href="mailto:fglaser@apple.com">mailto:fglaser@apple.com</a>]<span class=apple-converted-space> </span><b>On Behalf Of<span class=apple-converted-space> </span></b><a href="mailto:escha@apple.com">escha@apple.com</a><br><b>Sent:</b><span class=apple-converted-space> </span>Friday, February 2, 2018 4:32 PM<br><b>To:</b><span class=apple-converted-space> </span><a href="mailto:gberry@codeaurora.org">gberry@codeaurora.org</a><br><b>Cc:</b><span class=apple-converted-space> </span>Quentin Colombet <<a href="mailto:qcolombet@apple.com">qcolombet@apple.com</a>>; <a href="mailto:reviews+D41835+public+9c1dec7fb6e75ce0@reviews.llvm.org">reviews+D41835+public+9c1dec7fb6e75ce0@reviews.llvm.org</a>; Geoff Berry via Phabricator <<a href="mailto:reviews@reviews.llvm.org">reviews@reviews.llvm.org</a>>; <a href="mailto:javed.absar@arm.com">javed.absar@arm.com</a>; Matthias Braun <<a href="mailto:matze@braunis.de">matze@braunis.de</a>>; Jonas Paulsson <<a href="mailto:paulsson@linux.vnet.ibm.com">paulsson@linux.vnet.ibm.com</a>>; <a href="mailto:tstellar@redhat.com">tstellar@redhat.com</a>; Matt Arsenault <<a href="mailto:Matthew.Arsenault@amd.com">Matthew.Arsenault@amd.com</a>>; <a href="mailto:junbuml@codeaurora.org">junbuml@codeaurora.org</a>; <a href="mailto:marina.yatsina@intel.com">marina.yatsina@intel.com</a>; <a href="mailto:wei.ding2@amd.com">wei.ding2@amd.com</a>; <a href="mailto:kannan.narayanan@amd.com">kannan.narayanan@amd.com</a>; <a href="mailto:nhaehnle@gmail.com">nhaehnle@gmail.com</a>; Nemanja Ivanovic <<a href="mailto:nemanja.i.ibm@gmail.com">nemanja.i.ibm@gmail.com</a>>; llvm-commits <<a href="mailto:llvm-commits@lists.llvm.org">llvm-commits@lists.llvm.org</a>>; <a href="mailto:tpr.llvm@botech.co.uk">tpr.llvm@botech.co.uk</a><br><b>Subject:</b><span class=apple-converted-space> </span>Re: [PATCH] D41835: [MachineCopyPropagation] Extend pass to do COPY source forwarding<o:p></o:p></p></div></div></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal>looking at it again, it’s making more sense: your patch enabled MachineCopyPropagation in the RA pipeline. the pass might have *already* been broken, but it wasn’t running for us, and now it is, so it broke things in that way too.<o:p></o:p></p></div><div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div><div><div><p class=MsoNormal>—escha<o:p></o:p></p></div><div><div><p class=MsoNormal><br><br><br><o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><div><p class=MsoNormal>On Feb 2, 2018, at 1:26 PM,<span class=apple-converted-space> </span><a href="mailto:gberry@codeaurora.org"><span style='color:purple'>gberry@codeaurora.org</span></a><span class=apple-converted-space> </span>wrote:<o:p></o:p></p></div></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><div><div><p class=MsoNormal>escha,<o:p></o:p></p></div></div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div><div><div><p class=MsoNormal>I’m confused by your comment about bundles. It was known that this patch doesn’t handle forwarding into bundles, but it sounds like to me you are seeing problems with the dead COPY removal part of this pass, which was not intentionally changed by this patch (other than adding a DEBUG statement when it happens).<o:p></o:p></p></div></div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div><div><div><div><p class=MsoNormal>--<span class=apple-converted-space> </span><o:p></o:p></p></div></div><div><div><p class=MsoNormal>Geoff Berry<o:p></o:p></p></div></div><div><div><p class=MsoNormal>Employee of Qualcomm Datacenter Technologies, Inc.<o:p></o:p></p></div></div><div><div><p class=MsoNormal>Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.<o:p></o:p></p></div></div></div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><div><div><p class=MsoNormal><b>From:</b><span class=apple-converted-space> </span><a href="mailto:fglaser@apple.com"><span style='color:purple'>fglaser@apple.com</span></a><span class=apple-converted-space> </span>[<a href="mailto:fglaser@apple.com"><span style='color:purple'>mailto:fglaser@apple.com</span></a>]<span class=apple-converted-space> </span><b>On Behalf Of<span class=apple-converted-space> </span></b><a href="mailto:escha@apple.com"><span style='color:purple'>escha@apple.com</span></a><br><b>Sent:</b><span class=apple-converted-space> </span>Friday, February 2, 2018 4:10 PM<br><b>To:</b><span class=apple-converted-space> </span>Quentin Colombet <<a href="mailto:qcolombet@apple.com"><span style='color:purple'>qcolombet@apple.com</span></a>><br><b>Cc:</b><span class=apple-converted-space> </span>Geoff Berry <<a href="mailto:gberry@codeaurora.org"><span style='color:purple'>gberry@codeaurora.org</span></a>>;<span class=apple-converted-space> </span><a href="mailto:reviews+D41835+public+9c1dec7fb6e75ce0@reviews.llvm.org"><span style='color:purple'>reviews+D41835+public+9c1dec7fb6e75ce0@reviews.llvm.org</span></a>; Geoff Berry via Phabricator <<a href="mailto:reviews@reviews.llvm.org"><span style='color:purple'>reviews@reviews.llvm.org</span></a>>;<span class=apple-converted-space> </span><a href="mailto:javed.absar@arm.com"><span style='color:purple'>javed.absar@arm.com</span></a>; Matthias Braun <<a href="mailto:matze@braunis.de"><span style='color:purple'>matze@braunis.de</span></a>>; Jonas Paulsson <<a href="mailto:paulsson@linux.vnet.ibm.com"><span style='color:purple'>paulsson@linux.vnet.ibm.com</span></a>>;<span class=apple-converted-space> </span><a href="mailto:tstellar@redhat.com"><span style='color:purple'>tstellar@redhat.com</span></a>; Matt Arsenault <<a href="mailto:Matthew.Arsenault@amd.com"><span style='color:purple'>Matthew.Arsenault@amd.com</span></a>>;<span class=apple-converted-space> </span><a href="mailto:junbuml@codeaurora.org"><span style='color:purple'>junbuml@codeaurora.org</span></a>;<span class=apple-converted-space> </span><a href="mailto:marina.yatsina@intel.com"><span style='color:purple'>marina.yatsina@intel.com</span></a>;<span class=apple-converted-space> </span><a href="mailto:wei.ding2@amd.com"><span style='color:purple'>wei.ding2@amd.com</span></a>;<span class=apple-converted-space> </span><a href="mailto:kannan.narayanan@amd.com"><span style='color:purple'>kannan.narayanan@amd.com</span></a>;<span class=apple-converted-space> </span><a href="mailto:nhaehnle@gmail.com"><span style='color:purple'>nhaehnle@gmail.com</span></a>; Nemanja Ivanovic <<a href="mailto:nemanja.i.ibm@gmail.com"><span style='color:purple'>nemanja.i.ibm@gmail.com</span></a>>; llvm-commits <<a href="mailto:llvm-commits@lists.llvm.org"><span style='color:purple'>llvm-commits@lists.llvm.org</span></a>>;<span class=apple-converted-space> </span><a href="mailto:tpr.llvm@botech.co.uk"><span style='color:purple'>tpr.llvm@botech.co.uk</span></a><br><b>Subject:</b><span class=apple-converted-space> </span>Re: [PATCH] D41835: [MachineCopyPropagation] Extend pass to do COPY source forwarding<o:p></o:p></p></div></div></div></div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div><div><div><div><p class=MsoNormal><br><br><br><br><o:p></o:p></p></div></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><div><div><p class=MsoNormal>On Feb 2, 2018, at 12:55 PM, Quentin Colombet <<a href="mailto:qcolombet@apple.com"><span style='color:purple'>qcolombet@apple.com</span></a>> wrote:<o:p></o:p></p></div></div></div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div><div><div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div><div><div><div><p class=MsoNormal><br><br><br><br><o:p></o:p></p></div></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><div><div><p class=MsoNormal>On Feb 2, 2018, at 12:21 PM,<span class=apple-converted-space> </span><a href="mailto:escha@apple.com"><span style='color:purple'>escha@apple.com</span></a><span class=apple-converted-space> </span>wrote:<o:p></o:p></p></div></div></div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div><div><div><div><div><p class=MsoNormal>I mean, in that case we are likely to have to mark every single opcode (all 12,000 or so) with this requirement. At that point we might as well just opt out of the pass, I think? At least, it feels like a gross hack that papers over the fact that LLVM has changed how register classes work such that our entire approach is no longer valid.<o:p></o:p></p></div></div><div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div></div><div><div><div><p class=MsoNormal>Also, it seems very weird to make this constraint-violating behavior *opt-out*. Maybe it should be opt-in, i.e. put doesNotHaveExtraSrcRegAllocReq on all instructions it’s okay for?<o:p></o:p></p></div></div></div></div></div></blockquote><div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div></div><div><div><div><p class=MsoNormal>That sounds like a better approach to me.<o:p></o:p></p></div></div></div><div><div><div><p class=MsoNormal>After talking with escha, I agree that TableGen is not necessarily expressive enough to model all the constraints that need to be met and I would err on the safe side of being opt-in instead of opt-out.<o:p></o:p></p></div></div></div></div></div></div></blockquote><div><div><p class=MsoNormal> <o:p></o:p></p></div></div></div><div><div><div><p class=MsoNormal>this is actually worse than i initially realized. one of our targets is VLIW and is completely broken by this patch, *even if we opt out as described*, because it doesn’t iterate over the operands of a bundle. so for example:<o:p></o:p></p></div></div></div><div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div></div><div><div><div><p class=MsoNormal>r3 = COPY foo<o:p></o:p></p></div></div></div><div><div><div><p class=MsoNormal>BUNDLE_TYPE_FOO<o:p></o:p></p></div></div></div><div><div><div><p class=MsoNormal><thing that uses r3><o:p></o:p></p></div></div></div><div><div><div><p class=MsoNormal>END<o:p></o:p></p></div></div></div><div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div></div><div><div><div><p class=MsoNormal>it believes that r3 is dead because it doesn’t iterate over the bundle operands, so it never sees the use of r3.<o:p></o:p></p></div></div></div><div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div></div><div><div><div><p class=MsoNormal>—escha<o:p></o:p></p></div></div></div></div></blockquote></div></div></div></div></blockquote></div><p class=MsoNormal><o:p> </o:p></p></div></div></body></html>