<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=us-ascii"><meta name=Generator content="Microsoft Word 15 (filtered medium)"><!--[if !mso]><style>v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style><![endif]--><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:DengXian;
panose-1:2 1 6 0 3 1 1 1 1 1;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:DengXian;
panose-1:2 1 6 0 3 1 1 1 1 1;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
text-align:justify;
text-justify:inter-ideograph;
font-size:10.5pt;
font-family:DengXian;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
p.MsoListParagraph, li.MsoListParagraph, div.MsoListParagraph
{mso-style-priority:34;
margin:0cm;
margin-bottom:.0001pt;
text-align:justify;
text-justify:inter-ideograph;
text-indent:21.0pt;
font-size:10.5pt;
font-family:DengXian;}
p.msonormal0, li.msonormal0, div.msonormal0
{mso-style-name:msonormal;
mso-margin-top-alt:auto;
margin-right:0cm;
mso-margin-bottom-alt:auto;
margin-left:0cm;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
span.EmailStyle19
{mso-style-type:personal;
font-family:DengXian;
color:windowtext;}
span.EmailStyle20
{mso-style-type:personal-reply;
font-family:DengXian;
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:72.0pt 90.0pt 72.0pt 90.0pt;}
div.WordSection1
{page:WordSection1;}
/* List Definitions */
@list l0
{mso-list-id:174271520;
mso-list-type:hybrid;
mso-list-template-ids:1514035804 -1573731478 67698713 67698715 67698703 67698713 67698715 67698703 67698713 67698715;}
@list l0:level1
{mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:18.0pt;
text-indent:-18.0pt;}
@list l0:level2
{mso-level-number-format:alpha-lower;
mso-level-text:"%2\)";
mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:42.0pt;
text-indent:-21.0pt;}
@list l0:level3
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
margin-left:63.0pt;
text-indent:-21.0pt;}
@list l0:level4
{mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:84.0pt;
text-indent:-21.0pt;}
@list l0:level5
{mso-level-number-format:alpha-lower;
mso-level-text:"%5\)";
mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:105.0pt;
text-indent:-21.0pt;}
@list l0:level6
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
margin-left:126.0pt;
text-indent:-21.0pt;}
@list l0:level7
{mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:147.0pt;
text-indent:-21.0pt;}
@list l0:level8
{mso-level-number-format:alpha-lower;
mso-level-text:"%8\)";
mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:168.0pt;
text-indent:-21.0pt;}
@list l0:level9
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
margin-left:189.0pt;
text-indent:-21.0pt;}
@list l1
{mso-list-id:627318032;
mso-list-type:hybrid;
mso-list-template-ids:1514035804 -1573731478 67698713 67698715 67698703 67698713 67698715 67698703 67698713 67698715;}
@list l1:level1
{mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:18.0pt;
text-indent:-18.0pt;}
@list l1:level2
{mso-level-number-format:alpha-lower;
mso-level-text:"%2\)";
mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:42.0pt;
text-indent:-21.0pt;}
@list l1:level3
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
margin-left:63.0pt;
text-indent:-21.0pt;}
@list l1:level4
{mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:84.0pt;
text-indent:-21.0pt;}
@list l1:level5
{mso-level-number-format:alpha-lower;
mso-level-text:"%5\)";
mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:105.0pt;
text-indent:-21.0pt;}
@list l1:level6
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
margin-left:126.0pt;
text-indent:-21.0pt;}
@list l1:level7
{mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:147.0pt;
text-indent:-21.0pt;}
@list l1:level8
{mso-level-number-format:alpha-lower;
mso-level-text:"%8\)";
mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:168.0pt;
text-indent:-21.0pt;}
@list l1:level9
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
margin-left:189.0pt;
text-indent:-21.0pt;}
@list l2
{mso-list-id:1088648086;
mso-list-type:hybrid;
mso-list-template-ids:-953242672 827109010 67698713 67698715 67698703 67698713 67698715 67698703 67698713 67698715;}
@list l2:level1
{mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:18.0pt;
text-indent:-18.0pt;}
@list l2:level2
{mso-level-number-format:alpha-lower;
mso-level-text:"%2\)";
mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:42.0pt;
text-indent:-21.0pt;}
@list l2:level3
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
margin-left:63.0pt;
text-indent:-21.0pt;}
@list l2:level4
{mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:84.0pt;
text-indent:-21.0pt;}
@list l2:level5
{mso-level-number-format:alpha-lower;
mso-level-text:"%5\)";
mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:105.0pt;
text-indent:-21.0pt;}
@list l2:level6
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
margin-left:126.0pt;
text-indent:-21.0pt;}
@list l2:level7
{mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:147.0pt;
text-indent:-21.0pt;}
@list l2:level8
{mso-level-number-format:alpha-lower;
mso-level-text:"%8\)";
mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:168.0pt;
text-indent:-21.0pt;}
@list l2:level9
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
margin-left:189.0pt;
text-indent:-21.0pt;}
ol
{margin-bottom:0cm;}
ul
{margin-bottom:0cm;}
--></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=ZH-CN link="#0563C1" vlink="#954F72" style='text-justify-trim:punctuation'><div class=WordSection1><p class=MsoNormal><span lang=EN-US>A thing I forgot to mention is that a Rust feature named </span>“<span lang=EN-US>compiler plugin</span>”<span lang=EN-US> do satisfy the requirement of </span>“<span lang=EN-US>emitting extra debuginfo to the generated IR code</span>”<span lang=EN-US>, but it</span>’<span lang=EN-US>s unstable and won</span>’<span lang=EN-US>t be stabilized in the foreseeable future. Moreover, as to </span>“<span lang=EN-US>using lld as its linker and add the Enzyme pass to lld</span>”<span lang=EN-US>, compiler plugins help nothing.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal align=left style='text-align:left'><b><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'>From:</span></b><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> Chuyang Chen <chuyangchen@foxmail.com> <br><b>Sent:</b> Tuesday, March 30, 2021 11:44 PM<br><b>To:</b> wmoses@mit.edu<br><b>Cc:</b> llvm-dev@lists.llvm.org; 'Enzyme AD' <enzyme-dev@googlegroups.com><br><b>Subject:</b> [GSoC 2021] Some ideas & questions about the Enzyme GSoC project<o:p></o:p></span></p></div></div><p class=MsoNormal align=left style='text-align:left'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Hello, I</span>’<span lang=EN-US>m working on the GSoC project </span>“<span lang=EN-US>Integrate Enzyme into Rust to provide high-performance differentiation in Rust</span>”<span lang=EN-US>. I have skimmed over the codebase and now I have some preliminary ideas about the project.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>As you have said, the project can be divided to two main parts:<o:p></o:p></span></p><p class=MsoListParagraph style='margin-left:18.0pt;text-indent:-18.0pt;mso-list:l2 level1 lfo4'><![if !supportLists]><span lang=EN-US><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span lang=EN-US>passing and parsing Rust type metadata into LLVM / Enzyme type analysis, and<o:p></o:p></span></p><p class=MsoListParagraph style='margin-left:18.0pt;text-indent:-18.0pt;mso-list:l2 level1 lfo4'><![if !supportLists]><span lang=EN-US><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span lang=EN-US>integrating the Enzyme API/pass into rust.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Integrating Enzyme API to rust is trivial by using proc_macros in Rust. However, passing Rust type metadata to LLVM and integrating the Enzyme pass into rust is difficult if we don</span>’<span lang=EN-US>t modify the Rust compiler. The Rust compiler seems to lack ability to emit metadata to LLVM, and if we want to add the Enzyme pass without modifying the compiler, the only way is, I think, using a command like<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><img width=860 height=25 style='width:8.9583in;height:.2604in' id="_x56fe__x7247__x0020_1" src="cid:image001.png@01D725C1.57333AD0" alt="cid:image003.png@01D725BE.92A91F10"></span><span lang=EN-US><o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>which is not user-friendly. I sought hard for a nonintrusive way to implement them but got nothing, so it seems that the only option is modifying the Rust compiler to let it<o:p></o:p></span></p><p class=MsoListParagraph style='margin-left:18.0pt;text-indent:-18.0pt;mso-list:l0 level1 lfo6'><![if !supportLists]><span lang=EN-US><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span lang=EN-US>emit extra debuginfo to the generated IR code, and<o:p></o:p></span></p><p class=MsoListParagraph style='margin-left:18.0pt;text-indent:-18.0pt;mso-list:l0 level1 lfo6'><![if !supportLists]><span lang=EN-US><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span lang=EN-US>use lld as its linker and add the Enzyme pass to lld<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>with a specific option, say </span>“<span lang=EN-US>--enzyme</span>”<span lang=EN-US><o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>However, <i>is it appropriate to modify the compiler to just port a plugin to it, though the modification won</i></span><i>’<span lang=EN-US>t be big or impact the rest of the compiler?</span></i><span lang=EN-US><o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>PS: Another question is about differentiating closures in Rust, but that can be postponed to the following discussions.<o:p></o:p></span></p><div style='border:none;border-bottom:solid windowtext 1.0pt;padding:0cm 0cm 1.0pt 0cm'><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p></div><p class=MsoNormal align=right style='text-align:right;word-break:break-all'><span lang=EN-US>Chuyang Chen<o:p></o:p></span></p><p class=MsoNormal align=right style='text-align:right;word-break:break-all'><span lang=EN-US>MSc Student<o:p></o:p></span></p><p class=MsoNormal align=right style='text-align:right;word-break:break-all'><span lang=EN-US>At Department of Computer Science and Technology, Nanjing University<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p></div></body></html>