<html 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=Windows-1252">
<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:0cm;
font-size:12.0pt;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}
pre
{mso-style-priority:99;
mso-style-link:"HTML Preformatted Char";
margin:0cm;
margin-bottom:.0001pt;
font-size:10.0pt;
font-family:"Courier New";}
p.MsoListParagraph, li.MsoListParagraph, div.MsoListParagraph
{mso-style-priority:34;
margin-top:0cm;
margin-right:0cm;
margin-bottom:0cm;
margin-left:36.0pt;
font-size:12.0pt;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}
span.HTMLPreformattedChar
{mso-style-name:"HTML Preformatted Char";
mso-style-priority:99;
mso-style-link:"HTML Preformatted";
font-family:"Courier New";
mso-fareast-language:EN-GB;}
span.literal
{mso-style-name:literal;}
span.st0
{mso-style-name:st0;}
span.comment
{mso-style-name:comment;}
span.EmailStyle25
{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:612.0pt 792.0pt;
margin:72.0pt 72.0pt 72.0pt 72.0pt;}
div.WordSection1
{page:WordSection1;}
/* List Definitions */
@list l0
{mso-list-id:1234698314;
mso-list-template-ids:-1833503686;}
@list l0:level1
{mso-level-number-format:bullet;
mso-level-text:\F0B7 ;
mso-level-tab-stop:36.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;
mso-ansi-font-size:10.0pt;
font-family:Symbol;}
@list l0:level2
{mso-level-number-format:bullet;
mso-level-text:\F0B7 ;
mso-level-tab-stop:72.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;
mso-ansi-font-size:10.0pt;
font-family:Symbol;}
@list l0:level3
{mso-level-number-format:bullet;
mso-level-text:\F0B7 ;
mso-level-tab-stop:108.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;
mso-ansi-font-size:10.0pt;
font-family:Symbol;}
@list l0:level4
{mso-level-number-format:bullet;
mso-level-text:\F0B7 ;
mso-level-tab-stop:144.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;
mso-ansi-font-size:10.0pt;
font-family:Symbol;}
@list l0:level5
{mso-level-number-format:bullet;
mso-level-text:\F0B7 ;
mso-level-tab-stop:180.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;
mso-ansi-font-size:10.0pt;
font-family:Symbol;}
@list l0:level6
{mso-level-number-format:bullet;
mso-level-text:\F0B7 ;
mso-level-tab-stop:216.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;
mso-ansi-font-size:10.0pt;
font-family:Symbol;}
@list l0:level7
{mso-level-number-format:bullet;
mso-level-text:\F0B7 ;
mso-level-tab-stop:252.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;
mso-ansi-font-size:10.0pt;
font-family:Symbol;}
@list l0:level8
{mso-level-number-format:bullet;
mso-level-text:\F0B7 ;
mso-level-tab-stop:288.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;
mso-ansi-font-size:10.0pt;
font-family:Symbol;}
@list l0:level9
{mso-level-number-format:bullet;
mso-level-text:\F0B7 ;
mso-level-tab-stop:324.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;
mso-ansi-font-size:10.0pt;
font-family:Symbol;}
@list l1
{mso-list-id:1856117091;
mso-list-template-ids:1048894376;}
@list l1:level1
{mso-level-tab-stop:36.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l1:level2
{mso-level-tab-stop:72.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l1:level3
{mso-level-tab-stop:108.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l1:level4
{mso-level-tab-stop:144.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l1:level5
{mso-level-tab-stop:180.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l1:level6
{mso-level-tab-stop:216.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l1:level7
{mso-level-tab-stop:252.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l1:level8
{mso-level-tab-stop:288.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l1:level9
{mso-level-tab-stop:324.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
ol
{margin-bottom:0cm;}
ul
{margin-bottom:0cm;}
--></style>
</head>
<body lang="en-CZ" link="#0563C1" vlink="#954F72" style="word-wrap:break-word">
<div class="WordSection1">
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">These tools are helpers for specific use cases and they do not represent transformations, but rather they collect and provide information necessary for building code.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">For example I need to know actual stack when I plan to use stack-to-locals (and back) function in my generated code.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Another example (which we may embed) is to count max stack when the generator is off.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Optional custom logging of the exact instructions dropped to CodeBuilder is another requested use case.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">All of the above are expensive operations, so they should be applied on user request only.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">This API does not have much value for transformations, where user can easily listen to each transformed CodeElement and compute whatever is necessary. However when building code using various
“magic” (like blocks, constants auto-detection, and other conveniences…) it is important to see what instructions it really builds into.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="color:black">From:
</span></b><span style="color:black">Brian Goetz <brian.goetz@oracle.com><br>
<b>Date: </b>Friday, 19 August 2022 15:39<br>
<b>To: </b>Adam Sotona <adam.sotona@oracle.com>, classfile-api-dev@openjdk.org <classfile-api-dev@openjdk.org><br>
<b>Subject: </b>Re: Classfile API is missing CodeBuilder hook for various instructions-consuming computation tools</span><span style="color:black;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
</div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span style="font-size:13.5pt;font-family:"Courier New"">Before we start to do architectural surgery, let's back up a bit and try to distill some requirements and goals. What problems led you here? Are these
tools we expect people to run full-time, or mostly for debugging when something goes wrong? Can they be applied to ordinary classfiles, or do they have to work during building? Could this be framed as a kind of transform, instead of a new concept?
<br>
<br>
<br>
</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<div>
<p class="MsoNormal"><span style="font-size:11.0pt">On 8/19/2022 2:34 AM, Adam Sotona wrote:<o:p></o:p></span></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Hi,</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">I’ve started working on various helper tools that can give user answers during code building.</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Answers to questions like:</span><o:p></o:p></p>
<ol style="margin-top:0cm" start="1" type="1">
<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l1 level1 lfo3"><span lang="EN-US" style="font-size:11.0pt">What is actual instructions count</span><o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l1 level1 lfo3"><span lang="EN-US" style="font-size:11.0pt">What is actual/max depts of the stack</span><o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l1 level1 lfo3"><span lang="EN-US" style="font-size:11.0pt">Which locals have been used</span><o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l1 level1 lfo3"><span lang="EN-US" style="font-size:11.0pt">What kinds or exact types are at locals</span><o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l1 level1 lfo3"><span lang="EN-US" style="font-size:11.0pt">What kinds or exact types are on stack</span><o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l1 level1 lfo3"><span lang="EN-US" style="font-size:11.0pt">Show me a log of all instructions</span><o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l1 level1 lfo3"><span lang="EN-US" style="font-size:11.0pt">…</span><o:p></o:p></li></ol>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Each of this question has specific use case and calculation of each answer scarifies different amount of resources.</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Unfortunately implementation of tool answering any of the above questions requires:</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">- either heavy use of BufferedCodeBuilder (and complicate existing building or transformation blocks a lot)</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">- or hacking into CodeBuilder(s) implementation</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">I would like to propose a similar approach as Linux “tee” tool does, so user can attach another consumer of the CodeElements passed to the CodeBuilder.</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">It might be just a single method in CodeBuilder:</span><o:p></o:p></p>
<p class="MsoNormal" style="background:white"><span lang="EN-US" style="font-size:10.0pt;color:black">
</span><span style="font-size:10.0pt;color:black">default void <b>tee</b>(Consumer<CodeElement>
</span><span lang="EN-US" style="font-size:10.0pt;color:black">secondListener</span><span style="font-size:10.0pt;color:black">, Consumer<CodeBuilder> handler) {</span><o:p></o:p></p>
<p class="MsoNormal" style="background:white"><span style="font-size:10.0pt;color:black"> handler.accept(new TeeCodeBuilder(this,
</span><span lang="EN-US" style="font-size:10.0pt;color:black">secondListener</span><span style="font-size:10.0pt;color:black">));</span><o:p></o:p></p>
<p class="MsoNormal" style="background:white"><span style="font-size:10.0pt;color:black"> }</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Use case may then look for example like this:</span><o:p></o:p></p>
<pre style="background:white"><span style="color:black"> </span><span class="literal"><span style="color:#336BDD">var</span></span><span style="color:black"> stackCounter = ...</span><span class="comment"><span style="color:#969696">//custom computation tool</span></span><o:p></o:p></pre>
<pre style="background:white"><span style="color:black"> <span class="st0"><i>codeBuilder</i></span>.<span class="st0"><i>tee</i></span>(stackCounter, cb -> {</span><o:p></o:p></pre>
<pre style="background:white"><span style="color:black"> ... </span><span class="comment"><span style="color:#969696">//block of instructions to be counted</span></span><o:p></o:p></pre>
<pre style="background:white"><span style="color:black"> });</span><o:p></o:p></pre>
<pre style="background:white"><span style="color:black"> stackCounter.<span class="st0"><i>actual</i></span>();</span><o:p></o:p></pre>
<pre style="background:white"><span style="color:black"> stackCounter.<span class="st0"><i>max</i></span>();</span><o:p></o:p></pre>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">What do you think about this CodeBuilder hook for various instructions-consuming computation tools?</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Thanks,</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Adam</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"> </span><o:p></o:p></p>
</blockquote>
<p class="MsoNormal"><span style="font-size:11.0pt;mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
</div>
</body>
</html>