<div dir="ltr"><div>I'm definitely interested. Currently, I'm working on admittedly small tools that help discover module-tight coupling... sort of like a bad code metric, but also a highlight of code quality and organisation... issues. Although of course currently, I'm going off on the include level and am trying to assign (or refine an assign) of implementation to modules. (I think it's not a big revelation that directory-based organisations are rarely like Java packages...)</div><div><br></div><div>"Minimize sources by stripping away unused tokens."</div><div>You mentioned unused ">>tokens<<". One my question is: What is to be understood behind this? What constitutes an unused >token<.</div><div><br></div><div>;; Whisperity<br> </div></div><br><div class="gmail_quote"><div dir="ltr">Alex L via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org" target="_blank">cfe-dev@lists.llvm.org</a>> ezt írta (időpont: 2018. okt. 17., Sze, 3:53):<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div dir="ltr"><p style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue"">Hi,</p>
<p style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue";min-height:14px"><br></p>
<p style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue"">Bruno (CCed), Duncan (CCed) and I have been exploring if we can migrate some of our clients to explicit modules. As part of this work Duncan and I developed a new prototype dependency scanning service tool (clang-scan-deps) that computes the set of file dependencies for a particular compiler invocation using some optimizations that are outlined below. This tool makes the non-modular dependency scanning up to 10 times faster for particular workloads (e.g. llc target, 1542 C++ files) on one of our machines, when compared to parallel invocations of clang with -Eonly. We are still in the early stages of proper modules support, but our initial crude prototype can get up to 4x when run on the first 1000 files from clang’s compilation database for a build of LLVM with modules turned on.</p>
<p style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue";min-height:14px"><br></p>
<p style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue"">We still run the full Clang preprocessor. Here’s what we do to reduce its workload:</p>
<ul>
<li style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue"">Minimize sources by stripping away unused tokens. We keep only the interesting PP directives (#define, #if, #include, etc.), i.e. those that might impact the set of dependencies. </li>
<li style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue"">Assume the filesystem is immutable for one run of the service, and cache the files and their minimized contents in memory in a global cache.</li>
<li style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue"">Skip over excluded preprocessor ranges by bumping up the buffer pointer in the lexer instead of lexing the skipped tokens.</li>
</ul>
<p style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue";min-height:14px"><br></p>
<p style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue"">We intend to upstream this service in the upcoming months. We also would like to integrate this service into Clangd as part of our migration to Clangd to help us determine a good compilation command for a header file from a set of known compilation invocations.</p>
<p style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue";min-height:14px"><br></p>
<p style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue"">I posted a very rough WIP patch on Phabricator (<a href="https://reviews.llvm.org/D53354" target="_blank"><span style="color:rgb(220,161,13)">https://reviews.llvm.org/D53354</span></a>). It’s based on LLVM checkout r343343. Please take a look if you’re interested.</p>
<p style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue"">Duncan, Bruno and I will be at the LLVM dev meeting. We are interested in discussing this prototype and collecting feedback from anyone who might be interested in this work.</p>
<p style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue";min-height:14px"><br></p>
<p style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue"">Thanks,</p>
<p style="margin:0px;font-stretch:normal;font-size:12px;line-height:normal;font-family:"Helvetica Neue"">Alex</p></div></div>
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