<div class="gmail_quote">2009/3/17 Evan Cheng <span dir="ltr"><<a href="mailto:echeng@apple.com">echeng@apple.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div style="word-wrap:break-word"><br><div><div class="im"><div>On Mar 13, 2009, at 10:43 AM, John Mosby wrote:</div><blockquote type="cite"><div><div class="gmail_quote"><div>I started to reduce the traversals, then decided to work on edge splitting because I believe it may be needed to finish shrink wrapping.</div>
</div></div></blockquote><div>Hmm. I don't think edge splitting would be required for correctness, right? There is always a common predecessor / successor. For the first pass, we should not be shooting to optimal solution.</div>
</div></div></div></blockquote><div><br></div><div>That's correct, edge splitting is not really required. I have it as a side project for the purpose of learning more about the design of the Machine layer.</div><div> </div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div style="word-wrap:break-word"><div></div><div><div class="im"><blockquote type="cite"><div><div class="gmail_quote">
<div>Let me know if you think using live interval info would be worth investigating for shrink wrapping.</div></div></div></blockquote></div></div><div><div class="im"><div>The various passes currently do not compute / update live intervals for fixed stack slots so it's not appropriate for this. That's why the stack slot coloring pass does not color those slots. It would be a nice enhancement to add (but for a different reason). :-)</div>
</div></div></div></blockquote><div><br></div><div>Thanks for the confirmation. I figured out about fixed stack slots not participating in live intervals earlier but I was not certain if it was available via some other means. Since shrink wrapping is more related to PRE (applied to loads/stores), it makes more sense to do the simple analysis anyway.</div>
<div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div style="word-wrap:break-word"><div><div class="im"><blockquote type="cite"><div><div class="gmail_quote">
<div>I'm working on characterizing the runtime and vm overhead, I don't yet have a detailed picture.</div><div>My plan is to do the cleanups, put together a few larger test cases, go back and run regressions,</div>
<div>then the test suite. With the larger focussed test cases, I will get usable numbers for compile times, and</div><div>the test suite will extend the coverage.</div><div>Please let me know if there is a simpler or more standard way to tackle this for a new pass.</div>
</div></div></blockquote><div>I would just run the test suite once the code is cleaned up. There are enough tests to give us a good idea about the compile time / run time impact. Since shrink wrapping will be guarded by a command line option, you can just run the test suite with ENABLE_LLCBETA. It will report everything we need to know.</div>
</div></div></div></blockquote><div><br></div><div>Thanks, I was going to ask how ask about llc beta. I will still be adding some stats so I can see when and what it reduces.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div style="word-wrap:break-word"><div></div><div><div class="im"><blockquote type="cite"><div><div class="gmail_quote"><div>What about EH and shrink wrapping? Should I disable shrink wrapping in EH contexts?</div></div></div>
</blockquote><div>I am not sure. If tests using EH fails, we can just disable shrink wrapping for functions with EH.</div></div></div><div><div class="im"><blockquote type="cite"><div><div class="gmail_quote"><div>I have held off looking at maintaining debug info integrity, let me know if I should look at that or if it can wait a bit.</div>
</div></div></blockquote><div>It's not an immediate problem since -O0 -g means "fast" codegen and shrink wrapping is not run. We can worry about this later.</div></div></div></div></blockquote><div><br></div>
<div>I will be testing with some small EH examples (which Anton recommended in the beginning) and will take care of disabling it (per-function) if this proves to be necessary.</div><div><br></div><div>Thank you very much for the feedback!</div>
<div><br></div><div>John</div><div><br></div></div>