<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Mar 13, 2016, at 2:14 PM, tim Rowledge <<a href="mailto:tim@rowledge.org" class="">tim@rowledge.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">The clever bit is that the first part of the machine code we built for BoringClass>theRubberPullets does a check that the class of the receiver is the same as the boringClassTag we loaded. If it is, no problem, carry on. If it is not then we abort to a routine that builds a PIC - a Polymorphic Inline Cache, see the 2nd URL above - moves things around a bit (not quite randomly) and once more rewrites the call so that now it jumps to the beginning of the PIC. And then we carry on again (isn’t that a neat title for a movie?) with our processing.</span></div></blockquote></div><br class=""><div class="">Right. This is the interesting part. But here’s the question: what’s different in an image from 5-7 years ago to an image now? Who is carrying this information? The receiver or the CompiledMethod? </div><div class=""><br class=""></div><div class="">The answer (as I understand it) is that the CompiledMethod is carrying a cue for the JIT. Something is going on there. The receiver doesn’t know anything, I don’t think. (I appreciate the process is going to ping it. But the process is not starting there.)</div><div class=""><br class=""></div><div class="">There’s been lots of talk about byte codes and new byte code set, but that’s not it. If I explore a CompiledMethod in an old image or a new one, it’s not going to show me when a PIC is activating. The header gets incinerated and replaced with machine code. And then there’s a check to see if the header is now machine code ash called #isCogMethodReference:. That is the bifurcation between the old way and the new. If Yes, then go to JIT related code. If No, then it looks like it always has. </div><div class=""><br class=""></div><div class="">Thank you for the links. I’ll check them out in a bit. I think I’m reaching saturation for now. </div><div class=""><br class=""></div><div class="">Chris </div></body></html>