<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 Jun 25, 2015, at 5:21 PM, David Blaikie <<a href="mailto:dblaikie@gmail.com" class="">dblaikie@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><br class=""><div class="gmail_extra"><br class=""><div class="gmail_quote">On Thu, Jun 25, 2015 at 5:11 PM, Pete Cooper <span dir="ltr" class=""><<a href="mailto:peter_cooper@apple.com" target="_blank" class="">peter_cooper@apple.com</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word" class=""><br class=""><div class=""><span class=""><blockquote type="cite" class=""><div class="">On Jun 25, 2015, at 2:40 PM, David Blaikie <<a href="mailto:dblaikie@gmail.com" target="_blank" class="">dblaikie@gmail.com</a>> wrote:</div><br class=""><div class=""><div dir="ltr" class=""><br class=""><div class="gmail_extra"><br class=""><div class="gmail_quote">On Thu, Jun 25, 2015 at 2:30 PM, Pete Cooper <span dir="ltr" class=""><<a href="mailto:peter_cooper@apple.com" target="_blank" class="">peter_cooper@apple.com</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">Hi David<br class="">
<br class="">
Currently the only SDNode iterator over operands does so with SDUse*. Users frequently then call getNode() on the operand.<br class="">
<br class="">
This patch adds an iterator to SDNode which returns the SDNode of the operand. This allows more patterns to be converted to foreach. It is based on value_op_iterator which I found in User.h.<br class="">
<br class="">
For now i’ve only used it in a single place, but I found a bunch more in DAGCombiner for example which should be applicable. I would convert those in a later commit assuming you are ok with this solution.<br class=""></blockquote><div class=""><br class="">This immediately raises red flags:<br class=""><br class=""><div class=""> SDNode *operator*() const { return I->getNode(); }</div><div class=""> SDNode *operator->() const { return operator*(); }<br class=""><br class="">op* should return a T& and op-> should return T*<br class=""></div></div></div></div></div></div></blockquote></span>I’d forgotten about that.<span class=""><br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><div class=""><div class=""><br class="">If these SDNode*s can never be null, then perhaps this should be:<br class=""></div></div></div></div></div></div></blockquote></span>I wasn’t actually sure if they could be. My initial reaction was that null operands wouldn’t make sense, but it turns out we never checked. So here’s a patch which does actually ensure that the SDNode's referenced as operands are never null. It passes make check. I can put it on another email for review if you prefer I don’t add it here.</div></div></blockquote><div class=""><br class="">It might be worth a separate thread, or at least a drive-by by someone who deals with this part of the code. I don't really understand the necessity/merits/drawbacks of the 'SDUse::reset()" member function you've introduced.<br class=""></div></div></div></div></div></blockquote>No problem. Thanks for taking a look. I’ve just sent out an email to llvm-commits and asked Hal for review as I know he’s done lots of SD work.<br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><div class=""> </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" class=""><div class=""><br class=""></div><div class=""></div></div><br class=""><div style="word-wrap:break-word" class=""><div class=""></div><div class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><div class=""><div class=""><br class=""> SDNode &operator*<br class=""> SDNode *operator-><br class=""><br class="">? (because I assume you don't have an SDNode* lvalue to return a reference to) I assume the adapter helper can implement one of those in terms of the other so you only have to implement one of them? I forget how the adapter utility works.<br class=""></div></div></div></div></div></div></blockquote>I think it makes sense to do this. This will unfortunately be one of the few SDNode & in the entire codebase though, which makes it stand out. SDNode really does seem to always be a pointer. I’ll fix up the patch to do this soon.<br class=""></div></div></blockquote><div class=""><br class="">Yeah, there are a few types (read: Lots) like this in LLVM. I personally don't mind being more referential in spite of that, but I can understand others might feel less comfortable with that.<br class=""><br class="">If you wanted to preserve the pointer-ness, you'd have op* return SDNode * (this would be a bit incorrect, it should really be SDNode * const &, and you can do that by having an SDNode* member in the iterator that you init and return a ref to... technically that's the more correct option - I'm not entirely sure where that matters) and no op->.</div></div></div></div></div></blockquote>I like this solution. I tried SDNode * const & earlier but of course getNode() is a temporary so this doesn’t work. I’ll get a patch together which makes this change. Technically I guess that means we don’t need the nonnull SDNode patch, but I don’t see any harm in it anyway.</div><div><br class=""></div><div>Thanks,</div><div>Pete<br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word" class=""><div class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><div class=""> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<br class="">
BTW, been trying to work out if there would ever be a good solution for an iterator combined with isa<> or dyn_cast<>. If you look at the code this patch touches in AArch64ISelLowering, it is immediately followed by a dyn_cast. I’d really like to find a clean way to fold that it to the foreach loop, i.e.,<br class="">
<br class="">
for (auto *C : dyn_cast<ConstantSDNode>(N->op_nodes()))<br class="">
<br class="">
just a thought, but thats unrelated to this patch for now.<br class=""></blockquote><div class=""><br class="">Yep, though probably more in the form of a filtered range, I suspect:<br class=""><br class=""> for (auto &C : filtered_transform(N->op_nodes(), [](SDUse *U) { return U->getNode(); }))<br class=""><br class="">It'd be a bit tricky to deal with the value type of this range's iterators - chances are the predicate should return an Optional<T&> (Hmm, don't think our Optional template supports ref parameters yet anyway) or T* (not sure if we could generalize it so it could cope with Optional<T>, maybe - so we could support generators where the values are not already/permanently in-memory) and then the value_type is T.<br class=""></div></div></div></div></div></blockquote>Interesting. I hadn’t though to use Optional. I might try to implement something like this if i get time.</div><div class=""><br class=""></div><div class="">Cheers,</div><div class="">Pete<br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><div class=""> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<br class="">
Cheers,<br class="">
Pete<br class="">
<br class="">
</blockquote></div><br class=""></div></div>
</div></blockquote></div><br class=""></div><br class=""></blockquote></div><br class=""></div></div>
</div></blockquote></div><br class=""></body></html>