<div dir="ltr">CurrIter have only one use. <div><br></div><div><br></div><div><span style="color:rgb(80,0,80);font-size:12.8px">auto CurrIter = MI;</span><br style="color:rgb(80,0,80);font-size:12.8px"><span style="color:rgb(80,0,80);font-size:12.8px">++MI;</span><br style="color:rgb(80,0,80);font-size:12.8px"><span style="color:rgb(80,0,80);font-size:12.8px">Value *Member = *CurrIter;</span><br></div><div><span style="color:rgb(80,0,80);font-size:12.8px"><br></span></div><div>I can rewrite beginning of loop as<span style="color:rgb(80,0,80);font-size:12.8px"><br></span></div><div><span style="color:rgb(80,0,80);font-size:12.8px">Value *Member = *MI++;</span></div><div><span style="color:rgb(80,0,80);font-size:12.8px"><br></span></div><div><span style="color:rgb(80,0,80);font-size:12.8px">Which makes it trivial that it is range for loop.</span></div><div><span style="color:rgb(80,0,80);font-size:12.8px"><br></span></div><div><span style="color:rgb(80,0,80);font-size:12.8px">Of course I am not 100% sure, operator* and operator++ might do some weird things here, but I assumed they are sane.</span></div><div><span style="color:rgb(80,0,80);font-size:12.8px">Tests also passed</span></div><div><span style="color:rgb(80,0,80);font-size:12.8px"><br></span></div></div><div class="gmail_extra"><br><div class="gmail_quote">2016-12-29 2:20 GMT+01:00 Sean Silva <span dir="ltr"><<a href="mailto:chisophugis@gmail.com" target="_blank">chisophugis@gmail.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote"><span class="">On Wed, Dec 28, 2016 at 11:42 AM, Piotr Padlewski via llvm-commits <span dir="ltr"><<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: prazek<br>
Date: Wed Dec 28 13:42:49 2016<br>
New Revision: 290683<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=290683&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-pr<wbr>oject?rev=290683&view=rev</a><br>
Log:<br>
[NewGVN] Simplyfy loop NFC<br>
<br>
Modified:<br>
llvm/trunk/lib/Transforms/Scal<wbr>ar/NewGVN.cpp<br>
<br>
Modified: llvm/trunk/lib/Transforms/Scal<wbr>ar/NewGVN.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/NewGVN.cpp?rev=290683&r1=290682&r2=290683&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-pr<wbr>oject/llvm/trunk/lib/Transform<wbr>s/Scalar/NewGVN.cpp?rev=<wbr>290683&r1=290682&r2=290683&<wbr>view=diff</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- llvm/trunk/lib/Transforms/Scal<wbr>ar/NewGVN.cpp (original)<br>
+++ llvm/trunk/lib/Transforms/Scal<wbr>ar/NewGVN.cpp Wed Dec 28 13:42:49 2016<br>
@@ -1915,10 +1915,7 @@ bool NewGVN::eliminateInstructions(<wbr>Funct<br>
<br>
// Cleanup the congruence class.<br>
SmallPtrSet<Value *, 4> MembersLeft;<br>
- for (auto MI = CC->Members.begin(), ME = CC->Members.end(); MI != ME;) {<br>
- auto CurrIter = MI;<br>
- ++MI;<br>
- Value *Member = *CurrIter;<br>
+ for (Value * Member : CC->Members) {<br></blockquote><div><br></div></span><div>Is this correct? Usually this kind of loop where the iterator is incremented at the start of the loop will invalidate the iterator somewhere later, so rewriting it to be a range for (or a simple loop with the increment inside the `for` header where it usually goes) will introduce a nasty bug.</div><div><br></div><div>I haven't looked closely enough in this particular case, but I'd definitely like to see a bit more justification (ideally in the commit message in the future) for the safety of this refactoring when dealing with this kind of "increment at the beginning" loops.</div><span class="HOEnZb"><font color="#888888"><div><br></div><div>-- Sean Silva</div></font></span><span class=""><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
if (Member->getType()->isVoidTy()<wbr>) {<br>
MembersLeft.insert(Member);<br>
continue;<br>
<br>
<br>
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</blockquote></span></div><br></div></div>
</blockquote></div><br></div>