<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">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-<wbr>project?rev=290683&view=rev</a><br>
Log:<br>
[NewGVN] Simplyfy loop NFC<br>
<br>
Modified:<br>
    llvm/trunk/lib/Transforms/<wbr>Scalar/NewGVN.cpp<br>
<br>
Modified: llvm/trunk/lib/Transforms/<wbr>Scalar/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-<wbr>project/llvm/trunk/lib/<wbr>Transforms/Scalar/NewGVN.cpp?<wbr>rev=290683&r1=290682&r2=<wbr>290683&view=diff</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- llvm/trunk/lib/Transforms/<wbr>Scalar/NewGVN.cpp (original)<br>
+++ llvm/trunk/lib/Transforms/<wbr>Scalar/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><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><div><br></div><div>-- Sean Silva</div><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></div><br></div></div>