[PATCH] D49173: [DebugInfo] Make children iterator bidirectional

[David Blaikie via Phabricator via llvm-commits]

dblaikie added inline comments.


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Comment at: llvm/include/llvm/DebugInfo/DWARF/DWARFDie.h:354
 inline DWARFDie::iterator DWARFDie::end() const {
-  return iterator();
+  return iterator(getLastChild());
 }
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Why was this change needed?


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Comment at: llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp:595-599
+  // Find the previous DIE whose depth is the same as the Die's depth.
+  for (size_t I = getDIEIndex(Die) - 1; I >= 0; --I) {
+    if (DieArray[I].getDepth() == Depth)
+      return DWARFDie(this, &DieArray[I]);
+  }
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Unlike get(Next)Sibling, this loop may need to check for "<= Depth" and then return DWARFDie() if it's the < case.

When going forwards, there's always a null die sibling to break this loop (well, I guess a null die is returned from getSibling - and then no caller tries to call getSibling on the null die) - because it has the same depth.

But going backwards there's no null die to break the loop - oh, well, kind of.

So if you've got this arrangement: Unit{A{B,NULL},C{D,NULL},NULL}

And at D you "get previous" then you'll return the NULL child of A... which is still a null child, and that works I suppose. But you could've stopped searching once you saw C - because you've stepped out of C's children list by going to a shallower depth than the depth of D who's sibling you were searching for.



Oh... and it's undefined to dereference a begin iterator anyway, so none of that really matters, I suppose? :)


https://reviews.llvm.org/D49173