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Clarify that if a new value handle is added while dropping value handles

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hanging off a value, then the dropping code will intentionally not drop
it too (since this is almost certainly a bug).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109337 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2010-07-24 12:09:22 +00:00
parent f28dd88611
commit ffe8c8871a
1 changed files with 9 additions and 4 deletions
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13
lib/VMCore/Value.cpp
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@ -488,10 +488,15 @@ void ValueHandleBase::ValueIsDeleted(Value *V) {
ValueHandleBase *Entry = pImpl->ValueHandles[V];
assert(Entry && "Value bit set but no entries exist");
// We use a local ValueHandleBase as an iterator so that
// ValueHandles can add and remove themselves from the list without
// breaking our iteration. This is not really an AssertingVH; we
// just have to give ValueHandleBase some kind.
// We use a local ValueHandleBase as an iterator so that ValueHandles can add
// and remove themselves from the list without breaking our iteration. This
// is not really an AssertingVH; we just have to give ValueHandleBase a kind.
// Note that we deliberately do not the support the case when dropping a value
// handle results in a new value handle being permanently added to the list
// (as might occur in theory for CallbackVH's): the new value handle will not
// be processed and the checking code will meet out righteous punishment if
// the handle is still present once we have finished processing all the other
// value handles (it is fine to momentarily add then remove a value handle).
for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
Iterator.RemoveFromUseList();
Iterator.AddToExistingUseListAfter(Entry);