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CodeGen: Move the SlotIndexes BumpPtrAllocator before the list it allocates

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When a `SlotIndexes` is destroyed, `ileAllocator` will currently be
destructed before `IndexList`, but all of `IndexList`'s storage has
been allocated by `ileAllocator`. This means we'll call destructors on
garbage data, which is very bad. This can be avoided by putting the
BumpPtrAllocator earlier in the class than anything it allocates.

Unfortunately, I don't know how to test this. It depends very much on
memory layout, and the only evidence I have that this is actually
happening in practice are backtraces that might be explained by this.
By inspection though, the code is obviously dangerous/wrong, and this
is the right thing to do.

I'll follow up later with a patch that calls clearAndLeakNodesUnsafely
on the list, since there isn't much point in destructing them when
they're allocated in a BPA anyway, but I figured it makes sense to
commit the correctness fix separately from that optimization.

llvm-svn: 254794
This commit is contained in:
Justin Bogner 2015-12-04 23:00:54 +00:00
parent b8bd41122a
commit 6c86c50af0
1 changed files with 2 additions and 3 deletions
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5
include/llvm/CodeGen/SlotIndexes.h
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@ -333,6 +333,8 @@ namespace llvm {
/// This pass assigns indexes to each instruction.
class SlotIndexes : public MachineFunctionPass {
private:
// IndexListEntry allocator.
BumpPtrAllocator ileAllocator;
typedef ilist<IndexListEntry> IndexList;
IndexList indexList;
@ -353,9 +355,6 @@ namespace llvm {
/// and MBB id.
SmallVector<IdxMBBPair, 8> idx2MBBMap;
// IndexListEntry allocator.
BumpPtrAllocator ileAllocator;
IndexListEntry* createEntry(MachineInstr *mi, unsigned index) {
IndexListEntry *entry =
static_cast<IndexListEntry*>(