On Jun 17, 2011, at 9:46 AM, Chris Lattner wrote:
>
> On Jun 17, 2011, at 9:37 AM, Douglas Gregor wrote:
>
>> I'm deeply suspicious of AggExprEmitter::VisitBinAssign()'s
>> optimization where it emits the RHS of an aggregate assignment
>> directly into the LHS lvalue without checking whether there is any
>> aliasing between the LHS/RHS. However, I'm not in a position to
>> revisit this now.
>
> FWIW, it is making the assumption that the LHS/RHS either don't alias, or
> that they *exactly* alias. The LLVM optimizer (and gcc fwiw) make the
> assumption that memcpy(X,X, ...) is safe.
It's making the assumption that we can perform piecemeal initialization of the
LHS from the RHS, rather than building the RHS as a separate aggregate and then
memcpy'ing it over.
I have a more satisfying fix coming.
- Doug
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