On Apr 14, 2010, at 4:59 AM, Benjamin Kramer wrote:
>
> On 14.04.2010, at 01:39, Ted Kremenek wrote:
>
>> Author: kremenek
>> Date: Tue Apr 13 18:39:09 2010
>> New Revision: 101194
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=101194&view=rev
>> Log:
>> Introduce ASTVector, which is a std::vector-like class that allocates all
>> memory
>> using the allocator associated with an ASTContext. This is largely
>> copy-and-paste
>> from SmallVector, and should be refactored one day.
>
> I was thinking about this before and came to the conclusion that a
> BumpPtrAllocator + vector is a
> bad combination. Every time the vector resizes the old memory isn't freed and
> adds up. I guess
> it doesn't matter in smaller cases but it could become a huge memory waste if
> we're not checking every
> ASTVector's insert characteristics carefully. In my opinion a list-like data
> structure should be
> preferred (where applicable).
Yeah, I agree. The preferred usage for BumpPtrAllocators should either be
node-base data structures (list, graph, DAG, whatever) or non-resizable chunks
of memory. The best way to tackle InitListExpr, for example, would be to
compute the full set of initializers within SemaInit.cpp and then allocate them
in one big block via the BumpPtrAllocator.
IMO, "resizing" should not be part of the AST.
- Doug
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