[llvm-commits] [PATCH 12/20] [AVX] Make ListInits Unique

[Jakob Stoklund Olesen]

On Jul 19, 2011, at 1:11 PM, David Greene wrote:

> Make ListInit a FastFoldingSetNode to ensure ListInits are unique
> and only created once.  This will be important for AVX as lists
> will be used extensively to pass generic patterns, prefix
> information and other things to lower-level pattern-generation
> classes.

I don't really understand this approach. The FastFoldingSetNode base class adds 160 bytes of overhead, and it is guaranteed to at least double the memory used by a ListInit.

Now that you have a FoldingSet per Init subclass, you can just provide a Profile method instead. That reduces the overhead to just a pointer.

See APFloat for a simple example.

/jakob