Re: Faster Array#/MutableArray# copies

On 18/02/2011 19:42, Nathan Howell wrote:

On Fri, Feb 18, 2011 at 12:54 AM, Roman Leshchinskiy mailto:rl@cse.unsw.edu.au> wrote:

Max Bolingbroke wrote: > On 18 February 2011 01:18, Johan Tibell mailto:johan.tibell@gmail.com> wrote:> It seems like a sufficient solution for your needs would be for us to > use the LTO support in LLVM to inline across module boundaries - in > particular to inline primop implementations into their call sites. LLVM > would then probably deal with unrolling small loops with statically known > bounds.

Could we simply use this?

http://llvm.org/docs/LangRef.html#int_memcpy

Might be easier to implement a PrimOp inlining pass, and to run it before LLVM's built-in MemCpyOptimization pass [0]. This wouldn't generally be as good as LTO but would work without gold.

[0] http://llvm.org/doxygen/MemCpyOptimizer_8cpp_source.html

Ideally you'd want the heap check in the primop to be aggregated into the calling function's heap check, and the primop should allocate directly from the heap instead of calling out to the RTS allocate(). All this is a bit much to expect LLVM to do, but we could do it in the Glorious New Code Generator... For small arrays like this maybe we should have a new array type that leaves out all the card-marking stuff too (or just use tuples, as Roman suggested). Cheers, Simon