[LLVMdev] [Proposal] Parallelize post-IPO stage.

Eric Christopher echristo at gmail.com
Sun Jul 14 18:38:50 PDT 2013

On Sun, Jul 14, 2013 at 5:57 PM, Andrew Trick <atrick at apple.com> wrote:
> On Jul 12, 2013, at 3:49 PM, Shuxin Yang <shuxin.llvm at gmail.com> wrote:
> 6) Miscellaneous
> ===========
>   Will partitioning degrade performance in theory.  I think it depends on
> the definition of
> performance.  If performance means execution-time, I guess it dose not.
> However, if performance includes code-size, I think it may have some
> negative impact.
> Following is few scenario:
>   - constants generated by the post-IPO passes are not shared across
> partitions
>   - dead func may be detected during the post-IPO stage, and they may not be
> deleted.
> In don't know if it's feasible, but stable linker output, independent of the
> partioning, is highly desirable. One of the most irritating performance
> regressions to track down involves different versions of the host linker. If
> partitioning decisions are thrown into the mix, this could be annoying. Is
> it possible for the final link to do a better job cleaning up?

While I haven't yet read the rest of the proposal I'm going to comment
on this in particular. In my view this is an absolute requirement as
the compiler should produce the same output given the same input every
time with no deviation.


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