[LLVMdev] Postponing more passes in LTO

[Eric Christopher]

On Wed, Sep 17, 2014 at 6:46 AM, Daniel Stewart <stewartd at codeaurora.org>
wrote:

> Looking at the existing flow of passes for LTO, it appears that most all
> passes are run on a per file basis, before the call to the gold linker. I’m
> looking to get people’s feedback on whether there would be an advantage to
> waiting to run a number of these passes until the linking stage. For
> example, I believe I saw a post a little while back about postponing
> vectorization until the linking stage. It seems to me that there could be
> an advantage to postponing (some) passes until the linking stage, where the
> entire graph is available. In general, what do people think about the idea
> of a different flow of LTO where more passes are postponed until the
> linking stage?
>
>
>

I think there needs to be some amount of cleanup before cross module
inlining otherwise you're going to lose a lot of inlining chances that
you'd have had. It's a bit of a tradeoff. I remember working up a pipeline
with Chandler and Dan at one point and I believe Bob was in on the
discussion too. I don't have notes of the actual pipeline so I'm adding
them all to the thread to pipe up :)

-eric
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