[llvm-dev] [RFC] Machine Function Splitter - Split out cold blocks from machine functions using profile data

[Snehasish Kumar via llvm-dev]

+Rahman Lavaee <rahmanl at google.com> who is working on exception
support for basicblock sections.

On Mon, Aug 10, 2020 at 4:29 PM Modi Mo <modimo at fb.com> wrote:

> >Exceptions
>
> >All eh pads are grouped together regardless of their coldness and are
> part of the original function. There are outstanding issues with splitting
> eh pads if they reside in separate sections in the binary. This remains as
> part of future work.
>
>
>
> Can you elaborate more on the outstanding issues with splitting eh pads?
>
>
>
> From my dip into the unwind map in gcc_except_table the current encoding
> to landing pads using function-start relative offsets doesn’t extend well
> to moving the pads somewhere else. Are there additional issues with
> splitting specific pads out?
>
That's correct, we have a pending patch to add support for this.
https://reviews.llvm.org/D73739
IIUC with this patch, we can treat a set of ehpads as hot or cold and move
them around as needed.

>
>
> Best,
>
> Modi
>
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