[llvm-dev] Commit module to Git after each Pass

[Alexandre Isoard via llvm-dev]

If this is faster than -print-after-all we may actually consider pushing
that in the code base then? (after diligent code review of course)

Note that it uses the same printing method as -print-after-all:
- create a pass of the same pass kind as the pass we just ran
- use Module::print(raw_ostream) to print (except -print-after-all only
print the concerned part and into stdout)

If there is improvement to be done to print-after-all it might also improve
git-commit-after-all. (unless that only improve speed when printing
constructs smaller than module)

In any case, it is, to me, much more usable (and extensible) than
-print-after-all. But requires git to be in PATH (I'm curious if that works
on Windows).

On Thu, Mar 15, 2018 at 1:35 PM, Daniel Sanders <daniel_l_sanders at apple.com>
wrote:

> Does https://reviews.llvm.org/D44132 help at all?
>
>
> On 15 Mar 2018, at 09:16, Philip Reames via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
> The most likely answer is that the printer used by print-after-all is
> slow.  I know there were some changes made around passing in some form of
> state cache (metadata related?) and that running printers without doing so
> work, but are dog slow.  I suspect the print-after-all support was never
> updated.  Look at what we do for the normal IR emission "-S" and see if
> print-after-all is out of sync.
>
> Philip
>
> On 03/15/2018 08:45 AM, Alexandre Isoard via llvm-dev wrote:
>
> Huh. Great! 😁
>
> I don't believe my poor excuse from earlier (else we should map all pipes
> into files!), but I'm curious why we spend less time in system mode when
> going through file than pipe. Maybe /dev/null is not as efficient as we
> might think? I can't believe I'm saying that...
>
> On Thu, Mar 15, 2018, 08:25 Fedor Sergeev <fedor.sergeev at azul.com> wrote:
>
>> Well, git by itself is so focused on performance, so its not surprising
>> to me that even using git add/git commit does not cause
>> performance penalties.
>>
>
> Sure, but still, I write more stuff (entire module) into a slower
> destination (file). Even ignoring git execution time it's counter intuitive.
>
> The only difference is that while I write more, it overwrite itself
> continuously, instead of being a long linear steam. I was thinking of mmap
> the file instead of going through our raw_stream, but maybe that's
> unnecessary then...
>
>>
>
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-- 
*Alexandre Isoard*
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