[PATCH] D43578: -ftime-report switch support in Clang

[Richard Smith - zygoloid via Phabricator via cfe-commits]

rsmith added a comment.

In https://reviews.llvm.org/D43578#1067879, @avt77 wrote:

> In https://reviews.llvm.org/D43578#1067768, @rsmith wrote:
>
> > Last time I looked at doing this, I found that LLVM's timer infrastructure was fundamentally unsuitable for adding timers like these to Clang.
>
>
> Thank you for this answer. As I understand we should close both this review and https://reviews.llvm.org/D45619


I think https://reviews.llvm.org/D45619 is a good change, and I'd like to see that get committed.

If LLVM's timer infrastructure can be improved to correctly track time in recursive and mutually-recursive timing regions (and I believe it can be), we could continue with this patch; if you want to pursue that, my first questions would be:

Who is the audience for this information?
What information do they want from a time report?
How do we present that information in a way that's not misleading (given Clang's architecture)?
Can we deliver useful value compared to a modern, dedicated profiling tool?

> but you'd like to see something like MS has here <https://aras-p.info/blog/2017/10/23/Best-unknown-MSVC-flag-d2cgsummary/>, right?

Yes, that's the kind of information I think we should be looking at adding here -- I think that's exactly what Clang users would be looking for when they reach out to a compilation time report to try to figure out why their compile is slow.


https://reviews.llvm.org/D43578