[PATCH] D126061: [clang] Reject non-declaration C++11 attributes on declarations

Wed Jun 15 13:14:10 PDT 2022

mboehme added a comment.

In D126061#3585681 <https://reviews.llvm.org/D126061#3585681>, @nikic wrote:

> FYI this change had a measurable effect on compile-time (http://llvm-compile-time-tracker.com/compare.php?from=7acc88be0312c721bc082ed9934e381d297f4707&to=8c7b64b5ae2a09027c38db969a04fc9ddd0cd6bb&stat=instructions), about 0.5% regression for `O0` builds. Not sure if that's expected.

Thanks for the heads-up.

Without more extensive investigation, it's hard to say. I wasn't necessarily expecting a slowdown, but I can come up with various hypotheses for what might be causing it.

I've seen the instructions on the About <http://llvm-compile-time-tracker.com/about.php> page on how to reproduce results and will give that a go.

The first thing to analyze would be whether the slowdown occurs only on code that uses attributes (heavily) or also on code that doesn't use attributes.

There isn't any single substantial change in the code that would cause an obvious slowdown. I could speculate on some potential causes, but it seems better to measure instead. Is there any particular tooling that you would recommend for comparing profiler runs from two different compiler versions (one with my patch, one without)?

I'll post an update here when I find out more.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D126061/new/

https://reviews.llvm.org/D126061