[PATCH] D140828: [C++] Implement "Deducing this" (P0847R7)

Mon Oct 9 09:06:15 PDT 2023

aaron.ballman added a comment.

In D140828#4653389 <https://reviews.llvm.org/D140828#4653389>, @nikic wrote:

> FYI this causes some compile-time regression: http://llvm-compile-time-tracker.com/compare.php?from=bc7d88faf1a595ab59952a2054418cdd0d9eeee8&to=af4751738db89a142a8880c782d12d4201b222a8&stat=instructions:u About 0.7% for C++ code at `O0`. Sample for a file with >2% would be btSoftSoftCollisionAlgorithm.cpp.
>
> Not sure to what degree this is expected or not.

I think it's at least somewhat expected, but unfortunate. We basically have to check "is this an explicit object argument function or not" in a bunch of places in the compiler and I think that perhaps the extra branching is what's causing the perf situation. I'm not certain what can be done beyond "hook up a profiler and start poking around". Thoughts, @cor3ntin?

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D140828/new/

https://reviews.llvm.org/D140828