[PATCH] D118534: [X86] Update generic process model to x86-64-v3 to match with GCC

Sat Jan 29 07:55:03 PST 2022

lebedev.ri added a comment.

In D118534#3281771 <https://reviews.llvm.org/D118534#3281771>, @spatel wrote:

> The default tuning came up in the context of bsf vs. tzcnt here:
> D117912 <https://reviews.llvm.org/D117912>
> So I wasn't expecting a bump in default tuning yet, but I think it's great.
>
> But I agree that this change may cause a lot of surprises, so users need to be given notice (add a line to the clang release notes?) and wait for the 14.0 branch to be created.
>
> Should we have a test file that intentionally shows codegen changes as this setting gets updated?

Please note that there is a *very* important difference between `-march=` and `-mtune=`:

- `-march=` means: no, please, i really only intend to run this code on this specific CPU, so feel free to use all of the ISA available, and schedule for this cCPU too.
- while `-mtune=` means: i want to be able to run the code on earlier processors, but do schedule for this CPU though.

So this change really shouldn't affect available instruction sets.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D118534/new/

https://reviews.llvm.org/D118534