Re: [PATCH] x86: Disable XCHG to MOV optimization
Jan Beulich <[email protected]>
| Newsgroups | gmane.comp.gnu.binutils |
|---|---|
| Message-ID | <[email protected]> |
On 13.07.2026 17:31, H.J. Lu wrote: > On Mon, Jul 13, 2026 at 11:20 PM Jan Beulich <[email protected]> wrote: >> >> On 13.07.2026 17:10, H.J. Lu wrote: >>> On Mon, Jul 13, 2026 at 11:03 PM Jan Beulich <[email protected]> wrote: >>>> >>>> On 13.07.2026 14:08, H.J. Lu wrote: >>>>> I am going to check this patch into master as well as 2.47 branch. >>>>> I added optimize_for_unsafe, which is 0, and moved XCHG to MOV >>>>> optimization under it. We can add something like -Ounsafe later. >>>> >>>> But this is wrong, the optimization itself isn't unsafe. Please can we >>> >>> You can change it to a different name. But -O on master must work with >>> today's valgrind. >> >> That's your position. I continue to fail to see why -O needs to work on >> anything (valgrind or not) that depends on getting to see specific >> encodings for certain insns. Such uses of -O are simply wrong. Undoing > > You can add a different option. -O should work for all applications today. Again - no. It simply can't. (Ftaod when I say -O in this discussion, I generally mean all its forms.) Jan