On Wed, Sep 2, 2026 at 7:16 AM Michael Paquier <[email protected]> wrote: > > On Tue, Sep 01, 2026 at 02:26:38PM +0800, Ewan Young wrote: > > I see this went in as 8e483af5515 in the meantime -- thanks a lot for > > the commit and the credit! > > > > FWIW, the two um/div sites left out, int2um() and int2div(), turn out > > to be mixed rather than clean: clang 15 compiles the int16 > > __builtin_sub_overflow() one instruction worse on the hot path, while > > gcc 12 does one better (neg + jo). > > Please note that I'd be OK to look at this stuff again if we have > other similar opportunities. I am not really convinced by your > v2-0002. The other opportunities in v2-0001 could be reconsidered if > rewritten in a different way, but it's also tricky to evaluate due to > the with/without builtin and compiler requirements. > > I would accept something that proves to be a net benefit in rather new > versions of gcc and clang, as well as a net benefit with/without the > builtin. 8e483af5515 was exactly that, with less or the same amount of > instructions (the cash change was super nice) for all setups I have > tested (Linux and macos).
Fair enough on 0002 -- let's drop it. Thanks again for taking the good batch! > -- > Michael -- Regards, Ewan Young
