On 01/05/2020 11:38, JiangNing OS via Gcc-patches wrote: > Hi Kyrill, > > Can it be backported to gcc 8/9/10 branches? >
I'm not sure changing the defaults of things like this is a good idea on 'dot' releases. Having the option is one thing. Changing the default another thing entirely. R. > Thanks, > -Jiangning > >> -----Original Message----- >> From: Gcc-patches <[email protected]> On Behalf Of Kyrylo >> Tkachov >> Sent: Thursday, April 30, 2020 8:27 PM >> To: Kyrylo Tkachov <[email protected]>; Andrew Pinski >> <[email protected]>; Florian Weimer <[email protected]> >> Cc: [email protected]; [email protected] >> Subject: RE: Should ARMv8-A generic tuning default to -moutline-atomics >> >> >> >>> -----Original Message----- >>> From: Gcc-patches <[email protected]> On Behalf Of >>> Kyrylo Tkachov >>> Sent: 30 April 2020 11:57 >>> To: Andrew Pinski <[email protected]>; Florian Weimer >>> <[email protected]> >>> Cc: [email protected]; [email protected] >>> Subject: RE: Should ARMv8-A generic tuning default to >>> -moutline-atomics >>> >>> [Moving to gcc-patches] >>> >>>> -----Original Message----- >>>> From: Gcc <[email protected]> On Behalf Of Andrew Pinski via >>>> Gcc >>>> Sent: 30 April 2020 07:21 >>>> To: Florian Weimer <[email protected]> >>>> Cc: GCC Mailing List <[email protected]>; [email protected] >>>> Subject: Re: Should ARMv8-A generic tuning default to >>>> -moutline-atomics >>>> >>>> On Wed, Apr 29, 2020 at 6:25 AM Florian Weimer via Gcc >>>> <[email protected]> >>>> wrote: >>>>> >>>>> Distributions are receiving requests to build things with >>>>> -moutline-atomics: >>>>> >>>>> <https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=956418> >>>>> >>>>> Should this be reflected in the GCC upstream defaults for ARMv8-A >>>>> generic tuning? It does not make much sense to me if every >>>>> distribution has to overide these flags, either in their build >>>>> system or by patching GCC. >>>> >>>> At least we should make it a configure option. >>>> I do want the ability to default it for our (Marvell) toolchain for >>>> Linux (our bare metal toolchain will be defaulting to ARMv8.2-a >>>> anyways). >>> >>> After some internal discussions, I am open to having it on as a default. >>> Here are two versions. One has it as a tuning setting that CPUs can >>> override, the other just switches it on by default always unless >>> overridden by -mno- outline-atomics. >>> I slightly prefer the second one as it's cleaner and simpler, but >>> happy to take either. >>> Any preferences? >>> Thanks, >>> Kyrill >>> >>> ChangeLogs: >>> >>> 2020-04-30 Kyrylo Tkachov <[email protected]> >>> >>> * config/aarch64/aarch64-tuning-flags.def (no_outline_atomics): >>> Declare. >>> * config/aarch64/aarch64.h (TARGET_OUTLINE_ATOMICS): Define. >>> * config/aarch64/aarch64.opt (moutline-atomics): Change to Int >>> variable. >>> >>> 2020-04-30 Kyrylo Tkachov <[email protected]> >>> >>> * config/aarch64/aarch64.h (TARGET_OUTLINE_ATOMICS): Define. >>> * config/aarch64/aarch64.opt (moutline-atomics): Change to Int >>> variable. >>> * doc/invoke.texi (moutline-atomics): Document as on by default. >>> >> >> I've pushed this second variant after bootstrap and testing on aarch64-none- >> linux-gnu. >> Compiled a simple atomic-using testcase with all relevant combinations of - >> moutline-atomics and LSE and no-LSE -march options. >> Before the results were (as expected): >> |-moutline-atomics | -mno-outline-atomics | <no outline-atomics >> option >> -------------------------------------------------------------------------------- >> LSE | inline LSE | inline LSE | inline LSE >> no-LSE | outline | inline LDXR/STXR | inline LDX/STXR >> >> >> with this patch they are: >> -moutline-atomics | -mno-outline-atomics | <no outline-atomics >> option> >> -------------------------------------------------------------------------------- >> LSE | inline LSE | inline LSE | inline LSE >> no-LSE | outline | inline LDXR/STXR | outline >> >> Thanks, >> Kyrill
