2016-02-02 16:06 GMT+03:00 H.J. Lu <hjl.to...@gmail.com>: > On Tue, Feb 2, 2016 at 5:03 AM, Ilya Enkovich <enkovich....@gmail.com> wrote: >> 2016-02-02 15:46 GMT+03:00 H.J. Lu <hjl.to...@gmail.com>: >>> On Tue, Feb 2, 2016 at 4:30 AM, H.J. Lu <hjl.to...@gmail.com> wrote: >>>> On Tue, Feb 2, 2016 at 4:29 AM, Jakub Jelinek <ja...@redhat.com> wrote: >>>>> On Tue, Feb 02, 2016 at 01:24:26PM +0100, Uros Bizjak wrote: >>>>>> On Tue, Feb 2, 2016 at 12:53 PM, Jakub Jelinek <ja...@redhat.com> wrote: >>>>>> >>>>>> >> The bottom line is ix86_minimum_alignment must return the correct >>>>>> >> number for DImode or you can just turn off STV. My suggestion is >>>>>> >> to use my patch. >>>>>> > >>>>>> > Uros, any preferences here? I mean, it is possible to use >>>>>> > e.g. the ix86_option_override_internal and have H.J's >>>>>> > ix86_minimum_alignment >>>>>> > change as a safety net, in the usual case for >>>>>> > -mpreferred-stack-boundary=2 >>>>>> > we'll just disable TARGET_STV and ix86_minimum_alignment change won't >>>>>> > do >>>>>> > anything, as TARGET_STV will be false, and if for whatever case it gets >>>>>> > through (target attribute, -mincoming-stack-boundary=, ...) >>>>>> > ix86_minimum_alignment will be there to ensure enough stack alignment. >>>>>> > Most of the smaller -mpreferred-stack-boundary= uses are -mno-sse >>>>>> > anyway, >>>>>> > and that is something we don't want to affect. >>>>>> >>>>>> IMO, we should disable STV when -mpreferred-stack-boundary < 3, as STV >>>>>> is only an optimization. Perhaps we can also emit a "sorry" for >>>>>> explicit -mstv in case stack boundary requirement is not satisfied. >>>>>> *If* there is a need for -mstv with smaller stack boundary, we can >>>>>> revisit this decision for later gcc versions. >>>>>> >>>>>> I think disabling STV is less surprising option than increasing stack >>>>>> boundary behind the user's back. >>>>> >>>>> So, is http://gcc.gnu.org/ml/gcc-patches/2016-01/msg02129.html >>>>> ok for trunk then (alone or with additional sorry, incremental or not?)? >>>>> I believe it does just that. >>>> >>>> This patch is WRONG. >>>> >>>> -- >>>> H.J. >>> >>> You will run into the same ICE with >>> >>> -mincoming-stack-boundary=2 -msse2 -O2 -m32 >>> >>> in a leaf function which needs DImode spill/fill. >> >> Why would we need DImode spill/fill having no DImode registers? >> > > Because STV is enabled with > > -mincoming-stack-boundary=2 -msse2 -O2 -m32
I misread it as -mpreferred-... So why would we fail having a proper preferred stack alignment? AFAIK leaf function doesn't affect alignment until we finalize it after RA. > > > -- > H.J.
