2016-02-02 16:25 GMT+03:00 H.J. Lu <hjl.to...@gmail.com>: > On Tue, Feb 2, 2016 at 5:21 AM, Ilya Enkovich <enkovich....@gmail.com> wrote: >> 2016-02-02 16:14 GMT+03:00 H.J. Lu <hjl.to...@gmail.com>: >>> On Tue, Feb 2, 2016 at 5:11 AM, Ilya Enkovich <enkovich....@gmail.com> >>> wrote: >>>> 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. >>>> >>> >>> /* Finalize stack_realign_needed flag, which will guide prologue/epilogue >>> to be generated in correct form. */ >>> static void >>> ix86_finalize_stack_realign_flags (void) >>> { >>> /* Check if stack realign is really needed after reload, and >>> stores result in cfun */ >>> unsigned int incoming_stack_boundary >>> = (crtl->parm_stack_boundary > ix86_incoming_stack_boundary >>> ? crtl->parm_stack_boundary : ix86_incoming_stack_boundary); >>> unsigned int stack_realign >>> = (incoming_stack_boundary >>> < (crtl->is_leaf && !ix86_current_function_calls_tls_descriptor >>> ? crtl->max_used_stack_slot_alignment >>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ >> >> We call it after RA when all spill slots are allocated and check if we >> may relax stack alignment. Don't see any problem here. > > Please see > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69454#c26 > > Why did LRA crash then?
Because it tries a patch [1] which doesn't fix stack alignment and STV enabling and therefore doesn't resolve the problem when -mpreferred-stack-boundary=2 is used. Thanks, Ilya -- [1] https://gcc.gnu.org/bugzilla/attachment.cgi?id=37468&action=diff > > > -- > H.J.
