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? -- H.J.
