[PATCH][AArch64] Set TREE_TARGET_GLOBALS in aarch64_set_current_function when new tree is the default node to recalculate optab availability

[Kyrill Tkachov]

Hi Crhistophe,

On 29/02/16 14:10, Christophe Lyon wrote:
> On 26 February 2016 at 16:51, James Greenhalgh <james.greenhalgh@arm.com> wrote:
>> On Thu, Feb 25, 2016 at 11:04:21AM +0000, Kyrill Tkachov wrote:
>>> Hi all,
>>>
>>> Seems like aarch64 is suffering from something similar to PR 69245 as well.
>>> If a target pragma sets the target state to the same as the
>>> target_option_default_node the node is just a pointer to
>>> target_option_default_node rather than a distinct identical node. So we must
>>> still restore the target globals even when setting to
>>> target_option_default_node in order to force the midend to recompute the
>>> availability of various optabs.
>>>
>>> If we don't do it, we can get in a problem like in the testcase where the
>>> isa_flags are all set correctly, but the optab HAVE_* predicates have not
>>> been recomputed.
>>>
>>> There is also a related issue present when popping/resetting target pragmas
>>> for which I'll send out a patch separately.
>>>
>>> Bootstrapped and tested on aarch64.
>>>
>>> Ok for trunk?
>> OK.
>>
> Hi Kyrill,
>
> Since this patch, I'm seeing:
>    gcc.dg/torture/pr52429.c   -O2 -flto -fno-use-linker-plugin
> -flto-partition=none  (internal compiler error)
> on target aarch64-none-linux-gnu
>
> The log has:
> spawn -ignore SIGHUP
> /aci-gcc-fsf/builds/gcc-fsf-gccsrc/obj-aarch64-none-linux-gnu/gcc3/gcc/xgcc
> -B/aci-gcc-fsf/builds/gcc-fsf-gccsrc/obj-aarch64-none-linux-gnu/gcc
> 3/gcc/ /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.dg/torture/pr52429.c
> -fno-diagnostics-show-caret -fdiagnostics-color=never -O2 -flto
> -fno-use-linker-pl
> ugin -flto-partition=none -g -ftree-parallelize-loops=4
> -DSTACK_SIZE=16384 -S -o pr52429.s
> /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.dg/torture/pr52429.c:
> In function 'foo':
> /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.dg/torture/pr52429.c:24:1:
> internal compiler error: Segmentation fault
> 0xade075 crash_signal
>          /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/toplev.c:335
> 0x91f88e record_operand_costs
>          /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/ira-costs.c:1293
> 0x91fdba scan_one_insn
>          /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/ira-costs.c:1471
> 0x91fdba process_bb_for_costs
>          /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/ira-costs.c:1592
> 0x9214e7 find_costs_and_classes
>          /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/ira-costs.c:1699
> 0x922552 ira_set_pseudo_classes(bool, _IO_FILE*)
>          /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/ira-costs.c:2239
> 0x1061ecd alloc_global_sched_pressure_data
>          /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/haifa-sched.c:7244
> 0x1061ecd sched_init()
>          /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/haifa-sched.c:7394
> 0x10679ed haifa_sched_init()
>          /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/haifa-sched.c:7406
> 0xa84fae schedule_insns()
>          /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/sched-rgn.c:3504
> 0xa85864 rest_of_handle_sched
>          /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/sched-rgn.c:3717
> 0xa85864 execute
>          /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/sched-rgn.c:3825
>
> Don't you see this regression on your side?

I've reproduced it just now.
I had not seen it initially because the test requires a pthread target,
so it was marked UNSUPPORTED when I tested aarch64-none-elf :(
But this looks like a latent bug elsewhere.
I'll try to investigate, can you please open a PR?

Thanks,
Kyrill

> Thanks,
>
> Christophe.
>
>
>
>> Thanks,
>> James
>>
>>> Thanks,
>>> Kyrill
>>>
>>>
>>> 2016-02-25  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>>>
>>>      PR target/69245
>>>      * config/aarch64/aarch64.c (aarch64_set_current_function): Save/restore
>>>      target globals when switching to target_option_default_node.
>>>
>>> 2016-02-25  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>>>
>>>      PR target/69245
>>>      * gcc.target/aarch64/pr69245_1.c: New test.
>>