Re: [GCC, ARM] armv8 linux toolchain asan testcase fail due to stl missing conditional code

[Shiva Chen <shiva0217 at gmail dot com>]

Hi, Kyrill

I add the testcase as stl-cond.c.

Could you help to check the testcase ?

If it's OK, Could you help me to apply the patch ?


Thanks,

Shiva

2015-06-05 16:34 GMT+08:00 Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>:
> Hi Shiva,
>
> On 05/06/15 09:29, Shiva Chen wrote:
>>
>> Hi, Kyrill
>>
>> I update the patch as Richard's suggestion.
>>
>> -      return \"str<sync_sfx>\t%1, %0\";
>> +      return \"str%(<sync_sfx>%)\t%1, %0\";
>>       else
>> -      return \"stl<sync_sfx>\t%1, %0\";
>> +      return \"stl<sync_sfx>%?\t%1, %0\";
>>     }
>> -)
>> +  [(set_attr "predicable" "yes")
>> +   (set_attr "predicable_short_it" "no")])
>> +  [(set_attr "predicable" "yes")
>> +   (set_attr "predicable_short_it" "no")])
>>
>>
>> Let me sum up.
>>
>> We add predicable attribute to allow gcc do if-conversion in
>> ce1/ce2/ce3 not only in final phase by final_prescan_insn finite state
>> machine.
>>
>> We set predicalble_short_it to "no" to restrict conditional code
>> generation on armv8 with thumb mode.
>>
>> However, we could use the flags -mno-restrict-it to force generating
>> conditional code on thumb mode.
>>
>> Therefore, we have to consider the assembly output format for strb
>> with condition code on arm/thumb mode.
>>
>> Because arm/thumb mode use different syntax for strb,
>> we output the assembly as str%(<sync_sfx>%)
>> which will put the condition code in the right place according to
>> TARGET_UNIFIED_ASM.
>>
>> Is there still missing something ?
>
>
> That's all correct, and well summarised :)
> The patch looks good to me, but please include the testcase
> (test.c from earlier) appropriately marked up for the testsuite.
> I think to the level of dg-assemble, just so we know everything is
> wired up properly.
>
> Thanks for dealing with this.
> Kyrill
>
>
>>
>> Thanks,
>>
>> Shiva
>>
>> 2015-06-04 18:00 GMT+08:00 Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>:
>>>
>>> Hi Shiva,
>>>
>>> On 04/06/15 10:57, Shiva Chen wrote:
>>>>
>>>> Hi, Kyrill
>>>>
>>>> Thanks for the tips of syntax.
>>>>
>>>> It seems that correct syntax for
>>>>
>>>> ldrb with condition code is ldreqb
>>>>
>>>> ldab with condition code is ldabeq
>>>>
>>>>
>>>> So I modified the pattern as follow
>>>>
>>>>     {
>>>>       enum memmodel model = (enum memmodel) INTVAL (operands[2]);
>>>>       if (model == MEMMODEL_RELAXED
>>>>           || model == MEMMODEL_CONSUME
>>>>           || model == MEMMODEL_RELEASE)
>>>>         return \"ldr%?<sync_sfx>\\t%0, %1\";
>>>>       else
>>>>         return \"lda<sync_sfx>%?\\t%0, %1\";
>>>>     }
>>>>     [(set_attr "predicable" "yes")
>>>>      (set_attr "predicable_short_it" "no")])
>>>>
>>>> It seems we don't have to worry about thumb mode,
>>>
>>>
>>> I suggest you use Richard's suggestion from:
>>>   https://gcc.gnu.org/ml/gcc-patches/2015-06/msg00384.html
>>> to write this in a clean way.
>>>
>>>> Because we already set "predicable" "yes" and predicable_short_it" "no"
>>>> for the pattern.
>>>
>>>
>>> That's not quite true. The user may compile for armv8-a with
>>> -mno-restrict-it which will turn off this
>>> restriction for Thumb and allow the conditional execution of this.
>>> In any case, I think Richard's suggestion above should work.
>>>
>>> Thanks,
>>> Kyrill
>>>
>>>
>>>> The new patch could build gcc and run gcc regression test successfully.
>>>>
>>>> Please correct me if I still missing something.
>>>>
>>>> Thanks,
>>>>
>>>> Shiva
>>>>
>>>> -----Original Message-----
>>>> From: Richard Earnshaw [mailto:Richard.Earnshaw@foss.arm.com]
>>>> Sent: Thursday, June 04, 2015 4:42 PM
>>>> To: Kyrill Tkachov; Shiva Chen
>>>> Cc: Ramana Radhakrishnan; GCC Patches; nickc@redhat.com; Shiva Chen
>>>> Subject: Re: [GCC, ARM] armv8 linux toolchain asan testcase fail due to
>>>> stl missing conditional code
>>>>
>>>> On 04/06/15 09:17, Kyrill Tkachov wrote:
>>>>>
>>>>> Hi Shiva,
>>>>>
>>>>> On 04/06/15 04:13, Shiva Chen wrote:
>>>>>>
>>>>>> Hi, Ramana
>>>>>>
>>>>>> Currently, I work for Marvell and the company have copyright
>>>>>> assignment
>>>>>> on file.
>>>>>>
>>>>>> Hi, all
>>>>>>
>>>>>> After adding the attribute and rebuild gcc, I got the assembler error
>>>>>> message
>>>>>>
>>>>>> load_n.s:39: Error: bad instruction `ldrbeq r0,[r0]'
>>>>>>
>>>>>> When i look into armv8 ISA document, it seems ldrb Encoding A1 have
>>>>>> conditional code field.
>>>>>>
>>>>>> Does it mean we should also patch assembler or I just miss
>>>>>> understanding something ?
>>>>>>
>>>>>> Following command use to generate load_n.s:
>>>>>>
>>>>>> /home/shivac/build-system-trunk/Release/build/armv8-marvell-linux-gnu
>>>>>> eabihf-hard/gcc-final/./gcc/cc1 -fpreprocessed load_n.i -quiet
>>>>>> -dumpbase load_n.c -march=armv8-a -mfloat-abi=hard -mfpu=fp-armv8
>>>>>> -mtls-dialect=gnu -auxbase-strip .libs/load_1_.o -g3 -O2 -Wall
>>>>>> -Werror -version -fPIC -funwind-tables -o load_n.s
>>>>>>
>>>>>>
>>>>>> The test.c is a simple test case to reproduce missing conditional
>>>>>> code in mmap.c.
>>>>>>
>>>>>> Any suggestion ?
>>>>>
>>>>> I reproduced the assembler failure with your patch.
>>>>>
>>>>> The reason is that for arm mode we use divided syntax, where the
>>>>> condition field goes in a different place. So, while ldrbeq r0,[r0] is
>>>>> rejected, ldreqb r0, [r0] works.
>>>>> Since we always use divided syntax for arm mode, I think you'll need
>>>>> to put the condition field in the right place depending on arm or thumb
>>>>> mode.
>>>>> Ugh, this is becoming ugly :(
>>>>>
>>>> Use %(<suffix%) around the bit that changes for unified/divided syntax.
>>>>    The compiler will then put the condition in the correct place.
>>>>
>>>> So:
>>>>
>>>> +      return \"str%(<sync_sfx>%)\t%1, %0\";
>>>>
>>>> R.
>>>>
>>>>> Kyrill
>>>>>
>>>>>> Shiva
>>>>>>
>>>>>> 2015-06-03 17:29 GMT+08:00 Shiva Chen <shiva0217@gmail.com>:
>>>>>>>
>>>>>>> Hi, Ramana
>>>>>>>
>>>>>>> I'm not sure what copyright assignment means ?
>>>>>>>
>>>>>>> Does it mean the patch have copyright assignment or not ?
>>>>>>>
>>>>>>> I update the patch to add "predicable" and  "predicable_short_it"
>>>>>>> attribute as suggestion.
>>>>>>>
>>>>>>> However, I don't have svn write access yet.
>>>>>>>
>>>>>>> Shiva
>>>>>>>
>>>>>>> 2015-06-03 16:36 GMT+08:00 Kyrill Tkachov <kyrylo.tkachov@arm.com>:
>>>>>>>>
>>>>>>>> On 03/06/15 09:32, Ramana Radhakrishnan wrote:
>>>>>>>>>>
>>>>>>>>>> This pattern is not predicable though, i.e. it doesn't have the
>>>>>>>>>> "predicable" attribute set to "yes".
>>>>>>>>>> Therefore the compiler should be trying to branch around here
>>>>>>>>>> rather than try to do a cond_exec.
>>>>>>>>>> Why does the generated code above look like it's converted to
>>>>>>>>>> conditional execution?
>>>>>>>>>> Could you produce a self-contained reduced testcase for this?
>>>>>>>>>
>>>>>>>>> CCFSM state machine in ARM state.
>>>>>>>>>
>>>>>>>>> arm.c (final_prescan_insn).
>>>>>>>>
>>>>>>>> Ah ok.
>>>>>>>> This patch makes sense then.
>>>>>>>> As Ramana mentioned, please mark the pattern with "predicable" and
>>>>>>>> also set the "predicable_short_it" attribute to "no" so that it
>>>>>>>> will not be conditionalised in Thumb2 mode or when -mrestrict-it is
>>>>>>>> enabled.
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>> Kyrill
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>> Ramana
>>>>>>>>>
>>>>>>>>>> Thanks,
>>>>>>>>>> Kyrill
>>>>>>>>>>
>>>>>>>>>>> @@ -91,9 +91,9 @@
>>>>>>>>>>>          {
>>>>>>>>>>>            enum memmodel model = memmodel_from_int (INTVAL
>>>>>>>>>>> (operands[2]));
>>>>>>>>>>>            if (is_mm_relaxed (model) || is_mm_consume (model) ||
>>>>>>>>>>> is_mm_acquire (model))
>>>>>>>>>>> -      return \"str<sync_sfx>\t%1, %0\";
>>>>>>>>>>> +      return \"str<sync_sfx>%?\t%1, %0\";
>>>>>>>>>>>            else
>>>>>>>>>>> -      return \"stl<sync_sfx>\t%1, %0\";
>>>>>>>>>>> +      return \"stl<sync_sfx>%?\t%1, %0\";
>>>>>>>>>>>          }
>>>>>>>>>>>        )
>>>>>>>>>>>
>

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