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Re: [PATCH v2] ARM: Use different linker path for hardfloat ABI
- From: Richard Earnshaw <rearnsha at arm dot com>
- To: Andreas Jaeger <aj at suse dot com>
- Cc: Michael Hope <michael dot hope at linaro dot org>, "cross-distro at lists dot linaro dot org" <cross-distro at lists dot linaro dot org>, Carlos O'Donell <carlos at systemhalted dot org>, GCC Patches <gcc-patches at gcc dot gnu dot org>, "libc-ports at sourceware dot org" <libc-ports at sourceware dot org>, Richard Guenther <rguenther at suse dot de>
- Date: Wed, 23 May 2012 08:56:31 +0100
- Subject: Re: [PATCH v2] ARM: Use different linker path for hardfloat ABI
- References: <CANLjY-kZ6FakmtKkHjjC2YNgCBkydiNq8F81Fb7SgW0RE6iF5w@mail.gmail.com> <4F9576DE.9070608@arm.com> <CANLjY-=y8pnK2jJZ+mo212o=5b0yOMgvy5G=WhoKnJX_mOV1CQ@mail.gmail.com> <CADZpyixYZAGYv=i=Xe4fefcBsxqPb3onaC1RGnfzGJnRX+MF4Q@mail.gmail.com> <CANLjY-m8udADuOo1gMfR9NWa-iw_JHbtnsoRAF1of1cvzdxSTg@mail.gmail.com> <4F9EAE9D.3040509@arm.com> <CANLjY-nhVTqr1_xrM7NpyOnyWYZkT4hpWZJb2VKDAGVvSaf8Aw@mail.gmail.com> <4F9FA448.6090509@arm.com> <4FBC8DCB.6020006@suse.com>
On 23/05/12 08:12, Andreas Jaeger wrote:
> On 05/01/2012 10:52 AM, Richard Earnshaw wrote:
>> On 30/04/12 22:47, Michael Hope wrote:
>>> On 1 May 2012 03:24, Richard Earnshaw<rearnsha@arm.com> wrote:
>>>> On 27/04/12 00:27, Michael Hope wrote:
>>>>> On 27 April 2012 08:20, Carlos O'Donell<carlos@systemhalted.org> wrote:
>>>>>> On Mon, Apr 23, 2012 at 5:36 PM, Michael Hope<michael.hope@linaro.org> wrote:
>>>>>>> 2012-04-24 Michael Hope<michael.hope@linaro.org>
>>>>>>> Richard Earnshaw<rearnsha@arm.com>
>>>>>>>
>>>>>>> * config/arm/linux-eabi.h (GLIBC_DYNAMIC_LINKER_SOFT_FLOAT): Define.
>>>>>>> (GLIBC_DYNAMIC_LINKER_HARD_FLOAT): Define.
>>>>>>> (GLIBC_DYNAMIC_LINKER_DEFAULT): Define.
>>>>>>> (GLIBC_DYNAMIC_LINKER): Redefine to use the hard float path.
>>>>>>>
>>>>>>> diff --git a/gcc/config/arm/linux-eabi.h b/gcc/config/arm/linux-eabi.h
>>>>>>> index 80bd825..2ace6f0 100644
>>>>>>> --- a/gcc/config/arm/linux-eabi.h
>>>>>>> +++ b/gcc/config/arm/linux-eabi.h
>>>>>>> @@ -62,7 +62,17 @@
>>>>>>> /* Use ld-linux.so.3 so that it will be possible to run "classic"
>>>>>>> GNU/Linux binaries on an EABI system. */
>>>>>>> #undef GLIBC_DYNAMIC_LINKER
>>>>>>> -#define GLIBC_DYNAMIC_LINKER "/lib/ld-linux.so.3"
>>>>>>> +#define GLIBC_DYNAMIC_LINKER_SOFT_FLOAT "/lib/ld-linux.so.3"
>>>>>>> +#define GLIBC_DYNAMIC_LINKER_HARD_FLOAT "/lib/ld-linux-armhf.so.3"
>>>>>>> +#if TARGET_DEFAULT_FLOAT_ABI == ARM_FLOAT_ABI_HARD
>>>>>>> +#define GLIBC_DYNAMIC_LINKER_DEFAULT GLIBC_DYNAMIC_LINKER_HARD_FLOAT
>>>>>>> +#else
>>>>>>> +#define GLIBC_DYNAMIC_LINKER_DEFAULT GLIBC_DYNAMIC_LINKER_SOFT_FLOAT
>>>>>>> +#endif
>>>>>>> +#define GLIBC_DYNAMIC_LINKER \
>>>>>>> + "%{mfloat-abi=hard:" GLIBC_DYNAMIC_LINKER_HARD_FLOAT "} \
>>>>>>> + %{mfloat-abi=soft*:" GLIBC_DYNAMIC_LINKER_SOFT_FLOAT "} \
>>>>>>> + %{!mfloat-abi=*:" GLIBC_DYNAMIC_LINKER_DEFAULT "}"
>>>>>>>
>>>>>>> /* At this point, bpabi.h will have clobbered LINK_SPEC. We want to
>>>>>>> use the GNU/Linux version, not the generic BPABI version. */
>>>>>>
>>>>>> This patch is broken. Please fix this.
>>>>>>
>>>>>> You can't use a named enumeration in cpp equality.
>>>>>>
>>>>>> The type ARM_FLOAT_ABI_HARD is a named enumeration and evaluates to 0
>>>>>> as an unknown identifier.
>>>>>>
>>>>>> Therefore "#if TARGET_DEFAULT_FLOAT_ABI == ARM_FLOAT_ABI_HARD"
>>>>>> evaluates to "#if 0 == 0" and is always true.
>>>>>>
>>>>>> Watch out that "#define ARM_FLOAT_ABI_HARD ARM_FLOAT_ABI_HARD" for
>>>>>> such enums is not conforming C99/C11.
>>>>>>
>>>>>> I suggest you define the types as macros and then set the named enum
>>>>>> to those values, then use the macros in the header equality checks.
>>>>>>
>>>>>> e.g.
>>>>>> #define VAL1 0 then enum FOO { RVAL1 = VAL1, ... }
>>>>>>
>>>>>> Look at arm.h for the enum definition.
>>>>>
>>>>> I've looked further into this and I think the original pre-#if version
>>>>> is correct.
>>>>>
>>>>> The float ABI comes from these places:
>>>>> * The -mfloat-abi= command line argument, else
>>>>> * The --with-float= configure time argument, else
>>>>> * TARGET_DEFAULT_FLOAT_ABI from linux-eabi.h
>>>>>
>>>>> In the first case the ABI is explicit. In the second
>>>>> OPTION_DEFAULT_SPECS turns the configure time argument into an explict
>>>>> -mfloat-abi=.
>>>>>
>>>>> The patch below covers all cases, keeps the logic in the spec file,
>>>>> and adds a comment linking the two #defines.
>>>>>
>>>>> Tested by building with no configure flags, --wtih-float=softfp,
>>>>> --with-float=hard, and then running with all combinations of
>>>>> {,-mfloat-abi=softfp,-mfloat-abi=hard} {,-mglibc,-muclibc,-mbionic}.
>>>>>
>>>>> OK?
>>>>>
>>>>> -- Michael
>>>>>
>>>>> 2012-04-27 Michael Hope<michael.hope@linaro.org>
>>>>>
>>>>> * config/arm/linux-eabi.h (GLIBC_DYNAMIC_LINKER): Pick the loader
>>>>> using a spec rule.
>>>>>
>>>>
>>>> Michael,
>>>>
>>>> can you try this patch please. It should make it possible to then
>>>> create linux-eabihf.h containing just
>>>>
>>>> #undef TARGET_DEFAULT_FLOAT_ABI
>>>> #define TARGET_DEFAULT_FLOAT_ABI ARM_FLOAT_ABI_HARD
>>>> #undef GLIBC_DYNAMIC_LINKER_DEFAULT
>>>> #define GLIBC_DYNAMIC_LINKER_DEFAULT GLIBC_DYNAMIC_LINKER_HARD_FLOAT
>>>>
>>>> Which is not quite as simple as leaving out the second re-define, but
>>>> pretty close.
>>>
>>> Hi Richard. Your patch tests just fine. I like it. You could change
>>> the spec rule to the newer if-elseif-else form but that's a nit.
>>>
>>> -- Michael
>>>
>>
>> Great, thanks! I've committed it as is.
>
> I suggest to add this also to the gcc 4.7 branch. Richard (Earnshaw),
> could you do take care of this, please?
This is a behaviour change. It would need RM approval for a release branch.
R.