Re: [PATCH v2] ARM: Use different linker path for hardfloat ABI

[Richard Earnshaw <rearnsha at arm dot com>]

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.

R.