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

[Andreas Jaeger <aj@suse.com>]

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?

Thanks,
Andreas
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