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

[Richard Earnshaw <rearnsha at arm dot 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.