Move -mlong-double-128 away from platform-agnostic files

  The compiler flag -mlong-double-128 is platform-specific and shouldn't
be used in platform-agnostic directories, such as ldbl-128ibm and
ldbl-opt.
This was not a problem because all the architectures implying these
directories had to use -mlong-double-128 to set their long double type.
As powerpc64le is changing its default long double type to be binary
compatible with IEEE 128-bit floating point, this will have to change.

Tested on powerpc, powerpc64 and powerpc64le.
Tested with build-many-glibcs.py on alpha and s390x.

2018-05-28  Tulio Magno Quites Machado Filho  <tuliom@linux.ibm.com>

	* sysdeps/ieee754/ldbl-128ibm/Makefile: Move sysdeps-CFLAGS
	definition to...
	* sysdeps/powerpc/powerpc32/Makefile: ... here.
	* sysdeps/powerpc/powerpc64/be/Makefile: ... here.
	* sysdeps/powerpc/powerpc64/le/Makefile: ... and here.
	* sysdeps/ieee754/ldbl-opt/Makefile: Move sysdeps-CFLAGS
	definition to...
	* sysdeps/unix/sysv/linux/alpha/Makefile: ... here.
	* sysdeps/unix/sysv/linux/s390/Makefile: ... here.
	* sysdeps/unix/sysv/linux/sparc/sparc32/Makefile: ... and here.

Signed-off-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
---
 sysdeps/ieee754/ldbl-128ibm/Makefile           | 1 -
 sysdeps/ieee754/ldbl-opt/Makefile              | 3 ---
 sysdeps/powerpc/powerpc32/Makefile             | 2 ++
 sysdeps/powerpc/powerpc64/be/Makefile          | 1 +
 sysdeps/powerpc/powerpc64/le/Makefile          | 2 ++
 sysdeps/unix/sysv/linux/alpha/Makefile         | 4 ++++
 sysdeps/unix/sysv/linux/s390/Makefile          | 4 ++++
 sysdeps/unix/sysv/linux/sparc/sparc32/Makefile | 4 ++++
 8 files changed, 17 insertions(+), 4 deletions(-)
 create mode 100644 sysdeps/powerpc/powerpc64/be/Makefile
  

On Mon, 28 May 2018, Tulio Magno Quites Machado Filho wrote:

> The compiler flag -mlong-double-128 is platform-specific and shouldn't
> be used in platform-agnostic directories, such as ldbl-128ibm and
> ldbl-opt.

Theoretically, as a -m option, it's platform-specific.  But in practice, 
I'm not sure that's really the case - certainly all existing platforms 
using ldbl-opt support -mlong-double-128 and -mlong-double-64.  Indeed, 
sysdeps/ieee754/ldbl-opt/configure.ac tests that -mlong-double-128 is 
supported, and that __LONG_DOUBLE_128__ gets defined by the compiler; the 
ldbl-opt bits/long-double.h relies on that __LONG_DOUBLE_128__ macro; the 
ldbl-opt Makefile relies on -mlong-double-64 being available to build a 
test with that option (unfortunately there is only the one test for 
-mlong-double-64 support; new ieee128 interfaces should have more thorough 
test coverage added no later than when the interfaces are enabled for 
powerpc64le).

> This was not a problem because all the architectures implying these
> directories had to use -mlong-double-128 to set their long double type.
> As powerpc64le is changing its default long double type to be binary
> compatible with IEEE 128-bit floating point, this will have to change.

But as far as I know the option is still supported for powerpc64le.  And 
indeed it works fine together with -mabi=ieeelongdouble, and does not 
change the format away from IEEE, and -mlong-double-64 also works together 
with -mabi=ieeelongdouble (overriding it to make long double have the same 
ABI as double).

So what is the actual problem you're trying to fix here?  As far as I can 
tell, the existing code should work just fine for powerpc64le in the 
context of a changed long double default - you may need to *add* options 
somewhere else to ensure -mabi=ibmlongdouble or -mabi=ieeelongdouble are 
used to compile particular files (possibly together with 
-mno-gnu-attribute to avoid link errors for incompatible ABIs), but I 
don't see anything that would require -mlong-double-128 to be avoided, and 
thus don't see any need to duplicate the code using that option for 
different architectures.
  

Joseph Myers <joseph@codesourcery.com> writes:

> On Mon, 28 May 2018, Tulio Magno Quites Machado Filho wrote:
>
>> This was not a problem because all the architectures implying these
>> directories had to use -mlong-double-128 to set their long double type.
>> As powerpc64le is changing its default long double type to be binary
>> compatible with IEEE 128-bit floating point, this will have to change.
>
> But as far as I know the option is still supported for powerpc64le.  And 
> indeed it works fine together with -mabi=ieeelongdouble, and does not 
> change the format away from IEEE, and -mlong-double-64 also works together 
> with -mabi=ieeelongdouble (overriding it to make long double have the same 
> ABI as double).
>
> So what is the actual problem you're trying to fix here?

I'm trying to avoid compiler calls like this:

    gcc ... -mlong-double-128 ... \
    ... -mabi=ieeelongdouble ...

Because they make it hard to understand which long double format is being used
in a multiline compiler command.
  

On Fri, 1 Jun 2018, Tulio Magno Quites Machado Filho wrote:

> I'm trying to avoid compiler calls like this:
> 
>     gcc ... -mlong-double-128 ... \
>     ... -mabi=ieeelongdouble ...
> 
> Because they make it hard to understand which long double format is being used
> in a multiline compiler command.

I don't think they make it hard to understand; -mlong-double-128 says long 
double is 128-bit, which is true, and -mabi=ieeelongdouble says which 
particular 128-bit format is in use.

If you wanted to avoid redundant -mlong-double-128, I think the way would 
be to adjust the configure test in ldbl-opt so it sets (via 
LIBC_CONFIG_VAR) a Makefile variable to empty if -mlong-double-128 is the 
default, and to -mlong-double-128 if it's not the default, and then the 
ldbl-opt Makefile would use that variable in setting sysdep-CFLAGS.