Remove SPARC sqrt wrappers (bug 21973)

From: Joseph Myers <joseph@codesourcery.com>

  This patch, relative to a tree with
<https://sourceware.org/ml/libc-alpha/2017-08/msg00827.html> applied
(but with no essential dependence on that patch), removes the
SPARC-specific wrappers for sqrt and sqrtf.

These wrappers, by adding architecture-specific uses of _LIB_VERSION
and __kernel_standard, unnecessarily complicate cleanups of libm error
handling.  They also do not serve a useful optimization purpose.  GCC
knows about sqrt as a built-in function, and can generate direct calls
to a hardware square root instruction, either on its own, in the
-fno-math-errno case, or together with an inline check for the
argument being negative and a call to the out-of-line sqrt function
for error handling only in that case (and has been able to do so for a
long time).  Thus in practice the wrapper will only be called only in
the case of negative arguments, which is not a case it is useful to
optimize for.

The removal of the wrappers also uncovers, and fixes, an old bug.
32-bit SPARC libm used (checked with glibc 2.8 binaries) to have a
sqrtl compat symbol, version GLIBC_2.0, for old binaries when sqrtl
was an alias of sqrt (I don't have pre-glibc-2.4 binaries for SPARC to
hand to check for the sqrtl symbol in those).  This disappeared,
probably with:

commit 8847f0377003fbfe9cbe951ce9f8717d74f26247
Author: David S. Miller <davem@davemloft.net>
Date:   Tue Feb 28 22:37:58 2012 -0800

    Add sparc optimized sqrt{,f}.

Removing the wrappers brings back the generic ldbl-opt logic for
creating such compat symbols, and so restores the compat symbol that
should be there.  This could of course also be fixed in the wrappers -
but as noted above, the wrappers are optimizing a case it's not useful
to optimize, so the bug of the missing compat symbol serves to
illustrate the risks involved with the extra complexity of
architecture-specific function versions where not needed.

Tested with build-many-glibcs.py.

(Remark: it would be reasonable to add e_sqrt.c for sparc64, and e_sqrtf.c 
for sparc32 and sparc64, so that the software sqrt/sqrtf implementations 
don't get built into libm, but that's more a matter of code size reduction 
than of improving speed for any likely use case.)

2017-08-18  Joseph Myers  <joseph@codesourcery.com>

	[BZ #21973]
	* sysdeps/sparc/sparc32/fpu/w_sqrt_compat.S: Remove file.
	* sysdeps/sparc/sparc32/fpu/w_sqrtf_compat.S: Likewise.
	* sysdeps/sparc/sparc32/sparcv9/fpu/multiarch/w_sqrt_compat-vis3.S:
	Likewise.
	* sysdeps/sparc/sparc32/sparcv9/fpu/multiarch/w_sqrt_compat.S:
	Likewise.
	* sysdeps/sparc/sparc32/sparcv9/fpu/multiarch/w_sqrtf_compat-vis3.S:
	Likewise.
	* sysdeps/sparc/sparc32/sparcv9/fpu/multiarch/w_sqrtf_compat.S:
	Likewise.
	* sysdeps/sparc/sparc32/sparcv9/fpu/w_sqrt_compat.S : Likewise.
	* sysdeps/sparc/sparc32/sparcv9/fpu/w_sqrtf_compat.S: Likewise.
	* sysdeps/sparc/sparc64/fpu/w_sqrt_compat.S: Likewise.
	* sysdeps/sparc/sparc64/fpu/w_sqrtf_compat.S: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc32/libm.abilist: Add
	GLIBC_2.0 sqrtl symbol.

Remove SPARC sqrt wrappers (bug 21973)

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