The 53807741fb44edb8e7c094cb5e7d4ff4e92a6ec1 added a configure check
for 64-bit atomic operations that were not previously enabled on some
32-bit ABIs.

However, the NPTL semaphore code casts a sem_t to a new_sem and issues
a 64-bit atomic operation for __HAVE_64B_ATOMICS.  Since sem_t has
32-bit alignment on 32-bit architectures, this prevents the use of
64-bit atomics even if the ABI supports them.

Assume 64-bit atomic support from __WORDSIZE, which maps to how glibc
defines it before the broken change.  Also rename __HAVE_64B_ATOMICS
to USE_64B_ATOMICS to define better the flag meaning.

Checked on x86_64-linux-gnu and i686-linux-gnu.

Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

Remove ldbl-128/s_fma.c - it makes no sense to use emulated float128
operations to emulate FMA.  Benchmarking shows dbl-64/s_fma.c is about
twice as fast.  Remove redundant dbl-64/s_fma.c includes in targets
that were trying to work around this issue.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

i386 and m68k architectures should use math-use-builtins-sqrt.h rather
than relying on architecture-specific or inline assembly implementations.

The PowerPC optimization for PPC 601/603 (30 years old) is removed.

Tested on x86_64-linux-gnu and i686-linux-gnu.

Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

The only usage was for pthread_spin_lock, introduced by 12d2dd706099aa4,
as a way to optimize the code for certain architectures. Now that atomic
builtins are used by default, let the compiler use the best code sequence
for the atomic exchange.

Co-authored-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

Now that atomic builtins are used by default, we can rely on the
compiler to define when to use 64-bit atomic operations.

It allows the use of 64-bit atomic operations on some 32-bit ABIs where
they were not previously enabled due to missing pre-processor handling:
hppa, mips64n32, s390, and sparcv9.

Co-authored-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
Reviewed-by: Uros Bizjak <ubizjak@gmail.com>
Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

All ABIs, except alpha, powerpc, and x86_64, define it to
atomic_full_barrier/__sync_synchronize, which can be mapped to
__atomic_thread_fence (__ATOMIC_SEQ_CST) in most cases, with the
exception of aarch64 (where the acquire fence is generated as
'dmb ishld' instead of 'dmb ish').

For s390x, it defaults to a memory barrier where __sync_synchronize
emits a 'bcr 15,0' (which the manual describes as pipeline
synchronization).

For PowerPC, it allows the use of lwsync for additional chips
(since _ARCH_PWR4 does not cover all chips that support it).

Tested on aarch64-linux-gnu, where the acquire produces a different
instruction that the current code.

Co-authored-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

All ABIs save for sparcv9 and s390 defines it to __sync_synchronize,
which can be mapped to __atomic_thread_fence (__ATOMIC_SEQ_CST).

For Sparc, it uses a stricter #StoreStore|#LoadStore|#StoreLoad|#LoadLoad
instead of the #StoreLoad generated by __sync_synchronize.

For s390x, it defaults to a memory barrier where __sync_synchronize
emits a 'bcr 15,0' (which the manual describes as pipeline synchronization).

The barrier is used only in one place (pthread_mutex_setprioceiling),
and using a stricter barrier for s390 is ok performance-wise.

Co-authored-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

The l*[rint|round]f implements uses alpha 'cvtst/s', 'addt/suc',
adn 'cvttq/svd' which are not not fully IEEE compliant w.r.t
inexact-flag raising..  Use the software fallback implementation
instead.

Checked on alpha-linux-gnu.

Tested-by: Michael Cree <mcree@orcon.net.nz>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>

To avoid linknamespace issues on old standards.  It is required
if the fallback fma implementation is used if/when it is also
used internally for other implementation.
Reviewed-by: DJ Delorie <dj@redhat.com>