further optimization. libc_feholdsetround_aarch64_ctx now only needs to
read the FPCR in the typical case, avoiding a redundant FPSR read.
Performance results show a good improvement (5-10% on sin()) on cores with
expensive FPCR/FPSR instructions.
Trapping exceptions in AArch64 are optional. The relevant exception
control bits in FPCR are are defined as RES0 hence the absence of
support can be detected by reading back the FPCR and comparing with
the desired value.
This patch moves the AArch64 port to the main sysdeps hierarchy. The
move is essentially:
git mv ports/sysdeps/aarch64 sysdeps/aarch64
git mv ports/sysdeps/unix/sysv/linux/aarch64 sysdeps/unix/sysv/linux/aarch64
The README is updated and I've updated ChangeLog.aarch64 along the
lines of the ARM move. The AArch64 build has been tested to confirm
that there were no changes in objdump -dr output or the shared
objects.
