Add a macro that creates a 64bit value which has length number of ones
shifted across by the value of shift.
Backports commit ae2923b5c20a21c6457680330506a9c13873485c from qemu
A half-shuffle operation takes a word with zeros in the high half:
0000 0000 0000 0000 ABCD EFGH IJKL MNOP
and spreads the bits out so they are in every other bit of the word:
0A0B 0C0D 0E0F 0G0H 0I0J 0K0L 0M0N 0O0P
A half-unshuffle performs the reverse operation.
Provide functions in bitops.h which implement these operations
for 32-bit and 64-bit inputs, and add tests for them.
Backports commit b355438de52d0782983bf4bdc47936189a0c988b from qemu
Use atomic_or() for atomic bitmaps where several threads may set bits at
the same time. This avoids the race condition between threads loading
an element, bitwise ORing, and then storing the element.
When setting all bits in a word we can avoid atomic ops and instead just
use an smp_mb() at the end.
Most bitmap users don't need atomicity so introduce new functions.
Backports commit 9f02cfc84b85929947b32fe1674fbc6a429f332a from qemu
The documentation for sextract64() claims that the return type is
an int64_t, but the code itself disagrees. Fix the return type to
conform to the documentation and to bring it into line with
sextract32(), which returns int32_t.
Backports commit 4f9950520a115acf9c0a209f0befa45758ad0215 from qemu
