Seastar recently lost support for the experimental Concepts Technical
Specification (TS) and gained support for C++20 concepts. Re-enable
concepts in Scylla by updating our use of concepts to the C++20
standard.
This change:
- peels off uses of the GCC6_CONCEPT macro
- removes inclusions of <seastar/gcc6-concepts.hh>
- replaces function-style concepts (no longer supported) with
equation-style concepts
- semicolons added and removed as needed
- deprecated std::is_pod replaced by recommended replacement
- updates return type constraints to use concepts instead of
type names (either std::same_as or std::convertible_to, with
std::same_as chosen when possible)
No attempt is made to improve the concepts; this is a specification
update only.
Message-Id: <20200531110254.2555854-1-avi@scylladb.com>
It achieves 2.0x speedup on intel E5 and 1.1x to 2.5x speedup on
various arm64 microarchitectures.
The algorithm cuts data into blocks of 1024 bytes and calculates crc
for each block, which is furthur divided into three subblocks of 336
bytes(42 uint64) each, and 16 remaining bytes(2 uint64).
For each iteration, three independent crc are caculated for one uint64
from each subgroup. It increases IPC(instructions per cycle) much.
After subblocks are done, three crc and remaining two uint64 are
combined using carry-less multiplication to reach the final result
for one block of 1024 bytes.
Signed-off-by: Yibo Cai <yibo.cai@arm.com>
Message-Id: <1541042759-24767-1-git-send-email-yibo.cai@arm.com>
Replace the oblique process(T) overloads for integer types with
explicit process_le/be(T) methods that would interpret the given integer
as a stream of bytes using the corresponding endiannes.
For instance
process_le(0x11223344) would treat this integer as the following array of bytes:
{0x44, 0x33, 0x22, 0x11}.
process_be(0x11223344) on the other hand would treat this integer as if it's
{0x11, 0x22, 0x33, 0x44}.
Signed-off-by: Vlad Zolotarov <vladz@scylladb.com>
