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Falkor's memcpy and memmove share some implementation details, therefore, the two routines are moved to a single source file for code reuse. The two routines now share code for small and medium copies (up to and including 128 bytes). Large copies in memcpy do not handle overlap correctly, consequently, the loops for moving/copying more than 128 bytes stay separate for memcpy and memmove. To increase code reuse a number of small modifications were made: 1. The old implementation of memcpy copied the first 16-bytes as soon as the size of data was determined to be greater than 32 bytes. For memcpy code to also work when copying small/medium overlapping data, the first load and store was moved to the large copy case. 2. Medium memcpy case no longer assumes that 16 bytes were already copied and uses 8 registers to copy up to 128 bytes. 3. Small case for memmove was enlarged to that of memcpy, which is less than or equal to 32 bytes. 4. Medium case for memmove was enlarged to that of memcpy, which is less than or equal to 128 bytes. Other changes include: 1. Improve alignment of existing loop bodies. 2. 'Delouse' memmove and memcpy input arguments. Make sure that upper 32-bits of input registers are zeroed if unused. 3. Do one more iteration in memmove loops and reduce the number of copies made from the start/end of the buffer, depending on the direction of the memmove loop. Benchmarking: Looking at the results from bench-memcpy-random.out, we can see that now memmove_falkor is about 5% faster than memcpy_falkor_old, while memmove_falkor_old was more than 15% slower. The memcpy implementation remained largely unmodified, so there is no significant performance change. The reason for such a significant memmove performance gain is the increase of the upper bound on the small copy case to 32 bytes and the increase of the upper bound on the medium copy case to 128 bytes. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org> |
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This directory contains the sources of the GNU C Library. See the file "version.h" for what release version you have. The GNU C Library is the standard system C library for all GNU systems, and is an important part of what makes up a GNU system. It provides the system API for all programs written in C and C-compatible languages such as C++ and Objective C; the runtime facilities of other programming languages use the C library to access the underlying operating system. In GNU/Linux systems, the C library works with the Linux kernel to implement the operating system behavior seen by user applications. In GNU/Hurd systems, it works with a microkernel and Hurd servers. The GNU C Library implements much of the POSIX.1 functionality in the GNU/Hurd system, using configurations i[4567]86-*-gnu. When working with Linux kernels, this version of the GNU C Library requires Linux kernel version 3.2 or later. Also note that the shared version of the libgcc_s library must be installed for the pthread library to work correctly. The GNU C Library supports these configurations for using Linux kernels: aarch64*-*-linux-gnu alpha*-*-linux-gnu arm-*-linux-gnueabi csky-*-linux-gnuabiv2 hppa-*-linux-gnu i[4567]86-*-linux-gnu x86_64-*-linux-gnu Can build either x86_64 or x32 ia64-*-linux-gnu m68k-*-linux-gnu microblaze*-*-linux-gnu mips-*-linux-gnu mips64-*-linux-gnu powerpc-*-linux-gnu Hardware or software floating point, BE only. powerpc64*-*-linux-gnu Big-endian and little-endian. s390-*-linux-gnu s390x-*-linux-gnu riscv64-*-linux-gnu sh[34]-*-linux-gnu sparc*-*-linux-gnu sparc64*-*-linux-gnu If you are interested in doing a port, please contact the glibc maintainers; see https://www.gnu.org/software/libc/ for more information. See the file INSTALL to find out how to configure, build, and install the GNU C Library. You might also consider reading the WWW pages for the C library at https://www.gnu.org/software/libc/. The GNU C Library is (almost) completely documented by the Texinfo manual found in the `manual/' subdirectory. The manual is still being updated and contains some known errors and omissions; we regret that we do not have the resources to work on the manual as much as we would like. For corrections to the manual, please file a bug in the `manual' component, following the bug-reporting instructions below. Please be sure to check the manual in the current development sources to see if your problem has already been corrected. Please see https://www.gnu.org/software/libc/bugs.html for bug reporting information. We are now using the Bugzilla system to track all bug reports. This web page gives detailed information on how to report bugs properly. The GNU C Library is free software. See the file COPYING.LIB for copying conditions, and LICENSES for notices about a few contributions that require these additional notices to be distributed. License copyright years may be listed using range notation, e.g., 1996-2015, indicating that every year in the range, inclusive, is a copyrightable year that would otherwise be listed individually.