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download PDF document: simd.7.pdf

SIMD(7) FreeBSD Miscellaneous Information Manual SIMD(7)
NAME simd - SIMD enhancements
DESCRIPTION On some architectures, the FreeBSD libc provides enhanced implementations of commonly used functions, replacing the architecture-independent implementations used otherwise. Depending on architecture and function, an enhanced implementation of a function may either always be used or the libc detects at runtime which SIMD instruction set extensions are supported and picks the most suitable implementation automatically. On amd64, the environment variable ARCHLEVEL can be used to override this mechanism.
Enhanced functions are present for the following architectures:
FUNCTION AARCH64 ARM AMD64 I386 PPC64 bcmp S1 S bcopy S S S SV bzero S S S div S S index A S1 ldiv S S lldiv S memchr A S1 memcmp A S S1 S memccpy S1 memcpy S S S S SV memmove S S S S SV memrchr A S1 memset A S S S rindex A S1 S stpcpy A S1 stpncpy S1 strcat S1 S strchr A S1 S strchrnul A S1 strcmp S S S1 S strcpy A S1 S S2 strcspn S2 strlcat S1 strlcpy S1 strlen A S S1 strncat S1 strncmp S S S1 S strncpy S1 S2 strnlen A S1 strrchr A S1 S strpbrk S2 strsep S2 strspn S2 swab S timingsafe_bcmp S1 timingsafe_memcmp S wcschr S wcscmp S wcslen S wmemchr S variable is set to an architecture level from the list below and that architecture level is supported by the processor, SIMD enhancements up to ARCHLEVEL are used. If ARCHLEVEL is unset, not recognised, or not supported by the processor, the highest level of SIMD enhancements supported by the processor is used.
A suffix beginning with `:' or `+' in ARCHLEVEL is ignored and may be used for future extensions. The architecture level can be prefixed with a `!' character to force use of the requested architecture level, even if the processor does not advertise that it is supported. This usually causes applications to crash and should only be used for testing purposes or if architecture level detection yields incorrect results.
The architecture levels follow the AMD64 SysV ABI supplement:
scalar scalar enhancements only (no SIMD)
baseline cmov, cx8, x87 FPU, fxsr, MMX, osfxsr, SSE, SSE2
x86-64-v2 cx16, lahf/sahf, popcnt, SSE3, SSSE3, SSE4.1, SSE4.2
x86-64-v3 AVX, AVX2, BMI1, BMI2, F16C, FMA, lzcnt, movbe, osxsave
x86-64-v4 AVX-512F/BW/CD/DQ/VL
DIAGNOSTICS Illegal Instruction Printed by sh(1) if a command is terminated through delivery of a SIGILL signal, see signal(3).
Use of an unsupported architecture level was forced by setting ARCHLEVEL to a string beginning with a `!' character, causing a process to crash due to use of an unsupported instruction. Unset ARCHLEVEL, remove the `!' prefix or select a supported architecture level.
Message may also appear for unrelated reasons.
SEE ALSO string(3), arch(7)
H. J. Lu, Michael Matz, Milind Girkar, Jan Hubicka, Andreas Jaeger, and Mark Mitchell, "AMD64 Architecture Processor Supplement", System V Application Binary Interface, May 23, 2023, Version 1.0.
HISTORY Architecture-specific enhanced libc functions were added starting with FreeBSD 2.0 for i386, FreeBSD 6.0 for arm, FreeBSD 6.1 for amd64, FreeBSD 11.0 for aarch64, and FreeBSD 12.0 for powerpc64. SIMD-enhanced functions were first added with FreeBSD 13.0 for powerpc64 and with FreeBSD 14.1 for amd64.
A simd manual page appeared in FreeBSD 14.1.
AUTHOR Robert Clausecker <fuz@FreeBSD.org>
CAVEATS Other parts of FreeBSD such as cryptographic routines in the kernel or in
FreeBSD 14.2-RELEASE June 7, 2024 FreeBSD 14.2-RELEASE