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ARMv8 introduced special CPU instructions for calculating CRC-32C. Use them, when available, for speed. Like with the similar Intel CRC instructions, several factors affect whether the instructions can be used. The compiler intrinsics for them must be supported by the compiler, and the instructions must be supported by the target architecture. If the compilation target architecture does not support the instructions, but adding "-march=armv8-a+crc" makes them available, then we compile the code with a runtime check to determine if the host we're running on supports them or not. For the runtime check, use glibc getauxval() function. Unfortunately, that's not very portable, but I couldn't find any more portable way to do it. If getauxval() is not available, the CRC instructions will still be used if the target architecture supports them without any additional compiler flags, but the runtime check will not be available. Original patch by Yuqi Gu, heavily modified by me. Reviewed by Andres Freund, Thomas Munro. Discussion: https://www.postgresql.org/message-id/HE1PR0801MB1323D171938EABC04FFE7FA9E3110%40HE1PR0801MB1323.eurprd08.prod.outlook.com
PostgreSQL Database Management System ===================================== This directory contains the source code distribution of the PostgreSQL database management system. PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.