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On platforms without native 128-bit integer support, simplify the test for carry in int128_add_uint64() by noting that the low-part addition is unsigned integer arithmetic, which is just modular arithmetic. Therefore the test for carry can simply be written as "new value < old value" (i.e., a test for modular wrap-around). This can then be made branchless so that on modern compilers it produces the same machine instructions as native 128-bit addition, making it significantly simpler and faster. Similarly, the test for carry in int128_add_int64() can be written in much the same way, but with an extra term to compensate for the sign of the value being added. Again, on modern compilers this leads to branchless code, often identical to the native 128-bit integer addition machine code. Author: Dean Rasheed <dean.a.rasheed@gmail.com> Reviewed-by: John Naylor <johncnaylorls@gmail.com> Discussion: https://postgr.es/m/CAEZATCWgBMc9ZwKMYqQpaQz2X6gaamYRB+RnMsUNcdMcL2Mj_w@mail.gmail.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.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.