Visual Instruction Set (VIS) is a SIMD instruction system for SPARC V9 microprocessors developed by Sun Microsystems .
There are four versions of VIS: VIS 1, VIS 2, VIS 2+ and VIS 3. [1]
VIS 1 was introduced in 1994 and first introduced by Sun on UltraSPARC microprocessors (1995) and Fujitsu on SPARC64 GP microprocessors (2000).
VIS 2 was first used on the UltraSPARC III . All subsequent UltraSPARC and SPARC64 processors also supported this standard.
VIS 3 was first implemented in SPARC T4 .
VIS reuses existing 64-bit floating-point registers to store 8, 16, and 32-bit integer values. In this sense, VIS is more like MMX than other SIMD architectures such as SSE / SSE2 / AltiVec . However, Intel's MMX only shares 8 registers with a floating point device, while SPARC processors usually have a significantly larger number of registers (one of the characteristics of the RISC architecture).
VIS strictly follows the main idea of RISC: use concise and efficient commands. This principle is very different from the principle of operation of comparable extensions of CISC-processors , such as MMX / SSE / SSE2 / SSE3 / SSE4 / 3DNow! . In general, the RISC principle can make a program simpler and more efficient.
However, Intel and AMD can easily add new extensions to x86 / x64 processors, while Sun should be very careful when adding new extensions, which may be considered one of the advantages of CISC over RISC. Sometimes programmers have to use several VIS instructions to describe a single operation that can be written in one instruction in MMX / SSE, but keep in mind that fewer instructions do not necessarily entail better performance.
There are four ways to use VIS in code:
- Use the -mvis option in GCC
- Use assembler inside a program in a high-level programming language ( C , Ada )
- Use VSDK (VIS Software Developer's Kit)
- Use the multimedia library mediaLib , which has interfaces to C functions.