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The bottom bit of the opcode is used to indicate whether the AVX512 index register is considered a vector of sixteen signed 32-bit indexes (bit 0 not set) or eight signed 64-bit indexes (bit 0 set) The instructions all support operation masking by opmask registers. The only supported vector width is 512 bits.
The x86 instruction set has several times been extended with SIMD (Single instruction, multiple data) instruction set extensions.These extensions, starting from the MMX instruction set extension introduced with Pentium MMX in 1997, typically define sets of wide registers and instructions that subdivide these registers into fixed-size lanes and perform a computation for each lane in parallel.
The FMA instruction set is an extension to the 128 and 256-bit Streaming SIMD Extensions instructions in the x86 microprocessor instruction set to perform fused multiply–add (FMA) operations. [1] There are two variants: FMA4 is supported in AMD processors starting with the Bulldozer architecture. FMA4 was performed in hardware before FMA3 was.
These instructions are also available in 32-bit mode, in which they operate on 32-bit registers (eax, ebx, etc.) and values instead of their 16-bit (ax, bx, etc.) counterparts. The updated instruction set is grouped according to architecture ( i186 , i286 , i386 , i486 , i586 / i686 ) and is referred to as (32-bit) x86 and (64-bit) x86-64 (also ...
The registers XMM8 through XMM15 are accessible only in 64-bit operating mode. SSE used only a single data type for XMM registers: four 32-bit single-precision floating-point numbers; SSE2 would later expand the usage of the XMM registers to include: two 64-bit double-precision floating-point numbers or; two 64-bit integers or; four 32-bit ...
x86-64 (also known as x64, x86_64, AMD64, and Intel 64) [note 1] is a 64-bit extension of the x86 instruction set architecture first announced in 1999. It introduces two new operating modes: 64-bit mode and compatibility mode, along with a new four-level paging mechanism.
While what these instructions do is similar to bit level gather-scatter SIMD instructions, PDEP and PEXT instructions (like the rest of the BMI instruction sets) operate on general-purpose registers. [12] The instructions are available in 32-bit and 64-bit versions. An example using arbitrary source and selector in 32-bit mode is:
The REX prefix provides additional space for encoding 64-bit addressing modes and additional registers present in the x86-64 architecture. Bit-field W changes the operand size to 64 bits, R expands reg to 4 bits, B expands r/m (or opreg in the few opcodes that encode the register in the 3 lowest opcode bits, such as "POP reg"), and X and B expand index and base in the SIB byte.