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The x86 instruction set refers to the set of instructions that x86-compatible microprocessors support. The instructions are usually part of an executable program, often stored as a computer file and executed on the processor. The x86 instruction set has been extended several times, introducing wider registers and datatypes as well as new ...
The x86 instruction set includes string load, store, move, scan and compare instructions (lods, stos, movs, scas and cmps) which perform each operation to a specified size (b for 8-bit byte, w for 16-bit word, d for 32-bit double word) then increments/decrements (depending on DF, direction flag) the implicit address register (si for lods, di ...
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.
An instruction set architecture (ISA) is an abstract model of a computer, also referred to as computer architecture.A realization of an ISA is called an implementation.An ISA permits multiple implementations that may vary in performance, physical size, and monetary cost (among other things); because the ISA serves as the interface between software and hardware.
x86 (also known as 80x86 [3] or the 8086 family [4]) is a family of complex instruction set computer (CISC) instruction set architectures [a] initially developed by Intel based on the 8086 microprocessor and its 8-bit-external-bus variant, the 8088.
For example, the Intel Pentium and the AMD Athlon implement nearly identical versions of the x86 instruction set, but they have radically different internal designs. The concept of an architecture , distinct from the design of a specific machine, was developed by Fred Brooks at IBM during the design phase of System/360 .
Bit manipulation instructions sets (BMI sets) are extensions to the x86 instruction set architecture for microprocessors from Intel and AMD. The purpose of these instruction sets is to improve the speed of bit manipulation. All the instructions in these sets are non-SIMD and operate only on general-purpose registers.
; The 'enter' instruction can also do something similar); sub esp, 12 : 'enter' instruction could do this for us; mov [ebp-4], 3 : or mov [esp+8], 3; mov [ebp-8], 2 : or mov [esp+4], 2; mov [ebp-12], 1 : or mov [esp], 1 push 3 push 2 push 1 call callee; call subroutine 'callee' add esp, 12; remove call arguments from frame add eax, 5; modify ...