x86 Assembly

Basic idea

The instruction-set family Intel introduced with the 8086 (1978) and progressively extended (IA-32, x86-64). A CISC ISA: variable-length encoding, two-operand instructions, many addressing modes, dense binary code.

Key facts

• Word sizes: 16-bit (real), 32-bit (IA-32), 64-bit (x86-64 / AMD64).

• 16 general-purpose registers in x86-64: rax, rbx, ..., r8-r15.

• Call conventions (System V): args in rdi, rsi, rdx, rcx, r8, r9; return in rax.

• Two-operand: mov dst, src (Intel syntax) / mov src, dst (AT&T syntax).

• Memory model: x86-TSO (only store→load can reorder).