Flowchart of x86 Instruction Encoding: Prefixes and Escape Opcodes
By
gaul
A second-rack bagel that's nearly first-rack. Tasty stuff.
Summary
This article presents a technical flowchart explaining x86 instruction encoding, specifically focusing on prefixes and escape opcodes. It details how x86 processors decode instructions through various maps (legacy map 0, legacy map 1, and extended maps), showing the decision flow from 1-byte instructions to more complex multi-byte encodings. The content covers instruction prefixes, escape codes, and how different opcode ranges lead to various instruction types and extensions.
Key quotes
· 5 pulled1-byte instructions (legacy map 0)
2-byte instructions (legacy map 1)
operand type specified
escape opcodes
instruction prefixes
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