SIMD and Floating-Point x86-64 Instruction Encoding

About this book

SIMD and Floating-Point x86-64 Instruction Encoding — Volume 3 is an implementation-oriented technical reference covering the evolution and binary encoding of x86 floating-point, vector, cryptographic, and matrix-processing instructions. Building on the legacy/REX foundations and general-purpose instruction forms introduced in the previous volumes, this book advances into the increasingly sophisticated encoding systems used by modern x86-64 processors.

The volume follows the architectural progression from x87 floating-point and MMX through SSE, AVX, AVX2, FMA, cryptographic extensions, AVX-512, EVEX, and Intel AMX. This progression illustrates how x86 instruction encoding evolved from relatively compact legacy forms into modern vector and matrix encodings capable of expressing wider registers, additional operands, masking, broadcast operations, rounding controls, and specialized acceleration features.

A central objective of the book is to explain these instruction families from an implementer's perspective. Rather than presenting SIMD instructions merely as mnemonic catalogs, the material connects instruction forms with the actual encoding decisions required by an assembler, compiler backend, JIT engine, disassembler, or binary-analysis tool.

The book examines the transition between the major encoding models:

Legacy/x87/MMX → SSE prefixes → VEX → EVEX → AMX-related forms

Readers learn how opcode maps, mandatory prefixes, register fields, operand widths, vector lengths, ModR/M and SIB addressing, VEX fields, EVEX extensions, opmask registers, broadcast controls, embedded rounding, zeroing/merging semantics, and other encoding properties contribute to the final machine instruction.

Special attention is given to AVX and AVX2, where VEX encoding expands register selection and introduces non-destructive multi-operand forms, and to AVX-512, where EVEX substantially extends the encoding model with 512-bit vectors, additional registers, masking, broadcast, and other per-instruction controls.

The volume also covers important specialized instruction families, including FMA and hardware-assisted cryptographic operations, showing how acceleration features fit into the broader x86 encoding architecture. Intel AMX introduces another significant architectural direction through tile registers and matrix-oriented computation, requiring implementers to understand both its instruction representation and its relationship to processor state and feature availability.

Throughout the book, the recommended implementation method remains systematic:

identify the instruction family → select a legal form → determine the encoding scheme → resolve fields and operands → emit bytes in architectural order → independently verify the result.

This approach is especially important for SIMD instruction encoding because visually similar mnemonics may have legacy, VEX, or EVEX variants with different operand rules and binary representations.

The book is intended for developers building assemblers, compilers, JIT compilers, disassemblers, debuggers, virtual machines, binary translators, performance tools, and low-level development infrastructure. It is designed to complement—not replace—the authoritative Intel and AMD architecture documentation, which should always be consulted for exact instruction availability, exceptions, CPUID requirements, operating-mode restrictions, and architectural behavior.

Together with Volume 1: Foundations of x86-64 Instruction Encoding and Volume 2: General-Purpose x86-64 Instruction Encoding, this volume extends the series from the fundamental structure of machine instructions into the advanced vector, floating-point, cryptographic, and matrix-processing capabilities that define modern high-performance x86-64 computing.