# SPDX-License-Identifier: BSD-2-Clause # Copyright 1996-2025 The NASM Authors - All Rights Reserved # # List of registers and their classes; classes are defined in nasm.h # # The columns are: # # register name, assembler class, disassembler class(es), x86 register number[, token flag] # # If the register name ends in two numbers separated by a dash, then it is # repeated as many times as indicated, and the register number is # updated with it. # # If 'token flag' is present, this value will be assigned to tokflag field in # 'struct tokendata tokendata[]' table. Token flag can be used for specifying # special usage of corresponding register. E.g. opmask registers can be either # enclosed by curly braces or standalone operand depending on the usage. # # General-purpose registers al REG_AL reg8,reg8_rex 0 ah REG_HIGH reg8 4 ax REG_AX reg16 0 eax REG_EAX reg32 0 rax REG_RAX reg64 0 bl REG_BL reg8,reg8_rex 3 bh REG_HIGH reg8 7 bx REG_BX reg16 3 ebx REG_EBX reg32 3 rbx REG_RBX reg64 3 cl REG_CL reg8,reg8_rex 1 ch REG_HIGH reg8 5 cx REG_CX reg16 1 ecx REG_ECX reg32 1 rcx REG_RCX reg64 1 dl REG_DL reg8,reg8_rex 2 dh REG_HIGH reg8 6 dx REG_DX reg16 2 edx REG_EDX reg32 2 rdx REG_RDX reg64 2 spl REG8 reg8_rex 4 sp REG16 reg16 4 esp REG32 reg32 4 rsp REG64 reg64 4 bpl REG8 reg8_rex 5 bp REG16 reg16 5 ebp REG32 reg32 5 rbp REG64 reg64 5 sil REG8 reg8_rex 6 si REG16 reg16 6 esi REG32 reg32 6 rsi REG64 reg64 6 dil REG8 reg8_rex 7 di REG16 reg16 7 edi REG32 reg32 7 rdi REG64 reg64 7 r8-31b REG8 reg8_rex 8 r8-31w REG16 reg16 8 r8-31d REG32 reg32 8 r8-31 REG64 reg64 8 # Segment registers es REG_ES sreg 0 & 7 cs REG_CS sreg 1 ss REG_SS sreg 2 ds REG_DS sreg 3 fs REG_FS sreg 4 gs REG_GS sreg 5 segr6-7 REG_SEG67 sreg 6 # Control registers cr0-31 REG_CREG creg 0 # Debug registers dr0-31 REG_DREG dreg 0 # Test registers tr0-7 REG_TREG treg 0 & 7 # Floating-point registers st0-7 FPUREG fpureg 0 & 7 # MMX registers mm0-7 MMXREG mmxreg 0 & 7 # SSE/AVX registers xmm0-31 XMMREG xmmreg 0 ymm0-31 YMMREG ymmreg 0 zmm0-31 ZMMREG zmmreg 0 # AMX tile registers tmm0-7 TMMREG tmmreg 0 & 7 # Opmask registers k0 OPMASKREG opmaskreg 0 & 7 k1-7 OPMASKREG opmaskreg 1 TFLAG_BRC_OPT # Bounds registers (the mask here really is 7, not 3; # 4-7 were reserved encodings) bnd0-3 BNDREG bndreg 0 & 7