LabelRef = object
  case isLabel*: bool
  of true:
    lkind*: LabelRefKind
    lname*: string
    dynExpr*: string         ## placeholder, real expr handled in macro via id
    dynId*: int              ## resolved at macro expansion when possible
    loff*: int
  of false:
    nil

LabelRefKind = enum
  lrForward, lrBackward, lrGlobal, lrDynamic, lrAbsolute

MemOp = object
  hasBase*: bool
  base*: Register
  hasIndex*: bool
  index*: Register
  scale*: int
  disp*: int64
  hasDisp*: bool
  ripLabel*: LabelRef        ## for [glob(..)] / [fwd(..)] RIP-relative
  hasRip*: bool
  addrSizeOverride*: bool

Operand = object
  case kind*: OperandKind
  of okReg:
    reg*: Register
    regSize*: OpSize
  of okImm:
    imm*: int64
    immSize*: OpSize
  of okMem:
    mem*: MemOp
    memSize*: OpSize
  of okLabelRef:
    lbl*: LabelRef

OperandKind = enum
  okReg, okImm, okMem, okLabelRef

OpSize = enum
  szNone, sz8, sz16, sz32, sz64

RegClass = enum
  rcGpr,                    ## general purpose (size encoded separately)
  rcHigh8,                  ## AH/CH/DH/BH
  rcFpu,                    ## ST0..7
  rcMmx, rcXmm, rcSeg, rcControl, rcDebug, rcBound

Register = object
  code*: uint8
  cls*: RegClass

A64ExtLsl = 0

A64ExtSxtw = 2

A64ExtSxtx = 1

A64ExtUxtw = 4

A64ExtUxtx = 3

ah = (code: 4'u, cls: rcHigh8)

al = (code: 0'u, cls: rcGpr)

ax = (code: 0'u, cls: rcGpr)

bh = (code: 7'u, cls: rcHigh8)

bl = (code: 3'u, cls: rcGpr)

bp = (code: 5'u, cls: rcGpr)

bpl = (code: 5'u, cls: rcGpr)

bx = (code: 3'u, cls: rcGpr)

ch = (code: 5'u, cls: rcHigh8)

cl = (code: 1'u, cls: rcGpr)

cx = (code: 1'u, cls: rcGpr)

dh = (code: 6'u, cls: rcHigh8)

di = (code: 7'u, cls: rcGpr)

dil = (code: 7'u, cls: rcGpr)

dl = (code: 2'u, cls: rcGpr)

dx = (code: 2'u, cls: rcGpr)

eax = (code: 0'u, cls: rcGpr)

ebp = (code: 5'u, cls: rcGpr)

ebx = (code: 3'u, cls: rcGpr)

ecx = (code: 1'u, cls: rcGpr)

edi = (code: 7'u, cls: rcGpr)

edx = (code: 2'u, cls: rcGpr)

esi = (code: 6'u, cls: rcGpr)

esp = (code: 4'u, cls: rcGpr)

r8 = (code: 8'u, cls: rcGpr)

r8b = (code: 8'u, cls: rcGpr)

r8d = (code: 8'u, cls: rcGpr)

r9 = (code: 9'u, cls: rcGpr)

r9b = (code: 9'u, cls: rcGpr)

r9d = (code: 9'u, cls: rcGpr)

r10 = (code: 10'u, cls: rcGpr)

r10b = (code: 10'u, cls: rcGpr)

r10d = (code: 10'u, cls: rcGpr)

r11 = (code: 11'u, cls: rcGpr)

r11b = (code: 11'u, cls: rcGpr)

r11d = (code: 11'u, cls: rcGpr)

r12 = (code: 12'u, cls: rcGpr)

r12b = (code: 12'u, cls: rcGpr)

r12d = (code: 12'u, cls: rcGpr)

r13 = (code: 13'u, cls: rcGpr)

r13b = (code: 13'u, cls: rcGpr)

r13d = (code: 13'u, cls: rcGpr)

r14 = (code: 14'u, cls: rcGpr)

r14b = (code: 14'u, cls: rcGpr)

r14d = (code: 14'u, cls: rcGpr)

r15 = (code: 15'u, cls: rcGpr)

r15b = (code: 15'u, cls: rcGpr)

r15d = (code: 15'u, cls: rcGpr)

rax = (code: 0'u, cls: rcGpr)

rbp = (code: 5'u, cls: rcGpr)

rbx = (code: 3'u, cls: rcGpr)

rcx = (code: 1'u, cls: rcGpr)

rdi = (code: 7'u, cls: rcGpr)

rdx = (code: 2'u, cls: rcGpr)

rsi = (code: 6'u, cls: rcGpr)

rsp = (code: 4'u, cls: rcGpr)

si = (code: 6'u, cls: rcGpr)

sil = (code: 6'u, cls: rcGpr)

sp = (code: 4'u, cls: rcGpr)

spl = (code: 4'u, cls: rcGpr)

w0 = (code: 0'u, cls: rcGpr)

w1 = (code: 1'u, cls: rcGpr)

w2 = (code: 2'u, cls: rcGpr)

w3 = (code: 3'u, cls: rcGpr)

w4 = (code: 4'u, cls: rcGpr)

w5 = (code: 5'u, cls: rcGpr)

w6 = (code: 6'u, cls: rcGpr)

w7 = (code: 7'u, cls: rcGpr)

w8 = (code: 8'u, cls: rcGpr)

w9 = (code: 9'u, cls: rcGpr)

w10 = (code: 10'u, cls: rcGpr)

w11 = (code: 11'u, cls: rcGpr)

w12 = (code: 12'u, cls: rcGpr)

w13 = (code: 13'u, cls: rcGpr)

w14 = (code: 14'u, cls: rcGpr)

w15 = (code: 15'u, cls: rcGpr)

w16 = (code: 16'u, cls: rcGpr)

w17 = (code: 17'u, cls: rcGpr)

w18 = (code: 18'u, cls: rcGpr)

w19 = (code: 19'u, cls: rcGpr)

w20 = (code: 20'u, cls: rcGpr)

w21 = (code: 21'u, cls: rcGpr)

w22 = (code: 22'u, cls: rcGpr)

w23 = (code: 23'u, cls: rcGpr)

w24 = (code: 24'u, cls: rcGpr)

w25 = (code: 25'u, cls: rcGpr)

w26 = (code: 26'u, cls: rcGpr)

w27 = (code: 27'u, cls: rcGpr)

w28 = (code: 28'u, cls: rcGpr)

w29 = (code: 29'u, cls: rcGpr)

w30 = (code: 30'u, cls: rcGpr)

wsp = (code: 31'u, cls: rcGpr)

wzr = (code: 31'u, cls: rcGpr)

x0 = (code: 0'u, cls: rcGpr)

x1 = (code: 1'u, cls: rcGpr)

x2 = (code: 2'u, cls: rcGpr)

x3 = (code: 3'u, cls: rcGpr)

x4 = (code: 4'u, cls: rcGpr)

x5 = (code: 5'u, cls: rcGpr)

x6 = (code: 6'u, cls: rcGpr)

x7 = (code: 7'u, cls: rcGpr)

x8 = (code: 8'u, cls: rcGpr)

x9 = (code: 9'u, cls: rcGpr)

x10 = (code: 10'u, cls: rcGpr)

x11 = (code: 11'u, cls: rcGpr)

x12 = (code: 12'u, cls: rcGpr)

x13 = (code: 13'u, cls: rcGpr)

x14 = (code: 14'u, cls: rcGpr)

x15 = (code: 15'u, cls: rcGpr)

x16 = (code: 16'u, cls: rcGpr)

x17 = (code: 17'u, cls: rcGpr)

x18 = (code: 18'u, cls: rcGpr)

x19 = (code: 19'u, cls: rcGpr)

x20 = (code: 20'u, cls: rcGpr)

x21 = (code: 21'u, cls: rcGpr)

x22 = (code: 22'u, cls: rcGpr)

x23 = (code: 23'u, cls: rcGpr)

x24 = (code: 24'u, cls: rcGpr)

x25 = (code: 25'u, cls: rcGpr)

x26 = (code: 26'u, cls: rcGpr)

x27 = (code: 27'u, cls: rcGpr)

x28 = (code: 28'u, cls: rcGpr)

x29 = (code: 29'u, cls: rcGpr)

x30 = (code: 30'u, cls: rcGpr)

xmm0 = (code: 0'u, cls: rcXmm)

xmm1 = (code: 1'u, cls: rcXmm)

xmm2 = (code: 2'u, cls: rcXmm)

xmm3 = (code: 3'u, cls: rcXmm)

xmm4 = (code: 4'u, cls: rcXmm)

xmm5 = (code: 5'u, cls: rcXmm)

xmm6 = (code: 6'u, cls: rcXmm)

xmm7 = (code: 7'u, cls: rcXmm)

xmm8 = (code: 8'u, cls: rcXmm)

xmm9 = (code: 9'u, cls: rcXmm)

xmm10 = (code: 10'u, cls: rcXmm)

xmm11 = (code: 11'u, cls: rcXmm)

xmm12 = (code: 12'u, cls: rcXmm)

xmm13 = (code: 13'u, cls: rcXmm)

xmm14 = (code: 14'u, cls: rcXmm)

xmm15 = (code: 15'u, cls: rcXmm)

xsp = (code: 31'u, cls: rcGpr)

xzr = (code: 31'u, cls: rcGpr)