ref: 0b360327c6f4f4c79d8872c4b2dc486aba378f6d dir: /src/cmd/as/target/x86/opers.dat/
reg8 AREG_R8CLASS reg16 AREG_R16CLASS reg32 AREG_R32CLASS imm8 AIMM8 imm16 AIMM16 imm32 AIMM32 imm64 AIMM64 \(n\) ADIRECT sym ASYM string ASTR