image/svg+xml LAHF—Load Status Flags into AH Register Instruction Operand Encoding Description This instruction executes as described above in compatibility mode and legacy mode. It is valid in 64-bit mode only if CPUID.80000001H:ECX.LAHF-SAHF[bit 0] = 1. Operation IF 64-Bit Mode THEN IF CPUID.80000001H:ECX.LAHF-SAHF[bit 0] = 1; THEN AH := RFLAGS(SF:ZF:0:AF:0:PF:1:CF); ELSE #UD; FI; ELSE AH := EFLAGS(SF:ZF:0:AF:0:PF:1:CF); FI; Flags Affected None. The state of the flags in the EFLAGS register is not affected. Protected Mode Exceptions #UD If the LOCK prefix is used. Real-Address Mode Exceptions Same exceptions as in protected mode. Virtual-8086 Mode Exceptions Same exceptions as in protected mode. Compatibility Mode Exceptions Same exceptions as in protected mode. 64-Bit Mode Exceptions #UDIf CPUID.80000001H:ECX.LAHF-SAHF[bit 0] = 0. If the LOCK prefix is used. OpcodeInstructionOp/ En 64-Bit Mode Compat/ Leg Mode Description 9F LAHFZOInvalid*ValidLoad: AH := EFLAGS(SF:ZF:0:AF:0:PF:1:CF). NOTES: *Valid in specific steppings. See Description section. Op/EnOperand 1Operand 2Operand 3Operand 4 ZONANANANA This UNOFFICIAL reference was generated from the official Intel® 64 and IA-32 Architectures Software Developer’s Manual by a dumb script. There is no guarantee that some parts aren't mangled or broken and is distributed WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE .