popa
Pop All General-Purpose Registers
Pops into DI, SI, BP, SP, BX, DX, CX, AX (Invalid in 64-bit).
Pseudocode Operation
DI ← [SP+0]; SI ← [SP+2]; BP ← [SP+4]; SP ← SP + 6; BX ← [SP+0]; DX ← [SP+2]; CX ← [SP+4]; AX ← [SP+6]; SP ← SP + 8Encoding
Operands
Related
More in Base (32-bit only)
Reference
Instruction Forms
| Opcode | Instruction | Op/En | 64/32-bit Mode | CPUID | Description |
|---|---|---|---|---|---|
| 61 | POPA | ZO | Invalid Valid | Pop DI, SI, BP, BX, DX, CX, and AX. | |
| 61 | POPAD | ZO | Invalid Valid | Pop EDI, ESI, EBP, EBX, EDX, ECX, and EAX. |
Description
Pops doublewords (POPAD) or words (POPA) from the stack into the general-purpose registers. The registers are loaded in the following order: EDI, ESI, EBP, EBX, EDX, ECX, and EAX (if the operand-size attribute is 32) and DI, SI, BP, BX, DX, CX, and AX (if the operand-size attribute is 16). (These instructions reverse the operation of the PUSHA/PUSHAD instructions.) The value on the stack for the ESP or SP register is ignored. Instead, the ESP or SP register is incremented after each register is loaded. The POPA (pop all) and POPAD (pop all double) mnemonics reference the same opcode. The POPA instruction is intended for use when the operand-size attribute is 16 and the POPAD instruction for when the operand-size attribute is 32. Some assemblers may force the operand size to 16 when POPA is used and to 32 when POPAD is used (using the operand-size override prefix [66H] if necessary). Others may treat these mnemonics as synonyms (POPA/POPAD) and use the current setting of the operand-size attribute to determine the size of values to be popped from the stack, regardless of the mnemonic used. (The D flag in the current code segment’s segment descriptor determines the operand-size attribute.) This instruction executes as described in non-64-bit modes. It is not valid in 64-bit mode.
Operation
IF 64-Bit Mode THEN #UD; ELSE IF OperandSize = 32 (* Instruction = POPAD *) THEN EDI := Pop(); ESI := Pop(); EBP := Pop(); Increment ESP by 4; (* Skip next 4 bytes of stack *) EBX := Pop(); EDX := Pop(); ECX := Pop(); EAX := Pop(); ELSE (* OperandSize = 16, instruction = POPA *) DI := Pop(); SI := Pop(); BP := Pop(); Increment ESP by 2; (* Skip next 2 bytes of stack *) BX := Pop(); DX := Pop(); CX := Pop(); AX := Pop(); FI; FI;