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3-538 Vol. 2A LEAVE—High Level Procedure Exit
INSTRUCTION SET REFERENCE, A-M
LEAVE—High Level Procedure Exit
Description
Releases the stack frame set up by an earlier ENTER instruction. The LEAVE instruc-
tion copies the frame pointer (in the EBP register) into the stack pointer register
(ESP), which releases the stack space allocated to the stack frame. The old frame
pointer (the frame pointer for the calling procedure that was saved by the ENTER
instruction) is then popped from the stack into the EBP register, restoring the calling
procedure’s stack frame.
A RET instruction is commonly executed following a LEAVE instruction to return
program control to the calling procedure.
See “Procedure Calls for Block-Structured Languages” in Chapter 6 of the Intel® 64
and IA-32 Architectures Software Developer’s Manual, Volume 1, for detailed infor-
mation on the use of the ENTER and LEAVE instructions.
In 64-bit mode, the instruction’s default operation size is 64 bits; 32-bit operation
cannot be encoded. See the summary chart at the beginning of this section for
encoding data and limits.
Operation
IF StackAddressSize = 32
THEN
ESP ← EBP;
ELSE IF StackAddressSize
= 64
THEN RSP ← RBP; FI;
ELSE IF StackAddressSize
= 16
THEN SP ← BP; FI;
FI;
IF OperandSize
= 32
THEN EBP ← Pop();
ELSE IF OperandSize
= 64
THEN RBP ← Pop(); FI;
ELSE IF OperandSize
= 16
THEN BP ← Pop(); FI;
FI;
Opcode Instruction 64-Bit
Mode
Compat/
Leg Mode
Description
C9 LEAVE Valid Valid Set SP to BP, then pop BP.
C9 LEAVE N.E. Valid Set ESP to EBP, then pop EBP.
C9 LEAVE Valid N.E. Set RSP to RBP, then pop RBP.