9.2: Stack Instructions

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A push operation puts things onto the stack, and a pop operation takes things off the stack. The format for these commands is:

    push     <operand64> 
    pop      <operand64>

The operand can be a register or memory, but an immediate is not allowed. In general, push and pop operations will push the architecture size. Since the architecture is 64-bit, we will push and pop quadwords.

The stack is implemented in reverse in memory. Refer to the following sections for a detailed explanation of why.

Instruction	Explanation
push <op64>	Push the 64-bit operand on the stack. First, adjusts rsp accordingly (rsp-8) and then copy the operand to [rsp]. The operand may not be an immediate value. Operand is not changed.
Examples:	push rax push qword [qVal] ; value push qVal ; address
pop <op64>	Pop the 64-bit operand from the stack. Adjusts rsp accordingly (rsp+8). The operand may not be an immediate value. Operand is overwritten.
Examples:	pop rax pop qword [qVal] pop rsi

If more than 64-bits must be pushed, multiple push operations would be required. While it is possible to push and pop operands less than 64-bits, it is not recommended.

A more complete list of the instructions is located in Appendix B.