PUSH

Push a value onto the top of the SP stack.

Opcode	Bytes	Cycles	Form	Example
$29	2	2	`PUSH BYTE {BYTE}`	`PUSH BYTE 123`
$2A	2	2	`PUSH PAIR {S_BYTE}`	`PUSH PAIR 123`
$6E	3	2	`PUSH PAIR {PAIR}`	`PUSH PAIR 12345`
$2B	2	2	`PUSH INT {S_BYTE}`	`PUSH INT 123`
$6F	3	2	`PUSH INT {S_PAIR}`	`PUSH INT 12345`
$CD	4	2	`PUSH INT {U_TRIO}`	`PUSH INT $12_3ABC`
$FC	5	2	`PUSH INT {INT}`	`PUSH INT $1234_ABCD`
$2C	2	3	`PUSH B:_`	`PUSH B:1`
$2D	2	3	`PUSH P:_`	`PUSH P:2`
$2E	2	3	`PUSH I:_`	`PUSH I:4`
$16	1	2	`PUSH FP`	`PUSH FP`
$17	1	2	`PUSH GP`	`PUSH GP`
$18	1	2	`PUSH RETURN IP`	`PUSH RETURN IP`
$19	1	2	`PUSH FLAGS`	`PUSH FLAGS`

Notes

The SP stack is commonly used to store local variables and return addresses for function calls.
The SP stack grows forwards (pushing increases the SP register), whereas the GP stack grows backwards. (The "top" of the GP stack is actually the lowest memory address.)
For example, the effect of PUSH P:6 is write three bytes to the memory address indicated by SP. P:6 is a PAIR register consuming two bytes. Afterwards, 2 is added to the SP register.
For example, PUSH PAIR 123 works similarly except that the value pushed is the number 123. We must include the PAIR type specifier (two bytes), because by itself 123 doesn't indicate how many bytes to write.

PUSH RETURN IP and POP IP are used to call subroutines such as Hybrix function calls. PUSH RETURN IP pushes the address of the instruction following the next instruction, which is presumed to be a JUMP instruction. Consider the example below: PUSH RETURN IP will push $00C0_0A16, because that is where control should return after the JUMP NEAR subroutine has completed.

C0_0A0F: 16                PUSH FP
C0_0A10: 14                MOVE FP, SP
C0_0A11: 2B 01             PUSH INT 1
C0_0A13: 29 02             PUSH BYTE 2
C0_0A15: 18                PUSH RETURN IP
C0_0A16: 3C 0A             JUMP NEAR $C0_0A20
C0_0A18: 3B FB             ADD SP, -5
C0_0A1A: 1A                POP FP
C0_0A1B: 1C                POP IP
C0_0A1C: 00                ---

PUSH FLAGS pushes the CPU flags as a single byte.
If IO::STACK_GUARD is 1, then PUSH will trigger a stack fault event if the SP register becomes larger than the GP register.
POP undoes the action of PUSH.
POP IP undoes the action of PUSH RETURN IP.
This instruction does not affect the CPU condition flags.

Notes​

Notes