A small question about Pushf and Popf

walkerfred

Dear masters, Little D has begun to compile. I have encountered a small problem. I can't figure it out. I hope you can take the time to give me pointers. Thank you ~~
Little D studied Wang Shuang's "Assembly Language". He learned the flag register and encountered a small problem.
The flag register has several flag bits such as cf, pf, zf, sf, of, and df.
Pushf pushes the value of the flag register onto the stack
Popf is popping values
The main thing D didn't understand was, did Pushf push all the flag values ​​into the stack?
I have used debug to monitor that sp is fec before pushing the stack, and spee is fee after pushing the stack. Here we calculate the space of 2 bytes, and put the values ​​of cf, pf, zf, sf, of, and df. Obviously Isn't it enough, isn't pushf pushed all the flag values ​​into the stack, or is it just the stack part?
I hope that the master who knows can answer me, thank you very much! Thank you!

mars1004

Why aren't these values ​​enough? There is only one digit for each sign.

walkerfred

Seniors back upstairs ...
How do I put in the first place? Can you elaborate?
If it is 1, is it pushed directly into the stack instead of 01?
Just monitored the value just now ..
d 1802: ffec ffee
1802: ffe0 80 32 00
Why is there such a value ... I can't figure it out ...
Even if all the flag values ​​are put in .. There is no such strange number ...?

joygolden

What pushf performs is to push the entire flag (the value of the flag register onto the stack)
The flag register is also a 16-bit register, how can it not be enough? The stack operations are all word operations, with two bytes just pressing 16 bits. The landlord misunderstood the cf, zf, of, and other flag bits. These flag bits are actually contained in a 16-bit register, and each flag bit occupies only one bit.

mars1004

The upstairs is pretty good, the flag is also a 16-bit register, and each flag occupies one of them.

xukai8

nod The landlord probably got into a dead end. The flag register is either 16-bit or 32-bit, and pushf and popf work normally.
Otherwise, how to say "sign bit", because a sign only occupies 1 bit

walkerfred

Thank you masters~

zhm1983

Doesn't the stack grow from top to bottom? Why does sp grow bigger after pushf

wolf_d

Yes indeed. Pushf sp=sp-2, why has it increased?