FASMG: push_regs

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alorent

Joined: 05 Dec 2005
Posts: 221

alorent 02 May 2023, 15:58

Hi,

I'm starting with ARM64 code using thsq include file.

I want to implement a "push/pop" macro that accepts multiple registers such as:

Code:

push x0 x1 x2 x3 x4.....

pop  x4, x3, x2, x1, x0

I can create a "push" macro that accepts one argument but I'm lost accepting many of arguments:

Code:

macro push reg
    str reg, [sp, -8]!
end macro 

macro pop reg
    ldr reg, [sp], 8
end macro

Any help?

Thanks!

02 May 2023, 15:58

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8351
Location: Kraków, Poland

Tomasz Grysztar 02 May 2023, 16:06

If your multiple arguments are always going to be plain names, you can split them with a simple MATCH in a loop, like this:

Code:

calminstruction push? sequence*&
        local item
    loop:
        match item sequence?, sequence
        jno done ; if match failed, the remaining sequence was empty
        arrange item, =str item, [=sp, -8]!
        assemble item
        jump loop
    done:
end calminstruction

You can also check the variant I used in the x86 implementation, which even further limits what kind of arguments are allowed (with help of two-argument TRANSFORM to detect specific set of names).

02 May 2023, 16:06

alorent

Joined: 05 Dec 2005
Posts: 221

alorent 02 May 2023, 17:03

Thanks Tomasz! It worked great!

I just realized that the stack needs to be 16-byte aligned, so the ideal would be to insert two registers at once, like:

Code:

stp   x1, x2, [sp, 16]!

I'm not sure if that could be covered in fasmg where I read "pairs" of parameters, so something like:

Code:

push x1 x2 x3 x4

would generate:

Code:

stp   x1, x2, [sp, 16]!
stp   x3, x4, [sp, 16]!

Thanks again!

02 May 2023, 17:03

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8351
Location: Kraków, Poland

Tomasz Grysztar 02 May 2023, 17:15

Just code the loop accordingly:

Code:

calminstruction push? sequence*&
        local item, item2
    loop:
        match item sequence?, sequence
        jno done
        match item2 sequence?, sequence
        jno single
        arrange item, =stp item, item2, [=sp, 16]!
        assemble item
        jump loop
    single:
        arrange item, =str item, [=sp, -8]!
        assemble item
    done:
end calminstruction

You can structure CALM code in a way similar to how you would write assembly code - it was intended this way.

02 May 2023, 17:15

alorent

Joined: 05 Dec 2005
Posts: 221

alorent 02 May 2023, 20:33

Amazing Tomasz!

Thanks a million!

02 May 2023, 20:33

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