Fasm 1.73 Many cmp one jz.

flat assembler
Message board for the users of flat assembler.

Index > Main > Fasm 1.73 Many cmp one jz.

Goto page Previous 1, 2

Author

Thread

Overclick

Joined: 11 Jul 2020
Posts: 670
Location: Ukraine

Overclick 23 Jul 2020, 20:20

It doesn't seems to work as you reloading reg0

Your code in fasm will looks like this:

Code:

macro cmp a,[b] {
     sub rsp,8
     irp c, b  \{
        cmp       a,c
        pushfq
        pop      a
        or        [rsp],a
     \}
     popfq
}

Final version of my one. It accepts any size of operands as usual cmp does (figured by compiler ofcourse)

Code:

macro cmp a,[b] {
     c=0
     forward
     c=c+1
     common
     if c > 1
        push rax
        push qword 0
     forward
        if `a in <'rax','eax','ax','ah','al'> | \
           `b in <'rax','eax','ax','ah','al'>
            mov      rax,[rsp+8]
        end if
        cmp          a,b
        lahf
        or           [rsp],ah
     common
        pop rax
        shl          ax,8
        sahf
        pop rax
     else
        cmp          a,b
     end if
}

Last edited by Overclick on 23 Jul 2020, 22:36; edited 1 time in total

23 Jul 2020, 20:20

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20761
Location: In your JS exploiting you and your system

revolution 23 Jul 2020, 22:05

Overclick: If any flag is set upon entry then the compares have no effect, and those same flags are always set upon exit.

Also, consider making c local to avoid clashes.

Code:

local c
;...
     if c > 1
        push rax
        pushq 0 ;reset all flags
     forward

Last edited by revolution on 23 Jul 2020, 22:27; edited 1 time in total

23 Jul 2020, 22:05

bitRAKE

Joined: 21 Jul 2003
Posts: 4311
Location: vpcmpistri

bitRAKE 23 Jul 2020, 22:12

Overclick wrote:

It doesn't seems to work as you reloading reg0

Your code in fasm will looks like this:

Code:

macro cmp a,[b] {
     sub rsp,8
     irp c, b  \{
        cmp       a,c
        pushfq
        pop      a
        or        [rsp],a
     \}
     popfq
}

not really. the flags aren't POP'd until the end. "if % = %%"

_________________
¯\(°_o)/¯ AI may [not] have aided with the above reply.

23 Jul 2020, 22:12

Overclick

Joined: 11 Jul 2020
Posts: 670
Location: Ukraine

Overclick 23 Jul 2020, 22:23

bitRAKE, operand for cmp replaced for next interaction

revolution, you right.

23 Jul 2020, 22:23

bitRAKE

Joined: 21 Jul 2003
Posts: 4311
Location: vpcmpistri

bitRAKE 23 Jul 2020, 22:27

do you mean for:

Code:

compare r15, 1,2,3
compare r15, 6,7,8

Then yes, R15 would be overwritten.

_________________
¯\(°_o)/¯ AI may [not] have aided with the above reply.

23 Jul 2020, 22:27

Overclick

Joined: 11 Jul 2020
Posts: 670
Location: Ukraine

Overclick 23 Jul 2020, 22:40

Edited last version, there also I'm worried about full pack of flags replaced to 0. That why I changed popfq to:

Code:

        pop rax
        shl          ax,8
        sahf
        pop rax

23 Jul 2020, 22:40

Goto page Previous 1, 2

< Last Thread | Next Thread >

Forum Rules:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum