› ›

help with x86 assembler

rapheal2k8rapheal2k8
in x86 Assembly
please im trying to write a program which reads roman numerals and returns integers in x86 but im trying to avoid using ja near and jb near , je near in some parts of my code, is there any other standard jump instruction i can use?

Comments

  • MT2002MT2002
    jc,jcxz,jna,jnae,jnb,jnbe,jnc,jne,jng,jnge,jnl, jnle ,jno,jnz,jo,jp,jpo,
    js,jz...Theres alot of different jump instructions you can use.

    If you really want to avoid jump instructions you can also just put cs:eip on the stack and issue either a ret or retd instruction to go to it...
    [hr][size=1][leftbr].:EvolutionEngine[rightbr][leftbr].:MicroOS Operating System[rightbr][leftbr][link=http://www.brokenthorn.com]Website :: OS Development Series[rightbr][/link][/size]
  • BretBret
    : jc,jcxz,jna,jnae,jnb,jnbe,jnc,jne,jng,jnge,jnl, jnle
    : ,jno,jnz,jo,jp,jpo,
    : js,jz...Theres alot of different jump instructions you can use.
    :
    : If you really want to avoid jump instructions you can also just put
    : cs:eip on the stack and issue either a ret or retd instruction to go
    : to it...
    : [hr][size=1][leftbr].:EvolutionEngine[rightbr][leftbr].:MicroOS
    : Operating
    : System[rightbr][leftbr][link=http://www.brokenthorn.com]Website ::
    : OS Development Series[rightbr][/link][/size]

    Mostly out of curiosity, why are you wanting to avoid the use of those instructions? Is it conditional jumps in general you're trying to avoid, specifically the JA/JB/JE instructions (but things like JG, JL, and JMP would be OK), or the NEAR versions of them (but SHORT or FAR jumps would be OK)?

    Other than something like a trivial "Hello, World" world program, I'm not sure it is possible to completely avoid using conditional jumps.
  • ultranoultrano
    : : jc,jcxz,jna,jnae,jnb,jnbe,jnc,jne,jng,jnge,jnl, jnle
    : : ,jno,jnz,jo,jp,jpo,
    : : js,jz...Theres alot of different jump instructions you can use.
    : :
    : : If you really want to avoid jump instructions you can also just put
    : : cs:eip on the stack and issue either a ret or retd instruction to go
    : : to it...
    : : [hr][size=1][leftbr].:EvolutionEngine[rightbr][leftbr].:MicroOS
    : : Operating
    : : System[rightbr][leftbr][link=http://www.brokenthorn.com]Website ::
    : : OS Development Series[rightbr][/link][/size]
    :
    : Mostly out of curiosity, why are you wanting to avoid the use of
    : those instructions? Is it conditional jumps in general you're
    : trying to avoid, specifically the JA/JB/JE instructions (but things
    : like JG, JL, and JMP would be OK), or the NEAR versions of them (but
    : SHORT or FAR jumps would be OK)?
    :
    : Other than something like a trivial "Hello, World" world program,
    : I'm not sure it is possible to completely avoid using conditional
    : jumps.

    CMOVxx

    The alternative is to make 12 256-entry tables and switch between them similarly to state-machines.
    "ret" tricks are more expensive than jxx on modern cpus. And anyway, it doesn't look like code in need of optimization or note.
Sign In or Register to comment.

Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

Sign In Register

Categories

In this Discussion