Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
485 views
in Technique[技术] by (71.8m points)

x86 - complex IF statement in assembly

How should I write such an if statement in assembly?

if ((a == b AND a > c) OR c == b) { ...

Platform: Intel 32-bit machine, NASM syntax.

Update

For variable types and value, use whatever is more easy to understand. Integers would works fine for me, I guess.

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

In generic assembly, it will be basically something like this (a in ax, b in bx, c in cx):

    cmp  bx, cx
    jeq  istrue
    cmp  ax, cx
    jle  isfalse
    cmp  ax, bx
    jeq  istrue
isfalse:
    ; do false bit
    jmp  nextinstr
istrue:
    ; do true bit

nextinstr:
    ; carry on

If there's no false bit, it can be simplified to:

    cmp  bx, cx
    jeq  istrue
    cmp  ax, bx
    jne  nextinstr
    cmp  ax, cx
    jle  nextinstr
istrue:
    ; do true bit

nextinstr:
    ; carry on

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

1.4m articles

1.4m replys

5 comments

57.0k users

...