程序集x86中的Math.h库函数? [英] Math.h library functions in assembly x86?

问题描述

我试图将在Linux(fedora 9)下编写的C代码转换为汇编x86代码，但是，我在Math.h函数中遇到问题.该库中的功能(例如ceil，floor，log，log10，pow)在程序集x86中未定义.您能帮我解决这个问题吗?

I tried to convert C code that is written under Linux (fedora 9) to assembly x86 code, however, I have problem in a Math.h functions. The functions in this library such as ceil, floor, log, log10, pow are undefined in the assembly x86. Can you please help me to solve this problem?

谢谢.

推荐答案

大多数库函数不会用汇编语言定义，至少在直接映射到ADD指令的加法运算符意义上不是这样.如果要以汇编形式重写该库，则必须使用处理器可用的任何功能来实现该功能.大多数库函数将需要单独的汇编语言子例程，而不仅仅是单个操作.解决此问题的最简单方法是使各个库子例程独立运行，然后将它们合并到较大的程序中.

Most library functions won't be defined in assembly language, at least not in the sense of the addition operator directly mapping to the ADD instruction. If you want to re-write the library in assembly, you'll have to implement the function using whatever capabilities that your processor has available. Most library functions will require a separate assembly language subroutine, not just a single operation. The easiest way to approach this is to get the individual library subroutines working in isolation, then incorporate them into the larger program.

您可以编译C代码并检查反汇编后的输出，但是要当心编译器的优化，这些优化可能会使输出难以为人所知.

You can compile the C code and examine the disassembled output, but beware of compiler optimizations that can make the output hard for a human to follow.

请问这个任务的目的是什么?由于编译器本质上是C到汇编语言的翻译器，因此几乎不需要手动执行此操作.这是家庭作业吗?

May I ask what the purpose is behind this task? Since a compiler is essentially a C to assembly-language translator, there's rarely a need to do this by hand. Is this homework?

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