CSC448: Code Generation: Learning via GCC I [8/14]

A practical way to learn x86 assembly language and to understand the operation of a compiler is to look at the code generated by a C compiler.

Also beneficial when debugging C/C++ programs or identifying performance bottlenecks.

Consider loop.c:

file:loop.c [source]

00001: #include <stdio.h> 00002: #include <stdlib.h> 00003: 00004: int main (int argc, char *argv[]) 00005: { 00006: int x; 00007: 00008: x = 3; 00009: goto l2; 00010: l1: 00011: printf ("%d\n", x); 00012: x = x - 1; 00013: l2: 00014: if (0 <= x) goto l1; 00015: 00016: return 0; 00017: } 00018:

Compile, link, and run (use a ".exe" extension for loop on Windows):

$ gcc -o loop loop.c
$ ls -l loop*
-rwxrwxr-x    1 cpitcher cpitcher    13663 Feb 25 00:56 loop
-rw-rw-r--    1 cpitcher cpitcher      191 Feb 25 00:48 loop.c
$ ./loop 
3
2
1
0
$ rm loop