tests/bcj_test.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       bcj_test.c
   4 /// \brief      Source code of compress_prepared_bcj_*
   5 ///
   6 /// This is a simple program that should make the compiler to generate
   7 /// PC-relative branches, jumps, and calls. The compiled files can then
   8 /// be used to test the branch conversion filters. Note that this program
   9 /// itself does nothing useful.
  10 ///
  11 /// Compiling: gcc -std=c99 -fPIC -c bcj_test.c
  12 /// Don't optimize or strip.
  13 //
  14 //  Author:     Lasse Collin
  15 //
  16 //  This file has been put into the public domain.
  17 //  You can do whatever you want with this file.
  18 //
  19 ///////////////////////////////////////////////////////////////////////////////
  20
  21 extern int jump(int a, int b);
  22
  23
  24 extern int
  25 call(int a, int b)
  26 {
  27         if (a < b)
  28                 a = jump(a, b);
  29
  30         return a;
  31 }
  32
  33
  34 extern int
  35 jump(int a, int b)
  36 {
  37         // The loop generates conditional jump backwards.
  38         while (1) {
  39                 if (a < b) {
  40                         a *= 2;
  41                         a += 3 * b;
  42                         break;
  43                 } else {
  44                         // Put enough code here to prevent JMP SHORT on x86.
  45                         a += b;
  46                         a /= 2;
  47                         b += b % 5;
  48                         a -= b / 3;
  49                         b = 2 * b + a - 1;
  50                         a *= b + a + 1;
  51                         b += a - 1;
  52                         a += b * 2 - a / 5;
  53                 }
  54         }
  55
  56         return a;
  57 }
  58
  59
  60 int
  61 main(int argc, char **argv)
  62 {
  63         int a = call(argc, argc + 1);
  64         return a == 0;
  65 }