none/tests/amd64/looper.c

   1
   2 #include <stdio.h>
   3
   4 long long int arg = 0;
   5 long long int res = 0;
   6
   7 extern void loop_plain ( void );
   8 asm("\n"
   9 ".text\n"
  10 ".globl loop_plain\n"
  11 "loop_plain:\n"
  12 "\tpushq %rcx\n"
  13 "\tmovq $999, %rax\n"
  14 "\tmovq arg, %rcx\n"
  15
  16 ".Lmn123plain:\n"
  17 "\tdecq %rax\n"
  18 "\tdecq %rax\n"
  19 "\tdecq %rax\n"
  20 "\tloop .Lmn123plain\n"
  21
  22 "\tmovq %rax, res\n"
  23 "\tpopq %rcx\n"
  24 "\tret\n"
  25 ".previous\n"
  26 );
  27
  28 extern void loop_ne ( void );
  29 asm("\n"
  30 ".text\n"
  31 ".globl loop_ne\n"
  32 "loop_ne:\n"
  33 "\tpushq %rcx\n"
  34 "\tmovq $999, %rax\n"
  35 "\tmovq arg, %rcx\n"
  36
  37 ".Lmn123ne:\n"
  38 "\tdecq %rax\n"
  39 "\tdecq %rax\n"
  40 "\tdecq %rax\n"
  41 "\tloopne .Lmn123ne\n"
  42
  43 "\tmovq %rax, res\n"
  44 "\tpopq %rcx\n"
  45 "\tret\n"
  46 ".previous\n"
  47 );
  48
  49 extern void loop_e ( void );
  50 asm("\n"
  51 ".text\n"
  52 ".globl loop_e\n"
  53 "loop_e:\n"
  54 "\tpushq %rcx\n"
  55 "\tmovq $999, %rax\n"
  56 "\tmovq arg, %rcx\n"
  57
  58 ".Lmn123e:\n"
  59 "\tdecq %rax\n"
  60 "\tdecq %rax\n"
  61 "\tdecq %rax\n"
  62 /* invert the Z flag */
  63 "\tpushfq\n"
  64 "\txorq $64, 0(%rsp)\n"
  65 "\tpopfq\n"
  66 "\tloope .Lmn123e\n"
  67
  68 "\tmovq %rax, res\n"
  69 "\tpopq %rcx\n"
  70 "\tret\n"
  71 ".previous\n"
  72 );
  73
  74 int main ( void )
  75 {
  76    res = 0; arg = 10;  loop_plain(); printf("res = %lld\n", res);
  77
  78    res = 0; arg = 10;  loop_ne();    printf("res = %lld\n", res);
  79    res = 0; arg = 500; loop_ne();    printf("res = %lld\n", res);
  80
  81    res = 0; arg = 10;  loop_e();     printf("res = %lld\n", res);
  82    res = 0; arg = 500; loop_e();     printf("res = %lld\n", res);
  83
  84    return 0;
  85 }