doc/tutorial/loop.c

   1 #include "sljitLir.h"
   2
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5
   6 typedef long (SLJIT_FUNC *func2_t)(long a, long b);
   7
   8 /*
   9   This example, we generate a function like this:
  10
  11 long func(long a, long b)
  12 {
  13         long i;
  14         long ret = 0;
  15         for (i = 0; i < a; ++i) {
  16                 ret += b;
  17         }
  18         return ret;
  19 }
  20 */
  21
  22 static int loop(long a, long b)
  23 {
  24         void *code;
  25         unsigned long len;
  26         func2_t func;
  27
  28         struct sljit_label *loopstart;
  29         struct sljit_jump *out;
  30
  31         /* Create a SLJIT compiler */
  32         struct sljit_compiler *C = sljit_create_compiler(NULL, NULL);
  33
  34         /* 2 arg, 2 temp reg, 2 saved reg */
  35         sljit_emit_enter(C, 0, SLJIT_ARGS2(W, W, W), 2, 2, 0, 0, 0);
  36
  37         /* R0 = 0 */
  38         sljit_emit_op2(C, SLJIT_XOR, SLJIT_R1, 0, SLJIT_R1, 0, SLJIT_R1, 0);
  39         /* RET = 0 */
  40         sljit_emit_op1(C, SLJIT_MOV, SLJIT_RETURN_REG, 0, SLJIT_IMM, 0);
  41         /* loopstart: */
  42         loopstart = sljit_emit_label(C);
  43         /* R1 >= a --> jump out */
  44         out = sljit_emit_cmp(C, SLJIT_GREATER_EQUAL, SLJIT_R1, 0, SLJIT_S0, 0);
  45         /* RET += b */
  46         sljit_emit_op2(C, SLJIT_ADD, SLJIT_RETURN_REG, 0, SLJIT_RETURN_REG, 0, SLJIT_S1, 0);
  47         /* R1 += 1 */
  48         sljit_emit_op2(C, SLJIT_ADD, SLJIT_R1, 0, SLJIT_R1, 0, SLJIT_IMM, 1);
  49         /* jump loopstart */
  50         sljit_set_label(sljit_emit_jump(C, SLJIT_JUMP), loopstart);
  51         /* out: */
  52         sljit_set_label(out, sljit_emit_label(C));
  53
  54         /* return RET */
  55         sljit_emit_return(C, SLJIT_MOV, SLJIT_RETURN_REG, 0);
  56
  57         /* Generate machine code */
  58         code = sljit_generate_code(C);
  59         len = sljit_get_generated_code_size(C);
  60
  61         /* Execute code */
  62         func = (func2_t)code;
  63         printf("func return %ld\n", func(a, b));
  64
  65         /* dump_code(code, len); */
  66
  67         /* Clean up */
  68         sljit_free_compiler(C);
  69         sljit_free_code(code, NULL);
  70         return 0;
  71 }
  72
  73 int main()
  74 {
  75         return loop(4, 5);
  76 }