kit

kit
git clone https://git.ryansepassi.com/git/kit.git
Log | Files | Refs | README

gnu_labels_as_values_threaded.c (863B)

      1 /* GNU labels-as-values: a direct-threaded (computed-goto) bytecode
      2  * interpreter driven by a function-local static dispatch table built from
      3  * label addresses. Runs `push 3; push 4; add; push 5; mul; halt`, i.e.
      4  * (3 + 4) * 5 = 35. */
      5 enum { OP_PUSH, OP_ADD, OP_MUL, OP_HALT };
      6 
      7 int test_main(void) {
      8   static const unsigned char prog[] = {
      9       OP_PUSH, 3, OP_PUSH, 4, OP_ADD, OP_PUSH, 5, OP_MUL, OP_HALT,
     10   };
     11   static void* const tab[] = {
     12       &&do_push,
     13       &&do_add,
     14       &&do_mul,
     15       &&do_halt,
     16   };
     17   int stack[16];
     18   int sp = 0;
     19   const unsigned char* pc = prog;
     20 
     21   goto* tab[*pc++];
     22 
     23 do_push:
     24   stack[sp++] = *pc++;
     25   goto* tab[*pc++];
     26 do_add:
     27   stack[sp - 2] = stack[sp - 2] + stack[sp - 1];
     28   sp--;
     29   goto* tab[*pc++];
     30 do_mul:
     31   stack[sp - 2] = stack[sp - 2] * stack[sp - 1];
     32   sp--;
     33   goto* tab[*pc++];
     34 do_halt:
     35   return stack[sp - 1];
     36 }