[Libjit-developers] simple loop?

[jhanebach]

Hi,

I'm trying to get a feel of libjit and
cannot figure out how to create a simple loop :( 
My lame attempt: (VC 7.1 on WinXP)

        jit_context_t
context;
        jit_type_t
params[3];
        jit_type_t
signature;
        jit_function_t
function;
        jit_value_t
x, x1, y, z, one, zero;
        jit_value_t
temp1, temp2, i, j, i1, j1;
        jit_int
arg1, arg2, arg3;
        jit_label_t
outer = jit_label_undefined;
        jit_label_t
inner = jit_label_undefined;
        void
*args[3];
        jit_int
result;
        FILE
* output;
        jit_int
 data[20] = {17, 2, 3, 4, 5, 6, 7, 8, 9, 10,  /* input*/
         
              0, 0,
0, 0, 0, 0, 0, 0, 0, 0 }; /* output */
        /*
Create a context to hold the JIT's primary state */
        context
= jit_context_create();

        /*
Lock the context while we build and compile the function */
        jit_context_build_start(context);

        /*
Build the function signature */
        params[0]
= jit_type_create_pointer(jit_type_int, 1);
        params[1]
= jit_type_int;
        params[2]
= jit_type_int;
        signature
= jit_type_create_signature
         
      (jit_abi_cdecl, jit_type_int, params, 3, 1);

        /*
Create the function object */
        function
= jit_function_create(context, signature);
        output
= fopen("output.txt", "w");
        /*
Construct the function body */
        x
= jit_value_get_param(function, 0);
        y
= jit_value_get_param(function, 1);
        z
= jit_value_get_param(function, 2);
        i
= jit_value_create(function, jit_type_int);
        j
= jit_value_create(function, jit_type_int);
        zero
= jit_value_create_nint_constant(function, jit_type_int, 0);
        one
 = jit_value_create_nint_constant(function, jit_type_int, 1);
        x1
= jit_insn_add(function, x, y);         //
x1 = index into output part of data
        i1
= jit_insn_dup(function, z);          
  // init value for outer loop counter
        jit_insn_label(function,
&outer);
        j
= jit_insn_dup(function, y);          
      // reset inner loop counter
        
        jit_insn_label(function,
&inner);
        j1
= jit_insn_dup(function, j);          
        
        //
decrement inner loop counter - but doesn't generate what I expected it
to :(
        j
= jit_insn_sub(function, j1, one);  
        temp2
= jit_insn_load_elem(function, x, j, jit_type_int); // get the input element
        temp1
= jit_insn_load_elem(function, x1, j, jit_type_int); // and the output
element
        
        temp1
= jit_insn_add(function, temp1, temp2); // add them together
        jit_insn_store_elem(function,
x1, j, temp1); // and store in output
   
        jit_insn_branch_if(function,
j, &inner);  // if j != 0 continue inner loop
        i1
= jit_insn_dup(function, i);
        //
decrement i (still no luck)
        i
= jit_insn_sub(function, i1, one);
        jit_insn_branch_if(function,
i, &outer);  // if i + 0 continue outer loop

        jit_insn_return(function,
zero);
        jit_dump_function(output,
function, "before_compile");
        /*
Compile the function */
        jit_function_compile(function);

        /*
Unlock the context */
        jit_context_build_end(context);

        jit_dump_function(output,
function, "after_compile");
        /*
Execute the function and print the result */
        fclose(output);
        arg1
= 3;
        arg2
= 10;
        arg3
= 1000;
        args[0]
= &data;
        args[1]
= &arg2;
        args[2]
= &arg3;
        jit_function_apply(function,
args, &result);
   
        /*
Clean up */
        jit_context_destroy(context);

crashes inside  jit_function_apply
and the two dumps generate following output:

function before_compile(i1 : ptr, i2
: int, i3 : int) : int
        incoming_frame_posn(i1,
8)
        incoming_frame_posn(i2,
12)
        incoming_frame_posn(i3,
16)
        i11
= i1 + i2
        i12
= i3
.L0:
        i13
= i2
.L1:
        i14
= i13
        i15
= i14 - 1
        i16
= load_element_int(i1, i15)
        i17
= load_element_int(i11, i15)
        i18
= i17 + i16
        store_element_int(i11,
i15, i18)
        if
itrue(i15) then goto .L1
.L2:
        i19
= i7
        i20
= i19 - 1
        if
itrue(i20) then goto .L0
.L3:
        return_int(0)
        ends_in_dead
end

function after_compile(ptr, int, int)
: int
end

First problem - function after compile
appears to be empty !?
second problem - my loop counters don't
really get decremented

Can anybody give me an insight into
what I'm doing wrong? 
TIA

Jack