---

1.4.3 Setting things up ¶

First we create our types:

  state.int_type =
    gcc_jit_context_get_type (state.ctxt, GCC_JIT_TYPE_INT);
  state.bool_type =
    gcc_jit_context_get_type (state.ctxt, GCC_JIT_TYPE_BOOL);
  state.stack_type =
    gcc_jit_context_new_array_type (state.ctxt, NULL,
				    state.int_type, MAX_STACK_DEPTH);

along with extracting a useful int constant:

  state.const_one = gcc_jit_context_one (state.ctxt, state.int_type);

We’ll implement push and pop in terms of the stack array and stack_depth. Here are helper functions for adding statements to a block, implementing pushing and popping values:

static void
add_push (compilation_state *state,
	  gcc_jit_block *block,
	  gcc_jit_rvalue *rvalue,
	  gcc_jit_location *loc)
{
  /* stack[stack_depth] = RVALUE */
  gcc_jit_block_add_assignment (
    block,
    loc,
    /* stack[stack_depth] */
    gcc_jit_context_new_array_access (
      state->ctxt,
      loc,
      gcc_jit_lvalue_as_rvalue (state->stack),
      gcc_jit_lvalue_as_rvalue (state->stack_depth)),
    rvalue);

  /* "stack_depth++;".  */
  gcc_jit_block_add_assignment_op (
    block,
    loc,
    state->stack_depth,
    GCC_JIT_BINARY_OP_PLUS,
    state->const_one);
}

static void
add_pop (compilation_state *state,
	 gcc_jit_block *block,
	 gcc_jit_lvalue *lvalue,
	 gcc_jit_location *loc)
{
  /* "--stack_depth;".  */
  gcc_jit_block_add_assignment_op (
    block,
    loc,
    state->stack_depth,
    GCC_JIT_BINARY_OP_MINUS,
    state->const_one);

  /* "LVALUE = stack[stack_depth];".  */
  gcc_jit_block_add_assignment (
    block,
    loc,
    lvalue,
    /* stack[stack_depth] */
    gcc_jit_lvalue_as_rvalue (
      gcc_jit_context_new_array_access (
	state->ctxt,
	loc,
	gcc_jit_lvalue_as_rvalue (state->stack),
	gcc_jit_lvalue_as_rvalue (state->stack_depth))));
}

We will support single-stepping through the generated code in the debugger, so we need to create gcc_jit_location instances, one per operation in the source code. These will reference the lines of e.g. factorial.toy.

  for (pc = 0; pc < fn->fn_num_ops; pc++)
    {
      toyvm_op *op = &fn->fn_ops[pc];

      state.op_locs[pc] = gcc_jit_context_new_location (state.ctxt,
							fn->fn_filename,
							op->op_linenum,
							0); /* column */
    }

Let’s create the function itself. As usual, we create its parameter first, then use the parameter to create the function:

  state.param_arg =
    gcc_jit_context_new_param (state.ctxt, state.op_locs[0],
			       state.int_type, "arg");
  state.fn =
    gcc_jit_context_new_function (state.ctxt,
				  state.op_locs[0],
				  GCC_JIT_FUNCTION_EXPORTED,
				  state.int_type,
				  funcname,
				  1, &state.param_arg, 0);

We create the locals within the function.

  state.stack =
    gcc_jit_function_new_local (state.fn, NULL,
				state.stack_type, "stack");
  state.stack_depth =
    gcc_jit_function_new_local (state.fn, NULL,
				state.int_type, "stack_depth");
  state.x =
    gcc_jit_function_new_local (state.fn, NULL,
				state.int_type, "x");
  state.y =
    gcc_jit_function_new_local (state.fn, NULL,
				state.int_type, "y");