int expr_is_constant(struct expr *e){
if(!e) return 1; //null is a constant expression
if(expr_is_constant(e->left) == 0) return 0;
if(expr_is_constant(e->right) == 0) return 0;
if(e->kind == EXPR_IDENT) return 0;
else return 1;
}
int expr_is_constant(struct expr *e)
{
if (!e)
return 1;
if (e->kind == EXPR_VARIABLE
|| e->kind == EXPR_INCR
|| e->kind == EXPR_DECR
|| e->kind == EXPR_FUNCTION_CALL)
return 0;
return (expr_is_constant(e->left) && expr_is_constant(e->right));
}
/* Check for and simplify identities. Returns new number of expr terms.
* Sets e->op = EXPR_IDENT if numterms ends up being 1.
* Uses numterms parameter instead of e->numterms for basis of "new" number
* of terms.
* Assumes int_term is *only* integer term in e.
* NOTE: Really designed to only be used by expr_level_op().
*/
static int
expr_simplify_identity(yasm_expr *e, int numterms, int *int_term,
int simplify_reg_mul)
{
int i;
int save_numterms;
/* Don't do this step if it's 1*REG. Save and restore numterms so
* yasm_expr__contains() works correctly.
*/
save_numterms = e->numterms;
e->numterms = numterms;
if (simplify_reg_mul || e->op != YASM_EXPR_MUL
|| !yasm_intnum_is_pos1(e->terms[*int_term].data.intn)
|| !yasm_expr__contains(e, YASM_EXPR_REG)) {
/* Check for simple identities that delete the intnum.
* Don't delete if the intnum is the only thing in the expn.
*/
if ((*int_term == 0 && numterms > 1 &&
expr_can_destroy_int_left(e->op, e->terms[0].data.intn)) ||
(*int_term > 0 &&
expr_can_destroy_int_right(e->op,
e->terms[*int_term].data.intn))) {
/* Delete the intnum */
yasm_intnum_destroy(e->terms[*int_term].data.intn);
/* Slide everything to its right over by 1 */
if (*int_term != numterms-1) /* if it wasn't last.. */
memmove(&e->terms[*int_term], &e->terms[*int_term+1],
(numterms-1-*int_term)*sizeof(yasm_expr__item));
/* Update numterms */
numterms--;
*int_term = -1; /* no longer an int term */
}
}
e->numterms = save_numterms;
/* Check for simple identites that delete everything BUT the intnum.
* Don't bother if the intnum is the only thing in the expn.
*/
if (numterms > 1 && *int_term != -1 &&
expr_is_constant(e->op, e->terms[*int_term].data.intn)) {
/* Loop through, deleting everything but the integer term */
for (i=0; i<e->numterms; i++)
if (i != *int_term)
expr_delete_term(&e->terms[i], 1);
/* Move integer term to the first term (if not already there) */
if (*int_term != 0)
e->terms[0] = e->terms[*int_term]; /* structure copy */
/* Set numterms to 1 */
numterms = 1;
}
/* Compute NOT, NEG, and LNOT on single intnum. */
if (numterms == 1 && *int_term == 0 &&
(e->op == YASM_EXPR_NOT || e->op == YASM_EXPR_NEG ||
e->op == YASM_EXPR_LNOT))
yasm_intnum_calc(e->terms[0].data.intn, e->op, NULL);
/* Change expression to IDENT if possible. */
if (numterms == 1)
e->op = YASM_EXPR_IDENT;
/* Return the updated numterms */
return numterms;
}
