/* Look for simple identities that make the entire result constant:
* 0*&x, -1|x, etc.
*/
static int
expr_is_constant(yasm_expr_op op, yasm_intnum *intn)
{
int iszero = yasm_intnum_is_zero(intn);
return ((iszero && op == YASM_EXPR_MUL) ||
(iszero && op == YASM_EXPR_AND) ||
(iszero && op == YASM_EXPR_LAND) ||
(yasm_intnum_is_neg1(intn) && op == YASM_EXPR_OR));
}
/* Look for simple "left" identities like 0+x, 1*x, etc. */
static int
expr_can_destroy_int_left(yasm_expr_op op, yasm_intnum *intn)
{
int iszero = yasm_intnum_is_zero(intn);
return ((yasm_intnum_is_pos1(intn) && op == YASM_EXPR_MUL) ||
(iszero && op == YASM_EXPR_ADD) ||
(yasm_intnum_is_neg1(intn) && op == YASM_EXPR_AND) ||
(!iszero && op == YASM_EXPR_LAND) ||
(iszero && op == YASM_EXPR_OR) ||
(iszero && op == YASM_EXPR_LOR));
}
/* Look for simple "right" identities like x+|-0, x*&/1 */
static int
expr_can_destroy_int_right(yasm_expr_op op, yasm_intnum *intn)
{
int iszero = yasm_intnum_is_zero(intn);
int ispos1 = yasm_intnum_is_pos1(intn);
return ((ispos1 && op == YASM_EXPR_MUL) ||
(ispos1 && op == YASM_EXPR_DIV) ||
(iszero && op == YASM_EXPR_ADD) ||
(iszero && op == YASM_EXPR_SUB) ||
(yasm_intnum_is_neg1(intn) && op == YASM_EXPR_AND) ||
(!iszero && op == YASM_EXPR_LAND) ||
(iszero && op == YASM_EXPR_OR) ||
(iszero && op == YASM_EXPR_LOR) ||
(iszero && op == YASM_EXPR_SHL) ||
(iszero && op == YASM_EXPR_SHR));
}
static int
value_finalize_scan(yasm_value *value, yasm_expr *e,
/*@null@*/ yasm_bytecode *expr_precbc, int ssym_not_ok)
{
int i;
/*@dependent@*/ yasm_section *sect;
/*@dependent@*/ /*@null@*/ yasm_bytecode *precbc;
unsigned long shamt; /* for SHR */
/* Yes, this has a maximum upper bound on 32 terms, based on an
* "insane number of terms" (and ease of implementation) WAG.
* The right way to do this would be a stack-based alloca, but that's
* not ISO C. We really don't want to malloc here as this function is
* hit a lot!
*
* This is a bitmask to keep things small, as this is a recursive
* routine and we don't want to eat up stack space.
*/
unsigned long used; /* for ADD */
/* Thanks to this running after a simplify, we don't need to iterate
* down through IDENTs or handle SUB.
*
* We scan for a single symrec, gathering info along the way. After
* we've found the symrec, we keep scanning but error if we find
* another one. We pull out the single symrec and any legal operations
* performed on it.
*
* Also, if we find a float anywhere, we don't allow mixing of a single
* symrec with it.
*/
switch (e->op) {
case YASM_EXPR_ADD:
/* Okay for single symrec anywhere in expr.
* Check for single symrec anywhere.
* Handle symrec-symrec by checking for (-1*symrec)
* and symrec term pairs (where both symrecs are in the same
* segment).
*/
if (e->numterms > 32)
yasm__fatal(N_("expression on line %d has too many add terms;"
" internal limit of 32"), e->line);
used = 0;
for (i=0; i<e->numterms; i++) {
int j;
yasm_expr *sube;
yasm_intnum *intn;
yasm_symrec *sym;
/*@dependent@*/ yasm_section *sect2;
/*@dependent@*/ /*@null@*/ yasm_bytecode *precbc2;
/* First look for an (-1*symrec) term */
if (e->terms[i].type != YASM_EXPR_EXPR)
continue;
sube = e->terms[i].data.expn;
if (sube->op != YASM_EXPR_MUL || sube->numterms != 2) {
/* recurse instead */
if (value_finalize_scan(value, sube, expr_precbc,
ssym_not_ok))
return 1;
continue;
}
if (sube->terms[0].type == YASM_EXPR_INT &&
sube->terms[1].type == YASM_EXPR_SYM) {
intn = sube->terms[0].data.intn;
sym = sube->terms[1].data.sym;
} else if (sube->terms[0].type == YASM_EXPR_SYM &&
sube->terms[1].type == YASM_EXPR_INT) {
sym = sube->terms[0].data.sym;
intn = sube->terms[1].data.intn;
} else {
if (value_finalize_scan(value, sube, expr_precbc,
ssym_not_ok))
return 1;
continue;
}
if (!yasm_intnum_is_neg1(intn)) {
if (value_finalize_scan(value, sube, expr_precbc,
ssym_not_ok))
return 1;
continue;
}
/* Look for the same symrec term; even if both are external,
* they should cancel out.
*/
for (j=0; j<e->numterms; j++) {
if (e->terms[j].type == YASM_EXPR_SYM
&& e->terms[j].data.sym == sym
&& (used & (1<<j)) == 0) {
/* Mark as used */
used |= 1<<j;
/* Replace both symrec portions with 0 */
yasm_expr_destroy(sube);
e->terms[i].type = YASM_EXPR_INT;
e->terms[i].data.intn = yasm_intnum_create_uint(0);
e->terms[j].type = YASM_EXPR_INT;
e->terms[j].data.intn = yasm_intnum_create_uint(0);
break; /* stop looking */
}
}
if (j != e->numterms)
continue;
if (!yasm_symrec_get_label(sym, &precbc)) {
if (value_finalize_scan(value, sube, expr_precbc,
ssym_not_ok))
return 1;
continue;
}
sect2 = yasm_bc_get_section(precbc);
/* Now look for a unused symrec term in the same segment */
for (j=0; j<e->numterms; j++) {
if (e->terms[j].type == YASM_EXPR_SYM
&& yasm_symrec_get_label(e->terms[j].data.sym,
&precbc2)
&& (sect = yasm_bc_get_section(precbc2))
&& sect == sect2
&& (used & (1<<j)) == 0) {
/* Mark as used */
used |= 1<<j;
break; /* stop looking */
}
}
/* We didn't match in the same segment. If the
* -1*symrec is actually -1*curpos, we can match
* unused symrec terms in other segments and generate
* a curpos-relative reloc.
*
* Similarly, handle -1*symrec in other segment via the
* following transformation:
* other-this = (other-.)+(.-this)
* We can only do this transformation if "this" is in
* this expr's segment.
*
* Don't do this if we've already become curpos-relative.
* The unmatched symrec will be caught below.
*/
if (j == e->numterms && !value->curpos_rel
&& (yasm_symrec_is_curpos(sym)
|| (expr_precbc
&& sect2 == yasm_bc_get_section(expr_precbc)))) {
for (j=0; j<e->numterms; j++) {
if (e->terms[j].type == YASM_EXPR_SYM
&& !yasm_symrec_get_equ(e->terms[j].data.sym)
&& !yasm_symrec_is_special(e->terms[j].data.sym)
&& (used & (1<<j)) == 0) {
/* Mark as used */
used |= 1<<j;
/* Mark value as curpos-relative */
if (value->rel || ssym_not_ok)
return 1;
value->rel = e->terms[j].data.sym;
value->curpos_rel = 1;
if (yasm_symrec_is_curpos(sym)) {
/* Replace both symrec portions with 0 */
yasm_expr_destroy(sube);
e->terms[i].type = YASM_EXPR_INT;
e->terms[i].data.intn =
yasm_intnum_create_uint(0);
e->terms[j].type = YASM_EXPR_INT;
e->terms[j].data.intn =
yasm_intnum_create_uint(0);
} else {
/* Replace positive portion with curpos */
yasm_object *object =
yasm_section_get_object(sect2);
yasm_symtab *symtab = object->symtab;
e->terms[j].data.sym =
yasm_symtab_define_curpos
(symtab, ".", expr_precbc, e->line);
}
break; /* stop looking */
}
}
}
if (j == e->numterms)
return 1; /* We didn't find a match! */
}
/* Look for unmatched symrecs. If we've already found one or
* we don't WANT to find one, error out.
*/
for (i=0; i<e->numterms; i++) {
if (e->terms[i].type == YASM_EXPR_SYM
&& (used & (1<<i)) == 0) {
if (value->rel || ssym_not_ok)
return 1;
value->rel = e->terms[i].data.sym;
/* and replace with 0 */
e->terms[i].type = YASM_EXPR_INT;
e->terms[i].data.intn = yasm_intnum_create_uint(0);
}
}
break;
case YASM_EXPR_SHR:
/* Okay for single symrec in LHS and constant on RHS.
* Single symrecs are not okay on RHS.
* If RHS is non-constant, don't allow single symrec on LHS.
* XXX: should rshift be an expr instead??
*/
/* Check for single sym on LHS */
if (e->terms[0].type != YASM_EXPR_SYM)
break;
/* If we already have a sym, we can't take another one */
if (value->rel || ssym_not_ok)
return 1;
/* RHS must be a positive integer */
if (e->terms[1].type != YASM_EXPR_INT)
return 1; /* can't shift sym by non-constant integer */
shamt = yasm_intnum_get_uint(e->terms[1].data.intn);
if ((shamt + value->rshift) > YASM_VALUE_RSHIFT_MAX)
return 1; /* total shift would be too large */
/* Update value */
value->rshift += shamt;
value->rel = e->terms[0].data.sym;
/* Replace symbol with 0 */
e->terms[0].type = YASM_EXPR_INT;
e->terms[0].data.intn = yasm_intnum_create_uint(0);
/* Just leave SHR in place */
break;
case YASM_EXPR_SEG:
/* Okay for single symrec (can only be done once).
* Not okay for anything BUT a single symrec as an immediate
* child.
*/
if (e->terms[0].type != YASM_EXPR_SYM)
return 1;
if (value->seg_of)
return 1; /* multiple SEG not legal */
value->seg_of = 1;
if (value->rel || ssym_not_ok)
return 1; /* got a relative portion somewhere else? */
value->rel = e->terms[0].data.sym;
/* replace with ident'ed 0 */
e->op = YASM_EXPR_IDENT;
e->terms[0].type = YASM_EXPR_INT;
e->terms[0].data.intn = yasm_intnum_create_uint(0);
break;
case YASM_EXPR_WRT:
/* Okay for single symrec in LHS and either a register or single
* symrec (as an immediate child) on RHS.
* If a single symrec on RHS, can only be done once.
* WRT reg is left in expr for arch to look at.
*/
/* Handle RHS */
switch (e->terms[1].type) {
case YASM_EXPR_SYM:
if (value->wrt)
return 1;
value->wrt = e->terms[1].data.sym;
/* and drop the WRT portion */
e->op = YASM_EXPR_IDENT;
e->numterms = 1;
break;
case YASM_EXPR_REG:
break; /* ignore */
default:
return 1;
}
/* Handle LHS */
switch (e->terms[0].type) {
case YASM_EXPR_SYM:
if (value->rel || ssym_not_ok)
return 1;
value->rel = e->terms[0].data.sym;
/* and replace with 0 */
e->terms[0].type = YASM_EXPR_INT;
e->terms[0].data.intn = yasm_intnum_create_uint(0);
break;
case YASM_EXPR_EXPR:
/* recurse */
return value_finalize_scan(value, e->terms[0].data.expn,
expr_precbc, ssym_not_ok);
default:
break; /* ignore */
}
break;
default:
/* Single symrec not allowed anywhere */
for (i=0; i<e->numterms; i++) {
switch (e->terms[i].type) {
case YASM_EXPR_SYM:
return 1;
case YASM_EXPR_EXPR:
/* recurse */
return value_finalize_scan(value,
e->terms[i].data.expn,
expr_precbc, 1);
default:
break;
}
}
break;
}
return 0;
}
/* Transforms instances of symrec-symrec [symrec+(-1*symrec)] into single
* expritems if possible. Uses a simple n^2 algorithm because n is usually
* quite small. Also works for precbc-precbc (or symrec-precbc,
* precbc-symrec).
*/
static /*@only@*/ yasm_expr *
expr_xform_bc_dist_base(/*@returned@*/ /*@only@*/ yasm_expr *e,
/*@null@*/ void *cbd,
int (*callback) (yasm_expr__item *ei,
yasm_bytecode *precbc,
yasm_bytecode *precbc2,
void *cbd))
{
int i;
/*@dependent@*/ yasm_section *sect;
/*@dependent@*/ /*@null@*/ yasm_bytecode *precbc;
int numterms;
/* Handle symrec-symrec in ADD exprs by looking for (-1*symrec) and
* symrec term pairs (where both symrecs are in the same segment).
*/
if (e->op != YASM_EXPR_ADD)
return e;
for (i=0; i<e->numterms; i++) {
int j;
yasm_expr *sube;
yasm_intnum *intn;
yasm_symrec *sym = NULL;
/*@dependent@*/ yasm_section *sect2;
/*@dependent@*/ /*@null@*/ yasm_bytecode *precbc2;
/* First look for an (-1*symrec) term */
if (e->terms[i].type != YASM_EXPR_EXPR)
continue;
sube = e->terms[i].data.expn;
if (sube->op != YASM_EXPR_MUL || sube->numterms != 2)
continue;
if (sube->terms[0].type == YASM_EXPR_INT &&
(sube->terms[1].type == YASM_EXPR_SYM ||
sube->terms[1].type == YASM_EXPR_PRECBC)) {
intn = sube->terms[0].data.intn;
if (sube->terms[1].type == YASM_EXPR_PRECBC)
precbc = sube->terms[1].data.precbc;
else
sym = sube->terms[1].data.sym;
} else if ((sube->terms[0].type == YASM_EXPR_SYM ||
sube->terms[0].type == YASM_EXPR_PRECBC) &&
sube->terms[1].type == YASM_EXPR_INT) {
if (sube->terms[0].type == YASM_EXPR_PRECBC)
precbc = sube->terms[0].data.precbc;
else
sym = sube->terms[0].data.sym;
intn = sube->terms[1].data.intn;
} else
continue;
if (!yasm_intnum_is_neg1(intn))
continue;
if (sym && !yasm_symrec_get_label(sym, &precbc))
continue;
sect2 = yasm_bc_get_section(precbc);
/* Now look for a symrec term in the same segment */
for (j=0; j<e->numterms; j++) {
if (((e->terms[j].type == YASM_EXPR_SYM &&
yasm_symrec_get_label(e->terms[j].data.sym, &precbc2)) ||
(e->terms[j].type == YASM_EXPR_PRECBC &&
(precbc2 = e->terms[j].data.precbc))) &&
(sect = yasm_bc_get_section(precbc2)) &&
sect == sect2 &&
callback(&e->terms[j], precbc, precbc2, cbd)) {
/* Delete the matching (-1*symrec) term */
yasm_expr_destroy(sube);
e->terms[i].type = YASM_EXPR_NONE;
break; /* stop looking for matching symrec term */
}
}
}
/* Clean up any deleted (EXPR_NONE) terms */
numterms = 0;
for (i=0; i<e->numterms; i++) {
if (e->terms[i].type != YASM_EXPR_NONE)
e->terms[numterms++] = e->terms[i]; /* structure copy */
}
if (e->numterms != numterms) {
e->numterms = numterms;
e = yasm_xrealloc(e, sizeof(yasm_expr)+((numterms<2) ? 0 :
sizeof(yasm_expr__item)*(numterms-2)));
if (numterms == 1)
e->op = YASM_EXPR_IDENT;
}
return e;
}
