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#include "all.h"
void
getalias(Alias *a, Ref r, Fn *fn)
{
Con *c;
switch (rtype(r)) {
default:
die("unreachable");
case RTmp:
*a = fn->tmp[r.val].alias;
if (astack(a->type))
a->type = a->slot->type;
assert(a->type != ABot);
break;
case RCon:
c = &fn->con[r.val];
if (c->type == CAddr) {
a->type = ASym;
a->u.sym = c->sym;
} else
a->type = ACon;
a->offset = c->bits.i;
a->slot = 0;
break;
}
}
int
alias(Ref p, int op, int sp, Ref q, int sq, int *delta, Fn *fn)
{
Alias ap, aq;
int ovlap;
getalias(&ap, p, fn);
getalias(&aq, q, fn);
ap.offset += op;
/* when delta is meaningful (ovlap == 1),
* we do not overflow int because sp and
* sq are bounded by 2^28 */
*delta = ap.offset - aq.offset;
ovlap = ap.offset < aq.offset + sq && aq.offset < ap.offset + sp;
if (astack(ap.type) && astack(aq.type)) {
/* if both are offsets of the same
* stack slot, they alias iif they
* overlap */
if (ap.base == aq.base && ovlap)
return MustAlias;
return NoAlias;
}
if (ap.type == ASym && aq.type == ASym) {
/* they conservatively alias if the
* symbols are different, or they
* alias for sure if they overlap */
if (!symeq(ap.u.sym, aq.u.sym))
return MayAlias;
if (ovlap)
return MustAlias;
return NoAlias;
}
if ((ap.type == ACon && aq.type == ACon)
|| (ap.type == aq.type && ap.base == aq.base)) {
assert(ap.type == ACon || ap.type == AUnk);
/* if they have the same base, we
* can rely on the offsets only */
if (ovlap)
return MustAlias;
return NoAlias;
}
/* if one of the two is unknown
* there may be aliasing unless
* the other is provably local */
if (ap.type == AUnk && aq.type != ALoc)
return MayAlias;
if (aq.type == AUnk && ap.type != ALoc)
return MayAlias;
return NoAlias;
}
int
escapes(Ref r, Fn *fn)
{
Alias *a;
if (rtype(r) != RTmp)
return 1;
a = &fn->tmp[r.val].alias;
return !astack(a->type) || a->slot->type == AEsc;
}
static void
esc(Ref r, Fn *fn)
{
Alias *a;
assert(rtype(r) <= RType);
if (rtype(r) == RTmp) {
a = &fn->tmp[r.val].alias;
if (astack(a->type))
a->slot->type = AEsc;
}
}
static void
store(Ref r, int sz, Fn *fn)
{
Alias *a;
int64_t off;
bits m;
if (rtype(r) == RTmp) {
a = &fn->tmp[r.val].alias;
if (a->slot) {
assert(astack(a->type));
off = a->offset;
if (sz >= NBit
|| (off < 0 || off >= NBit))
m = -1;
else
m = (BIT(sz) - 1) << off;
a->slot->u.loc.m |= m;
}
}
}
void
fillalias(Fn *fn)
{
uint n, m;
int t, sz;
int64_t x;
Blk *b;
Phi *p;
Ins *i;
Con *c;
Alias *a, a0, a1;
for (t=0; t<fn->ntmp; t++)
fn->tmp[t].alias.type = ABot;
for (n=0; n<fn->nblk; ++n) {
b = fn->rpo[n];
for (p=b->phi; p; p=p->link) {
for (m=0; m<p->narg; m++)
esc(p->arg[m], fn);
assert(rtype(p->to) == RTmp);
a = &fn->tmp[p->to.val].alias;
assert(a->type == ABot);
a->type = AUnk;
a->base = p->to.val;
a->offset = 0;
a->slot = 0;
}
for (i=b->ins; i<&b->ins[b->nins]; ++i) {
a = 0;
if (!req(i->to, R)) {
assert(rtype(i->to) == RTmp);
a = &fn->tmp[i->to.val].alias;
assert(a->type == ABot);
if (Oalloc <= i->op && i->op <= Oalloc1) {
a->type = ALoc;
a->slot = a;
a->u.loc.sz = -1;
if (rtype(i->arg[0]) == RCon) {
c = &fn->con[i->arg[0].val];
x = c->bits.i;
if (c->type == CBits)
if (0 <= x && x <= NBit)
a->u.loc.sz = x;
}
} else {
a->type = AUnk;
a->slot = 0;
}
a->base = i->to.val;
a->offset = 0;
}
if (i->op == Ocopy) {
assert(a);
getalias(a, i->arg[0], fn);
}
if (i->op == Oadd) {
getalias(&a0, i->arg[0], fn);
getalias(&a1, i->arg[1], fn);
if (a0.type == ACon) {
*a = a1;
a->offset += a0.offset;
}
else if (a1.type == ACon) {
*a = a0;
a->offset += a1.offset;
}
}
if (req(i->to, R) || a->type == AUnk)
if (i->op != Oblit0) {
if (!isload(i->op))
esc(i->arg[0], fn);
if (!isstore(i->op))
if (i->op != Oargc)
esc(i->arg[1], fn);
}
if (i->op == Oblit0) {
++i;
assert(i->op == Oblit1);
assert(rtype(i->arg[0]) == RInt);
sz = abs(rsval(i->arg[0]));
store((i-1)->arg[1], sz, fn);
}
if (isstore(i->op))
store(i->arg[1], storesz(i), fn);
}
if (b->jmp.type != Jretc)
esc(b->jmp.arg, fn);
}
}
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