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#include "all.h"
static void
getalias(Alias *a, Ref r, Fn *fn)
{
Con *c;
switch (rtype(r)) {
default:
die("unreachable");
case RTmp:
*a = fn->tmp[r.val].alias;
assert(a->type != ABot);
break;
case RCon:
c = &fn->con[r.val];
if (c->type == CAddr) {
a->type = ASym;
strcpy(a->label, c->label);
} else
a->type = ACon;
a->offset = c->bits.i;
break;
}
}
int
alias(Ref p, int sp, Ref q, int sq, int *delta, Fn *fn)
{
Alias ap, aq;
int ovlap;
getalias(&ap, p, fn);
getalias(&aq, q, fn);
*delta = ap.offset - aq.offset;
ovlap = ap.offset < aq.offset + sq && aq.offset < ap.offset + sp;
if (ap.type & aq.type & 1) {
/* if both are offsets of the same
* stack slot, they alias iif they
* overlap */
if (req(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 (strcmp(ap.label, aq.label) != 0)
return MayAlias;
if (ovlap)
return MustAlias;
return NoAlias;
}
if ((ap.type == ACon && aq.type == ACon)
|| (ap.type == aq.type && req(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)
{
if (rtype(r) != RTmp)
return 1;
return fn->tmp[r.val].alias.type != ALoc;
}
static void
esc(Ref r, Fn *fn)
{
Alias *a;
assert(rtype(r) <= RType);
if (rtype(r) == RTmp) {
a = &fn->tmp[r.val].alias;
assert(a->type != ABot);
if (a->type == ALoc)
a->type = AEsc;
}
}
void
fillalias(Fn *fn)
{
uint n;
Blk *b;
Phi *p;
Ins *i;
Alias *a, a0, a1;
for (n=0; n<fn->nblk; ++n) {
b = fn->rpo[n];
for (p=b->phi; p; p=p->link) {
assert(rtype(p->to) == RTmp);
a = &fn->tmp[p->to.val].alias;
assert(a->type == ABot);
a->type = AUnk;
a->base = p->to;
a->offset = 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;
else
a->type = AUnk;
a->base = i->to;
a->offset = 0;
}
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 (!isload(i->op))
esc(i->arg[0], fn);
if (!isstore(i->op))
esc(i->arg[1], fn);
}
}
esc(b->jmp.arg, fn);
}
}
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