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#include "all.h"
static int
iscon(Ref r, int64_t bits, Fn *fn)
{
return rtype(r) == RCon
&& fn->con[r.val].type == CBits
&& fn->con[r.val].bits.i == bits;
}
static int
iscopy(Ins *i, Ref r, Fn *fn)
{
static bits extcpy[] = {
[WFull] = 0,
[Wsb] = BIT(Wsb) | BIT(Wsh) | BIT(Wsw),
[Wub] = BIT(Wub) | BIT(Wuh) | BIT(Wuw),
[Wsh] = BIT(Wsh) | BIT(Wsw),
[Wuh] = BIT(Wuh) | BIT(Wuw),
[Wsw] = BIT(Wsw),
[Wuw] = BIT(Wuw),
};
bits b;
Tmp *t;
switch (i->op) {
case Ocopy:
return 1;
case Omul:
case Odiv:
case Oudiv:
return iscon(i->arg[1], 1, fn);
case Oadd:
case Osub:
case Oor:
case Oxor:
case Osar:
case Oshl:
case Oshr:
return iscon(i->arg[1], 0, fn);
default:
break;
}
if (!isext(i->op) || rtype(r) != RTmp)
return 0;
if (i->op == Oextsw || i->op == Oextuw)
if (i->cls == Kw)
return 1;
t = &fn->tmp[r.val];
assert(KBASE(t->cls) == 0);
if (i->cls == Kl && t->cls == Kw)
return 0;
b = extcpy[t->width];
return (BIT(Wsb + (i->op-Oextsb)) & b) != 0;
}
static Ref
copyof(Ref r, Ref *cpy)
{
if (rtype(r) == RTmp && !req(cpy[r.val], R))
return cpy[r.val];
return r;
}
/* detects a cluster of phis/copies redundant with 'r';
* the algorithm is inspired by Section 3.2 of "Simple
* and Efficient SSA Construction" by Braun M. et al.
*/
static void
phisimpl(Phi *p, Ref r, Ref *cpy, Use ***pstk, BSet *ts, BSet *as, Fn *fn)
{
Use **stk, *u, *u1;
uint nstk, a;
int t;
Ref r1;
Phi *p0;
bszero(ts);
bszero(as);
p0 = &(Phi){.narg = 0};
stk = *pstk;
nstk = 1;
stk[0] = &(Use){.type = UPhi, .u.phi = p};
while (nstk) {
u = stk[--nstk];
if (u->type == UIns && iscopy(u->u.ins, r, fn)) {
p = p0;
t = u->u.ins->to.val;
}
else if (u->type == UPhi) {
p = u->u.phi;
t = p->to.val;
}
else
continue;
if (bshas(ts, t))
continue;
bsset(ts, t);
for (a=0; a<p->narg; a++) {
r1 = copyof(p->arg[a], cpy);
if (req(r1, r))
continue;
if (rtype(r1) != RTmp)
return;
bsset(as, r1.val);
}
u = fn->tmp[t].use;
u1 = &u[fn->tmp[t].nuse];
vgrow(pstk, nstk+(u1-u));
stk = *pstk;
for (; u<u1; u++)
stk[nstk++] = u;
}
bsdiff(as, ts);
if (!bscount(as))
for (t=0; bsiter(ts, &t); t++)
cpy[t] = r;
}
static void
subst(Ref *pr, Ref *cpy)
{
assert(rtype(*pr) != RTmp || !req(cpy[pr->val], R));
*pr = copyof(*pr, cpy);
}
/* requires use and rpo, breaks use */
void
copy(Fn *fn)
{
BSet ts[1], as[1];
Use **stk;
Phi *p, **pp;
Ins *i;
Blk *b;
uint n, a;
Ref *cpy, r;
int t;
bsinit(ts, fn->ntmp);
bsinit(as, fn->ntmp);
cpy = emalloc(fn->ntmp * sizeof cpy[0]);
stk = vnew(10, sizeof stk[0], PHeap);
/* 1. build the copy-of map */
for (n=0; n<fn->nblk; n++) {
b = fn->rpo[n];
for (p=b->phi; p; p=p->link) {
assert(rtype(p->to) == RTmp);
if (!req(cpy[p->to.val], R))
continue;
r = R;
for (a=0; a<p->narg; a++)
if (p->blk[a]->id < n)
r = copyof(p->arg[a], cpy);
assert(!req(r, R));
cpy[p->to.val] = p->to;
phisimpl(p, r, cpy, &stk, ts, as, fn);
}
for (i=b->ins; i<&b->ins[b->nins]; i++) {
assert(rtype(i->to) <= RTmp);
if (!req(cpy[i->to.val], R))
continue;
r = copyof(i->arg[0], cpy);
if (iscopy(i, r, fn))
cpy[i->to.val] = r;
else
cpy[i->to.val] = i->to;
}
}
/* 2. remove redundant phis/copies
* and rewrite their uses */
for (b=fn->start; b; b=b->link) {
for (pp=&b->phi; (p=*pp);) {
r = cpy[p->to.val];
if (!req(r, p->to)) {
*pp = p->link;
continue;
}
for (a=0; a<p->narg; a++)
subst(&p->arg[a], cpy);
pp=&p->link;
}
for (i=b->ins; i<&b->ins[b->nins]; i++) {
r = cpy[i->to.val];
if (!req(r, i->to)) {
*i = (Ins){.op = Onop};
continue;
}
subst(&i->arg[0], cpy);
subst(&i->arg[1], cpy);
}
subst(&b->jmp.arg, cpy);
}
if (debug['C']) {
fprintf(stderr, "\n> Copy information:");
for (t=Tmp0; t<fn->ntmp; t++) {
if (req(cpy[t], R)) {
fprintf(stderr, "\n%10s not seen!",
fn->tmp[t].name);
}
else if (!req(cpy[t], TMP(t))) {
fprintf(stderr, "\n%10s copy of ",
fn->tmp[t].name);
printref(cpy[t], fn, stderr);
}
}
fprintf(stderr, "\n\n> After copy elimination:\n");
printfn(fn, stderr);
}
vfree(stk);
free(cpy);
}
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