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do not account for interferences in phi classes

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Before this commit, I tried to make sure that
two interfering temporaries never ended up in
the same phi class.

This was to make sure that their register hints
were not counterproductively stepping on each
other's toes.  The idea is fine, but:

  * the implementation is clumsy because it
    mixes the orthogonal concepts of
    (i) interference and (ii) phi classes;

  * the hinting process in the register
    allocator is hard to understand because
    the disjoint-set data structure used for
    phi classes is cut in arbitrary places.

After this commit, the phi classes *really* are
phi classes represented with a proper disjoint-set
data structure.
This commit is contained in:
Quentin Carbonneaux 2017-05-16 11:33:41 -04:00
parent 51c46ba691
commit 425a2ed09c
3 changed files with 19 additions and 66 deletions
Download patch file Download diff file Expand all files Collapse all files

17
ssa.c
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@ -40,7 +40,7 @@ filluse(Fn *fn)
Blk *b;
Phi *p;
Ins *i;
int m, t, w;
int m, t, tp, w;
uint a;
Tmp *tmp;
@ -49,8 +49,8 @@ filluse(Fn *fn)
for (t=Tmp0; t<fn->ntmp; t++) {
tmp[t].ndef = 0;
tmp[t].nuse = 0;
tmp[t].phi = 0;
tmp[t].cls = 0;
tmp[t].phi = 0;
tmp[t].width = WFull;
if (tmp[t].use == 0)
tmp[t].use = vnew(0, sizeof(Use), Pfn);
@ -58,16 +58,17 @@ filluse(Fn *fn)
for (b=fn->start; b; b=b->link) {
for (p=b->phi; p; p=p->link) {
assert(rtype(p->to) == RTmp);
t = p->to.val;
tmp[t].ndef++;
tmp[t].cls = p->cls;
tmp[t].phi = p->to.val;
tp = p->to.val;
tmp[tp].ndef++;
tmp[tp].cls = p->cls;
tp = phicls(tp, fn->tmp);
for (a=0; a<p->narg; a++)
if (rtype(p->arg[a]) == RTmp) {
t = p->arg[a].val;
adduse(&tmp[t], UPhi, b, p);
if (!tmp[t].phi)
tmp[t].phi = p->to.val;
t = phicls(t, fn->tmp);
if (t != tp)
tmp[t].phi = tp;
}
}
for (i=b->ins; i-b->ins < b->nins; i++) {