mem.c

См. документацию.

#include "all.h"

/* require use, maintains use counts */
void
memopt(Fn *fn)
{
    Blk *b;
    Ins *i, *l;
    Tmp *t;
    Use *u, *ue;
    int s, k;

    /* promote uniform stack slots to temporaries */
    b = fn->start;
    for (i=b->ins; i-b->ins < b->nins; i++) {
        if (Oalloc > i->op || i->op > Oalloc1)
            continue;
        /* specific to NAlign == 3 */
        assert(rtype(i->to) == RTmp);
        t = &fn->tmp[i->to.val];
        if (t->ndef != 1)
            goto Skip;
        k = -1;
        s = -1;
        for (u=t->use; u != &t->use[t->nuse]; u++) {
            if (u->type != UIns)
                goto Skip;
            l = u->u.ins;
            if (isload(l->op))
            if (s == -1 || s == loadsz(l)) {
                s = loadsz(l);
                continue;
            }
            if (isstore(l->op))
            if (req(i->to, l->arg[1]) && !req(i->to, l->arg[0]))
            if (s == -1 || s == storesz(l))
            if (k == -1 || k == optab[l->op].argcls[0][0]) {
                s = storesz(l);
                k = optab[l->op].argcls[0][0];
                continue;
            }
            goto Skip;
        }
        /* get rid of the alloc and replace uses */
        *i = (Ins){.op = Onop};
        t->ndef--;
        ue = &t->use[t->nuse];
        for (u=t->use; u!=ue; u++) {
            l = u->u.ins;
            if (isstore(l->op)) {
                l->cls = k;
                l->op = Ocopy;
                l->to = l->arg[1];
                l->arg[1] = R;
                t->nuse--;
                t->ndef++;
            } else {
                if (k == -1)
                    err("slot %%%s is read but never stored to",
                        fn->tmp[l->arg[0].val].name);
                /* try to turn loads into copies so we
                 * can eliminate them later */
                switch(l->op) {
                case Oloadsw:
                case Oloaduw:
                    if (k == Kl)
                        goto Extend;
                case Oload:
                    if (KBASE(k) != KBASE(l->cls))
                        l->op = Ocast;
                    else
                        l->op = Ocopy;
                    break;
                default:
                Extend:
                    l->op = Oextsb + (l->op - Oloadsb);
                    break;
                }
            }
        }
    Skip:;
    }
    if (debug['M']) {
        fprintf(stderr, "\n> After memory optimization:\n");
        printfn(fn, stderr);
    }
}