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#include "all.h"
enum {
MaxIns = 2,
MaxPhis = 2,
};
static int
okbranch(Blk *b)
{
Ins *i;
int n;
n = 0;
for (i=b->ins; i<&b->ins[b->nins]; i++)
if (i->op != Odbgloc) {
if (pinned(i))
return 0;
if (i->op != Onop)
n++;
}
return n <= MaxIns;
}
static int
okjoin(Blk *b)
{
Phi *p;
int n;
n = 0;
for (p=b->phi; p; p=p->link) {
if (KBASE(p->cls) != 0)
return 0;
n++;
}
return n <= MaxPhis;
}
static int
okgraph(Blk *ifb, Blk *thenb, Blk *elseb, Blk *joinb)
{
if (joinb->npred != 2 || !okjoin(joinb))
return 0;
assert(thenb != elseb);
if (thenb != ifb && !okbranch(thenb))
return 0;
if (elseb != ifb && !okbranch(elseb))
return 0;
return 1;
}
static void
convert(Blk *ifb, Blk *thenb, Blk *elseb, Blk *joinb)
{
Ins *ins, sel;
Phi *p;
uint nins;
ins = vnew(0, sizeof ins[0], PHeap);
nins = 0;
addbins(&ins, &nins, ifb);
if (thenb != ifb)
addbins(&ins, &nins, thenb);
if (elseb != ifb)
addbins(&ins, &nins, elseb);
assert(joinb->npred == 2);
if (joinb->phi) {
sel = (Ins){
.op = Osel0, .cls = Kw,
.arg = {ifb->jmp.arg},
};
addins(&ins, &nins, &sel);
}
sel = (Ins){.op = Osel1};
for (p=joinb->phi; p; p=p->link) {
sel.to = p->to;
sel.cls = p->cls;
sel.arg[0] = phiarg(p, thenb);
sel.arg[1] = phiarg(p, elseb);
addins(&ins, &nins, &sel);
}
idup(ifb, ins, nins);
ifb->jmp.type = Jjmp;
ifb->jmp.arg = R;
ifb->s1 = joinb;
ifb->s2 = 0;
joinb->npred = 1;
joinb->pred[0] = ifb;
joinb->phi = 0;
vfree(ins);
}
/* eliminate if-then[-else] graphlets
* using sel instructions
* needs rpo pred use; breaks cfg use
*/
void
ifconvert(Fn *fn)
{
Blk *ifb, *thenb, *elseb, *joinb;
if (debug['K'])
fputs("\n> If-conversion:\n", stderr);
for (ifb=fn->start; ifb; ifb=ifb->link)
if (ifgraph(ifb, &thenb, &elseb, &joinb))
if (okgraph(ifb, thenb, elseb, joinb)) {
if (debug['K'])
fprintf(stderr,
" @%s -> @%s, @%s -> @%s\n",
ifb->name, thenb->name, elseb->name,
joinb->name);
convert(ifb, thenb, elseb, joinb);
}
if (debug['K']) {
fprintf(stderr, "\n> After if-conversion:\n");
printfn(fn, stderr);
}
}
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