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#include "ir.h"
static int
mulk(struct instr *ins, struct block *blk, int *curi)
{
vlong iv = intconval(ins->r);
enum irclass cls = ins->cls;
assert(iv > 1 && "trivial mul not handled by irbinop() ?");
/* This can be generalized to any sequence of shifts and
* adds/subtracts, but whether that's worth it depends on the number of them
* and the microarchitecture.. clang seems to stop after two shifts. Should
* we compute approximate cost of instrs to determine? For now just handle
* the po2 (+/- 1) case */
if (ispo2(iv)) {
/* x * 2^y ==> x << y */
ins->op = Oshl;
ins->r = mkref(RICON, ilog2(iv));
return 1;
} else if (ispo2(iv-1)) {
/* x * 5 ==> (x << 2) + x */
ins->op = Oadd;
ins->r = ins->l;
ins->l = insertinstr(blk, (*curi)++, mkinstr(Oshl, cls, ins->l, mkref(RICON, ilog2(iv-1))));
return 1;
} else if (ispo2(iv+1)) {
/* x * 7 ==> (x << 3) - x */
ins->op = Osub;
ins->r = ins->l;
ins->l = insertinstr(blk, (*curi)++, mkinstr(Oshl, cls, ins->l, mkref(RICON, ilog2(iv+1))));
return 1;
}
return 0;
}
static int
divmodk(struct instr *ins, struct block *blk, int *curi)
{
enum op op = ins->op;
enum irclass cls = ins->cls;
vlong iv = intconval(ins->r);
uint nbit = 8 * cls2siz[cls];
bool neg = (op == Odiv || op == Orem) && iv < 0;
if (ispo2(iv) || (neg && ispo2(-iv))) { /* simple po2 cases */
union ref temp;
uint s = ilog2(neg ? -iv : iv);
switch (op) {
default: assert(0);
case Oudiv: /* x / 2^s ==> x >> s */
ins->op = Oslr, ins->r = mkref(RICON, s);
return 1;
case Ourem: /* x % 2^s ==> x & 2^s-1 */
ins->op = Oand, ins->r = mkintcon(cls, iv - 1);
return 1;
case Odiv: case Orem:
/* have to adjust to round negatives toward zero */
/* x' = (((x < 0 ? -1 : 0) >>> (Nbit - s)) + x) */
temp = insertinstr(blk, (*curi)++, mkinstr(Osar, cls, ins->l, mkref(RICON, nbit - 1)));
temp = insertinstr(blk, (*curi)++, mkinstr(Oslr, cls, temp, mkref(RICON, nbit - s)));
temp = insertinstr(blk, (*curi)++, mkinstr(Oadd, cls, ins->l, temp));
if (op == Odiv) {
/* (-) (x' >> s) */
struct instr sar = mkinstr(Osar, cls, temp, mkref(RICON, s));
if (!neg) *ins = sar;
else {
temp = insertinstr(blk, (*curi)++, sar);
ins->op = Oneg, ins->l = temp, ins->r = NOREF;
}
} else {
/* x - (x' & -(2^s)) */
temp = insertinstr(blk, (*curi)++, mkinstr(Oand, cls, temp, mkintcon(cls, neg ? iv : -iv)));
ins->op = Osub, ins->r = temp;
}
break;
return 0;
}
}
return 0;
}
static int
ins(struct instr *ins, struct block *blk, int *curi)
{
int narg = opnarg[ins->op];
if (oisarith(ins->op)) {
union ref r = narg == 1 ? irunop(NULL, ins->op, ins->cls, ins->l)
: irbinop(NULL, ins->op, ins->cls, ins->l, ins->r);
if (r.bits) {
*ins = mkinstr(Onop,0,);
replcuses(mkref(RTMP, ins - instrtab), r);
return 1;
}
}
enum irclass k = ins->cls;
switch (ins->op) {
case Omul:
if (kisflt(k)) break;
if (isnumcon(ins->l)) rswap(ins->l, ins->r); /* put const in rhs */
if (isintcon(ins->r)) return mulk(ins, blk, curi);
break;
case Odiv: case Oudiv: case Orem: case Ourem:
if (kisflt(k)) break;
if (isintcon(ins->r)) return divmodk(ins, blk, curi);
}
return 0;
}
static void
jmpfind(struct block **final, struct block **pblk)
{
struct block **p2 = &final[(*pblk)->id];
if (*p2 && !(*p2)->phi.n) {
jmpfind(final, p2);
*pblk = *p2;
}
}
static void
fillpredsrec(struct block *blk)
{
while (blk && !wasvisited(blk)) {
markvisited(blk);
if (!blk->s1) return;
if (!blk->s1->phi.n) addpred(blk->s1, blk);
if (!blk->s2) {
blk = blk->s1;
continue;
}
if (!blk->s2->phi.n) addpred(blk->s2, blk);
fillpredsrec(blk->s1);
blk = blk->s2;
}
}
static void
fillpreds(struct function *fn)
{
struct block *blk = fn->entry, *next;
do {
if (blk->phi.n) continue;
if (blk->npred > 1)
xbfree(blk->_pred);
blk->npred = 0;
blk->_pred = NULL;
} while ((blk = blk->lnext) != fn->entry);
startbbvisit();
fillpredsrec(fn->entry);
blk = fn->entry->lnext;
do { /* remove dead blocks */
next = blk->lnext;
if (!blk->npred) freeblk(fn, blk);
} while ((blk = next) != fn->entry);
}
void
simpl(struct function *fn)
{
FREQUIRE(FNUSE);
int inschange = 0,
blkchange = 0;
struct block **jmpfinal = allocz(fn->passarena, fn->nblk * sizeof *jmpfinal, 0);
struct block *blk = fn->entry;
do {
/* merge blocks:
* @blk:
* ... (1)
* b @s
* @s:
* ... (2)
* b {...}
*=>
* @blk:
* ... (1)
* ... (2)
* b {...}
* */
if (blk != fn->entry) while (blk->s1 && !blk->s2 && blk->s1->npred == 1 && !blk->phi.n) {
struct block *s = blk->s1;
vpushn(&blk->ins, s->ins.p, s->ins.n);
blk->jmp = blk->s1->jmp;
for (int i = 0; i < 2; ++i) {
struct block *ss = (&s->s1)[i];
if (ss) for (int j = 0; j < ss->npred; ++j) {
if (blkpred(ss, j) == s) {
blkpred(ss, j) = blk;
break;
}
}
}
/* breaks use for temps used in s */
if (s->ins.n || s->jmp.arg[0].t == RTMP || s->jmp.arg[1].t == RTMP)
fn->prop &= ~FNUSE;
blk->s1 = s->s1;
blk->s2 = s->s2;
freeblk(fn, s);
}
} while ((blk = blk->lnext) != fn->entry);
if (!(fn->prop & FNUSE)) filluses(fn);
do {
for (int i = 0; i < blk->phi.n; ++i) {; }
for (int i = 0; i < blk->ins.n; ++i) {
inschange += ins(&instrtab[blk->ins.p[i]], blk, &i);
}
/* thread jumps.. */
if (!blk->phi.n && !blk->ins.n) {
if (blk->jmp.t == Jb && !blk->s2) {
jmpfind(jmpfinal, &blk->s1);
if (blk->s1 != blk) {
++blkchange;
jmpfinal[blk->id] = blk->s1;
}
}
}
} while ((blk = blk->lnext) != fn->entry);
if (blkchange) {
do {
if (blk->s1) jmpfind(jmpfinal, &blk->s1);
if (blk->s2) jmpfind(jmpfinal, &blk->s2);
if (blk->s1 && blk->s1 == blk->s2) {
memset(blk->jmp.arg, 0, sizeof blk->jmp.arg);
blk->s2 = NULL;
}
} while ((blk = blk->lnext) != fn->entry);
fillpreds(fn);
}
}
/* vim:set ts=3 sw=3 expandtab: */
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