ref: d552fed38514dc799c7fea95dfb632c8816c3f60
dir: /sys/src/cmd/kc/reg.c/
#include "gc.h"
Reg*
rega(void)
{
Reg *r;
r = freer;
if(r == R) {
r = alloc(sizeof(*r));
} else
freer = r->link;
*r = zreg;
return r;
}
int
rcmp(const void *a1, const void *a2)
{
Rgn *p1, *p2;
int c1, c2;
p1 = (Rgn*)a1;
p2 = (Rgn*)a2;
c1 = p2->cost;
c2 = p1->cost;
if(c1 -= c2)
return c1;
return p2->varno - p1->varno;
}
void
regopt(Prog *p)
{
Reg *r, *r1, *r2;
Prog *p1;
int i, z;
long initpc, val, npc;
ulong vreg;
Bits bit;
struct
{
long m;
long c;
Reg* p;
} log5[6], *lp;
firstr = R;
lastr = R;
nvar = 0;
regbits = 0;
for(z=0; z<BITS; z++) {
externs.b[z] = 0;
params.b[z] = 0;
consts.b[z] = 0;
addrs.b[z] = 0;
}
/*
* pass 1
* build aux data structure
* allocate pcs
* find use and set of variables
*/
val = 5L * 5L * 5L * 5L * 5L;
lp = log5;
for(i=0; i<5; i++) {
lp->m = val;
lp->c = 0;
lp->p = R;
val /= 5L;
lp++;
}
val = 0;
for(; p != P; p = p->link) {
switch(p->as) {
case ADATA:
case AGLOBL:
case ANAME:
case ASIGNAME:
continue;
}
r = rega();
if(firstr == R) {
firstr = r;
lastr = r;
} else {
lastr->link = r;
r->p1 = lastr;
lastr->s1 = r;
lastr = r;
}
r->prog = p;
r->pc = val;
val++;
lp = log5;
for(i=0; i<5; i++) {
lp->c--;
if(lp->c <= 0) {
lp->c = lp->m;
if(lp->p != R)
lp->p->log5 = r;
lp->p = r;
(lp+1)->c = 0;
break;
}
lp++;
}
r1 = r->p1;
if(r1 != R)
switch(r1->prog->as) {
case ARETURN:
case AJMP:
case ARETT:
r->p1 = R;
r1->s1 = R;
}
/*
* left side always read
*/
bit = mkvar(&p->from, p->as==AMOVW);
for(z=0; z<BITS; z++)
r->use1.b[z] |= bit.b[z];
/*
* right side depends on opcode
*/
bit = mkvar(&p->to, 0);
if(bany(&bit))
switch(p->as) {
default:
diag(Z, "reg: unknown asop: %A", p->as);
break;
/*
* right side write
*/
case ANOP:
case AMOVB:
case AMOVBU:
case AMOVH:
case AMOVHU:
case AMOVW:
case AFMOVF:
case AFMOVD:
for(z=0; z<BITS; z++)
r->set.b[z] |= bit.b[z];
break;
/*
* funny
*/
case AJMPL:
for(z=0; z<BITS; z++)
addrs.b[z] |= bit.b[z];
break;
}
}
if(firstr == R)
return;
initpc = pc - val;
npc = val;
/*
* pass 2
* turn branch references to pointers
* build back pointers
*/
for(r = firstr; r != R; r = r->link) {
p = r->prog;
if(p->to.type == D_BRANCH) {
val = p->to.offset - initpc;
r1 = firstr;
while(r1 != R) {
r2 = r1->log5;
if(r2 != R && val >= r2->pc) {
r1 = r2;
continue;
}
if(r1->pc == val)
break;
r1 = r1->link;
}
if(r1 == R) {
nearln = p->lineno;
diag(Z, "ref not found\n%P", p);
continue;
}
if(r1 == r) {
nearln = p->lineno;
diag(Z, "ref to self\n%P", p);
continue;
}
r->s2 = r1;
r->p2link = r1->p2;
r1->p2 = r;
}
}
if(debug['R']) {
p = firstr->prog;
print("\n%L %D\n", p->lineno, &p->from);
}
/*
* pass 2.5
* find looping structure
*/
for(r = firstr; r != R; r = r->link)
r->active = 0;
change = 0;
loopit(firstr, npc);
if(debug['R'] && debug['v']) {
print("\nlooping structure:\n");
for(r = firstr; r != R; r = r->link) {
print("%ld:%P", r->loop, r->prog);
for(z=0; z<BITS; z++)
bit.b[z] = r->use1.b[z] |
r->use2.b[z] | r->set.b[z];
if(bany(&bit)) {
print("\t");
if(bany(&r->use1))
print(" u1=%B", r->use1);
if(bany(&r->use2))
print(" u2=%B", r->use2);
if(bany(&r->set))
print(" st=%B", r->set);
}
print("\n");
}
}
/*
* pass 3
* iterate propagating usage
* back until flow graph is complete
*/
loop1:
change = 0;
for(r = firstr; r != R; r = r->link)
r->active = 0;
for(r = firstr; r != R; r = r->link)
if(r->prog->as == ARETURN)
prop(r, zbits, zbits);
loop11:
/* pick up unreachable code */
i = 0;
for(r = firstr; r != R; r = r1) {
r1 = r->link;
if(r1 && r1->active && !r->active) {
prop(r, zbits, zbits);
i = 1;
}
}
if(i)
goto loop11;
if(change)
goto loop1;
/*
* pass 4
* iterate propagating register/variable synchrony
* forward until graph is complete
*/
loop2:
change = 0;
for(r = firstr; r != R; r = r->link)
r->active = 0;
synch(firstr, zbits);
if(change)
goto loop2;
/*
* pass 5
* isolate regions
* calculate costs (paint1)
*/
r = firstr;
if(r) {
for(z=0; z<BITS; z++)
bit.b[z] = (r->refahead.b[z] | r->calahead.b[z]) &
~(externs.b[z] | params.b[z] | addrs.b[z] | consts.b[z]);
if(bany(&bit)) {
nearln = r->prog->lineno;
warn(Z, "used and not set: %B", bit);
if(debug['R'] && !debug['w'])
print("used and not set: %B\n", bit);
}
}
if(debug['R'] && debug['v'])
print("\nprop structure:\n");
for(r = firstr; r != R; r = r->link)
r->act = zbits;
rgp = region;
nregion = 0;
for(r = firstr; r != R; r = r->link) {
if(debug['R'] && debug['v'])
print("%P\n set = %B; rah = %B; cal = %B\n",
r->prog, r->set, r->refahead, r->calahead);
for(z=0; z<BITS; z++)
bit.b[z] = r->set.b[z] &
~(r->refahead.b[z] | r->calahead.b[z] | addrs.b[z]);
if(bany(&bit)) {
nearln = r->prog->lineno;
warn(Z, "set and not used: %B", bit);
if(debug['R'])
print("set an not used: %B\n", bit);
excise(r);
}
for(z=0; z<BITS; z++)
bit.b[z] = LOAD(r) & ~(r->act.b[z] | addrs.b[z]);
while(bany(&bit)) {
i = bnum(bit);
rgp->enter = r;
rgp->varno = i;
change = 0;
if(debug['R'] && debug['v'])
print("\n");
paint1(r, i);
bit.b[i/32] &= ~(1L<<(i%32));
if(change <= 0) {
if(debug['R'])
print("%L$%d: %B\n",
r->prog->lineno, change, blsh(i));
continue;
}
rgp->cost = change;
nregion++;
if(nregion >= NRGN) {
warn(Z, "too many regions");
goto brk;
}
rgp++;
}
}
brk:
qsort(region, nregion, sizeof(region[0]), rcmp);
/*
* pass 6
* determine used registers (paint2)
* replace code (paint3)
*/
rgp = region;
for(i=0; i<nregion; i++) {
bit = blsh(rgp->varno);
vreg = paint2(rgp->enter, rgp->varno);
vreg = allreg(vreg, rgp);
if(debug['R']) {
if(rgp->regno >= NREG)
print("%L$%d F%d: %B\n",
rgp->enter->prog->lineno,
rgp->cost,
rgp->regno-NREG,
bit);
else
print("%L$%d R%d: %B\n",
rgp->enter->prog->lineno,
rgp->cost,
rgp->regno,
bit);
}
if(rgp->regno != 0)
paint3(rgp->enter, rgp->varno, vreg, rgp->regno);
rgp++;
}
/*
* pass 7
* peep-hole on basic block
*/
if(!debug['R'] || debug['P'])
peep();
/*
* pass 8
* recalculate pc
*/
val = initpc;
for(r = firstr; r != R; r = r1) {
r->pc = val;
p = r->prog;
p1 = P;
r1 = r->link;
if(r1 != R)
p1 = r1->prog;
for(; p != p1; p = p->link) {
switch(p->as) {
default:
val++;
break;
case ANOP:
case ADATA:
case AGLOBL:
case ANAME:
case ASIGNAME:
break;
}
}
}
pc = val;
/*
* fix up branches
*/
if(debug['R'])
if(bany(&addrs))
print("addrs: %B\n", addrs);
r1 = 0; /* set */
for(r = firstr; r != R; r = r->link) {
p = r->prog;
if(p->to.type == D_BRANCH)
p->to.offset = r->s2->pc;
r1 = r;
}
/*
* last pass
* eliminate nops
* free aux structures
*/
for(p = firstr->prog; p != P; p = p->link){
while(p->link && p->link->as == ANOP)
p->link = p->link->link;
}
if(r1 != R) {
r1->link = freer;
freer = firstr;
}
}
/*
* add mov b,rn
* just after r
*/
void
addmove(Reg *r, int bn, int rn, int f)
{
Prog *p, *p1;
Adr *a;
Var *v;
p1 = alloc(sizeof(*p1));
*p1 = zprog;
p = r->prog;
p1->link = p->link;
p->link = p1;
p1->lineno = p->lineno;
v = var + bn;
a = &p1->to;
a->sym = v->sym;
a->name = v->name;
a->offset = v->offset;
a->etype = v->etype;
a->type = D_OREG;
if(a->etype == TARRAY || a->sym == S)
a->type = D_CONST;
p1->as = AMOVW;
if(v->etype == TCHAR || v->etype == TUCHAR)
p1->as = AMOVB;
if(v->etype == TSHORT || v->etype == TUSHORT)
p1->as = AMOVH;
if(v->etype == TFLOAT)
p1->as = AFMOVF;
if(v->etype == TDOUBLE)
p1->as = AFMOVD;
p1->from.type = D_REG;
p1->from.reg = rn;
if(rn >= NREG) {
p1->from.type = D_FREG;
p1->from.reg = rn-NREG;
}
if(!f) {
p1->from = *a;
*a = zprog.from;
a->type = D_REG;
a->reg = rn;
if(rn >= NREG) {
a->type = D_FREG;
a->reg = rn-NREG;
}
if(v->etype == TUCHAR)
p1->as = AMOVBU;
if(v->etype == TUSHORT)
p1->as = AMOVHU;
}
if(debug['R'])
print("%P\t.a%P\n", p, p1);
}
Bits
mkvar(Adr *a, int docon)
{
Var *v;
int i, t, n, et, z;
long o;
Bits bit;
Sym *s;
t = a->type;
if(t == D_REG && a->reg != NREG)
regbits |= RtoB(a->reg);
if(t == D_FREG && a->reg != NREG)
regbits |= FtoB(a->reg);
s = a->sym;
o = a->offset;
et = a->etype;
if(s == S) {
if(t != D_CONST || !docon || a->reg != NREG)
goto none;
et = TLONG;
}
if(t == D_CONST) {
if(s == S && sval(o))
goto none;
}
n = a->name;
v = var;
for(i=0; i<nvar; i++) {
if(s == v->sym)
if(n == v->name)
if(o == v->offset)
goto out;
v++;
}
if(s)
if(s->name[0] == '.')
goto none;
if(nvar >= NVAR) {
if(debug['w'] > 1 && s)
warn(Z, "variable not optimized: %s", s->name);
goto none;
}
i = nvar;
nvar++;
v = &var[i];
v->sym = s;
v->offset = o;
v->etype = et;
v->name = n;
if(debug['R'])
print("bit=%2d et=%2d %D\n", i, et, a);
out:
bit = blsh(i);
if(n == D_EXTERN || n == D_STATIC)
for(z=0; z<BITS; z++)
externs.b[z] |= bit.b[z];
if(n == D_PARAM)
for(z=0; z<BITS; z++)
params.b[z] |= bit.b[z];
if(v->etype != et || !typechlpfd[et]) /* funny punning */
for(z=0; z<BITS; z++)
addrs.b[z] |= bit.b[z];
if(t == D_CONST) {
if(s == S) {
for(z=0; z<BITS; z++)
consts.b[z] |= bit.b[z];
return bit;
}
if(et != TARRAY)
for(z=0; z<BITS; z++)
addrs.b[z] |= bit.b[z];
for(z=0; z<BITS; z++)
params.b[z] |= bit.b[z];
return bit;
}
if(t == D_OREG)
return bit;
none:
return zbits;
}
void
prop(Reg *r, Bits ref, Bits cal)
{
Reg *r1, *r2;
int z;
for(r1 = r; r1 != R; r1 = r1->p1) {
for(z=0; z<BITS; z++) {
ref.b[z] |= r1->refahead.b[z];
if(ref.b[z] != r1->refahead.b[z]) {
r1->refahead.b[z] = ref.b[z];
change++;
}
cal.b[z] |= r1->calahead.b[z];
if(cal.b[z] != r1->calahead.b[z]) {
r1->calahead.b[z] = cal.b[z];
change++;
}
}
switch(r1->prog->as) {
case AJMPL:
for(z=0; z<BITS; z++) {
cal.b[z] |= ref.b[z] | externs.b[z];
ref.b[z] = 0;
}
break;
case ATEXT:
for(z=0; z<BITS; z++) {
cal.b[z] = 0;
ref.b[z] = 0;
}
break;
case ARETURN:
for(z=0; z<BITS; z++) {
cal.b[z] = externs.b[z];
ref.b[z] = 0;
}
}
for(z=0; z<BITS; z++) {
ref.b[z] = (ref.b[z] & ~r1->set.b[z]) |
r1->use1.b[z] | r1->use2.b[z];
cal.b[z] &= ~(r1->set.b[z] | r1->use1.b[z] | r1->use2.b[z]);
r1->refbehind.b[z] = ref.b[z];
r1->calbehind.b[z] = cal.b[z];
}
if(r1->active)
break;
r1->active = 1;
}
for(; r != r1; r = r->p1)
for(r2 = r->p2; r2 != R; r2 = r2->p2link)
prop(r2, r->refbehind, r->calbehind);
}
/*
* find looping structure
*
* 1) find reverse postordering
* 2) find approximate dominators,
* the actual dominators if the flow graph is reducible
* otherwise, dominators plus some other non-dominators.
* See Matthew S. Hecht and Jeffrey D. Ullman,
* "Analysis of a Simple Algorithm for Global Data Flow Problems",
* Conf. Record of ACM Symp. on Principles of Prog. Langs, Boston, Massachusetts,
* Oct. 1-3, 1973, pp. 207-217.
* 3) find all nodes with a predecessor dominated by the current node.
* such a node is a loop head.
* recursively, all preds with a greater rpo number are in the loop
*/
long
postorder(Reg *r, Reg **rpo2r, long n)
{
Reg *r1;
r->rpo = 1;
r1 = r->s1;
if(r1 && !r1->rpo)
n = postorder(r1, rpo2r, n);
r1 = r->s2;
if(r1 && !r1->rpo)
n = postorder(r1, rpo2r, n);
rpo2r[n] = r;
n++;
return n;
}
long
rpolca(long *idom, long rpo1, long rpo2)
{
long t;
if(rpo1 == -1)
return rpo2;
while(rpo1 != rpo2){
if(rpo1 > rpo2){
t = rpo2;
rpo2 = rpo1;
rpo1 = t;
}
while(rpo1 < rpo2){
t = idom[rpo2];
if(t >= rpo2)
fatal(Z, "bad idom");
rpo2 = t;
}
}
return rpo1;
}
int
doms(long *idom, long r, long s)
{
while(s > r)
s = idom[s];
return s == r;
}
int
loophead(long *idom, Reg *r)
{
long src;
src = r->rpo;
if(r->p1 != R && doms(idom, src, r->p1->rpo))
return 1;
for(r = r->p2; r != R; r = r->p2link)
if(doms(idom, src, r->rpo))
return 1;
return 0;
}
void
loopmark(Reg **rpo2r, long head, Reg *r)
{
if(r->rpo < head || r->active == head)
return;
r->active = head;
r->loop += LOOP;
if(r->p1 != R)
loopmark(rpo2r, head, r->p1);
for(r = r->p2; r != R; r = r->p2link)
loopmark(rpo2r, head, r);
}
void
loopit(Reg *r, long nr)
{
Reg *r1;
long i, d, me;
if(nr > maxnr) {
rpo2r = alloc(nr * sizeof(Reg*));
idom = alloc(nr * sizeof(long));
maxnr = nr;
}
d = postorder(r, rpo2r, 0);
if(d > nr)
fatal(Z, "too many reg nodes");
nr = d;
for(i = 0; i < nr / 2; i++){
r1 = rpo2r[i];
rpo2r[i] = rpo2r[nr - 1 - i];
rpo2r[nr - 1 - i] = r1;
}
for(i = 0; i < nr; i++)
rpo2r[i]->rpo = i;
idom[0] = 0;
for(i = 0; i < nr; i++){
r1 = rpo2r[i];
me = r1->rpo;
d = -1;
if(r1->p1 != R && r1->p1->rpo < me)
d = r1->p1->rpo;
for(r1 = r1->p2; r1 != nil; r1 = r1->p2link)
if(r1->rpo < me)
d = rpolca(idom, d, r1->rpo);
idom[i] = d;
}
for(i = 0; i < nr; i++){
r1 = rpo2r[i];
r1->loop++;
if(r1->p2 != R && loophead(idom, r1))
loopmark(rpo2r, i, r1);
}
}
void
synch(Reg *r, Bits dif)
{
Reg *r1;
int z;
for(r1 = r; r1 != R; r1 = r1->s1) {
for(z=0; z<BITS; z++) {
dif.b[z] = (dif.b[z] &
~(~r1->refbehind.b[z] & r1->refahead.b[z])) |
r1->set.b[z] | r1->regdiff.b[z];
if(dif.b[z] != r1->regdiff.b[z]) {
r1->regdiff.b[z] = dif.b[z];
change++;
}
}
if(r1->active)
break;
r1->active = 1;
for(z=0; z<BITS; z++)
dif.b[z] &= ~(~r1->calbehind.b[z] & r1->calahead.b[z]);
if(r1->s2 != R)
synch(r1->s2, dif);
}
}
ulong
allreg(ulong b, Rgn *r)
{
Var *v;
int i;
v = var + r->varno;
r->regno = 0;
switch(v->etype) {
default:
diag(Z, "unknown etype %d/%d", bitno(b), v->etype);
break;
case TCHAR:
case TUCHAR:
case TSHORT:
case TUSHORT:
case TINT:
case TUINT:
case TLONG:
case TULONG:
case TIND:
case TARRAY:
i = BtoR(~b);
if(i && r->cost > 0) {
r->regno = i;
return RtoB(i);
}
break;
case TDOUBLE:
case TFLOAT:
i = BtoF(~b);
if(i && r->cost > 0) {
r->regno = i+NREG;
return FtoB(i);
}
break;
}
return 0;
}
void
paint1(Reg *r, int bn)
{
Reg *r1;
Prog *p;
int z;
ulong bb;
z = bn/32;
bb = 1L<<(bn%32);
if(r->act.b[z] & bb)
return;
for(;;) {
if(!(r->refbehind.b[z] & bb))
break;
r1 = r->p1;
if(r1 == R)
break;
if(!(r1->refahead.b[z] & bb))
break;
if(r1->act.b[z] & bb)
break;
r = r1;
}
if(LOAD(r) & ~(r->set.b[z]&~(r->use1.b[z]|r->use2.b[z])) & bb) {
change -= CLOAD * r->loop;
if(debug['R'] && debug['v'])
print("%ld%P\tld %B $%d\n", r->loop,
r->prog, blsh(bn), change);
}
for(;;) {
r->act.b[z] |= bb;
p = r->prog;
if(r->use1.b[z] & bb) {
change += CREF * r->loop;
if(p->to.type == D_FREG && p->as == AMOVW)
change = -CINF; /* cant go Rreg to Freg */
if(debug['R'] && debug['v'])
print("%ld%P\tu1 %B $%d\n", r->loop,
p, blsh(bn), change);
}
if((r->use2.b[z]|r->set.b[z]) & bb) {
change += CREF * r->loop;
if(p->from.type == D_FREG && p->as == AMOVW)
change = -CINF; /* cant go Rreg to Freg */
if(debug['R'] && debug['v'])
print("%ld%P\tu2 %B $%d\n", r->loop,
p, blsh(bn), change);
}
if(STORE(r) & r->regdiff.b[z] & bb) {
change -= CLOAD * r->loop;
if(debug['R'] && debug['v'])
print("%ld%P\tst %B $%d\n", r->loop,
p, blsh(bn), change);
}
if(r->refbehind.b[z] & bb)
for(r1 = r->p2; r1 != R; r1 = r1->p2link)
if(r1->refahead.b[z] & bb)
paint1(r1, bn);
if(!(r->refahead.b[z] & bb))
break;
r1 = r->s2;
if(r1 != R)
if(r1->refbehind.b[z] & bb)
paint1(r1, bn);
r = r->s1;
if(r == R)
break;
if(r->act.b[z] & bb)
break;
if(!(r->refbehind.b[z] & bb))
break;
}
}
ulong
paint2(Reg *r, int bn)
{
Reg *r1;
int z;
ulong bb, vreg;
z = bn/32;
bb = 1L << (bn%32);
vreg = regbits;
if(!(r->act.b[z] & bb))
return vreg;
for(;;) {
if(!(r->refbehind.b[z] & bb))
break;
r1 = r->p1;
if(r1 == R)
break;
if(!(r1->refahead.b[z] & bb))
break;
if(!(r1->act.b[z] & bb))
break;
r = r1;
}
for(;;) {
r->act.b[z] &= ~bb;
vreg |= r->regu;
if(r->refbehind.b[z] & bb)
for(r1 = r->p2; r1 != R; r1 = r1->p2link)
if(r1->refahead.b[z] & bb)
vreg |= paint2(r1, bn);
if(!(r->refahead.b[z] & bb))
break;
r1 = r->s2;
if(r1 != R)
if(r1->refbehind.b[z] & bb)
vreg |= paint2(r1, bn);
r = r->s1;
if(r == R)
break;
if(!(r->act.b[z] & bb))
break;
if(!(r->refbehind.b[z] & bb))
break;
}
return vreg;
}
void
paint3(Reg *r, int bn, long rb, int rn)
{
Reg *r1;
Prog *p;
int z;
ulong bb;
z = bn/32;
bb = 1L << (bn%32);
if(r->act.b[z] & bb)
return;
for(;;) {
if(!(r->refbehind.b[z] & bb))
break;
r1 = r->p1;
if(r1 == R)
break;
if(!(r1->refahead.b[z] & bb))
break;
if(r1->act.b[z] & bb)
break;
r = r1;
}
if(LOAD(r) & ~(r->set.b[z] & ~(r->use1.b[z]|r->use2.b[z])) & bb)
addmove(r, bn, rn, 0);
for(;;) {
r->act.b[z] |= bb;
p = r->prog;
if(r->use1.b[z] & bb) {
if(debug['R'])
print("%P", p);
addreg(&p->from, rn);
if(debug['R'])
print("\t.c%P\n", p);
}
if((r->use2.b[z]|r->set.b[z]) & bb) {
if(debug['R'])
print("%P", p);
addreg(&p->to, rn);
if(debug['R'])
print("\t.c%P\n", p);
}
if(STORE(r) & r->regdiff.b[z] & bb)
addmove(r, bn, rn, 1);
r->regu |= rb;
if(r->refbehind.b[z] & bb)
for(r1 = r->p2; r1 != R; r1 = r1->p2link)
if(r1->refahead.b[z] & bb)
paint3(r1, bn, rb, rn);
if(!(r->refahead.b[z] & bb))
break;
r1 = r->s2;
if(r1 != R)
if(r1->refbehind.b[z] & bb)
paint3(r1, bn, rb, rn);
r = r->s1;
if(r == R)
break;
if(r->act.b[z] & bb)
break;
if(!(r->refbehind.b[z] & bb))
break;
}
}
void
addreg(Adr *a, int rn)
{
a->sym = 0;
a->name = D_NONE;
a->type = D_REG;
a->reg = rn;
if(rn >= NREG) {
a->type = D_FREG;
a->reg = rn-NREG;
}
}
/*
* bit reg
* 0 R9
* 1 R10
* ... ...
* 4 R13
* 5 R16
* ... ...
* 20 R31
*/
long
RtoB(int r)
{
if(r >= 9 && r <= 13)
return 1L << (r-9);
if(r >= 16 && r <= 31)
return 1L << (r-11);
return 0;
}
int
BtoR(long b)
{
int r;
b &= 0x001fffffL;
if(b == 0)
return 0;
r = bitno(b) + 9;
if(r >= 14)
r += 2;
return r;
}
/*
* bit reg
* 22 F4
* 23 F6
* ... ...
* 31 F22
*/
long
FtoB(int f)
{
if(f < 4 || f > 22 || (f&1))
return 0;
return 1L << (f/2 + 20);
}
BtoF(long b)
{
b &= 0xffc00000L;
if(b == 0)
return 0;
return bitno(b)*2 - 40;
}