ref: a3b95d3e567c0ef60f9f1ead26124fb706dec20d
dir: /sys/src/cmd/tc/peep.c/
#include "gc.h"
void
peep(void)
{
Reg *r, *r1, *r2;
Prog *p, *p1;
int t;
/*
* complete R structure
*/
t = 0;
for(r=firstr; r!=R; r=r1) {
r1 = r->link;
if(r1 == R)
break;
p = r->prog->link;
while(p != r1->prog)
switch(p->as) {
default:
r2 = rega();
r->link = r2;
r2->link = r1;
r2->prog = p;
r2->p1 = r;
r->s1 = r2;
r2->s1 = r1;
r1->p1 = r2;
r = r2;
t++;
case ADATA:
case AGLOBL:
case ANAME:
case ASIGNAME:
p = p->link;
}
}
loop1:
t = 0;
for(r=firstr; r!=R; r=r->link) {
p = r->prog;
if(p->as == AMOVW || p->as == AMOVF || p->as == AMOVD)
if(regtyp(&p->to)) {
if(p->from.type == D_CONST)
constprop(&p->from, &p->to, r->s1);
else if(regtyp(&p->from))
if(p->from.type == p->to.type) {
if(copyprop(r)) {
excise(r);
t++;
} else
if(subprop(r) && copyprop(r)) {
excise(r);
t++;
}
}
}
}
if(t)
goto loop1;
/*
* look for MOVB x,R; MOVB R,R
*/
for(r=firstr; r!=R; r=r->link) {
p = r->prog;
switch(p->as) {
default:
continue;
case AEOR:
/*
* EOR -1,x,y => MVN x,y
*/
if(p->from.type == D_CONST && p->from.offset == -1) {
p->as = AMVN;
p->from.type = D_REG;
if(p->reg != NREG)
p->from.reg = p->reg;
else
p->from.reg = p->to.reg;
p->reg = NREG;
}
continue;
case AMOVH:
case AMOVHU:
case AMOVB:
case AMOVBU:
if(p->to.type != D_REG)
continue;
break;
}
r1 = r->link;
if(r1 == R)
continue;
p1 = r1->prog;
if(p1->as != p->as)
continue;
if(p1->from.type != D_REG || p1->from.reg != p->to.reg)
continue;
if(p1->to.type != D_REG || p1->to.reg != p->to.reg)
continue;
excise(r1);
}
}
void
excise(Reg *r)
{
Prog *p;
p = r->prog;
p->as = ANOP;
p->from = zprog.from;
p->to = zprog.to;
p->reg = zprog.reg; /**/
}
Reg*
uniqp(Reg *r)
{
Reg *r1;
r1 = r->p1;
if(r1 == R) {
r1 = r->p2;
if(r1 == R || r1->p2link != R)
return R;
} else
if(r->p2 != R)
return R;
return r1;
}
Reg*
uniqs(Reg *r)
{
Reg *r1;
r1 = r->s1;
if(r1 == R) {
r1 = r->s2;
if(r1 == R)
return R;
} else
if(r->s2 != R)
return R;
return r1;
}
int
regtyp(Adr *a)
{
if(a->type == D_REG)
return 1;
if(a->type == D_FREG)
return 1;
return 0;
}
/*
* the idea is to substitute
* one register for another
* from one MOV to another
* MOV a, R0
* ADD b, R0 / no use of R1
* MOV R0, R1
* would be converted to
* MOV a, R1
* ADD b, R1
* MOV R1, R0
* hopefully, then the former or latter MOV
* will be eliminated by copy propagation.
*/
int
subprop(Reg *r0)
{
Prog *p;
Adr *v1, *v2;
Reg *r;
int t;
p = r0->prog;
v1 = &p->from;
if(!regtyp(v1))
return 0;
v2 = &p->to;
if(!regtyp(v2))
return 0;
for(r=uniqp(r0); r!=R; r=uniqp(r)) {
if(uniqs(r) == R)
break;
p = r->prog;
switch(p->as) {
case ABL:
case ABX:
return 0;
// case ACMP:
// case ACMN:
case AADD:
case ASUB:
// case ASLL:
// case ASRL:
// case ASRA:
// case AORR:
// case AAND:
// case AEOR:
// case AMUL:
// case ADIV:
// case ADIVU:
// case ACMPF:
// case ACMPD:
// case AADDD:
// case AADDF:
// case ASUBD:
// case ASUBF:
// case AMULD:
// case AMULF:
// case ADIVD:
// case ADIVF:
if(p->to.type == v1->type)
if(p->to.reg == v1->reg) {
if(p->reg == NREG)
p->reg = p->to.reg;
goto gotit;
}
break;
case AMOVF:
case AMOVD:
case AMOVW:
if(p->to.type == v1->type)
if(p->to.reg == v1->reg)
goto gotit;
break;
case AMOVM:
t = 1<<v2->reg;
if((p->from.type == D_CONST && (p->from.offset&t)) ||
(p->to.type == D_CONST && (p->to.offset&t)))
return 0;
break;
}
if(copyau(&p->from, v2) ||
copyau1(p, v2) ||
copyau(&p->to, v2))
break;
if(copysub(&p->from, v1, v2, 0) ||
copysub1(p, v1, v2, 0) ||
copysub(&p->to, v1, v2, 0))
break;
}
return 0;
gotit:
copysub(&p->to, v1, v2, 1);
if(debug['P']) {
print("gotit: %D->%D\n%P", v1, v2, r->prog);
if(p->from.type == v2->type)
print(" excise");
print("\n");
}
for(r=uniqs(r); r!=r0; r=uniqs(r)) {
p = r->prog;
copysub(&p->from, v1, v2, 1);
copysub1(p, v1, v2, 1);
copysub(&p->to, v1, v2, 1);
if(debug['P'])
print("%P\n", r->prog);
}
t = v1->reg;
v1->reg = v2->reg;
v2->reg = t;
if(debug['P'])
print("%P last\n", r->prog);
return 1;
}
/*
* The idea is to remove redundant copies.
* v1->v2 F=0
* (use v2 s/v2/v1/)*
* set v1 F=1
* use v2 return fail
* -----------------
* v1->v2 F=0
* (use v2 s/v2/v1/)*
* set v1 F=1
* set v2 return success
*/
int
copyprop(Reg *r0)
{
Prog *p;
Adr *v1, *v2;
Reg *r;
p = r0->prog;
v1 = &p->from;
v2 = &p->to;
if(copyas(v1, v2))
return 1;
for(r=firstr; r!=R; r=r->link)
r->active = 0;
return copy1(v1, v2, r0->s1, 0);
}
int
copy1(Adr *v1, Adr *v2, Reg *r, int f)
{
int t;
Prog *p;
if(r->active) {
if(debug['P'])
print("act set; return 1\n");
return 1;
}
r->active = 1;
if(debug['P'])
print("copy %D->%D f=%d\n", v1, v2, f);
for(; r != R; r = r->s1) {
p = r->prog;
if(debug['P'])
print("%P", p);
if(!f && uniqp(r) == R) {
f = 1;
if(debug['P'])
print("; merge; f=%d", f);
}
t = copyu(p, v2, A);
switch(t) {
case 2: /* rar, cant split */
if(debug['P'])
print("; %Drar; return 0\n", v2);
return 0;
case 3: /* set */
if(debug['P'])
print("; %Dset; return 1\n", v2);
return 1;
case 1: /* used, substitute */
case 4: /* use and set */
if(f) {
if(!debug['P'])
return 0;
if(t == 4)
print("; %Dused+set and f=%d; return 0\n", v2, f);
else
print("; %Dused and f=%d; return 0\n", v2, f);
return 0;
}
if(copyu(p, v2, v1)) {
if(debug['P'])
print("; sub fail; return 0\n");
return 0;
}
if(debug['P'])
print("; sub%D/%D", v2, v1);
if(t == 4) {
if(debug['P'])
print("; %Dused+set; return 1\n", v2);
return 1;
}
break;
}
if(!f) {
t = copyu(p, v1, A);
if(!f && (t == 2 || t == 3 || t == 4)) {
f = 1;
if(debug['P'])
print("; %Dset and !f; f=%d", v1, f);
}
}
if(debug['P'])
print("\n");
if(r->s2)
if(!copy1(v1, v2, r->s2, f))
return 0;
}
return 1;
}
/*
* The idea is to remove redundant constants.
* $c1->v1
* ($c1->v2 s/$c1/v1)*
* set v1 return
* The v1->v2 should be eliminated by copy propagation.
*/
void
constprop(Adr *c1, Adr *v1, Reg *r)
{
Prog *p;
if(debug['C'])
print("constprop %D->%D\n", c1, v1);
for(; r != R; r = r->s1) {
p = r->prog;
if(debug['C'])
print("%P", p);
if(uniqp(r) == R) {
if(debug['C'])
print("; merge; return\n");
return;
}
if(p->as == AMOVW && copyas(&p->from, c1)) {
if(debug['C'])
print("; sub%D/%D", &p->from, v1);
p->from = *v1;
} else if(copyu(p, v1, A) > 1) {
if(debug['C'])
print("; %Dset; return\n", v1);
return;
}
if(debug['C'])
print("\n");
if(r->s2)
constprop(c1, v1, r->s2);
}
}
/*
* return
* 1 if v only used (and substitute),
* 2 if read-alter-rewrite
* 3 if set
* 4 if set and used
* 0 otherwise (not touched)
*/
int
copyu(Prog *p, Adr *v, Adr *s)
{
switch(p->as) {
default:
if(debug['P'])
print(" (?)");
return 2;
case AMOVM:
if(v->type != D_REG)
return 0;
if(p->from.type == D_CONST) { /* read reglist, read/rar */
if(s != A) {
if(p->from.offset&(1<<v->reg))
return 1;
if(copysub(&p->to, v, s, 1))
diag(Z, "movm dst being replaced"); // was return 1;
return 0;
}
if(copyau(&p->to, v))
return 2; // register updated in thumb // was return 1;
if(p->from.offset&(1<<v->reg))
return 1;
} else { /* read/rar, write reglist */
if(s != A) {
if(p->to.offset&(1<<v->reg))
return 1;
if(copysub(&p->from, v, s, 1))
diag(Z, "movm src being replaced"); // was return 1;
return 0;
}
if(copyau(&p->from, v)) {
// if(p->to.offset&(1<<v->reg))
// return 4;
return 2; // register updated in thumb // was return 1;
}
if(p->to.offset&(1<<v->reg))
return 3;
}
return 0;
case ANOP: /* read, write */
case AMOVW:
case AMOVF:
case AMOVD:
case AMOVH:
case AMOVHU:
case AMOVB:
case AMOVBU:
case AMOVDW:
case AMOVWD:
case AMOVFD:
case AMOVDF:
if(s != A) {
if(copysub(&p->from, v, s, 1))
return 1;
if(!copyas(&p->to, v))
if(copysub(&p->to, v, s, 1))
return 1;
return 0;
}
if(copyas(&p->to, v)) {
if(copyau(&p->from, v))
return 4;
return 3;
}
if(copyau(&p->from, v))
return 1;
if(copyau(&p->to, v))
return 1;
return 0;
case ASLL:
case ASRL:
case ASRA:
case AORR:
case AAND:
case AEOR:
case AMUL:
case ADIV:
case ADIVU:
case AADDF:
case AADDD:
case ASUBF:
case ASUBD:
case AMULF:
case AMULD:
case ADIVF:
case ADIVD:
case ACMPF:
case ACMPD:
case ACMP:
case ACMN:
if(copyas(&p->to, v))
return 2;
/*FALLTHROUGH*/
case AADD: /* read, read, write */
case ASUB:
if(s != A) {
if(copysub(&p->from, v, s, 1))
return 1;
if(copysub1(p, v, s, 1))
return 1;
if(!copyas(&p->to, v))
if(copysub(&p->to, v, s, 1))
return 1;
return 0;
}
if(copyas(&p->to, v)) {
if(p->reg == NREG)
p->reg = p->to.reg;
if(copyau(&p->from, v))
return 4;
if(copyau1(p, v))
return 4;
return 3;
}
if(copyau(&p->from, v))
return 1;
if(copyau1(p, v))
return 1;
if(copyau(&p->to, v))
return 1;
return 0;
case ABEQ: /* read, read */
case ABNE:
case ABCS:
case ABHS:
case ABCC:
case ABLO:
case ABMI:
case ABPL:
case ABVS:
case ABVC:
case ABHI:
case ABLS:
case ABGE:
case ABLT:
case ABGT:
case ABLE:
if(s != A) {
if(copysub(&p->from, v, s, 1))
return 1;
return copysub1(p, v, s, 1);
}
if(copyau(&p->from, v))
return 1;
if(copyau1(p, v))
return 1;
return 0;
case AB: /* funny */
if(s != A) {
if(copysub(&p->to, v, s, 1))
return 1;
return 0;
}
if(copyau(&p->to, v))
return 1;
return 0;
case ARET: /* funny */
if(v->type == D_REG)
if(v->reg == REGRET)
return 2;
if(v->type == D_FREG)
if(v->reg == FREGRET)
return 2;
case ABL: /* funny */
case ABX:
if(v->type == D_REG) {
if(v->reg <= REGEXT && v->reg > exregoffset)
return 2;
if(v->reg == REGARG)
return 2;
}
if(v->type == D_FREG)
if(v->reg <= FREGEXT && v->reg > exfregoffset)
return 2;
if(s != A) {
if(copysub(&p->to, v, s, 1))
return 1;
return 0;
}
if(copyau(&p->to, v))
return 4;
return 3;
case ATEXT: /* funny */
if(v->type == D_REG)
if(v->reg == REGARG)
return 3;
return 0;
}
/* not reached */
}
int
a2type(Prog *p)
{
switch(p->as) {
case ACMP:
case ACMN:
case AADD:
case ASUB:
case ASLL:
case ASRL:
case ASRA:
case AORR:
case AAND:
case AEOR:
case AMUL:
case ADIV:
case ADIVU:
return D_REG;
case ACMPF:
case ACMPD:
case AADDF:
case AADDD:
case ASUBF:
case ASUBD:
case AMULF:
case AMULD:
case ADIVF:
case ADIVD:
return D_FREG;
}
return D_NONE;
}
/*
* direct reference,
* could be set/use depending on
* semantics
*/
int
copyas(Adr *a, Adr *v)
{
if(regtyp(v)) {
if(a->type == v->type)
if(a->reg == v->reg)
return 1;
} else if(v->type == D_CONST) { /* for constprop */
if(a->type == v->type)
if(a->name == v->name)
if(a->sym == v->sym)
if(a->reg == v->reg)
if(a->offset == v->offset)
return 1;
}
return 0;
}
/*
* either direct or indirect
*/
int
copyau(Adr *a, Adr *v)
{
if(copyas(a, v))
return 1;
if(v->type == D_REG) {
if(a->type == D_OREG) {
if(v->reg == a->reg)
return 1;
}
}
return 0;
}
int
copyau1(Prog *p, Adr *v)
{
if(regtyp(v)) {
if(a2type(p) == v->type)
if(p->reg == v->reg) {
if(a2type(p) != v->type)
print("botch a2type %P\n", p);
return 1;
}
}
return 0;
}
/*
* substitute s for v in a
* return failure to substitute
*/
int
copysub(Adr *a, Adr *v, Adr *s, int f)
{
if(f)
if(copyau(a, v)) {
a->reg = s->reg;
}
return 0;
}
int
copysub1(Prog *p1, Adr *v, Adr *s, int f)
{
if(f)
if(copyau1(p1, v))
p1->reg = s->reg;
return 0;
}