ref: 7d7650dffc20c3853eb1acd551c9a02f73751ae3
dir: /sys/src/cmd/8c/peep.c/
#include "gc.h"
static int
needc(Prog *p)
{
while(p != P) {
switch(p->as) {
case AADCL:
case ASBBL:
case ARCRL:
return 1;
case AADDL:
case ASUBL:
case AJMP:
case ARET:
case ACALL:
return 0;
default:
if(p->to.type == D_BRANCH)
return 0;
}
p = p->link;
}
return 0;
}
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;
}
}
pc = 0; /* speculating it won't kill */
loop1:
t = 0;
for(r=firstr; r!=R; r=r->link) {
p = r->prog;
switch(p->as) {
case AMOVL:
if(regtyp(&p->to))
if(regtyp(&p->from)) {
if(copyprop(r)) {
excise(r);
t++;
}
if(subprop(r) && copyprop(r)) {
excise(r);
t++;
}
}
break;
case AMOVBLSX:
case AMOVBLZX:
case AMOVWLSX:
case AMOVWLZX:
if(regtyp(&p->to)) {
r1 = uniqs(r);
if(r1 != R) {
p1 = r1->prog;
if(p->as == p1->as && p->to.type == p1->from.type)
p1->as = AMOVL;
}
}
break;
case AADDL:
case AADDW:
if(p->from.type != D_CONST || needc(p->link))
break;
if(p->from.offset == -1){
if(p->as == AADDL)
p->as = ADECL;
else
p->as = ADECW;
p->from = zprog.from;
}
else if(p->from.offset == 1){
if(p->as == AADDL)
p->as = AINCL;
else
p->as = AINCW;
p->from = zprog.from;
}
break;
case ASUBL:
case ASUBW:
if(p->from.type != D_CONST || needc(p->link))
break;
if(p->from.offset == -1) {
if(p->as == ASUBL)
p->as = AINCL;
else
p->as = AINCW;
p->from = zprog.from;
}
else if(p->from.offset == 1){
if(p->as == ASUBL)
p->as = ADECL;
else
p->as = ADECW;
p->from = zprog.from;
}
break;
case ACMPL:
if(p->to.type != D_CONST || p->to.offset != 0 || regtyp(&p->from) == 0)
break;
if(p->link == P || (p->link->as != AJEQ && p->link->as != AJNE))
break;
r1 = uniqp(r);
while(r1 != R && r1->prog->as == ANOP)
r1 = uniqp(r1);
if(r1 == R || r1->prog->to.type != p->from.type)
break;
p1 = r1->prog;
switch(p1->as){
case ASALL:
case ASARL:
case ASHLL:
case ASHRL:
/* shift doesnt affect ZF when shift count is zero */
if(p1->from.type != D_CONST || p1->from.offset == 0)
break;
case AANDL:
case AORL:
case AXORL:
case ANEGL:
case AADDL:
case AADCL:
case ASUBL:
case ASBBL:
case AINCL:
case ADECL:
excise(r);
}
break;
}
}
if(t)
goto loop1;
}
void
excise(Reg *r)
{
Prog *p;
p = r->prog;
p->as = ANOP;
p->from = zprog.from;
p->to = zprog.to;
}
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)
{
int t;
t = a->type;
if(t >= D_AX && t <= D_DI)
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 ACALL:
return 0;
case AIMULL:
case AIMULW:
if(p->to.type != D_NONE)
break;
case ADIVB:
case ADIVL:
case ADIVW:
case AIDIVB:
case AIDIVL:
case AIDIVW:
case AIMULB:
case AMULB:
case AMULL:
case AMULW:
case AROLB:
case AROLL:
case AROLW:
case ARORB:
case ARORL:
case ARORW:
case ASALB:
case ASALL:
case ASALW:
case ASARB:
case ASARL:
case ASARW:
case ASHLB:
case ASHLL:
case ASHLW:
case ASHRB:
case ASHRL:
case ASHRW:
case AREP:
case AREPN:
case ACWD:
case ACDQ:
case ASTOSB:
case ASTOSL:
case AMOVSB:
case AMOVSL:
case AFSTSW:
return 0;
case AORL:
case AANDL:
case AXORL:
case AADDL:
case AADCL:
/*
* can swap when:
* ADD R2, R1
* MOV R1, R2
* convert to:
* ADD R1, R2
* MOV R2, R1 / no use for R1
*/
if(p->to.type == v1->type && p->from.type == v2->type){
copysub(&p->from, v2, v1, 1);
goto gotit;
}
break;
case AMOVL:
if(p->to.type == v1->type)
goto gotit;
break;
}
if(copyau(&p->from, v2) ||
copyau(&p->to, v2))
break;
if(copysub(&p->from, 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);
copysub(&p->to, v1, v2, 1);
if(debug['P'])
print("%P\n", r->prog);
}
t = v1->type;
v1->type = v2->type;
v2->type = 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("; %D rar; return 0\n", v2);
return 0;
case 3: /* set */
if(debug['P'])
print("; %D set; 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("; %D used+set and f=%d; return 0\n", v2, f);
else
print("; %D used 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("; %D used+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("; %D set 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;
}
/*
* 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("unknown op %A\n", p->as);
return 2;
case ANEGB:
case ANEGW:
case ANEGL:
case ANOTB:
case ANOTW:
case ANOTL:
if(copyas(&p->to, v))
return 2;
break;
case ALEAL: /* lhs addr, rhs store */
if(copyas(&p->from, v))
return 2;
case ANOP: /* rhs store */
case AMOVL:
case AMOVBLSX:
case AMOVBLZX:
case AMOVWLSX:
case AMOVWLZX:
if(copyas(&p->to, v)) {
if(s != A)
return copysub(&p->from, v, s, 1);
if(copyau(&p->from, v))
return 4;
return 3;
}
goto caseread;
case AROLB:
case AROLL:
case AROLW:
case ARORB:
case ARORL:
case ARORW:
case ASALB:
case ASALL:
case ASALW:
case ASARB:
case ASARL:
case ASARW:
case ASHLB:
case ASHLL:
case ASHLW:
case ASHRB:
case ASHRL:
case ASHRW:
if(copyas(&p->to, v))
return 2;
if(copyas(&p->from, v))
if(p->from.type == D_CX)
return 2;
goto caseread;
case AADDB: /* rhs rar */
case AADDL:
case AADDW:
case AANDB:
case AANDL:
case AANDW:
case ADECL:
case ADECW:
case AINCL:
case AINCW:
case ASUBB:
case ASUBL:
case ASUBW:
case AORB:
case AORL:
case AORW:
case AXORB:
case AXORL:
case AXORW:
case AMOVB:
case AMOVW:
case AFMOVB:
case AFMOVBP:
case AFMOVD:
case AFMOVDP:
case AFMOVF:
case AFMOVFP:
case AFMOVL:
case AFMOVLP:
case AFMOVV:
case AFMOVVP:
case AFMOVW:
case AFMOVWP:
case AFMOVX:
case AFMOVXP:
case AFADDDP:
case AFADDW:
case AFADDL:
case AFADDF:
case AFADDD:
case AFMULDP:
case AFMULW:
case AFMULL:
case AFMULF:
case AFMULD:
case AFSUBDP:
case AFSUBW:
case AFSUBL:
case AFSUBF:
case AFSUBD:
case AFSUBRDP:
case AFSUBRW:
case AFSUBRL:
case AFSUBRF:
case AFSUBRD:
case AFDIVDP:
case AFDIVW:
case AFDIVL:
case AFDIVF:
case AFDIVD:
case AFDIVRDP:
case AFDIVRW:
case AFDIVRL:
case AFDIVRF:
case AFDIVRD:
if(copyas(&p->to, v))
return 2;
goto caseread;
case ACMPL: /* read only */
case ACMPW:
case ACMPB:
case AFCOMB:
case AFCOMBP:
case AFCOMD:
case AFCOMDP:
case AFCOMDPP:
case AFCOMF:
case AFCOMFP:
case AFCOML:
case AFCOMLP:
case AFCOMW:
case AFCOMWP:
case AFUCOM:
case AFUCOMP:
case AFUCOMPP:
caseread:
if(s != A) {
if(copysub(&p->from, v, s, 1))
return 1;
return copysub(&p->to, v, s, 1);
}
if(copyau(&p->from, v))
return 1;
if(copyau(&p->to, v))
return 1;
break;
case AJGE: /* no reference */
case AJNE:
case AJLE:
case AJEQ:
case AJHI:
case AJLS:
case AJMI:
case AJPL:
case AJGT:
case AJLT:
case AJCC:
case AJCS:
case AADJSP:
case AFLDZ:
case AWAIT:
break;
case AIMULL:
case AIMULW:
if(p->to.type != D_NONE) {
if(copyas(&p->to, v))
return 2;
goto caseread;
}
case ADIVB:
case ADIVL:
case ADIVW:
case AIDIVB:
case AIDIVL:
case AIDIVW:
case AIMULB:
case AMULB:
case AMULL:
case AMULW:
case ACWD:
case ACDQ:
if(v->type == D_AX || v->type == D_DX)
return 2;
goto caseread;
case AREP:
case AREPN:
if(v->type == D_CX)
return 2;
goto caseread;
case AMOVSB:
case AMOVSL:
if(v->type == D_DI || v->type == D_SI)
return 2;
goto caseread;
case ASTOSB:
case ASTOSL:
if(v->type == D_AX || v->type == D_DI)
return 2;
goto caseread;
case AFSTSW:
if(v->type == D_AX)
return 2;
goto caseread;
case AJMP: /* 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 == REGRET)
return 2;
if(s != A)
return 1;
return 3;
case ACALL: /* funny */
if(REGARG>=0 && v->type == REGARG)
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;
}
return 0;
}
/*
* direct reference,
* could be set/use depending on
* semantics
*/
int
copyas(Adr *a, Adr *v)
{
if(a->type != v->type)
return 0;
if(regtyp(v))
return 1;
if(v->type == D_AUTO || v->type == D_PARAM)
if(v->offset == a->offset)
return 1;
return 0;
}
/*
* either direct or indirect
*/
int
copyau(Adr *a, Adr *v)
{
if(copyas(a, v))
return 1;
if(regtyp(v)) {
if(a->type-D_INDIR == v->type)
return 1;
if(a->index == v->type)
return 1;
}
return 0;
}
/*
* substitute s for v in a
* return failure to substitute
*/
int
copysub(Adr *a, Adr *v, Adr *s, int f)
{
int t;
if(copyas(a, v)) {
t = s->type;
if(t >= D_AX && t <= D_DI) {
if(f)
a->type = t;
}
return 0;
}
if(regtyp(v)) {
t = v->type;
if(a->type == t+D_INDIR) {
if(s->type == D_BP && a->index != D_NONE)
return 1; /* can't use BP-base with index */
if(f)
a->type = s->type+D_INDIR;
// return 0;
}
if(a->index == t) {
if(f)
a->index = s->type;
return 0;
}
return 0;
}
return 0;
}