ref: fb7dd4b3a868cb8987049c95bb32e6425a73c8b9
dir: /utils/5c/peep.c/
#include "gc.h"
int xtramodes(Reg*, Adr*);
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 == ASLL || p->as == ASRL || p->as == ASRA) {
/*
* elide shift into D_SHIFT operand of subsequent instruction
*/
if(shiftprop(r)) {
excise(r);
t++;
}
}
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);
}
for(r=firstr; r!=R; r=r->link) {
p = r->prog;
switch(p->as) {
case AMOVW:
case AMOVB:
case AMOVBU:
if(p->from.type == D_OREG && p->from.offset == 0)
xtramodes(r, &p->from);
else if(p->to.type == D_OREG && p->to.offset == 0)
xtramodes(r, &p->to);
else
continue;
break;
case ACMP:
/*
* elide CMP $0,x if calculation of x can set condition codes
*/
if(p->from.type != D_CONST || p->from.offset != 0)
continue;
r2 = r->s1;
if(r2 == R)
continue;
t = r2->prog->as;
switch(t) {
default:
continue;
case ABEQ:
case ABNE:
case ABMI:
case ABPL:
break;
case ABGE:
t = ABPL;
break;
case ABLT:
t = ABMI;
break;
case ABHI:
t = ABNE;
break;
case ABLS:
t = ABEQ;
break;
}
r1 = r;
do
r1 = uniqp(r1);
while (r1 != R && r1->prog->as == ANOP);
if(r1 == R)
continue;
p1 = r1->prog;
if(p1->to.type != D_REG)
continue;
if(p1->to.reg != p->reg)
if(!(p1->as == AMOVW && p1->from.type == D_REG && p1->from.reg == p->reg))
continue;
switch(p1->as) {
default:
continue;
case AMOVW:
if(p1->from.type != D_REG)
continue;
case AAND:
case AEOR:
case AORR:
case ABIC:
case AMVN:
case ASUB:
case ARSB:
case AADD:
case AADC:
case ASBC:
case ARSC:
break;
}
p1->scond |= C_SBIT;
r2->prog->as = t;
excise(r);
continue;
}
}
predicate();
}
void
excise(Reg *r)
{
Prog *p;
p = r->prog;
p->as = ANOP;
p->scond = zprog.scond;
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:
return 0;
case ACMP:
case ACMN:
case AADD:
case ASUB:
case ARSB:
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);
}
}
/*
* ASLL x,y,w
* .. (not use w, not set x y w)
* AXXX w,a,b (a != w)
* .. (not use w)
* (set w)
* ----------- changed to
* ..
* AXXX (x<<y),a,b
* ..
*/
#define FAIL(msg) { if(debug['H']) print("\t%s; FAILURE\n", msg); return 0; }
int
shiftprop(Reg *r)
{
Reg *r1;
Prog *p, *p1, *p2;
int n, o;
Adr a;
p = r->prog;
if(p->to.type != D_REG)
FAIL("BOTCH: result not reg");
n = p->to.reg;
a = zprog.from;
if(p->reg != NREG && p->reg != p->to.reg) {
a.type = D_REG;
a.reg = p->reg;
}
if(debug['H'])
print("shiftprop\n%P", p);
r1 = r;
for(;;) {
/* find first use of shift result; abort if shift operands or result are changed */
r1 = uniqs(r1);
if(r1 == R)
FAIL("branch");
if(uniqp(r1) == R)
FAIL("merge");
p1 = r1->prog;
if(debug['H'])
print("\n%P", p1);
switch(copyu(p1, &p->to, A)) {
case 0: /* not used or set */
if((p->from.type == D_REG && copyu(p1, &p->from, A) > 1) ||
(a.type == D_REG && copyu(p1, &a, A) > 1))
FAIL("args modified");
continue;
case 3: /* set, not used */
FAIL("BOTCH: noref");
}
break;
}
/* check whether substitution can be done */
switch(p1->as) {
default:
FAIL("non-dpi");
case AAND:
case AEOR:
case AADD:
case AADC:
case AORR:
case ASUB:
case ARSB:
case ASBC:
case ARSC:
if(p1->reg == n || (p1->reg == NREG && p1->to.type == D_REG && p1->to.reg == n)) {
if(p1->from.type != D_REG)
FAIL("can't swap");
p1->reg = p1->from.reg;
p1->from.reg = n;
switch(p1->as) {
case ASUB:
p1->as = ARSB;
break;
case ARSB:
p1->as = ASUB;
break;
case ASBC:
p1->as = ARSC;
break;
case ARSC:
p1->as = ASBC;
break;
}
if(debug['H'])
print("\t=>%P", p1);
}
case ABIC:
case ACMP:
case ACMN:
if(p1->reg == n)
FAIL("can't swap");
if(p1->reg == NREG && p1->to.reg == n)
FAIL("shift result used twice");
case AMVN:
if(p1->from.type == D_SHIFT)
FAIL("shift result used in shift");
if(p1->from.type != D_REG || p1->from.reg != n)
FAIL("BOTCH: where is it used?");
break;
}
/* check whether shift result is used subsequently */
p2 = p1;
if(p1->to.reg != n)
for (;;) {
r1 = uniqs(r1);
if(r1 == R)
FAIL("inconclusive");
p1 = r1->prog;
if(debug['H'])
print("\n%P", p1);
switch(copyu(p1, &p->to, A)) {
case 0: /* not used or set */
continue;
case 3: /* set, not used */
break;
default:/* used */
FAIL("reused");
}
break;
}
/* make the substitution */
p2->from.type = D_SHIFT;
p2->from.reg = NREG;
o = p->reg;
if(o == NREG)
o = p->to.reg;
switch(p->from.type){
case D_CONST:
o |= (p->from.offset&0x1f)<<7;
break;
case D_REG:
o |= (1<<4) | (p->from.reg<<8);
break;
}
switch(p->as){
case ASLL:
o |= 0<<5;
break;
case ASRL:
o |= 1<<5;
break;
case ASRA:
o |= 2<<5;
break;
}
p2->from.offset = o;
if(debug['H'])
print("\t=>%P\tSUCCEED\n", p2);
return 1;
}
Reg*
findpre(Reg *r, Adr *v)
{
Reg *r1;
for(r1=uniqp(r); r1!=R; r=r1,r1=uniqp(r)) {
if(uniqs(r1) != r)
return R;
switch(copyu(r1->prog, v, A)) {
case 1: /* used */
case 2: /* read-alter-rewrite */
return R;
case 3: /* set */
case 4: /* set and used */
return r1;
}
}
return R;
}
Reg*
findinc(Reg *r, Reg *r2, Adr *v)
{
Reg *r1;
Prog *p;
for(r1=uniqs(r); r1!=R && r1!=r2; r=r1,r1=uniqs(r)) {
if(uniqp(r1) != r)
return R;
switch(copyu(r1->prog, v, A)) {
case 0: /* not touched */
continue;
case 4: /* set and used */
p = r1->prog;
if(p->as == AADD)
if(p->from.type == D_CONST)
if(p->from.offset > -4096 && p->from.offset < 4096)
return r1;
default:
return R;
}
}
return R;
}
int
nochange(Reg *r, Reg *r2, Prog *p)
{
Adr a[3];
int i, n;
if(r == r2)
return 1;
n = 0;
if(p->reg != NREG && p->reg != p->to.reg) {
a[n].type = D_REG;
a[n++].reg = p->reg;
}
switch(p->from.type) {
case D_SHIFT:
a[n].type = D_REG;
a[n++].reg = p->from.offset&0xf;
case D_REG:
a[n].type = D_REG;
a[n++].reg = p->from.reg;
}
if(n == 0)
return 1;
for(; r!=R && r!=r2; r=uniqs(r)) {
p = r->prog;
for(i=0; i<n; i++)
if(copyu(p, &a[i], A) > 1)
return 0;
}
return 1;
}
int
findu1(Reg *r, Adr *v)
{
for(; r != R; r = r->s1) {
if(r->active)
return 0;
r->active = 1;
switch(copyu(r->prog, v, A)) {
case 1: /* used */
case 2: /* read-alter-rewrite */
case 4: /* set and used */
return 1;
case 3: /* set */
return 0;
}
if(r->s2)
if (findu1(r->s2, v))
return 1;
}
return 0;
}
int
finduse(Reg *r, Adr *v)
{
Reg *r1;
for(r1=firstr; r1!=R; r1=r1->link)
r1->active = 0;
return findu1(r, v);
}
int
xtramodes(Reg *r, Adr *a)
{
Reg *r1, *r2, *r3;
Prog *p, *p1;
Adr v;
p = r->prog;
if(debug['h'] && p->as == AMOVB && p->from.type == D_OREG) /* byte load */
return 0;
v = *a;
v.type = D_REG;
r1 = findpre(r, &v);
if(r1 != R) {
p1 = r1->prog;
if(p1->to.type == D_REG && p1->to.reg == v.reg)
switch(p1->as) {
case AADD:
if(p1->from.type == D_REG ||
(p1->from.type == D_SHIFT && (p1->from.offset&(1<<4)) == 0 &&
(p->as != AMOVB || (a == &p->from && (p1->from.offset&~0xf) == 0))) ||
(p1->from.type == D_CONST &&
p1->from.offset > -4096 && p1->from.offset < 4096))
if(nochange(uniqs(r1), r, p1)) {
if(a != &p->from || v.reg != p->to.reg)
if (finduse(r->s1, &v)) {
if(p1->reg == NREG || p1->reg == v.reg)
/* pre-indexing */
p->scond |= C_WBIT;
else return 0;
}
switch (p1->from.type) {
case D_REG:
/* register offset */
a->type = D_SHIFT;
a->offset = p1->from.reg;
break;
case D_SHIFT:
/* scaled register offset */
a->type = D_SHIFT;
case D_CONST:
/* immediate offset */
a->offset = p1->from.offset;
break;
}
if(p1->reg != NREG)
a->reg = p1->reg;
excise(r1);
return 1;
}
break;
case AMOVW:
if(p1->from.type == D_REG)
if((r2 = findinc(r1, r, &p1->from)) != R) {
for(r3=uniqs(r2); r3->prog->as==ANOP; r3=uniqs(r3))
;
if(r3 == r) {
/* post-indexing */
p1 = r2->prog;
a->reg = p1->to.reg;
a->offset = p1->from.offset;
p->scond |= C_PBIT;
if(!finduse(r, &r1->prog->to))
excise(r1);
excise(r2);
return 1;
}
}
break;
}
}
if(a != &p->from || a->reg != p->to.reg)
if((r1 = findinc(r, R, &v)) != R) {
/* post-indexing */
p1 = r1->prog;
a->offset = p1->from.offset;
p->scond |= C_PBIT;
excise(r1);
return 1;
}
return 0;
}
/*
* 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))
return 1;
return 0;
}
if(copyau(&p->to, v)) {
if(p->scond&C_WBIT)
return 2;
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))
return 1;
return 0;
}
if(copyau(&p->from, v)) {
if(p->scond&C_WBIT)
return 2;
if(p->to.offset&(1<<v->reg))
return 4;
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(p->scond&(C_WBIT|C_PBIT))
if(v->type == D_REG) {
if(p->from.type == D_OREG || p->from.type == D_SHIFT) {
if(p->from.reg == v->reg)
return 2;
} else {
if(p->to.reg == v->reg)
return 2;
}
}
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 AADD: /* read, read, write */
case ASUB:
case ARSB:
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:
case ACASE:
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 */
if(v->type == D_REG) {
if(v->reg <= REGEXT && v->reg > exregoffset)
return 2;
if(v->reg == (uchar)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 == (uchar)REGARG)
return 3;
return 0;
}
}
int
a2type(Prog *p)
{
switch(p->as) {
case ACMP:
case ACMN:
case AADD:
case ASUB:
case ARSB:
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;
} else if(a->type == D_SHIFT) {
if((a->offset&0xf) == v->reg)
return 1;
if((a->offset&(1<<4)) && (a->offset>>8) == v->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)) {
if(a->type == D_SHIFT) {
if((a->offset&0xf) == v->reg)
a->offset = (a->offset&~0xf)|s->reg;
if((a->offset&(1<<4)) && (a->offset>>8) == v->reg)
a->offset = (a->offset&~(0xf<<8))|(s->reg<<8);
} else
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;
}
struct {
int opcode;
int notopcode;
int scond;
int notscond;
} predinfo[] = {
{ ABEQ, ABNE, 0x0, 0x1, },
{ ABNE, ABEQ, 0x1, 0x0, },
{ ABCS, ABCC, 0x2, 0x3, },
{ ABHS, ABLO, 0x2, 0x3, },
{ ABCC, ABCS, 0x3, 0x2, },
{ ABLO, ABHS, 0x3, 0x2, },
{ ABMI, ABPL, 0x4, 0x5, },
{ ABPL, ABMI, 0x5, 0x4, },
{ ABVS, ABVC, 0x6, 0x7, },
{ ABVC, ABVS, 0x7, 0x6, },
{ ABHI, ABLS, 0x8, 0x9, },
{ ABLS, ABHI, 0x9, 0x8, },
{ ABGE, ABLT, 0xA, 0xB, },
{ ABLT, ABGE, 0xB, 0xA, },
{ ABGT, ABLE, 0xC, 0xD, },
{ ABLE, ABGT, 0xD, 0xC, },
};
typedef struct {
Reg *start;
Reg *last;
Reg *end;
int len;
} Joininfo;
enum {
Join,
Split,
End,
Branch,
Setcond,
Toolong
};
enum {
Falsecond,
Truecond,
Delbranch,
Keepbranch
};
int
isbranch(Prog *p)
{
return (ABEQ <= p->as) && (p->as <= ABLE);
}
int
predicable(Prog *p)
{
if (isbranch(p)
|| p->as == ANOP
|| p->as == AXXX
|| p->as == ADATA
|| p->as == AGLOBL
|| p->as == AGOK
|| p->as == AHISTORY
|| p->as == ANAME
|| p->as == ASIGNAME
|| p->as == ATEXT
|| p->as == AWORD
|| p->as == ADYNT
|| p->as == AINIT
|| p->as == ABCASE
|| p->as == ACASE)
return 0;
return 1;
}
/*
* Depends on an analysis of the encodings performed by 5l.
* These seem to be all of the opcodes that lead to the "S" bit
* being set in the instruction encodings.
*
* C_SBIT may also have been set explicitly in p->scond.
*/
int
modifiescpsr(Prog *p)
{
return (p->scond&C_SBIT)
|| p->as == ATST
|| p->as == ATEQ
|| p->as == ACMN
|| p->as == ACMP
|| p->as == AMULU
|| p->as == ADIVU
|| p->as == AMUL
|| p->as == ADIV
|| p->as == AMOD
|| p->as == AMODU
|| p->as == ABL;
}
/*
* Find the maximal chain of instructions starting with r which could
* be executed conditionally
*/
int
joinsplit(Reg *r, Joininfo *j)
{
j->start = r;
j->last = r;
j->len = 0;
do {
if (r->p2 && (r->p1 || r->p2->p2link)) {
j->end = r;
return Join;
}
if (r->s1 && r->s2) {
j->end = r;
return Split;
}
j->last = r;
if (r->prog->as != ANOP)
j->len++;
if (!r->s1 && !r->s2) {
j->end = r->link;
return End;
}
if (r->s2) {
j->end = r->s2;
return Branch;
}
if (modifiescpsr(r->prog)) {
j->end = r->s1;
return Setcond;
}
r = r->s1;
} while (j->len < 4);
j->end = r;
return Toolong;
}
Reg *
successor(Reg *r)
{
if (r->s1)
return r->s1;
else
return r->s2;
}
void
applypred(Reg *rstart, Joininfo *j, int cond, int branch)
{
int pred;
Reg *r;
if(j->len == 0)
return;
if (cond == Truecond)
pred = predinfo[rstart->prog->as - ABEQ].scond;
else
pred = predinfo[rstart->prog->as - ABEQ].notscond;
for (r = j->start; ; r = successor(r)) {
if (r->prog->as == AB) {
if (r != j->last || branch == Delbranch)
excise(r);
else {
if (cond == Truecond)
r->prog->as = predinfo[rstart->prog->as - ABEQ].opcode;
else
r->prog->as = predinfo[rstart->prog->as - ABEQ].notopcode;
}
}
else if (predicable(r->prog))
r->prog->scond = (r->prog->scond&~C_SCOND)|pred;
if (r->s1 != r->link) {
r->s1 = r->link;
r->link->p1 = r;
}
if (r == j->last)
break;
}
}
void
predicate(void)
{
Reg *r;
int t1, t2;
Joininfo j1, j2;
for(r=firstr; r!=R; r=r->link) {
if (isbranch(r->prog)) {
t1 = joinsplit(r->s1, &j1);
t2 = joinsplit(r->s2, &j2);
if(j1.last->link != j2.start)
continue;
if(j1.end == j2.end)
if((t1 == Branch && (t2 == Join || t2 == Setcond)) ||
(t2 == Join && (t1 == Join || t1 == Setcond))) {
applypred(r, &j1, Falsecond, Delbranch);
applypred(r, &j2, Truecond, Delbranch);
excise(r);
continue;
}
if(t1 == End || t1 == Branch) {
applypred(r, &j1, Falsecond, Keepbranch);
excise(r);
continue;
}
}
}
}