void
gen(Node *n)
{
Node *l, nod;
Prog *sp, *spc, *spb;
Case *cn;
long sbc, scc;
int snbreak, sncontin;
int f, o, oldreach;
loop:
if(n == Z)
return;
nearln = n->lineno;
o = n->op;
if(debug['G'])
if(o != OLIST)
print("%L %O\n", nearln, o);
if(!canreach) {
switch(o) {
case OLABEL:
case OCASE:
case OLIST:
case OBREAK:
case OFOR:
case OWHILE:
case ODWHILE:
/* all handled specially - see switch body below */
break;
default:
if(warnreach) {
warn(n, "unreachable code %O", o);
warnreach = 0;
}
}
}
switch(o) {
default:
complex(n);
cgen(n, Z);
break;
case OLIST:
gen(n->left);
rloop:
n = n->right;
goto loop;
case ORETURN:
canreach = 0;
warnreach = !suppress;
complex(n);
if(n->type == T)
break;
l = n->left;
if(l == Z) {
noretval(3);
gbranch(ORETURN);
break;
}
if(typecmplx[n->type->etype]) {
sugen(l, nodret, n->type->width);
noretval(3);
gbranch(ORETURN);
break;
}
regret(&nod, n);
cgen(l, &nod);
regfree(&nod);
if(typefd[n->type->etype])
noretval(1);
else
noretval(2);
gbranch(ORETURN);
break;
case OLABEL:
canreach = 1;
l = n->left;
if(l) {
l->pc = pc;
if(l->label)
patch(l->label, pc);
}
gbranch(OGOTO); /* prevent self reference in reg */
patch(p, pc);
goto rloop;
case OGOTO:
canreach = 0;
warnreach = !suppress;
n = n->left;
if(n == Z)
return;
if(n->complex == 0) {
diag(Z, "label undefined: %s", n->sym->name);
return;
}
if(suppress)
return;
gbranch(OGOTO);
if(n->pc) {
patch(p, n->pc);
return;
}
if(n->label)
patch(n->label, pc-1);
n->label = p;
return;
case OCASE:
canreach = 1;
l = n->left;
if(cases == C)
diag(n, "case/default outside a switch");
if(l == Z) {
newcase();
cases->val = 0;
cases->def = 1;
cases->label = pc;
cases->isv = 0;
goto rloop;
}
complex(l);
if(l->type == T)
goto rloop;
if(l->op == OCONST)
if(typeword[l->type->etype] && l->type->etype != TIND) {
newcase();
cases->val = l->vconst;
cases->def = 0;
cases->label = pc;
cases->isv = typev[l->type->etype];
goto rloop;
}
diag(n, "case expression must be integer constant");
goto rloop;
case OSWITCH:
l = n->left;
complex(l);
if(l->type == T)
break;
if(!typechlvp[l->type->etype] || l->type->etype == TIND) {
diag(n, "switch expression must be integer");
break;
}
gbranch(OGOTO); /* entry */
sp = p;
cn = cases;
cases = C;
newcase();
sbc = breakpc;
breakpc = pc;
snbreak = nbreak;
nbreak = 0;
gbranch(OGOTO);
spb = p;
gen(n->right); /* body */
if(canreach){
gbranch(OGOTO);
patch(p, breakpc);
nbreak++;
}
patch(sp, pc);
doswit(l);
patch(spb, pc);
cases = cn;
breakpc = sbc;
canreach = nbreak!=0;
if(canreach == 0)
warnreach = !suppress;
nbreak = snbreak;
break;
case OWHILE:
case ODWHILE:
l = n->left;
gbranch(OGOTO); /* entry */
sp = p;
scc = continpc;
continpc = pc;
gbranch(OGOTO);
spc = p;
sbc = breakpc;
breakpc = pc;
snbreak = nbreak;
nbreak = 0;
gbranch(OGOTO);
spb = p;
patch(spc, pc);
if(n->op == OWHILE)
patch(sp, pc);
bcomplex(l, Z); /* test */
patch(p, breakpc);
if(l->op != OCONST || vconst(l) == 0)
nbreak++;
if(n->op == ODWHILE)
patch(sp, pc);
gen(n->right); /* body */
gbranch(OGOTO);
patch(p, continpc);
patch(spb, pc);
continpc = scc;
breakpc = sbc;
canreach = nbreak!=0;
if(canreach == 0)
warnreach = !suppress;
nbreak = snbreak;
break;
case OFOR:
l = n->left;
if(!canreach && l->right->left && warnreach) {
warn(n, "unreachable code FOR");
warnreach = 0;
}
gen(l->right->left); /* init */
gbranch(OGOTO); /* entry */
sp = p;
/*
* if there are no incoming labels in the
* body and the top's not reachable, warn
*/
if(!canreach && warnreach && deadheads(n)) {
warn(n, "unreachable code %O", o);
warnreach = 0;
}
scc = continpc;
continpc = pc;
gbranch(OGOTO);
spc = p;
sbc = breakpc;
breakpc = pc;
snbreak = nbreak;
nbreak = 0;
sncontin = ncontin;
ncontin = 0;
gbranch(OGOTO);
spb = p;
patch(spc, pc);
gen(l->right->right); /* inc */
patch(sp, pc);
if(l->left != Z) { /* test */
bcomplex(l->left, Z);
patch(p, breakpc);
if(l->left->op != OCONST || vconst(l->left) == 0)
nbreak++;
}
canreach = 1;
gen(n->right); /* body */
if(canreach){
gbranch(OGOTO);
patch(p, continpc);
ncontin++;
}
if(!ncontin && l->right->right && warnreach) {
warn(l->right->right, "unreachable FOR inc");
warnreach = 0;
}
patch(spb, pc);
continpc = scc;
breakpc = sbc;
canreach = nbreak!=0;
if(canreach == 0)
warnreach = !suppress;
nbreak = snbreak;
ncontin = sncontin;
break;
case OCONTINUE:
if(continpc < 0) {
diag(n, "continue not in a loop");
break;
}
gbranch(OGOTO);
patch(p, continpc);
ncontin++;
canreach = 0;
warnreach = !suppress;
break;
case OBREAK:
if(breakpc < 0) {
diag(n, "break not in a loop");
break;
}
/*
* Don't complain about unreachable break statements.
* There are breaks hidden in yacc's output and some people
* write return; break; in their switch statements out of habit.
* However, don't confuse the analysis by inserting an
* unreachable reference to breakpc either.
*/
if(!canreach)
break;
gbranch(OGOTO);
patch(p, breakpc);
nbreak++;
canreach = 0;
warnreach = !suppress;
break;
case OIF:
l = n->left;
if(bcomplex(l, n->right)) {
if(typefd[l->type->etype])
f = !l->fconst;
else
f = !l->vconst;
if(debug['c'])
print("%L const if %s\n", nearln, f ? "false" : "true");
if(f) {
canreach = 1;
supgen(n->right->left);
oldreach = canreach;
canreach = 1;
gen(n->right->right);
/*
* treat constant ifs as regular ifs for
* reachability warnings.
*/
if(!canreach && oldreach && debug['w'] < 2)
warnreach = 0;
}
else {
canreach = 1;
gen(n->right->left);
oldreach = canreach;
canreach = 1;
supgen(n->right->right);
/*
* treat constant ifs as regular ifs for
* reachability warnings.
*/
if(!oldreach && canreach && debug['w'] < 2)
warnreach = 0;
canreach = oldreach;
}
}
else {
sp = p;
canreach = 1;
if(n->right->left != Z)
gen(n->right->left);
oldreach = canreach;
canreach = 1;
if(n->right->right != Z) {
gbranch(OGOTO);
patch(sp, pc);
sp = p;
gen(n->right->right);
}
patch(sp, pc);
canreach = canreach || oldreach;
if(canreach == 0)
warnreach = !suppress;
}
break;
case OSET:
case OUSED:
case OPREFETCH:
usedset(n->left, o);
break;
}
}
void
gen(Node *n)
{
Node *l, nod;
Prog *sp, *spc, *spb;
Case *cn;
long sbc, scc;
int o, f;
loop:
if(n == Z)
return;
nearln = n->lineno;
o = n->op;
if(debug['G'])
if(o != OLIST)
print("%L %O\n", nearln, o);
retok = 0;
switch(o) {
default:
complex(n);
cgen(n, Z);
break;
case OLIST:
gen(n->left);
rloop:
n = n->right;
goto loop;
case ORETURN:
retok = 1;
complex(n);
if(n->type == T)
break;
l = n->left;
if(l == Z) {
noretval(3);
gbranch(ORETURN);
break;
}
if(typesuv[n->type->etype]) {
sugen(l, nodret, n->type->width);
noretval(3);
gbranch(ORETURN);
break;
}
regret(&nod, n);
cgen(l, &nod);
regfree(&nod);
if(typefd[n->type->etype])
noretval(1);
else
noretval(2);
gbranch(ORETURN);
break;
case OLABEL:
l = n->left;
if(l) {
l->pc = pc;
if(l->label)
patch(l->label, pc);
}
gbranch(OGOTO); /* prevent self reference in reg */
patch(p, pc);
goto rloop;
case OGOTO:
retok = 1;
n = n->left;
if(n == Z)
return;
if(n->complex == 0) {
diag(Z, "label undefined: %s", n->sym->name);
return;
}
if(suppress)
return;
gbranch(OGOTO);
if(n->pc) {
patch(p, n->pc);
return;
}
if(n->label)
patch(n->label, pc-1);
n->label = p;
return;
case OCASE:
l = n->left;
if(cases == C)
diag(n, "case/default outside a switch");
if(l == Z) {
casf();
cases->val = 0;
cases->def = 1;
cases->label = pc;
goto rloop;
}
complex(l);
if(l->type == T)
goto rloop;
if(l->op == OCONST)
if(typechl[l->type->etype]) {
casf();
cases->val = l->vconst;
cases->def = 0;
cases->label = pc;
goto rloop;
}
diag(n, "case expression must be integer constant");
goto rloop;
case OSWITCH:
l = n->left;
complex(l);
if(l->type == T)
break;
if(!typechl[l->type->etype]) {
diag(n, "switch expression must be integer");
break;
}
gbranch(OGOTO); /* entry */
sp = p;
cn = cases;
cases = C;
casf();
sbc = breakpc;
breakpc = pc;
gbranch(OGOTO);
spb = p;
gen(n->right);
gbranch(OGOTO);
patch(p, breakpc);
patch(sp, pc);
regalloc(&nod, l, Z);
nod.type = types[TLONG];
cgen(l, &nod);
doswit(&nod);
regfree(&nod);
patch(spb, pc);
cases = cn;
breakpc = sbc;
break;
case OWHILE:
case ODWHILE:
l = n->left;
gbranch(OGOTO); /* entry */
sp = p;
scc = continpc;
continpc = pc;
gbranch(OGOTO);
spc = p;
sbc = breakpc;
breakpc = pc;
gbranch(OGOTO);
spb = p;
patch(spc, pc);
if(n->op == OWHILE)
patch(sp, pc);
bcomplex(l, Z); /* test */
patch(p, breakpc);
if(n->op == ODWHILE)
patch(sp, pc);
gen(n->right); /* body */
gbranch(OGOTO);
patch(p, continpc);
patch(spb, pc);
continpc = scc;
breakpc = sbc;
break;
case OFOR:
l = n->left;
gen(l->right->left); /* init */
gbranch(OGOTO); /* entry */
sp = p;
scc = continpc;
continpc = pc;
gbranch(OGOTO);
spc = p;
sbc = breakpc;
breakpc = pc;
gbranch(OGOTO);
spb = p;
patch(spc, pc);
gen(l->right->right); /* inc */
patch(sp, pc);
if(l->left != Z) { /* test */
bcomplex(l->left, Z);
patch(p, breakpc);
}
gen(n->right); /* body */
gbranch(OGOTO);
patch(p, continpc);
patch(spb, pc);
continpc = scc;
breakpc = sbc;
break;
case OCONTINUE:
if(continpc < 0) {
diag(n, "continue not in a loop");
break;
}
gbranch(OGOTO);
patch(p, continpc);
break;
case OBREAK:
if(breakpc < 0) {
diag(n, "break not in a loop");
break;
}
gbranch(OGOTO);
patch(p, breakpc);
break;
case OIF:
l = n->left;
if(bcomplex(l, n->right)) {
if(typefd[l->type->etype])
f = !l->fconst;
else
f = !l->vconst;
if(debug['c'])
print("%L const if %s\n", nearln, f ? "false" : "true");
if(f) {
supgen(n->right->left);
gen(n->right->right);
}
else {
gen(n->right->left);
supgen(n->right->right);
}
}
else {
sp = p;
if(n->right->left != Z)
gen(n->right->left);
if(n->right->right != Z) {
gbranch(OGOTO);
patch(sp, pc);
sp = p;
gen(n->right->right);
}
patch(sp, pc);
}
break;
case OSET:
case OUSED:
usedset(n->left, o);
break;
}
}
