void
walkswitch(Node *sw)
{
/*
* reorder the body into (OLIST, cases, statements)
* cases have OGOTO into statements.
* both have inserted OBREAK statements
*/
walkstmtlist(sw->ninit);
if(sw->ntest == N) {
sw->ntest = nodbool(1);
typecheck(&sw->ntest, Erv);
}
if(sw->ntest->op == OTYPESW) {
typeswitch(sw);
//dump("sw", sw);
return;
}
exprswitch(sw);
}
/*
* convert switch of the form
* switch v := i.(type) { case t1: ..; case t2: ..; }
* into if statements
*/
static void
typeswitch(Node *sw)
{
Node *def;
NodeList *cas, *hash;
Node *a, *n;
Case *c, *c0, *c1;
int ncase;
Type *t;
Val v;
if(sw->ntest == nil)
return;
if(sw->ntest->right == nil) {
setlineno(sw);
yyerror("type switch must have an assignment");
return;
}
walkexpr(&sw->ntest->right, &sw->ninit);
if(!istype(sw->ntest->right->type, TINTER)) {
yyerror("type switch must be on an interface");
return;
}
cas = nil;
/*
* predeclare temporary variables
* and the boolean var
*/
facename = temp(sw->ntest->right->type);
a = nod(OAS, facename, sw->ntest->right);
typecheck(&a, Etop);
cas = list(cas, a);
casebody(sw, facename);
boolname = temp(types[TBOOL]);
typecheck(&boolname, Erv);
hashname = temp(types[TUINT32]);
typecheck(&hashname, Erv);
t = sw->ntest->right->type;
if(isnilinter(t))
a = syslook("efacethash", 1);
else
a = syslook("ifacethash", 1);
argtype(a, t);
a = nod(OCALL, a, N);
a->list = list1(facename);
a = nod(OAS, hashname, a);
typecheck(&a, Etop);
cas = list(cas, a);
c0 = mkcaselist(sw, Stype);
if(c0 != C && c0->type == Tdefault) {
def = c0->node->right;
c0 = c0->link;
} else {
def = nod(OBREAK, N, N);
}
/*
* insert if statement into each case block
*/
for(c=c0; c!=C; c=c->link) {
n = c->node;
switch(c->type) {
case Ttypenil:
v.ctype = CTNIL;
a = nod(OIF, N, N);
a->ntest = nod(OEQ, facename, nodlit(v));
typecheck(&a->ntest, Erv);
a->nbody = list1(n->right); // if i==nil { goto l }
n->right = a;
break;
case Ttypevar:
case Ttypeconst:
n->right = typeone(n);
break;
}
}
/*
* generate list of if statements, binary search for constant sequences
*/
while(c0 != C) {
if(c0->type != Ttypeconst) {
n = c0->node;
cas = list(cas, n->right);
c0=c0->link;
continue;
}
// identify run of constants
c1 = c = c0;
while(c->link!=C && c->link->type==Ttypeconst)
c = c->link;
c0 = c->link;
c->link = nil;
// sort by hash
c1 = csort(c1, typecmp);
// for debugging: linear search
if(0) {
for(c=c1; c!=C; c=c->link) {
n = c->node;
cas = list(cas, n->right);
}
continue;
}
// combine adjacent cases with the same hash
ncase = 0;
for(c=c1; c!=C; c=c->link) {
ncase++;
hash = list1(c->node->right);
while(c->link != C && c->link->hash == c->hash) {
hash = list(hash, c->link->node->right);
c->link = c->link->link;
}
c->node->right = liststmt(hash);
}
// binary search among cases to narrow by hash
cas = list(cas, typebsw(c1, ncase));
}
if(nerrors == 0) {
cas = list(cas, def);
sw->nbody = concat(cas, sw->nbody);
sw->list = nil;
walkstmtlist(sw->nbody);
}
}
/*
* normal (expression) switch.
* rebulid case statements into if .. goto
*/
static void
exprswitch(Node *sw)
{
Node *def;
NodeList *cas;
Node *a;
Case *c0, *c, *c1;
Type *t;
int arg, ncase;
casebody(sw, N);
arg = Snorm;
if(isconst(sw->ntest, CTBOOL)) {
arg = Strue;
if(sw->ntest->val.u.bval == 0)
arg = Sfalse;
}
walkexpr(&sw->ntest, &sw->ninit);
t = sw->type;
if(t == T)
return;
/*
* convert the switch into OIF statements
*/
exprname = N;
cas = nil;
if(arg != Strue && arg != Sfalse) {
exprname = temp(sw->ntest->type);
cas = list1(nod(OAS, exprname, sw->ntest));
typechecklist(cas, Etop);
} else {
exprname = nodbool(arg == Strue);
}
c0 = mkcaselist(sw, arg);
if(c0 != C && c0->type == Tdefault) {
def = c0->node->right;
c0 = c0->link;
} else {
def = nod(OBREAK, N, N);
}
loop:
if(c0 == C) {
cas = list(cas, def);
sw->nbody = concat(cas, sw->nbody);
sw->list = nil;
walkstmtlist(sw->nbody);
return;
}
// deal with the variables one-at-a-time
if(!okforcmp[t->etype] || c0->type != Texprconst) {
a = exprbsw(c0, 1, arg);
cas = list(cas, a);
c0 = c0->link;
goto loop;
}
// do binary search on run of constants
ncase = 1;
for(c=c0; c->link!=C; c=c->link) {
if(c->link->type != Texprconst)
break;
ncase++;
}
// break the chain at the count
c1 = c->link;
c->link = C;
// sort and compile constants
c0 = csort(c0, exprcmp);
a = exprbsw(c0, ncase, arg);
cas = list(cas, a);
c0 = c1;
goto loop;
}
/*
* convert switch of the form
* switch v := i.(type) { case t1: ..; case t2: ..; }
* into if statements
*/
void
typeswitch(Node *sw)
{
Node *def;
NodeList *cas;
Node *a;
Case *c, *c0, *c1;
int ncase;
Type *t;
if(sw->ntest == nil)
return;
if(sw->ntest->right == nil) {
setlineno(sw);
yyerror("type switch must have an assignment");
return;
}
walkexpr(&sw->ntest->right, &sw->ninit);
if(!istype(sw->ntest->right->type, TINTER)) {
yyerror("type switch must be on an interface");
return;
}
cas = nil;
/*
* predeclare temporary variables
* and the boolean var
*/
facename = nod(OXXX, N, N);
tempname(facename, sw->ntest->right->type);
a = nod(OAS, facename, sw->ntest->right);
typecheck(&a, Etop);
cas = list(cas, a);
casebody(sw, facename);
boolname = nod(OXXX, N, N);
tempname(boolname, types[TBOOL]);
typecheck(&boolname, Erv);
hashname = nod(OXXX, N, N);
tempname(hashname, types[TUINT32]);
typecheck(&hashname, Erv);
t = sw->ntest->right->type;
if(isnilinter(t))
a = syslook("efacethash", 1);
else
a = syslook("ifacethash", 1);
argtype(a, t);
a = nod(OCALL, a, N);
a->list = list1(facename);
a = nod(OAS, hashname, a);
typecheck(&a, Etop);
cas = list(cas, a);
c0 = mkcaselist(sw, Stype);
if(c0 != C && c0->type == Tdefault) {
def = c0->node->right;
c0 = c0->link;
} else {
def = nod(OBREAK, N, N);
}
loop:
if(c0 == C) {
cas = list(cas, def);
sw->nbody = concat(cas, sw->nbody);
sw->list = nil;
walkstmtlist(sw->nbody);
return;
}
// deal with the variables one-at-a-time
if(c0->type != Ttypeconst) {
a = typebsw(c0, 1);
cas = list(cas, a);
c0 = c0->link;
goto loop;
}
// do binary search on run of constants
ncase = 1;
for(c=c0; c->link!=C; c=c->link) {
if(c->link->type != Ttypeconst)
break;
ncase++;
}
// break the chain at the count
c1 = c->link;
c->link = C;
// sort and compile constants
c0 = csort(c0, typecmp);
a = typebsw(c0, ncase);
cas = list(cas, a);
c0 = c1;
goto loop;
}