Node*
typebsw(Case *c0, int ncase)
{
NodeList *cas;
Node *a, *n;
Case *c;
int i, half;
Val v;
cas = nil;
if(ncase < Ncase) {
for(i=0; i<ncase; i++) {
n = c0->node;
switch(c0->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 }
cas = list(cas, a);
break;
case Ttypevar:
a = typeone(n);
cas = list(cas, a);
break;
case Ttypeconst:
a = nod(OIF, N, N);
a->ntest = nod(OEQ, hashname, nodintconst(c0->hash));
typecheck(&a->ntest, Erv);
a->nbody = list1(typeone(n));
cas = list(cas, a);
break;
}
c0 = c0->link;
}
return liststmt(cas);
}
// find the middle and recur
c = c0;
half = ncase>>1;
for(i=1; i<half; i++)
c = c->link;
a = nod(OIF, N, N);
a->ntest = nod(OLE, hashname, nodintconst(c->hash));
typecheck(&a->ntest, Erv);
a->nbody = list1(typebsw(c0, half));
a->nelse = list1(typebsw(c->link, ncase-half));
return a;
}
/*
* 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);
}
}