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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
/*
* function literals aka closures
*/
#include <u.h>
#include <libc.h>
#include "go.h"
void
closurehdr(Node *ntype)
{
Node *n, *name, *a;
NodeList *l;
n = nod(OCLOSURE, N, N);
n->ntype = ntype;
n->funcdepth = funcdepth;
funchdr(n);
// steal ntype's argument names and
// leave a fresh copy in their place.
// references to these variables need to
// refer to the variables in the external
// function declared below; see walkclosure.
n->list = ntype->list;
n->rlist = ntype->rlist;
ntype->list = nil;
ntype->rlist = nil;
for(l=n->list; l; l=l->next) {
name = l->n->left;
if(name)
name = newname(name->sym);
a = nod(ODCLFIELD, name, l->n->right);
a->isddd = l->n->isddd;
if(name)
name->isddd = a->isddd;
ntype->list = list(ntype->list, a);
}
for(l=n->rlist; l; l=l->next) {
name = l->n->left;
if(name)
name = newname(name->sym);
ntype->rlist = list(ntype->rlist, nod(ODCLFIELD, name, l->n->right));
}
}
Node*
closurebody(NodeList *body)
{
Node *func, *v;
NodeList *l;
if(body == nil)
body = list1(nod(OEMPTY, N, N));
func = curfn;
func->nbody = body;
func->endlineno = lineno;
funcbody(func);
// closure-specific variables are hanging off the
// ordinary ones in the symbol table; see oldname.
// unhook them.
// make the list of pointers for the closure call.
for(l=func->cvars; l; l=l->next) {
v = l->n;
v->closure->closure = v->outer;
v->heapaddr = nod(OADDR, oldname(v->sym), N);
}
return func;
}
static Node* makeclosure(Node *func);
void
typecheckclosure(Node *func, int top)
{
Node *oldfn;
NodeList *l;
Node *v;
oldfn = curfn;
typecheck(&func->ntype, Etype);
func->type = func->ntype->type;
// Type check the body now, but only if we're inside a function.
// At top level (in a variable initialization: curfn==nil) we're not
// ready to type check code yet; we'll check it later, because the
// underlying closure function we create is added to xtop.
if(curfn && func->type != T) {
curfn = func;
typechecklist(func->nbody, Etop);
curfn = oldfn;
}
// type check the & of closed variables outside the closure,
// so that the outer frame also grabs them and knows they
// escape.
func->enter = nil;
for(l=func->cvars; l; l=l->next) {
v = l->n;
if(v->type == T) {
// if v->type is nil, it means v looked like it was
// going to be used in the closure but wasn't.
// this happens because when parsing a, b, c := f()
// the a, b, c gets parsed as references to older
// a, b, c before the parser figures out this is a
// declaration.
v->op = 0;
continue;
}
// For a closure that is called in place, but not
// inside a go statement, avoid moving variables to the heap.
if ((top & (Ecall|Eproc)) == Ecall)
v->heapaddr->etype = 1;
typecheck(&v->heapaddr, Erv);
func->enter = list(func->enter, v->heapaddr);
v->heapaddr = N;
}
// Create top-level function
xtop = list(xtop, makeclosure(func));
}
static Node*
makeclosure(Node *func)
{
Node *xtype, *v, *addr, *xfunc, *cv;
NodeList *l, *body;
static int closgen;
char *p;
vlong offset;
/*
* wrap body in external function
* that begins by reading closure parameters.
*/
xtype = nod(OTFUNC, N, N);
xtype->list = func->list;
xtype->rlist = func->rlist;
// create the function
xfunc = nod(ODCLFUNC, N, N);
snprint(namebuf, sizeof namebuf, "func·%.3d", ++closgen);
xfunc->nname = newname(lookup(namebuf));
xfunc->nname->sym->flags |= SymExported; // disable export
xfunc->nname->ntype = xtype;
xfunc->nname->defn = xfunc;
declare(xfunc->nname, PFUNC);
xfunc->nname->funcdepth = func->funcdepth;
xfunc->funcdepth = func->funcdepth;
xfunc->endlineno = func->endlineno;
// declare variables holding addresses taken from closure
// and initialize in entry prologue.
body = nil;
offset = widthptr;
xfunc->needctxt = func->cvars != nil;
for(l=func->cvars; l; l=l->next) {
v = l->n;
if(v->op == 0)
continue;
addr = nod(ONAME, N, N);
p = smprint("&%s", v->sym->name);
addr->sym = lookup(p);
free(p);
addr->ntype = nod(OIND, typenod(v->type), N);
addr->class = PAUTO;
addr->addable = 1;
addr->ullman = 1;
addr->used = 1;
addr->curfn = xfunc;
xfunc->dcl = list(xfunc->dcl, addr);
v->heapaddr = addr;
cv = nod(OCLOSUREVAR, N, N);
cv->type = ptrto(v->type);
cv->xoffset = offset;
body = list(body, nod(OAS, addr, cv));
offset += widthptr;
}
typechecklist(body, Etop);
walkstmtlist(body);
xfunc->enter = body;
xfunc->nbody = func->nbody;
xfunc->dcl = concat(func->dcl, xfunc->dcl);
if(xfunc->nbody == nil)
fatal("empty body - won't generate any code");
typecheck(&xfunc, Etop);
xfunc->closure = func;
func->closure = xfunc;
func->nbody = nil;
func->list = nil;
func->rlist = nil;
return xfunc;
}
Node*
walkclosure(Node *func, NodeList **init)
{
Node *clos, *typ;
NodeList *l;
char buf[20];
int narg;
// If no closure vars, don't bother wrapping.
if(func->cvars == nil)
return func->closure->nname;
// Create closure in the form of a composite literal.
// supposing the closure captures an int i and a string s
// and has one float64 argument and no results,
// the generated code looks like:
//
// clos = &struct{F uintptr; A0 *int; A1 *string}{func·001, &i, &s}
//
// The use of the struct provides type information to the garbage
// collector so that it can walk the closure. We could use (in this case)
// [3]unsafe.Pointer instead, but that would leave the gc in the dark.
// The information appears in the binary in the form of type descriptors;
// the struct is unnamed so that closures in multiple packages with the
// same struct type can share the descriptor.
narg = 0;
typ = nod(OTSTRUCT, N, N);
typ->list = list1(nod(ODCLFIELD, newname(lookup("F")), typenod(types[TUINTPTR])));
for(l=func->cvars; l; l=l->next) {
if(l->n->op == 0)
continue;
snprint(buf, sizeof buf, "A%d", narg++);
typ->list = list(typ->list, nod(ODCLFIELD, newname(lookup(buf)), l->n->heapaddr->ntype));
}
clos = nod(OCOMPLIT, N, nod(OIND, typ, N));
clos->esc = func->esc;
clos->right->implicit = 1;
clos->list = concat(list1(nod(OCFUNC, func->closure->nname, N)), func->enter);
// Force type conversion from *struct to the func type.
clos = nod(OCONVNOP, clos, N);
clos->type = func->type;
typecheck(&clos, Erv);
// typecheck will insert a PTRLIT node under CONVNOP,
// tag it with escape analysis result.
clos->left->esc = func->esc;
// non-escaping temp to use, if any.
// orderexpr did not compute the type; fill it in now.
if(func->alloc != N) {
func->alloc->type = clos->left->left->type;
func->alloc->orig->type = func->alloc->type;
clos->left->right = func->alloc;
func->alloc = N;
}
walkexpr(&clos, init);
return clos;
}
static Node *makepartialcall(Node*, Type*, Node*);
void
typecheckpartialcall(Node *fn, Node *sym)
{
switch(fn->op) {
case ODOTINTER:
case ODOTMETH:
break;
default:
fatal("invalid typecheckpartialcall");
}
// Create top-level function.
fn->nname = makepartialcall(fn, fn->type, sym);
fn->right = sym;
fn->op = OCALLPART;
fn->type = fn->nname->type;
}
static Node*
makepartialcall(Node *fn, Type *t0, Node *meth)
{
Node *ptr, *n, *fld, *call, *xtype, *xfunc, *cv, *savecurfn;
Type *rcvrtype, *basetype, *t;
NodeList *body, *l, *callargs, *retargs;
char *p;
Sym *sym;
Pkg *spkg;
static Pkg* gopkg;
int i, ddd;
// TODO: names are not right
rcvrtype = fn->left->type;
if(exportname(meth->sym->name))
p = smprint("%-hT.%s·fm", rcvrtype, meth->sym->name);
else
p = smprint("%-hT.(%-S)·fm", rcvrtype, meth->sym);
basetype = rcvrtype;
if(isptr[rcvrtype->etype])
basetype = basetype->type;
if(basetype->etype != TINTER && basetype->sym == S)
fatal("missing base type for %T", rcvrtype);
spkg = nil;
if(basetype->sym != S)
spkg = basetype->sym->pkg;
if(spkg == nil) {
if(gopkg == nil)
gopkg = mkpkg(strlit("go"));
spkg = gopkg;
}
sym = pkglookup(p, spkg);
free(p);
if(sym->flags & SymUniq)
return sym->def;
sym->flags |= SymUniq;
savecurfn = curfn;
curfn = N;
xtype = nod(OTFUNC, N, N);
i = 0;
l = nil;
callargs = nil;
ddd = 0;
xfunc = nod(ODCLFUNC, N, N);
curfn = xfunc;
for(t = getinargx(t0)->type; t; t = t->down) {
snprint(namebuf, sizeof namebuf, "a%d", i++);
n = newname(lookup(namebuf));
n->class = PPARAM;
xfunc->dcl = list(xfunc->dcl, n);
callargs = list(callargs, n);
fld = nod(ODCLFIELD, n, typenod(t->type));
if(t->isddd) {
fld->isddd = 1;
ddd = 1;
}
l = list(l, fld);
}
xtype->list = l;
i = 0;
l = nil;
retargs = nil;
for(t = getoutargx(t0)->type; t; t = t->down) {
snprint(namebuf, sizeof namebuf, "r%d", i++);
n = newname(lookup(namebuf));
n->class = PPARAMOUT;
xfunc->dcl = list(xfunc->dcl, n);
retargs = list(retargs, n);
l = list(l, nod(ODCLFIELD, n, typenod(t->type)));
}
xtype->rlist = l;
xfunc->dupok = 1;
xfunc->nname = newname(sym);
xfunc->nname->sym->flags |= SymExported; // disable export
xfunc->nname->ntype = xtype;
xfunc->nname->defn = xfunc;
declare(xfunc->nname, PFUNC);
// Declare and initialize variable holding receiver.
body = nil;
xfunc->needctxt = 1;
cv = nod(OCLOSUREVAR, N, N);
cv->xoffset = widthptr;
cv->type = rcvrtype;
if(cv->type->align > widthptr)
cv->xoffset = cv->type->align;
ptr = nod(ONAME, N, N);
ptr->sym = lookup("rcvr");
ptr->class = PAUTO;
ptr->addable = 1;
ptr->ullman = 1;
ptr->used = 1;
ptr->curfn = xfunc;
xfunc->dcl = list(xfunc->dcl, ptr);
if(isptr[rcvrtype->etype] || isinter(rcvrtype)) {
ptr->ntype = typenod(rcvrtype);
body = list(body, nod(OAS, ptr, cv));
} else {
ptr->ntype = typenod(ptrto(rcvrtype));
body = list(body, nod(OAS, ptr, nod(OADDR, cv, N)));
}
call = nod(OCALL, nod(OXDOT, ptr, meth), N);
call->list = callargs;
call->isddd = ddd;
if(t0->outtuple == 0) {
body = list(body, call);
} else {
n = nod(OAS2, N, N);
n->list = retargs;
n->rlist = list1(call);
body = list(body, n);
n = nod(ORETURN, N, N);
body = list(body, n);
}
xfunc->nbody = body;
typecheck(&xfunc, Etop);
sym->def = xfunc;
xtop = list(xtop, xfunc);
curfn = savecurfn;
return xfunc;
}
Node*
walkpartialcall(Node *n, NodeList **init)
{
Node *clos, *typ;
// Create closure in the form of a composite literal.
// For x.M with receiver (x) type T, the generated code looks like:
//
// clos = &struct{F uintptr; R T}{M.T·f, x}
//
// Like walkclosure above.
if(isinter(n->left->type)) {
// Trigger panic for method on nil interface now.
// Otherwise it happens in the wrapper and is confusing.
n->left = cheapexpr(n->left, init);
checknil(n->left, init);
}
typ = nod(OTSTRUCT, N, N);
typ->list = list1(nod(ODCLFIELD, newname(lookup("F")), typenod(types[TUINTPTR])));
typ->list = list(typ->list, nod(ODCLFIELD, newname(lookup("R")), typenod(n->left->type)));
clos = nod(OCOMPLIT, N, nod(OIND, typ, N));
clos->esc = n->esc;
clos->right->implicit = 1;
clos->list = list1(nod(OCFUNC, n->nname->nname, N));
clos->list = list(clos->list, n->left);
// Force type conversion from *struct to the func type.
clos = nod(OCONVNOP, clos, N);
clos->type = n->type;
typecheck(&clos, Erv);
// typecheck will insert a PTRLIT node under CONVNOP,
// tag it with escape analysis result.
clos->left->esc = n->esc;
// non-escaping temp to use, if any.
// orderexpr did not compute the type; fill it in now.
if(n->alloc != N) {
n->alloc->type = clos->left->left->type;
n->alloc->orig->type = n->alloc->type;
clos->left->right = n->alloc;
n->alloc = N;
}
walkexpr(&clos, init);
return clos;
}