lower: 제네릭 인스턴스와 메서드

모노모피제이션이 실제로 코드를 만드는 자리가 여기다. 프론트엔드는 어떤
인스턴스가 존재하는지만 정했다. 검사기가 인스턴스마다 선언·바인딩·유닛·링크
이름을 기록하고, lowering 이 그 바인딩을 다시 걸고 같은 본문을 자기 이름으로
내린다. 제네릭 선언 자체는 코드가 없다.

comptime 인자는 값이 아니므로 호출에서 넘기지 않고 파라미터 자리도 잡지
않는다. 메서드 호출은 도달한 대상을 첫 인자로 넘긴다 -- self: Self 든
self: &Self 든 수신자의 주소로 같다. 구조체 메서드가 아예 lowering 되지
않고 있었다.

exec.py 13/13.

fec/src/check.c

@@ -464,12 +464,14 @@ static void pop_bindings(FeCheck *c, const FeBindSave *save);
 static void bind_self(FeCheck *c, FeType *owner);
 static void instance_key(char *out, const char *unit, const char *name,
                          FeType **args, unsigned count);
-static int instance_record(FeCheck *c, const char *key, FeLoc loc);
+static int instance_record(FeCheck *c, const char *key, FeLoc loc,
+                           FeNode *decl, FeUnit *home, FeType *owner);
+static const char *instance_cname(FeCheck *c, const char *key);
 static int instance_descend(FeCheck *c, FeLoc loc);
 static void instantiate_body(FeCheck *c, FeUnit *home, FeNode *decl,
                              FeType *owner, FeBindSave *bindings, FeLoc site);
 static void check_instance_method(FeCheckerState *s, FeType *owner,
-                                  FeNode *method, FeLoc site);
+                                  FeNode *method, FeLoc site, FeNode *call);
 
 typedef struct FeFlowSlot {
     FeSym *sym;
@@ -1318,7 +1320,7 @@ static FeType *check_expr_core(FeCheckerState *s, FeNode *n)
                     fe_type_intern(&c->types,"void");
                 if (bound) {
                     pop_bindings(c,&msave);
-                    check_instance_method(s,et,method,n->loc);
+                    check_instance_method(s,et,method,n->loc,n);
                 }
                 return n->sem_type;
             }
@@ -2249,6 +2251,14 @@ static void instance_key(char *out, const char *unit, const char *name,
 
 /* Already built, or being built right now. Re-asking for a pending instance is
    how a recursive generic terminates, so it must not look like a new one. */
+static const char *instance_cname(FeCheck *c, const char *key)
+{
+    unsigned i;
+    for (i=0;i<c->instance_count;++i)
+        if (!strcmp(c->instances[i].key,key)) return c->instances[i].cname;
+    return 0;
+}
+
 static int instance_known(FeCheck *c, const char *key)
 {
     unsigned i;
@@ -2257,14 +2267,27 @@ static int instance_known(FeCheck *c, const char *key)
     return 0;
 }
 
-static int instance_record(FeCheck *c, const char *key, FeLoc loc)
+static int instance_record(FeCheck *c, const char *key, FeLoc loc,
+                           FeNode *decl, FeUnit *home, FeType *owner)
 {
+    FeInstance *inst;
+    unsigned i;
     if (instance_known(c,key)) return 0;
     if (c->instance_count>=FE_GENERIC_INSTANCE_MAX) {
         err(c,loc,"too many generic instances");
         return -1;
     }
-    strcpy(c->instances[c->instance_count].key,key);
+    inst=&c->instances[c->instance_count];
+    strcpy(inst->key,key);
+    inst->decl=decl;
+    inst->home=home ? home->name : 0;
+    inst->owner=owner;
+    inst->cname=unit_cname(c,key);
+    /* The bindings in force right now are the ones this instance was built
+       with, and lowering has to see exactly those again. */
+    inst->bind_count=c->types.param_count;
+    for (i=0;i<c->types.param_count && i<FE_TYPE_PARAM_MAX;++i)
+        inst->binds[i]=c->types.params[i];
     ++c->instance_count;
     return 1;
 }
@@ -2357,7 +2380,7 @@ static FeType *instantiate_struct(FeCheck *c, FeUnit *home, const char *name,
         return unknown(c);
     }
     instance_key(key,home->name,name,args,count);
-    if (instance_record(c,key,loc)<0) return unknown(c);
+    if (instance_record(c,key,loc,decl,home,0)<0) return unknown(c);
     return build_struct_instance(c,home,decl,key,args,count);
 }
 
@@ -2537,8 +2560,10 @@ static FeType *check_generic_call(FeCheckerState *s, FeNode *n, FeSym *sym,
     instance_key(key,home->name,decl->text,args,want);
     push_bindings(c,&save,decl,args,want);
     result=check_call_args(s,n,sym,home->name,want);
+    fresh=instance_record(c,key,n->loc,decl,home,0);
     pop_bindings(c,&save);
-    fresh=instance_record(c,key,n->loc);
+    /* The call goes to this instance, not to the declaration it came from. */
+    if (n->a) n->a->cname=(char *)instance_cname(c,key);
     if (fresh>0) {
         if (!instance_descend(c,n->loc)) return result;
         push_bindings(c,&save,decl,args,want);
@@ -2572,8 +2597,9 @@ static FeType *check_static_method_call(FeCheckerState *s, FeNode *n,
     push_instance_bindings(c,&save,owner);
     bind_self(c,owner);
     result=check_call_args(s,n,&fake,home->name,0);
+    fresh=instance_record(c,key,n->loc,method,home,owner);
     pop_bindings(c,&save);
-    fresh=instance_record(c,key,n->loc);
+    if (n->a) n->a->cname=(char *)instance_cname(c,key);
     if (fresh>0) {
         if (!instance_descend(c,n->loc)) return result;
         push_instance_bindings(c,&save,owner);
@@ -2587,7 +2613,7 @@ static FeType *check_static_method_call(FeCheckerState *s, FeNode *n,
 
 /* The body of a method on a generic instance, checked once per instance. */
 static void check_instance_method(FeCheckerState *s, FeType *owner,
-                                  FeNode *method, FeLoc site)
+                                  FeNode *method, FeLoc site, FeNode *call)
 {
     FeCheck *c=s->c;
     FeUnit *home=current_unit(c);
@@ -2596,7 +2622,17 @@ static void check_instance_method(FeCheckerState *s, FeType *owner,
     FeType *self_args[1];
     self_args[0]=owner;
     instance_key(key,home->name,method->text,self_args,1);
-    if (instance_record(c,key,site)<=0) return;
+    {
+        FeBindSave probe;
+        int fresh;
+        push_instance_bindings(c,&probe,owner);
+        bind_self(c,owner);
+        fresh=instance_record(c,key,site,method,home,owner);
+        pop_bindings(c,&probe);
+        /* The call names this instance's copy of the method. */
+        if (call && call->a) call->a->cname=(char *)instance_cname(c,key);
+        if (fresh<=0) return;
+    }
     if (!instance_descend(c,site)) return;
     push_instance_bindings(c,&save,owner);
     bind_self(c,owner);

fec/src/check.h

@@ -14,6 +14,15 @@ typedef struct FeScope FeScope;
 #define FE_GENERIC_INSTANCE_MAX 512
 typedef struct FeInstance {
     char key[FE_GENERIC_KEY_MAX];
+    /* What lowering needs to build this instance's code: the declaration, the
+       arguments bound while it was checked, the unit those names belong to,
+       and the name the linker will see. */
+    FeNode *decl;
+    FeTypeBind binds[FE_TYPE_PARAM_MAX];
+    unsigned bind_count;
+    const char *home;
+    const char *cname;
+    FeType *owner;               /* set when the instance is a method */
 } FeInstance;
 
 /* The checker spans a whole build, not one file. Names cross unit boundaries,

fec/src/lower.c

@@ -62,6 +62,8 @@ static void lower_stmt(Lower *L, FeNode *n);
 static void store_into(Lower *L, FeIrPlace dst, Slot value, FeNode *n,
                        unsigned long size);
 static void lower_for(Lower *L, FeNode *n);
+static int fn_is_generic(const FeNode *fn);
+static void lower_fn_as(Lower *L, FeNode *fn, const char *name);
 static Slot lower_slice(Lower *L, FeNode *n);
 static void guard(Lower *L, unsigned ok, FeIrTrap reason, unsigned long line);
 static void lower_match(Lower *L, FeNode *n);
@@ -450,7 +452,7 @@ static Slot lower_call(Lower *L, FeNode *n)
 {
     unsigned args[16];
     unsigned count = 0;
-    FeNode *arg;
+    FeNode *arg = n->children;
     FeType *ret = n->sem_type;
     FeIrType rt = ir_type(ret);
     unsigned result_local = 0;
@@ -468,7 +470,28 @@ static Slot lower_call(Lower *L, FeNode *n)
                                    ir_align(ret), "result");
         args[count++] = fe_ir_addr(L->m, L->b, fe_ir_at_local(result_local, 0));
     }
-    for (arg = n->children; arg; arg = arg->next) {
+    /* A method call passes what it was reached through as its first argument.
+       `self: Self` and `self: &Self` are the same thing here: the address of
+       the receiver, because an aggregate never travels in a register. */
+    if (n->a && n->a->kind == FE_N_MEMBER && n->sem_decl) {
+        FeNode *first = n->sem_decl->a ? n->sem_decl->a->children : 0;
+        if (first && first->text && !strcmp(first->text, "self")) {
+            Slot recv = lower_expr(L, n->a->a);
+            args[count++] = recv.is_place ? as_address(L, recv, n->a->a)
+                                          : recv.temp;
+        }
+    }
+    /* A generic call passes its type arguments first. They were consumed when
+       the instance was chosen and carry no value, so they are not passed. */
+    {
+        FeNode *p;
+        for (p = n->sem_decl && n->sem_decl->a ? n->sem_decl->a->children : 0;
+             p && arg; p = p->next) {
+            if (!(p->flags & FE_NODE_COMPTIME)) break;
+            arg = arg->next;
+        }
+    }
+    for (; arg; arg = arg->next) {
         Slot a = lower_expr(L, arg);
         if (count >= 16) { fail(L, "too many arguments", n); break; }
         args[count++] = a.type == FE_IR_MEM ? as_address(L, a, arg)
@@ -1286,13 +1309,22 @@ static void lower_global(Lower *L, FeNode *n)
     fe_ir_global(L->m, n->cname, ir_type(t), size, ir_align(t), init);
 }
 
-static void lower_fn(Lower *L, FeNode *fn)
+static int fn_is_generic(const FeNode *fn)
+{
+    FeNode *p;
+    if (!fn) return 0;
+    for (p = fn->a ? fn->a->children : 0; p; p = p->next)
+        if (p->flags & FE_NODE_COMPTIME) return 1;
+    return 0;
+}
+
+static void lower_fn_as(Lower *L, FeNode *fn, const char *name)
 {
     FeNode *p;
     FeType *ret = fn->b ? fe_type_from_ast(&L->c->types, fn->b) : 0;
     FeIrFunc *f;
-    if (!fn->cname) return;
-    f = fe_ir_func(L->m, fn->cname, ir_type(ret), ir_size(ret));
+    if (!name) return;
+    f = fe_ir_func(L->m, name, ir_type(ret), ir_size(ret));
     if (!f) return;
     L->fn = f;
     L->ret_type = ret;
@@ -1302,10 +1334,16 @@ static void lower_fn(Lower *L, FeNode *fn)
     if (f->returns_by_address)
         L->ret_local = fe_ir_local(L->m, f, FE_IR_PTR, 4, 4, "result");
     for (p = fn->a ? fn->a->children : 0; p; p = p->next) {
-        FeType *pt = fe_type_from_ast(&L->c->types, p->a);
+        FeType *pt;
+        int by_address;
+        unsigned local;
+        /* A comptime parameter was consumed at compile time; it has no
+           storage and takes no argument slot. */
+        if (p->flags & FE_NODE_COMPTIME) continue;
+        pt = fe_type_from_ast(&L->c->types, p->a);
         /* An aggregate parameter arrives as an address. */
-        int by_address = ir_type(pt) == FE_IR_MEM;
-        unsigned local = by_address
+        by_address = ir_type(pt) == FE_IR_MEM;
+        local = by_address
             ? fe_ir_local(L->m, f, FE_IR_PTR, 4, 4, p->text)
             : fe_ir_local(L->m, f, ir_type(pt), ir_size(pt), ir_align(pt),
                           p->text);
@@ -1323,6 +1361,11 @@ static void lower_fn(Lower *L, FeNode *fn)
     fe_ir_ret(L->b, 0, 0);
 }
 
+static void lower_fn(Lower *L, FeNode *fn)
+{
+    lower_fn_as(L, fn, fn->cname);
+}
+
 int fe_lower_program(FeCheck *c, FeIrModule *out)
 {
     Lower L;
@@ -1353,12 +1396,41 @@ int fe_lower_program(FeCheck *c, FeIrModule *out)
                 f = fe_ir_func(out, n->cname, ir_type(ret), ir_size(ret));
                 if (f) f->is_extern = 1;
             }
-            else if (n->kind == FE_N_FN && n->c) {
+            else if (n->kind == FE_N_FN && n->c && !fn_is_generic(n)) {
                 lower_fn(&L, n);
                 /* The entry unit is the one the build was rooted at. */
                 if (u == 0 && n->text && !strcmp(n->text, "main"))
                     out->entry_main = n->cname;
             }
     }
+    /* Each instance the checker reached is a function of its own: the same
+       body, read with different types bound, under its own link name. This is
+       where monomorphisation actually produces code -- the front end only
+       decided which instances exist. */
+    for (u = 0; u < c->instance_count && !L.failed; ++u) {
+        FeInstance *inst = &c->instances[u];
+        FeUnit *home;
+        FeTypeBind save[FE_TYPE_PARAM_MAX];
+        unsigned save_count;
+        unsigned k;
+        if (!inst->decl || !inst->decl->c || !inst->cname || !inst->home)
+            continue;
+        home = 0;
+        for (k = 0; k < c->build->count; ++k)
+            if (!strcmp(c->build->units[k].name, inst->home))
+                home = &c->build->units[k];
+        if (!home) continue;
+        c->ast = &home->ast;
+        c->unit = home;
+        c->types.unit_name = home->name;
+        save_count = c->types.param_count;
+        for (k = 0; k < FE_TYPE_PARAM_MAX; ++k) save[k] = c->types.params[k];
+        c->types.param_count = inst->bind_count;
+        for (k = 0; k < inst->bind_count && k < FE_TYPE_PARAM_MAX; ++k)
+            c->types.params[k] = inst->binds[k];
+        lower_fn_as(&L, inst->decl, inst->cname);
+        c->types.param_count = save_count;
+        for (k = 0; k < FE_TYPE_PARAM_MAX; ++k) c->types.params[k] = save[k];
+    }
     return !L.failed;
 }

fec/tests/exec/generic.fe

@@ -0,0 +1,21 @@
+// EXIT:39
+unit generic;
+
+struct Box(T) {
+    value: T,
+
+    pub fn new(v: T) -> Self { return Self{ value: v }; }
+    pub fn get(self: &Self) -> T { return self.value; }
+}
+
+fn id(comptime T: type, v: T) -> T { return v; }
+
+fn twice(comptime T: type, v: T) -> T { return v + v; }
+
+fn main() -> i32 {
+    let a: i32 = id(i32, 7);
+    let b: u8 = id(u8, 9 as u8);
+    let c: i32 = twice(i32, 10);
+    let box: Box(i32) = Box(i32).new(3);
+    return a + (b as i32) + c + box.get();
+}