self hosting

src/cc/cc.h

@@ -232,14 +232,19 @@ typedef enum {
 	NSIZEOF,
 	NIF,
 	NDECL,
-	NEXPRSTMT
+	NEXPRSTMT,
+	NBUILTIN
 } Nodekind;
 
 typedef struct {
 	int offset;
 	Node *n;
 } InitMember;
 
+typedef enum {
+	BUILTIN_VASTART
+} Builtinkind;
+
 struct Node {
 	/* type tag, one of the N* types */
 	Nodekind t;
@@ -371,6 +376,15 @@ struct Node {
 		struct {
 			CTy *type;
 		} Sizeof;
+		struct {
+			Builtinkind t;
+			union {
+				struct {
+					Node *valist;
+					Node *param;
+				} Vastart;
+			};
+		} Builtin;
 	};
 };
 
@@ -393,8 +407,11 @@ struct Sym {
 			char *label;
 		} Global;
 		struct {
-			int isparam;
 			StkSlot *slot;
+			/* XXX make a Param sym type */ 
+			CTy *functy;
+			int paramidx;
+			int isparam;
 		} Local;
 		struct {
 			int64 v;

src/cc/parse.c

@@ -38,6 +38,7 @@ static Node  *primaryexpr(void);
 static Node  *declorstmt(void);
 static Node  *decl(void);
 static Node  *declinit(CTy *);
+static Node  *vastart();
 static void   fbody(void);
 static CTy   *declspecs(int *);
 
@@ -729,6 +730,8 @@ fbody(void)
 		if(nt->name) {
 			sym = definesym(&curfunc->pos, SCAUTO, nt->name, nt->type, 0);
 			sym->Local.isparam = 1;
+			sym->Local.paramidx = i;
+			sym->Local.functy = curfunc->type;
 			vecappend(curfunc->Func.params, sym);
 		}
 	}
@@ -2274,6 +2277,8 @@ primaryexpr(void)
 
 	switch (tok->k) {
 	case TOKIDENT:
+		if(strcmp(tok->v, "__builtin_va_start") == 0)
+			return vastart();
 		sym = lookup(syms, tok->v);
 		if(!sym)
 			errorposf(&tok->pos, "undefined symbol %s", tok->v);
@@ -2327,3 +2332,27 @@ primaryexpr(void)
 	return 0;
 }
 
+static Node *
+vastart()
+{
+	Node *n, *valist, *param;
+
+	n = mknode(NBUILTIN, &tok->pos);
+	expect(TOKIDENT);
+	expect('(');
+	valist = assignexpr();
+	expect(',');
+	param = assignexpr();
+	expect(')');
+	n->type = cvoid;
+	n->Builtin.t = BUILTIN_VASTART;
+	n->Builtin.Vastart.param = param;
+	n->Builtin.Vastart.valist = valist;
+	if(param->t != NIDENT)
+		errorposf(&n->pos, "expected an identifer in va_start");
+	if(param->Ident.sym->k != SYMLOCAL 
+	   || !param->Ident.sym->Local.isparam)
+		errorposf(&n->pos, "expected a parameter symbol in va_start");
+	return n;
+}
+

src/cmd/6c/emit.c

@@ -74,7 +74,7 @@ calcslotoffsets(Node *f)
 {
 	int i, tsz, curoffset;
 	StkSlot *s;
-
+	
 	curoffset = 0;
 	for(i = 0; i < f->Func.stkslots->len; i++) {
 		s = vecget(f->Func.stkslots, i);
@@ -85,6 +85,8 @@ calcslotoffsets(Node *f)
 		if(curoffset % s->align)
 			curoffset = (curoffset - (curoffset % s->align) + s->align);
 		s->offset = -curoffset;
+		if(f->type->Func.isvararg)
+			s->offset -= 176;
 	}
 	if(curoffset % 16)
 		curoffset = (curoffset - (curoffset % 16) + 16);
@@ -121,6 +123,16 @@ func(Node *f, char *label, int isglobal)
 	out("%s:\n", label);
 	pushq("rbp");
 	outi("movq %%rsp, %%rbp\n");
+    if (f->type->Func.isvararg) {
+    	stackoffset += 176;
+	 	outi("sub $176, %%rsp\n");
+		outi("movq %%rdi, (%%rsp)\n");
+		outi("movq %%rsi, 8(%%rsp)\n");
+		outi("movq %%rdx, 16(%%rsp)\n");
+		outi("movq %%rcx, 24(%%rsp)\n");
+		outi("movq %%r8, 32(%%rsp)\n");
+		outi("movq %%r9, 40(%%rsp)\n");
+    }
 	if (f->Func.localsz) {
 		outi("sub $%d, %%rsp\n", f->Func.localsz);
 		stackoffset += f->Func.localsz;
@@ -768,6 +780,22 @@ str(Node *n)
 	outi("movq (%%rax), %%rax\n", l);
 }
 
+static void
+vastart(Node *n)
+{
+	int argend;
+
+	expr(n->Builtin.Vastart.valist);
+	/* XXX currently only support int args */
+	argend = (n->Builtin.Vastart.param->Ident.sym->Local.paramidx + 1) * 8;
+    pushq("rcx");
+    outi("movl $%d, (%%rax)\n", argend);
+    outi("movl $%d, 4(%%rax)\n", 48 + 0 * 16);
+    outi("leaq %d(%%rbp), %%rcx\n", -176);
+    outi("movq %%rcx, 16(%%rax)\n");
+    popq("rcx");
+}
+
 static void
 expr(Node *n)
 {
@@ -814,6 +842,15 @@ expr(Node *n)
 	case NINCDEC:
 		incdec(n);
 		break;
+	case NBUILTIN:
+		switch(n->Builtin.t) {
+		case BUILTIN_VASTART:
+			vastart(n);
+			break;
+		default:
+			errorposf(&n->pos, "unimplemented builtin");
+		}
+		break;
 	default:
 		errorf("unimplemented emit expr %d\n", n->t);
 	}

src/selfhost/stdarg.h

@@ -8,12 +8,7 @@ typedef struct {
 
 typedef __va_elem va_list[1];
 
-#define va_start(X, Y) do { \
-                            (X)[0].gp_offset = 0; \
-                            (X)[0].fp_offset = 0; \
-                            (X)[0].overflow_arg_area = 0; \
-                            (X)[0].reg_save_area = 0;\
-                       } while(0);
+#define va_start(X, Y) __builtin_va_start((X), (Y))
 #define va_end(X) (X)
 
 int vfprintf(FILE *stream, const char *format, va_list ap);