added sq_tailcall()

include/squirrel.h

@@ -332,6 +332,7 @@ SQUIRREL_API SQRESULT sq_throwerror(HSQUIRRELVM v,const SQChar *err);
 SQUIRREL_API SQRESULT sq_throwobject(HSQUIRRELVM v);
 SQUIRREL_API void sq_reseterror(HSQUIRRELVM v);
 SQUIRREL_API void sq_getlasterror(HSQUIRRELVM v);
+SQUIRREL_API SQRESULT sq_tailcall(HSQUIRRELVM v, SQInteger nparams);
 
 /*raw object handling*/
 SQUIRREL_API SQRESULT sq_getstackobj(HSQUIRRELVM v,SQInteger idx,HSQOBJECT *po);

squirrel/sqapi.cpp

@@ -1188,6 +1188,25 @@ SQRESULT sq_call(HSQUIRRELVM v,SQInteger params,SQBool retval,SQBool raiseerror)
     return sq_throwerror(v,_SC("call failed"));
 }
 
+SQRESULT sq_tailcall(HSQUIRRELVM v, SQInteger nparams)
+{
+	SQObjectPtr &res = v->GetUp(-(nparams + 1));
+	if (type(res) != OT_CLOSURE) {
+		return sq_throwerror(v, _SC("only closure can be tail called"));
+	}
+	SQClosure *clo = _closure(res);
+	if (clo->_function->_bgenerator)
+	{
+		return sq_throwerror(v, _SC("generators cannot be tail called"));
+	}
+	
+	SQInteger stackbase = (v->_top - nparams) - v->_stackbase;
+	if (!v->TailCall(clo, stackbase, nparams)) {
+		return SQ_ERROR;
+	}
+	return SQ_TAILCALL_FLAG;
+}
+
 SQRESULT sq_suspendvm(HSQUIRRELVM v)
 {
     return v->Suspend();

squirrel/sqbaselib.cpp

@@ -885,7 +885,12 @@ static SQInteger closure_pcall(HSQUIRRELVM v)
 
 static SQInteger closure_call(HSQUIRRELVM v)
 {
-    return SQ_SUCCEEDED(sq_call(v,sq_gettop(v)-1,SQTrue,SQTrue))?1:SQ_ERROR;
+	SQObjectPtr &c = stack_get(v, -1);
+	if (type(c) == OT_CLOSURE && (_closure(c)->_function->_bgenerator == false))
+	{
+		return sq_tailcall(v, sq_gettop(v) - 1);
+	}
+	return SQ_SUCCEEDED(sq_call(v, sq_gettop(v) - 1, SQTrue, SQTrue)) ? 1 : SQ_ERROR;
 }
 
 static SQInteger _closure_acall(HSQUIRRELVM v,SQBool raiseerror)

squirrel/sqvm.cpp

@@ -744,7 +744,8 @@ exception_restore:
                         continue;
                     case OT_NATIVECLOSURE: {
                         bool suspend;
-                        _GUARD(CallNative(_nativeclosure(clo), arg3, _stackbase+arg2, clo,suspend));
+						bool tailcall;
+                        _GUARD(CallNative(_nativeclosure(clo), arg3, _stackbase+arg2, clo, (SQInt32)sarg0, suspend, tailcall));
                         if(suspend){
                             _suspended = SQTrue;
                             _suspended_target = sarg0;
@@ -753,7 +754,7 @@ exception_restore:
                             outres = clo;
                             return true;
                         }
-                        if(sarg0 != -1) {
+                        if(sarg0 != -1 && !tailcall) {
                             STK(arg0) = clo;
                         }
                                            }
@@ -772,10 +773,10 @@ exception_restore:
                                 _GUARD(StartCall(_closure(clo), -1, arg3, stkbase, false));
                                 break;
                             case OT_NATIVECLOSURE:
-                                bool suspend;
+                                bool dummy;
                                 stkbase = _stackbase+arg2;
                                 _stack._vals[stkbase] = inst;
-                                _GUARD(CallNative(_nativeclosure(clo), arg3, stkbase, clo,suspend));
+                                _GUARD(CallNative(_nativeclosure(clo), arg3, stkbase, clo, -1, dummy, dummy));
                                 break;
                             default: break; //shutup GCC 4.x
                         }
@@ -1139,7 +1140,7 @@ void SQVM::CallDebugHook(SQInteger type,SQInteger forcedline)
     _debughook = true;
 }
 
-bool SQVM::CallNative(SQNativeClosure *nclosure, SQInteger nargs, SQInteger newbase, SQObjectPtr &retval, bool &suspend)
+bool SQVM::CallNative(SQNativeClosure *nclosure, SQInteger nargs, SQInteger newbase, SQObjectPtr &retval, SQInt32 target,bool &suspend, bool &tailcall)
 {
     SQInteger nparamscheck = nclosure->_nparamscheck;
     SQInteger newtop = newbase + nargs + nclosure->_noutervalues;
@@ -1169,6 +1170,7 @@ bool SQVM::CallNative(SQNativeClosure *nclosure, SQInteger nargs, SQInteger newb
 
     if(!EnterFrame(newbase, newtop, false)) return false;
     ci->_closure  = nclosure;
+	ci->_target = target;
 
     SQInteger outers = nclosure->_noutervalues;
     for (SQInteger i = 0; i < outers; i++) {
@@ -1183,7 +1185,12 @@ bool SQVM::CallNative(SQNativeClosure *nclosure, SQInteger nargs, SQInteger newb
     _nnativecalls--;
 
     suspend = false;
-    if (ret == SQ_SUSPEND_FLAG) {
+	tailcall = false;
+	if (ret == SQ_TAILCALL_FLAG) {
+		tailcall = true;
+		return true;
+	}
+    else if (ret == SQ_SUSPEND_FLAG) {
         suspend = true;
     }
     else if (ret < 0) {
@@ -1202,6 +1209,23 @@ bool SQVM::CallNative(SQNativeClosure *nclosure, SQInteger nargs, SQInteger newb
     return true;
 }
 
+bool SQVM::TailCall(SQClosure *closure, SQInteger parambase,SQInteger nparams)
+{
+	SQInteger last_top = _top;
+	SQObjectPtr clo = closure;
+	if (ci->_root)
+	{
+		Raise_Error("root calls cannot invoke tailcalls");
+		return false;
+	}
+	for (SQInteger i = 0; i < nparams; i++) STK(i) = STK(parambase + i);
+	bool ret = StartCall(closure, ci->_target, nparams, _stackbase, true);
+	if (last_top >= _top) {
+		_top = last_top;
+	}
+	return ret;
+}
+
 #define FALLBACK_OK         0
 #define FALLBACK_NO_MATCH   1
 #define FALLBACK_ERROR      2
@@ -1551,8 +1575,8 @@ SQInteger prevstackbase = _stackbase;
         return Execute(closure, nparams, stackbase, outres, raiseerror);
         break;
     case OT_NATIVECLOSURE:{
-        bool suspend;
+        bool dummy;
-        return CallNative(_nativeclosure(closure), nparams, stackbase, outres,suspend);
+        return CallNative(_nativeclosure(closure), nparams, stackbase, outres, -1, dummy, dummy);
 
                           }
         break;

squirrel/sqvm.h

@@ -8,6 +8,7 @@
 #define MIN_STACK_OVERHEAD 15
 
 #define SQ_SUSPEND_FLAG -666
+#define SQ_TAILCALL_FLAG -777
 #define DONT_FALL_BACK 666
 //#define EXISTS_FALL_BACK -1
 
@@ -56,7 +57,8 @@ public:
     bool Init(SQVM *friendvm, SQInteger stacksize);
     bool Execute(SQObjectPtr &func, SQInteger nargs, SQInteger stackbase, SQObjectPtr &outres, SQBool raiseerror, ExecutionType et = ET_CALL);
     //starts a native call return when the NATIVE closure returns
-    bool CallNative(SQNativeClosure *nclosure, SQInteger nargs, SQInteger newbase, SQObjectPtr &retval,bool &suspend);
+    bool CallNative(SQNativeClosure *nclosure, SQInteger nargs, SQInteger newbase, SQObjectPtr &retval, SQInt32 target, bool &suspend,bool &tailcall);
+	bool TailCall(SQClosure *closure, SQInteger firstparam, SQInteger nparams);
     //starts a SQUIRREL call in the same "Execution loop"
     bool StartCall(SQClosure *closure, SQInteger target, SQInteger nargs, SQInteger stackbase, bool tailcall);
     bool CreateClassInstance(SQClass *theclass, SQObjectPtr &inst, SQObjectPtr &constructor);