Added new code hints for use at the end of a function

git-svn-id: svn://svn.cc65.org/cc65/trunk@552 b7a2c559-68d2-44c3-8de9-860c34a00d81

src/cc65/codegen.c

@@ -485,6 +485,12 @@ void g_leave (int flags, int val)
     int k;
     char buf [40];
 
+    /* CF_REG is set if we're returning a value from the function */
+    if ((flags & CF_REG) == 0) {
+	AddCodeHint ("x:-");
+	AddCodeHint ("a:-");
+    }
+
     /* How many bytes of locals do we have to drop? */
     k = -oursp;
 
@@ -499,8 +505,10 @@ void g_leave (int flags, int val)
      	/* Drop stackframe or leave with rts */
      	k += funcargs;
      	if (k == 0) {
+	    AddCodeHint ("y:-");	/* Y register no longer used */
      	    AddCodeLine ("\trts");
      	} else if (k <= 8) {
+	    AddCodeHint ("y:-");	/* Y register no longer used */
      	    AddCodeLine ("\tjmp\tincsp%d", k);
      	} else {
      	    CheckLocalOffs (k);
@@ -515,6 +523,9 @@ void g_leave (int flags, int val)
      	    /* We've a stack frame to drop */
      	    ldyconst (k);
      	    strcat (buf, "y");
+     	} else {
+	    /* Y register no longer used */
+	    AddCodeHint ("y:-");	
 	}
      	if (flags & CF_CONST) {
      	    if ((flags & CF_TYPE) != CF_LONG) {

src/cc65/function.c

@@ -198,6 +198,7 @@ void NewFunc (SymEntry* Func)
 /* Parse argument declarations and function body. */
 {
     int isbrk;
+    unsigned Flags;
 
     /* Get the function descriptor from the function entry */
     FuncDesc* D = DecodePtr (Func->Type+1);
@@ -251,7 +252,9 @@ void NewFunc (SymEntry* Func)
      	}
 #endif
 	RestoreRegVars (0);
-        g_leave (CF_NONE, 0);
+
+	Flags = HasVoidReturn (CurrentFunc)? CF_NONE : CF_REG;
+        g_leave (Flags, 0);				      
     }
 
     /* Dump literal data created by the function */

src/cc65/optimize.c

@@ -536,6 +536,14 @@ static int IsLocalLabel (const Line* L)
 
 
 
+static int IsExtLabel (const Line* L)
+/* Return true if the line is an external label line */
+{
+    return (L->Line [0] == '_');
+}
+
+
+
 static int IsLabel (const Line* L)
 /* Return true if the line is a label line */
 {
@@ -1136,13 +1144,15 @@ static unsigned RVUInt2 (Line* L,
 	     	L = GetTargetLine (L->Line+5);
 	    }
 
-	    /* Get the next instruction line */
+	    /* Get the next line, skip local labels */
-       	    L = NextInstruction (L);
+	    do {
+       	    	L = NextCodeSegLine (L);
+	    } while (L && (IsLocalLabel (L) || L->Line[0] == '\0'));
 
 	    /* Bail out if we're done */
-	    if (L == 0 || IsLabel (L)) {
+	    if (L == 0 || IsExtLabel (L)) {
-	    	/* Something is wrong */
+	    	/* End of function reached */
-	    	return REG_ALL;
+	    	goto ExitPoint;
 	    }
 
 	    /* Check if we had this line already. If so, bail out, if not,
@@ -1154,8 +1164,19 @@ static unsigned RVUInt2 (Line* L,
 
 	} while (LineMatch (L, "\tjmp\tL") || LineMatch (L, "\tbra\tL"));
 
+	/* Special handling of code hints */
+       	if (IsHintLine (L)) {
+
+	    if (IsHint (L, "a:-") && (Used & REG_A) == 0) {
+		Unused |= REG_A;
+	    } else if (IsHint (L, "x:-") && (Used & REG_X) == 0) {
+		Unused |= REG_X;
+	    } else if (IsHint (L, "y:-") && (Used & REG_Y) == 0) {
+		Unused |= REG_Y;
+	    }
+
 	/* Special handling for branches */
-	if (LineMatchX (L, ShortBranches) >= 0 ||
+	} else if (LineMatchX (L, ShortBranches) >= 0 ||
 	    LineMatchX (L, LongBranches) >= 0) {
 	    const char* Target = L->Line+5;
 	    if (Target[0] == 'L') {
@@ -1169,12 +1190,12 @@ static unsigned RVUInt2 (Line* L,
 	       	U1 = RVUInt1 (L, LC, Used, Unused);
 	       	return U1 | U2;		/* Used in any of the branches */
 	    }
-	}
+	} else {
 
 	    /* Search for the instruction in this line */
 	    I = FindCmd (L);
 
-	/* If we don't find it, assume all other registers are */
+	    /* If we don't find it, assume all other registers are used */
 	    if (I < 0) {
 		break;
 	    }
@@ -1204,6 +1225,8 @@ static unsigned RVUInt2 (Line* L,
 		Unused |= R;
 	    }
 
+	}
+
        	/* If we know about all registers, bail out */
        	if ((Used | Unused) == REG_ALL) {
 	    break;

src/cc65/stmt.c

@@ -166,7 +166,7 @@ static void doreturn (void)
 /* Handle 'return' statement here */
 {
     struct expent lval;
-    unsigned etype = 0;		/* Type of return expression */
+    unsigned Flags = 0;	       	/* Code generator flags */
     int HaveVal = 0;		/* Do we have a return value in ax? */
 
 
@@ -177,7 +177,7 @@ static void doreturn (void)
        	}
        	if (evalexpr (CF_NONE, hie0, &lval) == 0) {
        	    /* Constant value */
-       	    etype = CF_CONST;
+       	    Flags = CF_CONST;
        	} else {
     	    /* Value in the primary register */
     	    HaveVal = 1;
@@ -185,13 +185,13 @@ static void doreturn (void)
 
     	/* Convert the return value to the type of the function result */
     	if (!HasVoidReturn (CurrentFunc)) {
-       	    etype |= assignadjust (GetReturnType (CurrentFunc), &lval) & ~CF_CONST;
+       	    Flags |= (assignadjust (GetReturnType (CurrentFunc), &lval) & ~CF_CONST) | CF_REG;
     	}
     } else if (!HasVoidReturn (CurrentFunc)) {
     	Error ("Function `%s' must return a value", GetFuncName (CurrentFunc));
     }
     RestoreRegVars (HaveVal);
-    g_leave (etype, lval.e_const);
+    g_leave (Flags, lval.e_const);
 }