Do not save any register variables when entering main(). Do not restore the C

stack when leaving main(). Both are unnecessary and just bloat the executable.

src/cc65/codegen.c

@@ -507,9 +507,13 @@ void g_enter (unsigned flags, unsigned argsize)
 
 
 
-void g_leave (void)
+void g_leave (int IsMainFunc)
 /* Function epilogue */
 {
+    /* In the main function nothing has to be dropped because the program
+    ** is terminated anyway.
+    */
+    if (!IsMainFunc) {
         /* How many bytes of locals do we have to drop? */
         unsigned ToDrop = (unsigned) -StackPtr;
 
@@ -536,6 +540,7 @@ void g_leave (void)
             AddCodeLine ("jsr leave");
 
         }
+    }
 
     /* Add the final rts */
     AddCodeLine ("rts");

src/cc65/codegen.h

@@ -247,7 +247,7 @@ void g_scale (unsigned flags, long val);
 void g_enter (unsigned flags, unsigned argsize);
 /* Function prologue */
 
-void g_leave (void);
+void g_leave (int IsMainFunc);
 /* Function epilogue */
 
 

src/cc65/function.c

@@ -646,11 +646,13 @@ void NewFunc (SymEntry* Func, FuncDesc* D)
     /* Output the function exit code label */
     g_defcodelabel (F_GetRetLab (CurrentFunc));
 
-    /* Restore the register variables */
+    /* Restore the register variables (not necessary for main function) */
+    if (!F_IsMainFunc (CurrentFunc)) {
         F_RestoreRegVars (CurrentFunc);
+    }
 
     /* Generate the exit code */
-    g_leave ();
+    g_leave (F_IsMainFunc (CurrentFunc));
 
     /* Emit references to imports/exports */
     EmitExternals ();

src/cc65/locals.c

@@ -111,22 +111,31 @@ static void ParseRegisterDecl (Declarator* Decl, int Reg)
     /* Get the size of the variable */
     unsigned Size = SizeOf (Decl->Type);
 
-    /* Save the current contents of the register variable on stack */
-    F_AllocLocalSpace (CurrentFunc);
-    g_save_regvars (Reg, Size);
-
-    /* Add the symbol to the symbol table. We do that now, because for register
-    ** variables the current stack pointer is implicitly used as location for
-    ** the save area.
-    */
-    Sym = AddLocalSym (Decl->Ident, Decl->Type, Decl->StorageClass, Reg);
-
     /* Check for an optional initialization */
     if (CurTok.Tok == TOK_ASSIGN) {
 
         /* Skip the '=' */
         NextToken ();
 
+        /* If the register variable is initialized, the initialization code may
+        ** access other already declared variables. This means that we have to
+        ** allocate them now.
+        */
+        F_AllocLocalSpace (CurrentFunc);
+
+        /* Save the current contents of the register variable on stack. This is
+        ** not necessary for the main function.
+        */
+        if (!F_IsMainFunc (CurrentFunc)) {
+            g_save_regvars (Reg, Size);
+        }
+
+        /* Add the symbol to the symbol table. We do that now, because for
+        ** register variables the current stack pointer is implicitly used
+        ** as location for the save area (unused in case of main()).
+        */
+        Sym = AddLocalSym (Decl->Ident, Decl->Type, Decl->StorageClass, Reg);
+
         /* Special handling for compound types */
         if (IsCompound) {
 
@@ -173,6 +182,21 @@ static void ParseRegisterDecl (Declarator* Decl, int Reg)
 
         /* Mark the variable as referenced */
         Sym->Flags |= SC_REF;
+    } else {
+
+        /* Save the current contents of the register variable on stack. This is
+        ** not necessary for the main function.
+        */
+        if (!F_IsMainFunc (CurrentFunc)) {
+            F_AllocLocalSpace (CurrentFunc);
+            g_save_regvars (Reg, Size);
+        }
+
+        /* Add the symbol to the symbol table. We do that now, because for
+        ** register variables the current stack pointer is implicitly used
+        ** as location for the save area (unused in case of main()).
+        */
+        Sym = AddLocalSym (Decl->Ident, Decl->Type, Decl->StorageClass, Reg);
     }
 
     /* Cannot allocate a variable of unknown size */