re PR target/45099 ([avr] Warning could be issued for use of register variables that will fail.)

	PR target/45099
	* config/avr/avr.c (avr_function_arg_advance): Error if a fixed
	register is needed for a function argument.

From-SVN: r173791

gcc/ChangeLog

+2011-05-16  Georg-Johann Lay  <avr@gjlay.de>
+
+	PR target/45099
+	* config/avr/avr.c (avr_function_arg_advance): Error if a fixed
+	register is needed for a function argument.
+
 2011-05-16  Richard Guenther  <rguenther@suse.de>
 
 	* gimple.c (struct type_hash_pair): New type.

gcc/config/avr/avr.c

@@ -1796,6 +1796,20 @@ avr_function_arg_advance (CUMULATIVE_ARGS *cum, enum machine_mode mode,
       cfun->machine->sibcall_fails = 1;
     }
 
+  /* Test if all registers needed by the ABI are actually available.  If the
+     user has fixed a GPR needed to pass an argument, an (implicit) function
+     call would clobber that fixed register.  See PR45099 for an example.  */
+  
+  if (cum->regno >= 0)
+    {
+      int regno;
+
+      for (regno = cum->regno; regno < cum->regno + bytes; regno++)
+        if (fixed_regs[regno])
+          error ("Register %s is needed to pass a parameter but is fixed",
+                 reg_names[regno]);
+    }
+      
   if (cum->nregs <= 0)
     {
       cum->nregs = 0;