EGCS bad on loop invariant optimization ?

[John Carr]

Try this patch.

Sun Apr 19 18:07:14 1998  John Carr  <jfc@mit.edu>

	* alias.c (true_dependence): If neither mode is QI or BLK and the
	modes are different, X and MEM do not alias.

*** alias.c~	Fri Apr 17 15:54:33 1998
--- alias.c	Sun Apr 19 18:06:30 1998
***************
*** 863,878 ****
  			    SIZE_FOR_MODE (x), x_addr, 0))
      return 0;
  
    /* If both references are struct references, or both are not, nothing
       is known about aliasing.
  
-      If either reference is QImode or BLKmode, ANSI C permits aliasing.
- 
       If both addresses are constant, or both are not, nothing is known
       about aliasing.  */
    if (MEM_IN_STRUCT_P (x) == MEM_IN_STRUCT_P (mem)
-       || mem_mode == QImode || mem_mode == BLKmode
-       || GET_MODE (x) == QImode || GET_MODE (x) == BLKmode
        || GET_CODE (x_addr) == AND || GET_CODE (mem_addr) == AND
        || varies (x_addr) == varies (mem_addr))
      return 1;
--- 863,884 ----
  			    SIZE_FOR_MODE (x), x_addr, 0))
      return 0;
  
+   /* If either reference is QImode or BLKmode, ANSI C permits aliasing.
+      Otherwise, if the types are different there is no aliasing.  */
+   if (mem_mode == QImode || mem_mode == BLKmode
+       || GET_MODE (x) == QImode || GET_MODE (x) == BLKmode)
+     return 1;
+ 
+   if (mem_mode != GET_MODE (x))
+     return 0;
+ 
    /* If both references are struct references, or both are not, nothing
       is known about aliasing.
  
       If both addresses are constant, or both are not, nothing is known
       about aliasing.  */
+ 
    if (MEM_IN_STRUCT_P (x) == MEM_IN_STRUCT_P (mem)
        || GET_CODE (x_addr) == AND || GET_CODE (mem_addr) == AND
        || varies (x_addr) == varies (mem_addr))
      return 1;