Re: memref_conflict_p

[Michael Hayes <m dot hayes at elec dot canterbury dot ac dot nz>]

Jeffrey A Law writes:
 > Can you fix up those minor issues and resubmit?  (I believe it'll be OK when
 > you resubmit, but I'd like to peek at it again).

Here's a cleaned up patch, keeping the n_refs argument for generality.


Sun Nov 29 22:17:59 1998  Michael Hayes  <m.hayes@elec.canterbury.ac.nz>

	* alias.c (addr_side_effect_eval): New function.
	(memrefs_conflict_p): Use it.
	* rtl.h (addr_side_effect_eval): Prototype it.

Index: rtl.h
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/rtl.h,v
retrieving revision 1.68
diff -c -3 -p -r1.68 rtl.h
*** rtl.h	1998/11/27 10:09:10	1.68
--- rtl.h	1998/11/29 09:14:21
*************** extern void end_alias_analysis		PROTO ((
*** 1520,1524 ****
--- 1520,1525 ----
  
  extern void record_base_value		PROTO ((int, rtx, int));
  extern void record_alias_subset         PROTO ((int, int));
+ extern void addr_side_effect_eval	PROTO ((rtx, int, int));
  
  #endif /* _RTL_H */
Index: alias.c
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/alias.c,v
retrieving revision 1.42
diff -c -3 -p -r1.42 alias.c
*** alias.c	1998/10/21 09:53:17	1.42
--- alias.c	1998/11/29 09:14:22
*************** base_alias_check (x, y, x_mode, y_mode)
*** 860,865 ****
--- 860,904 ----
    return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
  }
  
+ /* Modify the memory address ADDR to evaluate and remove the address
+    side effect.  The returned address is that of the (N_REFS + 1)th
+    memory reference.  */
+ 
+ rtx
+ addr_side_effect_eval (addr, size, n_refs)
+      rtx addr;
+      int size;
+      int n_refs;
+ {
+   int offset;
+   
+   switch (GET_CODE (addr))
+     {
+     case PRE_INC:
+       offset = (n_refs + 1) * size;
+       break;
+     case PRE_DEC:
+       offset = -(n_refs + 1) * size;
+       break;
+     case POST_INC:
+       offset = n_refs * size;
+       break;
+     case POST_DEC:
+       offset = -n_refs * size;
+       break;
+ 
+     default:
+       return addr;
+     }
+   
+   if (offset)
+     addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
+   else
+     addr = XEXP (addr, 0);
+ 
+   return addr;
+ }
+ 
  /* Return nonzero if X and Y (memory addresses) could reference the
     same location in memory.  C is an offset accumulator.  When
     C is nonzero, we are testing aliases between X and Y + C.
*************** memrefs_conflict_p (xsize, x, ysize, y, 
*** 889,901 ****
    else if (GET_CODE (x) == LO_SUM)
      x = XEXP (x, 1);
    else
!     x = canon_rtx (x);
    if (GET_CODE (y) == HIGH)
      y = XEXP (y, 0);
    else if (GET_CODE (y) == LO_SUM)
      y = XEXP (y, 1);
    else
!     y = canon_rtx (y);
  
    if (rtx_equal_for_memref_p (x, y))
      {
--- 928,940 ----
    else if (GET_CODE (x) == LO_SUM)
      x = XEXP (x, 1);
    else
!     x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
    if (GET_CODE (y) == HIGH)
      y = XEXP (y, 0);
    else if (GET_CODE (y) == LO_SUM)
      y = XEXP (y, 1);
    else
!     y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
  
    if (rtx_equal_for_memref_p (x, y))
      {