invoke.texi (-fstrict-aliasing): Document.

	* invoke.texi (-fstrict-aliasing): Document.
	* rtl.texi (MEM_ALIAS_SET): Document.
	* flags.h (flag_strict_aliasing): Declare.
	* toplev.c (flag_strict_aliasing): Define.
	(f_options): Add -strict-aliasing.
	(main): Set flag_strict_aliasing if -O2 or higher.
	* tree.h (tree_type): Add alias_set field.
	(TYPE_ALIAS_SET): New macro.
	(TYPE_ALIAS_SET_KNOWN_P): Likewise.
	(get_alias_set): Declare.
	* tree.c (lang_get_alias_set): Define.
	(make_node): Initialize TYPE_ALIAS_SET.
	(get_alias_set): New function.
	* print-tree.c (print_node): Dump the alias set for a type.
	* c-tree.h (c_get_alias_set): Declare.
	* c-common.c (c_get_alias_set): New function.
	* c-decl.c (init_decl_processing): Set lang_get_alias_set.
	* expr.c (protect_from_queue): Propogage alias sets.
	(expand_assignment): Calculate alias set for new MEMs.
	(expand_expr): Likewise.
	* function.c (put_var_into_stack): Likewise.
	(put_reg_into_stack): Likewise.
	(gen_mem_addressof): Likewise.
	(assign_parms): Likewise.
	* stmt.c (expand_decl): Likewise.
	* varasm.c (make_decl_rtl): Eliminate redundant clearing of
	DECL_RTL.  Calculate alias set for new MEMs.
	* rtl.def (REG): Add dummy operand.
	(MEM): Add extra operand to store the MEM_ALIAS_SET.
	* rtl.h (MEM_ALIAS_SET): New macro.
	(gen_rtx_MEM): Declare.
	* emit-rtl.c (gen_rtx_MEM): New function.
	* gengenrtl.c (sepcial_rtx): Make MEMs special.
	* alias.c (CHECK_ALIAS_SETS_FOR_CONSISTENCY): New macro.
	(DIFFERENT_ALIAS_SETS_P): Likewise.
	(canon_rtx): Propogate the alias set to the new MEM.
	(true_dependence): Check the alias sets.
	(anti_dependence): Likewise.
	(output_dependence): Likewise.
	* explow.c (stabilize): Progoate alias sets.
	* integrate.c (copy_rtx_and_substitute): Likewise.
	* final.c (alter_subreg): Make sure not to leave MEM_IN_STRUCT_P
	in an unpredictable state.  Propogate alias sets.
	* reload1.c (reload): Clear MEM_ALIAS_SET for new MEMs about which
	we have no alias information.

From-SVN: r20719

1 files changed, 32 insertions, 0 deletions

diff --git a/gcc/alias.c b/gcc/alias.c
index 99df4fa..ab65bc4 100644
--- a/gcc/alias.c
+++ b/gcc/alias.c
@@ -42,6 +42,28 @@ static rtx find_base_value		PROTO((rtx));
 
 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
 
+/* Perform a basic sanity check.  Namely, that there are	
+   no alias sets if we're not doing strict aliasing.  This helps     
+   to catch bugs whereby someone uses PUT_CODE, but doesn't clear
+   MEM_ALIAS_SET, or where a MEM is allocated in some way other
+   than by the use of gen_rtx_MEM, and the MEM_ALIAS_SET is not
+   cleared.  */			
+#ifdef ENABLE_CHECKING	
+#define CHECK_ALIAS_SETS_FOR_CONSISTENCY(MEM1, MEM2)	\
+  (!flag_strict_aliasing				\
+   && (MEM_ALIAS_SET (MEM1) || MEM_ALIAS_SET (MEM2))	\
+   ? (abort (), 0) : 0)
+#else 
+#define CHECK_ALIAS_SETS_FOR_CONSISTENCY(MEM1, MEM2) 0
+#endif
+
+/* Returns nonzero if MEM1 and MEM2 do not alias because they are in
+   different alias sets.  */
+#define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2)		\
+  (CHECK_ALIAS_SETS_FOR_CONSISTENCY(MEM1, MEM2),	\
+   MEM_ALIAS_SET (MEM1) && MEM_ALIAS_SET (MEM2)		\
+   && MEM_ALIAS_SET (MEM1) != MEM_ALIAS_SET (MEM2))
+
 /* Cap the number of passes we make over the insns propagating alias
    information through set chains.
 
@@ -372,6 +394,7 @@ canon_rtx (x)
 	  MEM_VOLATILE_P (new) = MEM_VOLATILE_P (x);
 	  RTX_UNCHANGING_P (new) = RTX_UNCHANGING_P (x);
 	  MEM_IN_STRUCT_P (new) = MEM_IN_STRUCT_P (x);
+	  MEM_ALIAS_SET (new) = MEM_ALIAS_SET (x);
 	  x = new;
 	}
     }
@@ -874,6 +897,9 @@ true_dependence (mem, mem_mode, x, varies)
   if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
     return 1;
 
+  if (DIFFERENT_ALIAS_SETS_P (x, mem))
+    return 0;
+
   /* If X is an unchanging read, then it can't possibly conflict with any
      non-unchanging store.  It may conflict with an unchanging write though,
      because there may be a single store to this address to initialize it.
@@ -947,6 +973,9 @@ anti_dependence (mem, x)
   x = canon_rtx (x);
   mem = canon_rtx (mem);
 
+  if (DIFFERENT_ALIAS_SETS_P (x, mem))
+    return 0;
+
   x_addr = XEXP (x, 0);
   mem_addr = XEXP (mem, 0);
 
@@ -978,6 +1007,9 @@ output_dependence (mem, x)
   x = canon_rtx (x);
   mem = canon_rtx (mem);
 
+  if (DIFFERENT_ALIAS_SETS_P (x, mem))
+    return 0;
+
   return (memrefs_conflict_p (SIZE_FOR_MODE (mem), XEXP (mem, 0),
 			      SIZE_FOR_MODE (x), XEXP (x, 0), 0)
 	  && ! (MEM_IN_STRUCT_P (mem) && rtx_addr_varies_p (mem)