re PR rtl-optimization/70484 (Wrong optimization with aliasing and access via char)

2016-04-04  Richard Biener  <rguenther@suse.de>

	PR rtl-optimization/70484
	* rtl.h (canon_output_dependence): Declare.
	* alias.c (canon_output_dependence): New function.
	* dse.c (record_store): Use canon_output_dependence rather
	than canon_true_dependence.

	* gcc.dg/torture/pr70484.c: New testcase.

From-SVN: r234709

gcc/ChangeLog

+2016-04-04  Richard Biener  <rguenther@suse.de>
+
+	PR rtl-optimization/70484
+	* rtl.h (canon_output_dependence): Declare.
+	* alias.c (canon_output_dependence): New function.
+	* dse.c (record_store): Use canon_output_dependence rather
+	than canon_true_dependence.
+
 2016-03-30  Jan Hubicka  <hubicka@ucw.cz>
 
 	PR ipa/68881

gcc/alias.c

@@ -3057,6 +3057,20 @@ output_dependence (const_rtx mem, const_rtx x)
 			     /*mem_canonicalized=*/false,
 			     /*x_canonicalized*/false, /*writep=*/true);
 }
+
+/* Likewise, but we already have a canonicalized MEM, and X_ADDR for X.
+   Also, consider X in X_MODE (which might be from an enclosing
+   STRICT_LOW_PART / ZERO_EXTRACT).
+   If MEM_CANONICALIZED is true, MEM is canonicalized.  */
+
+int
+canon_output_dependence (const_rtx mem, bool mem_canonicalized,
+			 const_rtx x, machine_mode x_mode, rtx x_addr)
+{
+  return write_dependence_p (mem, x, x_mode, x_addr,
+			     mem_canonicalized, /*x_canonicalized=*/true,
+			     /*writep=*/true);
+}
 
 
 

gcc/dse.c

@@ -1609,10 +1609,9 @@ record_store (rtx body, bb_info_t bb_info)
 	   the value of store_info.  If it is, set the rhs to NULL to
 	   keep it from being used to remove a load.  */
 	{
-	  if (canon_true_dependence (s_info->mem,
-				     GET_MODE (s_info->mem),
-				     s_info->mem_addr,
-				     mem, mem_addr))
+	  if (canon_output_dependence (s_info->mem, true,
+				       mem, GET_MODE (mem),
+				       mem_addr))
 	    {
 	      s_info->rhs = NULL;
 	      s_info->const_rhs = NULL;

gcc/rtl.h

@@ -3652,6 +3652,8 @@ extern int anti_dependence (const_rtx, const_rtx);
 extern int canon_anti_dependence (const_rtx, bool,
 				  const_rtx, machine_mode, rtx);
 extern int output_dependence (const_rtx, const_rtx);
+extern int canon_output_dependence (const_rtx, bool,
+				    const_rtx, machine_mode, rtx);
 extern int may_alias_p (const_rtx, const_rtx);
 extern void init_alias_target (void);
 extern void init_alias_analysis (void);

gcc/testsuite/ChangeLog

+2016-04-04  Richard Biener  <rguenther@suse.de>
+
+	PR rtl-optimization/70484
+	* gcc.dg/torture/pr70484.c: New testcase.
+
 2016-04-04  Marek Polacek  <polacek@redhat.com>
 
 	PR c/70307

gcc/testsuite/gcc.dg/torture/pr70484.c

+/* { dg-do run } */
+
+extern void abort (void);
+
+int __attribute__((noinline,noclone))
+f(int *pi, long *pl)
+{
+  *pi = 1;
+  *pl = 0;
+  return *(char *)pi;
+}
+
+int main()
+{
+  union { long l; int i; } a;
+  if (f (&a.i, &a.l) != 0)
+    abort ();
+  return 0;
+}