re PR target/35258 (two memcpy calls merged incorrectly with -O1)

2008-02-25  Andreas Krebbel  <krebbel1@de.ibm.com>

	PR target/35258
	* cse.c (cse_insn): Avoid creation of overlapping MEMs.
	* alias.c (nonoverlapping_memrefs_p): Export for use in other modules.
	* alias.h (nonoverlapping_memrefs_p): Likewise.

2008-02-25  Andreas Krebbel  <krebbel1@de.ibm.com>

	PR target/35258
	* gcc.dg/pr35258.c: New testcase.

From-SVN: r132628

gcc/ChangeLog

+2008-02-25  Andreas Krebbel  <krebbel1@de.ibm.com>
+
+	PR target/35258
+	* cse.c (cse_insn): Avoid creation of overlapping MEMs.
+	* alias.c (nonoverlapping_memrefs_p): Export for use in other modules.
+	* alias.h (nonoverlapping_memrefs_p): Likewise.
+
 2008-02-25  Jan Beulich  <jbeulich@novell.com>
 
 	* Makefile.in: Also prefix uses of crt0.o and mcrt0.o with

gcc/alias.c

@@ -164,7 +164,6 @@ static int aliases_everything_p (const_rtx);
 static bool nonoverlapping_component_refs_p (const_tree, const_tree);
 static tree decl_for_component_ref (tree);
 static rtx adjust_offset_for_component_ref (tree, rtx);
-static int nonoverlapping_memrefs_p (const_rtx, const_rtx);
 static int write_dependence_p (const_rtx, const_rtx, int);
 
 static void memory_modified_1 (rtx, const_rtx, void *);
@@ -1976,7 +1975,7 @@ adjust_offset_for_component_ref (tree x, rtx offset)
 /* Return nonzero if we can determine the exprs corresponding to memrefs
    X and Y and they do not overlap.  */
 
-static int
+int
 nonoverlapping_memrefs_p (const_rtx x, const_rtx y)
 {
   tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);

gcc/alias.h

@@ -28,6 +28,7 @@ extern alias_set_type get_varargs_alias_set (void);
 extern alias_set_type get_frame_alias_set (void);
 extern bool component_uses_parent_alias_set (const_tree);
 extern bool alias_set_subset_of (alias_set_type, alias_set_type);
+extern int nonoverlapping_memrefs_p (const_rtx, const_rtx);
 
 /* This alias set can be used to force a memory to conflict with all
    other memories, creating a barrier across which no memory reference

gcc/cse.c

@@ -4753,6 +4753,23 @@ cse_insn (rtx insn, rtx libcall_insn)
 	      src_elt_cost = MAX_COST;
 	    }
 
+	  /* Avoid creation of overlapping memory moves.  */
+	  if (MEM_P (trial) && MEM_P (SET_DEST (sets[i].rtl)))
+	    {
+	      rtx src, dest;
+
+	      /* BLKmode moves are not handled by cse anyway.  */
+	      if (GET_MODE (trial) == BLKmode)
+		break;
+
+	      src = canon_rtx (trial);
+	      dest = canon_rtx (SET_DEST (sets[i].rtl));
+
+	      if (!MEM_P (src) || !MEM_P (dest)
+		  || !nonoverlapping_memrefs_p (src, dest))
+		break;
+	    }
+
 	  /* We don't normally have an insn matching (set (pc) (pc)), so
 	     check for this separately here.  We will delete such an
 	     insn below.

gcc/testsuite/ChangeLog

+2008-02-25  Andreas Krebbel  <krebbel1@de.ibm.com>
+
+	PR target/35258
+	* gcc.dg/pr35258.c: New testcase.
+
 2008-02-25  Jan Beulich  <jbeulich@novell.com>
 
 	* gcc.dg/20020426-2.c: Remove bogus workaround.

gcc/testsuite/gcc.dg/pr35258.c

+/* { dg-do run } */
+/* { dg-options "-O1" } */
+
+extern void *memcpy (void *, const void *, __SIZE_TYPE__);
+extern int memcmp (const void *, const void *, __SIZE_TYPE__);
+extern void abort(void);
+
+char str[9] = "1234";
+
+void
+bar (void)
+{
+  unsigned int temp;
+  char *p = &str[2];
+
+  memcpy (&temp, &str[1], 4);
+  memcpy (p, &temp, 4);
+  str[1] = '.';
+}
+
+int main()
+{
+  bar();
+  if (memcmp (str, "1.234", 5) != 0)
+    abort ();
+
+  return 0;
+}