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[PATCH] Fix the one entry mem{{,p}cpy,move,set} optimization aliasing issues (PR middle-end/29272, take 2)


On Sun, Oct 08, 2006 at 10:47:14PM -0700, Mark Mitchell wrote:
> >+     we can use its alias set, otherwise we'd need to make
> >+     sure we go through alias set 0.  */
> >+  inner = var;
> >+  while (handled_component_p (inner))
> >+    inner = TREE_OPERAND (inner, 0);
> >+  if (! SSA_VAR_P (inner))
> >+    return 0;
> 
> This predicate should be factored out as a function, so that we avoid 
> code duplication.

Ok to commit this then?
Let's keep discussing how to improve it after it gets committed,
so that the trunk isn't broken for too long.

2006-10-09  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/29272
	* builtins.c (var_decl_component_p): New function.
	(fold_builtin_memset, fold_builtin_memory_op): Restrict
	single entry optimization to variables and components thereof.

	* gcc.c-torture/execute/20060930-2.c: New test.

--- gcc/builtins.c.jj	2006-10-09 15:45:53.000000000 +0200
+++ gcc/builtins.c	2006-10-09 15:52:52.000000000 +0200
@@ -7893,6 +7893,17 @@ fold_builtin_exponent (tree fndecl, tree
   return 0;
 }
 
+/* Return true if VAR is a VAR_DECL or a component thereof.  */
+
+static bool
+var_decl_component_p (tree var)
+{
+  tree inner = var;
+  while (handled_component_p (inner))
+    inner = TREE_OPERAND (inner, 0);
+  return SSA_VAR_P (inner);
+}
+
 /* Fold function call to builtin memset.  Return
    NULL_TREE if no simplification can be made.  */
 
@@ -7933,6 +7944,9 @@ fold_builtin_memset (tree arglist, tree 
       && !POINTER_TYPE_P (TREE_TYPE (var)))
     return 0;
 
+  if (! var_decl_component_p (var))
+    return 0;
+
   length = tree_low_cst (len, 1);
   if (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (var))) != length
       || get_pointer_alignment (dest, BIGGEST_ALIGNMENT) / BITS_PER_UNIT
@@ -8044,6 +8058,9 @@ fold_builtin_memory_op (tree arglist, tr
 	  && !SCALAR_FLOAT_TYPE_P (TREE_TYPE (destvar)))
 	return 0;
 
+      if (! var_decl_component_p (destvar))
+	return 0;
+
       srcvar = src;
       STRIP_NOPS (srcvar);
       if (TREE_CODE (srcvar) != ADDR_EXPR)
@@ -8058,6 +8075,9 @@ fold_builtin_memory_op (tree arglist, tr
 	  && !SCALAR_FLOAT_TYPE_P (TREE_TYPE (srcvar)))
 	return 0;
 
+      if (! var_decl_component_p (srcvar))
+	return 0;
+
       length = tree_low_cst (len, 1);
       if (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (destvar))) != length
 	  || get_pointer_alignment (dest, BIGGEST_ALIGNMENT) / BITS_PER_UNIT
--- gcc/testsuite/gcc.c-torture/execute/20060930-2.c.jj	2006-10-09 15:54:31.000000000 +0200
+++ gcc/testsuite/gcc.c-torture/execute/20060930-2.c	2006-10-09 15:54:40.000000000 +0200
@@ -0,0 +1,31 @@
+/* PR middle-end/29272 */
+
+extern void abort (void);
+
+struct S { struct S *s; } s;
+struct T { struct T *t; } t;
+
+static inline void
+foo (void *s)
+{
+  struct T *p = s;
+  __builtin_memcpy (&p->t, &t.t, sizeof (t.t));
+}
+
+void *
+__attribute__((noinline))
+bar (void *p, struct S *q)
+{
+  q->s = &s;
+  foo (p);
+  return q->s;
+}
+
+int
+main (void)
+{
+  t.t = &t;
+  if (bar (&s, &s) != (void *) &t)
+    abort ();
+  return 0;
+}


	Jakub


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