re PR tree-optimization/48694 (possible memory hog bug)

2011-04-26  Richard Guenther  <rguenther@suse.de>

	PR middle-end/48694
	* tree.h (OEP_CONSTANT_ADDRESS_OF): New operand_equal_flag.
	* fold-const.c (operand_equal_p): For TREE_CONSTANT ADDR_EXPRs
	compare the operands with OEP_CONSTANT_ADDRESS_OF.  Treat
	trees with TREE_SIDE_EFFECTS equal when OEP_CONSTANT_ADDRESS_OF
	is set.

	* gcc.dg/torture/pr48694-1.c: New testcase.
	* gcc.dg/torture/pr48694-2.c: Likewise.

From-SVN: r172954

5 files changed, 48 insertions, 3 deletions

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 8f90f6f..1aa0dec 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -2473,9 +2473,12 @@ operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags)
      equal if they have no side effects.  If we have two identical
      expressions with side effects that should be treated the same due
      to the only side effects being identical SAVE_EXPR's, that will
-     be detected in the recursive calls below.  */
+     be detected in the recursive calls below.
+     If we are taking an invariant address of two identical objects
+     they are necessarily equal as well.  */
   if (arg0 == arg1 && ! (flags & OEP_ONLY_CONST)
       && (TREE_CODE (arg0) == SAVE_EXPR
+	  || (flags & OEP_CONSTANT_ADDRESS_OF)
 	  || (! TREE_SIDE_EFFECTS (arg0) && ! TREE_SIDE_EFFECTS (arg1))))
     return 1;
 
@@ -2538,7 +2541,8 @@ operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags)
 
       case ADDR_EXPR:
 	return operand_equal_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg1, 0),
-				0);
+				TREE_CONSTANT (arg0) && TREE_CONSTANT (arg1)
+				? OEP_CONSTANT_ADDRESS_OF : 0);
       default:
 	break;
       }
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index f464fa4..5efb6b1 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2011-04-26  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/48694
+	* gcc.dg/torture/pr48694-1.c: New testcase.
+	* gcc.dg/torture/pr48694-2.c: Likewise.
+
 2011-04-25  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* g++.dg/ext/underlying_type1.C: New.
diff --git a/gcc/testsuite/gcc.dg/torture/pr48694-1.c b/gcc/testsuite/gcc.dg/torture/pr48694-1.c
new file mode 100644
index 0000000..810366b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr48694-1.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+
+extern volatile int g_89[5][9];
+extern int g, *gp;
+void func_64()
+{
+  int i;
+  for (i = 0; i < 1; )
+    {
+      for (g = 0; g < 1; )
+	return;
+      gp = (int *)&g_89[g][0];
+    }
+}
diff --git a/gcc/testsuite/gcc.dg/torture/pr48694-2.c b/gcc/testsuite/gcc.dg/torture/pr48694-2.c
new file mode 100644
index 0000000..4791ac3
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr48694-2.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+
+extern volatile int g_4[1][4];
+extern int g_7;
+void modify(int *);
+void func_2()
+{
+  int l_46 = 4;
+  if (g_7)
+    modify(&l_46);
+  else
+    {
+      int i;
+      for (i = 0; i != 5; i += 1)
+	{
+	  volatile int *vp = &g_4[0][l_46];
+	  *vp = 0;
+	}
+    }
+}
diff --git a/gcc/tree.h b/gcc/tree.h
index 0bc98cd..8f25832 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -5118,7 +5118,8 @@ extern tree fold_fma (location_t, tree, tree, tree, tree);
 enum operand_equal_flag
 {
   OEP_ONLY_CONST = 1,
-  OEP_PURE_SAME = 2
+  OEP_PURE_SAME = 2,
+  OEP_CONSTANT_ADDRESS_OF = 4
 };
 
 extern int operand_equal_p (const_tree, const_tree, unsigned int);