2012-10-31  Florian Weimer  <fweimer@redhat.com>

	* init.c (build_new_1): Do not check for arithmetic overflow if
	inner array size is 1.

	* g++.dg/init/new40.C: New.

--- gcc/cp/init.c	(revision 193033)
+++ gcc/cp/init.c	(working copy)
@@ -2176,6 +2176,8 @@ build_new_1 (VEC(tree,gc) **placement, t
   double_int inner_nelts_count = double_int_one;
   tree inner_nelts = NULL_TREE;
   tree alloc_call, alloc_expr;
+  /* Size of the inner array elements. */
+  double_int inner_size;
   /* The address returned by the call to "operator new".  This node is
      a VAR_DECL and is therefore reusable.  */
   tree alloc_node;
@@ -2318,8 +2320,6 @@ build_new_1 (VEC(tree,gc) **placement, t
       double_int max_size
 	= double_int_lshift (double_int_one, TYPE_PRECISION (sizetype) - 1,
 			     HOST_BITS_PER_DOUBLE_INT, false);
-      /* Size of the inner array elements. */
-      double_int inner_size;
       /* Maximum number of outer elements which can be allocated. */
       double_int max_outer_nelts;
       tree max_outer_nelts_tree;
@@ -2438,7 +2438,15 @@ build_new_1 (VEC(tree,gc) **placement, t
 	  if (array_p && TYPE_VEC_NEW_USES_COOKIE (elt_type))
 	    size = size_binop (PLUS_EXPR, size, cookie_size);
 	  else
-	    cookie_size = NULL_TREE;
+	    {
+	      cookie_size = NULL_TREE;
+	      /* No size arithmetic necessary, so the size check is
+		 not needed. */
+	      if (outer_nelts_check != NULL
+		  && double_int_one_p (inner_size)
+		  && inner_nelts == NULL_TREE)
+		outer_nelts_check = NULL_TREE;
+	    }
 	  /* Perform the overflow check.  */
 	  if (outer_nelts_check != NULL_TREE)
             size = fold_build3 (COND_EXPR, sizetype, outer_nelts_check,
@@ -2474,7 +2482,15 @@ build_new_1 (VEC(tree,gc) **placement, t
 	  /* Use a global operator new.  */
 	  /* See if a cookie might be required.  */
 	  if (!(array_p && TYPE_VEC_NEW_USES_COOKIE (elt_type)))
-	    cookie_size = NULL_TREE;
+	    {
+	      cookie_size = NULL_TREE;
+	      /* No size arithmetic necessary, so the size check is
+		 not needed. */
+	      if (outer_nelts_check != NULL
+		  && double_int_one_p (inner_size)
+		  && inner_nelts == NULL_TREE)
+		outer_nelts_check = NULL_TREE;
+	    }
 
 	  alloc_call = build_operator_new_call (fnname, placement,
 						&size, &cookie_size,
--- gcc/testsuite/g++.dg/init/new40.C	(revision 0)
+++ gcc/testsuite/g++.dg/init/new40.C	(working copy)
@@ -0,0 +1,112 @@
+// Testcase for overflow handling in operator new[].
+// Optimization of unnecessary overflow checks.
+// { dg-do run }
+
+#include <assert.h>
+#include <stdlib.h>
+#include <stdexcept>
+
+static size_t magic_allocation_size
+  = 1 + (size_t (1) << (sizeof (size_t) * 8 - 1));
+
+struct exc : std::bad_alloc {
+};
+
+static size_t expected_size;
+
+struct pod_with_new {
+  char ch;
+  void *operator new[] (size_t sz)
+  {
+    if (sz != expected_size)
+      abort ();
+    throw exc ();
+  }
+};
+
+struct with_new {
+  char ch;
+  with_new () { }
+  ~with_new () { }
+  void *operator new[] (size_t sz)
+  {
+    if (sz != size_t (-1))
+      abort ();
+    throw exc ();
+  }
+};
+
+struct non_pod {
+  char ch;
+  non_pod () { }
+  ~non_pod () { }
+};
+
+void *
+operator new (size_t sz) _GLIBCXX_THROW (std::bad_alloc)
+{
+  if (sz != expected_size)
+    abort ();
+  throw exc ();
+}
+
+int
+main ()
+{
+  if (sizeof (pod_with_new) == 1)
+    expected_size = magic_allocation_size;
+  else
+    expected_size = -1;
+
+  try {
+    new pod_with_new[magic_allocation_size];
+    abort ();
+  } catch (exc &) {
+  }
+
+  if (sizeof (with_new) == 1)
+    expected_size = magic_allocation_size;
+  else
+    expected_size = -1;
+
+  try {
+    new with_new[magic_allocation_size];
+    abort ();
+  } catch (exc &) {
+  }
+
+  expected_size = magic_allocation_size;
+  try {
+    new char[magic_allocation_size];
+    abort ();
+  } catch (exc &) {
+  }
+
+  expected_size = -1;
+
+  try {
+    new pod_with_new[magic_allocation_size][2];
+    abort ();
+  } catch (exc &) {
+  }
+
+  try {
+    new with_new[magic_allocation_size][2];
+    abort ();
+  } catch (exc &) {
+  }
+
+  try {
+    new char[magic_allocation_size][2];
+    abort ();
+  } catch (exc &) {
+  }
+
+  try {
+    new non_pod[magic_allocation_size];
+    abort ();
+  } catch (exc &) {
+  }
+
+  return 0;
+}