diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e9dca619baa..c57f46eac80 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2007-12-10  Eric Botcazou  <ebotcazou@libertysurf.fr>
+
+	PR target/34403
+	* config/i386/i386.c (ix86_expand_movmem): Punt if the count is large.
+	(ix86_expand_setmem): Likewise.
+
 2007-12-10  Kenneth Zadeck <zadeck@naturalbridge.com>
 
 	PR rtl-optimization/34302
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 9d2c14438a9..ebbf48957ba 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -15282,7 +15282,7 @@ smallest_pow2_greater_than (int val)
 }
 
 /* Expand string move (memcpy) operation.  Use i386 string operations when
-   profitable.  expand_clrmem contains similar code. The code depends upon
+   profitable.  expand_setmem contains similar code.  The code depends upon
    architecture, block size and alignment, but always has the same
    overall structure:
 
@@ -15333,6 +15333,10 @@ ix86_expand_movmem (rtx dst, rtx src, rtx count_exp, rtx align_exp,
   if (CONST_INT_P (expected_size_exp) && count == 0)
     expected_size = INTVAL (expected_size_exp);
 
+  /* Make sure we don't need to care about overflow later on.  */
+  if (count > ((unsigned HOST_WIDE_INT) 1 << 30))
+    return 0;
+
   /* Step 0: Decide on preferred algorithm, desired alignment and
      size of chunks to be copied by main loop.  */
 
@@ -15657,6 +15661,10 @@ ix86_expand_setmem (rtx dst, rtx count_exp, rtx val_exp, rtx align_exp,
   if (CONST_INT_P (expected_size_exp) && count == 0)
     expected_size = INTVAL (expected_size_exp);
 
+  /* Make sure we don't need to care about overflow later on.  */
+  if (count > ((unsigned HOST_WIDE_INT) 1 << 30))
+    return 0;
+
   /* Step 0: Decide on preferred algorithm, desired alignment and
      size of chunks to be copied by main loop.  */
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 2f438dae809..8ff13b4fb12 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2007-12-10  Eric Botcazou  <ebotcazou@libertysurf.fr>
+
+	* g++.dg/opt/memcpy1.C: New test.
+
 2007-12-10  Tobias Burnus  <burnus@net-b.de>
 
 	PR fortran/34425
diff --git a/gcc/testsuite/g++.dg/opt/memcpy1.C b/gcc/testsuite/g++.dg/opt/memcpy1.C
new file mode 100644
index 00000000000..f9887ee2314
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/memcpy1.C
@@ -0,0 +1,79 @@
+// PR target/34403
+// Origin: Martin Michlmayr <tbm@cyrius.com>
+
+// { dg-do compile }
+// { dg-options "-O" }
+
+typedef unsigned char uint8_t;
+typedef uint8_t uint8;
+typedef long unsigned int size_t;
+class csVector2
+{
+public:float x;
+};
+class csBox2
+{
+};
+struct iBase
+{
+};
+struct iClipper2D:public virtual iBase
+{
+};
+template < class Class > class scfImplementation:public virtual iBase
+{
+};
+template < class Class, class I1 > class scfImplementation1:public
+scfImplementation < Class >,
+  public I1
+{
+};
+class csClipper:public scfImplementation1 < csClipper, iClipper2D >
+{
+};
+class csBoxClipper:public csClipper
+{
+  csBox2 region;
+  virtual uint8 Clip (csVector2 * InPolygon, size_t InCount,
+                      csVector2 * OutPolygon, size_t & OutCount);
+};
+struct StatusOutputNone
+{
+};
+namespace CS
+{
+  template < typename BoxTest, typename StatusOutput > class BoxClipper
+  {
+    BoxTest boxTest;
+    StatusOutput statOut;
+    const csBox2 & region;
+    csVector2 *InP;
+    size_t InV;
+    csVector2 *OutP;
+    size_t OutV;
+  public:  BoxClipper (const BoxTest & boxTest, const StatusOutput & statOut,
+                  const csBox2 & region, csVector2 * InP, size_t InV,
+                  csVector2 * OutP):boxTest (boxTest), statOut (statOut),
+      region (region), InP (InP), InV (InV), OutP (OutP), OutV (-1)
+    {
+    }
+    uint8 Clip ()
+    {
+      __builtin_memcpy (this->OutP, InP, OutV * sizeof (csVector2));
+    }
+  };
+}
+struct BoxTestAll
+{
+};
+uint8
+csBoxClipper::Clip (csVector2 * InPolygon, size_t InCount,
+                    csVector2 * OutPolygon, size_t & OutCount)
+{
+  BoxTestAll b;
+  StatusOutputNone n;
+  CS::BoxClipper < BoxTestAll, StatusOutputNone > boxClip (b, n, region,
+                                                           InPolygon, InCount,
+                                                           OutPolygon);
+  uint8 Clipped = boxClip.Clip ();
+}