diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5067ae1a9e5..73c0c366812 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2009-06-23  Andreas Krebbel  <krebbel1@de.ibm.com>
+
+	* tree-ssa-math-opts.c (find_bswap): Increase the search depth in
+	order to match bswaps with signed source operands.
+
 2009-06-23  Rainer Orth  <ro@TechFak.Uni-Bielefeld.DE>
 
 	* sdbout.c (sdbout_one_type): Fix braces in switch.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 7dbb38fcff8..7158684ca12 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2009-06-23  Andreas Krebbel  <krebbel1@de.ibm.com>
+
+	* gcc.dg/optimize-bswapsi-1.c: Add new bswap implementation.
+	* gcc.dg/optimize-bswapdi-1.c: Likewise.
+
 2009-06-22  Adam Nemet  <anemet@caviumnetworks.com>
 
 	* gcc.target/mips/truncate-3.c: New test.
diff --git a/gcc/testsuite/gcc.dg/optimize-bswapdi-1.c b/gcc/testsuite/gcc.dg/optimize-bswapdi-1.c
index 45fb2af2b30..449dc19f765 100644
--- a/gcc/testsuite/gcc.dg/optimize-bswapdi-1.c
+++ b/gcc/testsuite/gcc.dg/optimize-bswapdi-1.c
@@ -24,5 +24,25 @@ swap64 (uint64_t in)
   return __const_swab64 (in);
 }
 
-/* { dg-final { scan-tree-dump-times "64 bit bswap implementation found at" 1 "bswap" } } */
+/* This variant is currently used by libgcc.  The difference is that
+   the bswap source and destination have a signed integer type which
+   requires a slightly higher search depth in order to dive through
+   the cast as well.  */
+
+typedef int DItype __attribute__ ((mode (DI)));
+DItype
+swap64_b (DItype u)
+{
+  return ((((u) & 0xff00000000000000ull) >> 56)
+	  | (((u) & 0x00ff000000000000ull) >> 40)
+	  | (((u) & 0x0000ff0000000000ull) >> 24)
+	  | (((u) & 0x000000ff00000000ull) >>  8)
+	  | (((u) & 0x00000000ff000000ull) <<  8)
+	  | (((u) & 0x0000000000ff0000ull) << 24)
+	  | (((u) & 0x000000000000ff00ull) << 40)
+	  | (((u) & 0x00000000000000ffull) << 56));
+}
+
+
+/* { dg-final { scan-tree-dump-times "64 bit bswap implementation found at" 2 "bswap" } } */
 /* { dg-final { cleanup-tree-dump "bswap" } } */
diff --git a/gcc/testsuite/gcc.dg/optimize-bswapsi-1.c b/gcc/testsuite/gcc.dg/optimize-bswapsi-1.c
index fc77296d522..7b27b930838 100644
--- a/gcc/testsuite/gcc.dg/optimize-bswapsi-1.c
+++ b/gcc/testsuite/gcc.dg/optimize-bswapsi-1.c
@@ -31,5 +31,21 @@ swap32_b (uint32_t in)
   return a;
 }
 
-/* { dg-final { scan-tree-dump-times "32 bit bswap implementation found at" 2 "bswap" } } */
+/* This variant is currently used by libgcc.  The difference is that
+   the bswap source and destination have a signed integer type which
+   requires a slightly higher search depth in order to dive through
+   the cast as well.  */
+
+typedef int SItype __attribute__ ((mode (SI)));
+
+SItype
+swap32_c (SItype u)
+{
+  return ((((u) & 0xff000000) >> 24)
+	  | (((u) & 0x00ff0000) >>  8)
+	  | (((u) & 0x0000ff00) <<  8)
+	  | (((u) & 0x000000ff) << 24));
+}
+
+/* { dg-final { scan-tree-dump-times "32 bit bswap implementation found at" 3 "bswap" } } */
 /* { dg-final { cleanup-tree-dump "bswap" } } */
diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c
index 7e4e1bd5eb6..20ddbad5e55 100644
--- a/gcc/tree-ssa-math-opts.c
+++ b/gcc/tree-ssa-math-opts.c
@@ -1125,9 +1125,14 @@ find_bswap (gimple stmt)
   struct symbolic_number n;
   tree source_expr;
 
+  /* The last parameter determines the depth search limit.  It usually
+     correlates directly to the number of bytes to be touched.  We
+     increase that number by one here in order to also cover signed ->
+     unsigned conversions of the src operand as can be seen in
+     libgcc.  */
   source_expr =  find_bswap_1 (stmt, &n,
 			       TREE_INT_CST_LOW (
-				 TYPE_SIZE_UNIT (gimple_expr_type (stmt))));
+				 TYPE_SIZE_UNIT (gimple_expr_type (stmt))) + 1);
 
   if (!source_expr)
     return NULL_TREE;