Remove redundant comparison in debug mode

[François Dumont]

Verifying number of comparisons invoked in different algos and different 
modes I remarked this small performance issue.

2012-08-01  François Dumont  <fdum...@gcc.gnu.org>
    * include/debug/functions.h (__check_partition_lower_aux): Remove
    redundant comparison with pivot value.
    (__check_partition_upper_aux): Likewise.

Tested under Linux x86_64 debug mode.

Ok for trunk ?

François
Index: include/debug/functions.h
===================================================================
--- include/debug/functions.h	(revision 189985)
+++ include/debug/functions.h	(working copy)
@@ -354,8 +354,12 @@
     {
       while (__first != __last && *__first < __value)
 	++__first;
-      while (__first != __last && !(*__first < __value))
-	++__first;
+      if (__first != __last)
+	{
+	  ++__first;
+	  while (__first != __last && !(*__first < __value))
+	    ++__first;
+	}
       return __first == __last;
     }
 
@@ -368,8 +372,10 @@
 			const _Safe_iterator<_Iterator, _Sequence>& __last,
 			const _Tp& __value,
 			std::random_access_iterator_tag __tag)
-    { return __check_partitioned_lower_aux(__first.base(), __last.base(),
-					   __value, __tag); }
+    {
+      return __check_partitioned_lower_aux(__first.base(), __last.base(),
+					   __value, __tag);
+    }
 
   // _GLIBCXX_RESOLVE_LIB_DEFECTS
   // 270. Binary search requirements overly strict
@@ -378,8 +384,10 @@
     inline bool
     __check_partitioned_lower(_ForwardIterator __first,
 			      _ForwardIterator __last, const _Tp& __value)
-    { return __check_partitioned_lower_aux(__first, __last, __value,
-					   std::__iterator_category(__first)); }
+    {
+      return __check_partitioned_lower_aux(__first, __last, __value,
+					   std::__iterator_category(__first));
+    }
 
   template<typename _ForwardIterator, typename _Tp>
     inline bool
@@ -389,8 +397,12 @@
     {
       while (__first != __last && !(__value < *__first))
 	++__first;
-      while (__first != __last && __value < *__first)
-	++__first;
+      if (__first != __last)
+	{
+	  ++__first;
+	  while (__first != __last && __value < *__first)
+	    ++__first;
+	}
       return __first == __last;
     }
 
@@ -403,15 +415,19 @@
 			const _Safe_iterator<_Iterator, _Sequence>& __last,
 			const _Tp& __value,
 			std::random_access_iterator_tag __tag)
-    { return __check_partitioned_upper_aux(__first.base(), __last.base(),
-					   __value, __tag); }
+    {
+      return __check_partitioned_upper_aux(__first.base(), __last.base(),
+					   __value, __tag);
+    }
 
   template<typename _ForwardIterator, typename _Tp>
     inline bool
     __check_partitioned_upper(_ForwardIterator __first,
 			      _ForwardIterator __last, const _Tp& __value)
-    { return __check_partitioned_upper_aux(__first, __last, __value,
-					   std::__iterator_category(__first)); }
+    {
+      return __check_partitioned_upper_aux(__first, __last, __value,
+					   std::__iterator_category(__first));
+    }
 
   template<typename _ForwardIterator, typename _Tp, typename _Pred>
     inline bool
@@ -422,8 +438,12 @@
     {
       while (__first != __last && bool(__pred(*__first, __value)))
 	++__first;
-      while (__first != __last && !bool(__pred(*__first, __value)))
-	++__first;
+      if (__first != __last)
+	{
+	  ++__first;
+	  while (__first != __last && !bool(__pred(*__first, __value)))
+	    ++__first;
+	}
       return __first == __last;
     }
 
@@ -437,8 +457,10 @@
 			const _Safe_iterator<_Iterator, _Sequence>& __last,
 			const _Tp& __value, _Pred __pred,
 			std::random_access_iterator_tag __tag)
-    { return __check_partitioned_lower_aux(__first.base(), __last.base(),
-					   __value, __pred, __tag); }
+    {
+      return __check_partitioned_lower_aux(__first.base(), __last.base(),
+					   __value, __pred, __tag);
+    }
 
   // Determine if a sequence is partitioned w.r.t. this element.
   template<typename _ForwardIterator, typename _Tp, typename _Pred>
@@ -446,8 +468,10 @@
     __check_partitioned_lower(_ForwardIterator __first,
 			      _ForwardIterator __last, const _Tp& __value,
 			      _Pred __pred)
-    { return __check_partitioned_lower_aux(__first, __last, __value, __pred,
-					   std::__iterator_category(__first)); }
+    {
+      return __check_partitioned_lower_aux(__first, __last, __value, __pred,
+					   std::__iterator_category(__first));
+    }
 
   template<typename _ForwardIterator, typename _Tp, typename _Pred>
     inline bool
@@ -458,8 +482,12 @@
     {
       while (__first != __last && !bool(__pred(__value, *__first)))
 	++__first;
-      while (__first != __last && bool(__pred(__value, *__first)))
-	++__first;
+      if (__first != __last)
+	{
+	  ++__first;
+	  while (__first != __last && bool(__pred(__value, *__first)))
+	    ++__first;
+	}
       return __first == __last;
     }
 
@@ -473,16 +501,20 @@
 			const _Safe_iterator<_Iterator, _Sequence>& __last,
 			const _Tp& __value, _Pred __pred,
 			std::random_access_iterator_tag __tag)
-    { return __check_partitioned_upper_aux(__first.base(), __last.base(),
-					   __value, __pred, __tag); }
+    {
+      return __check_partitioned_upper_aux(__first.base(), __last.base(),
+					   __value, __pred, __tag);
+    }
 
   template<typename _ForwardIterator, typename _Tp, typename _Pred>
     inline bool
     __check_partitioned_upper(_ForwardIterator __first,
 			      _ForwardIterator __last, const _Tp& __value,
 			      _Pred __pred)
-    { return __check_partitioned_upper_aux(__first, __last, __value, __pred,
-					   std::__iterator_category(__first)); }
+    {
+      return __check_partitioned_upper_aux(__first, __last, __value, __pred,
+					   std::__iterator_category(__first));
+    }
 
   // Helper struct to detect random access safe iterators.
   template<typename _Iterator>