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stl_algo.h (__lg<>(_Size)): Slightly tweak. 

2007-10-25  Paolo Carlini  <pcarlini@suse.de>

	* include/bits/stl_algo.h (__lg<>(_Size)): Slightly tweak.
	(__lg(int), __lg(long), __lg(long long)): Add, overloads
	exploiting __builtin_clz*.

From-SVN: r129624
This commit is contained in:
Paolo Carlini 2007-10-25 10:11:58 +00:00 committed by Paolo Carlini
parent 0bf2cf8907
commit 1fcd0a2c50
2 changed files with 21 additions and 3 deletions
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6
libstdc++-v3/ChangeLog
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@ -1,3 +1,9 @@
2007-10-25 Paolo Carlini <pcarlini@suse.de>
* include/bits/stl_algo.h (__lg<>(_Size)): Slightly tweak.
(__lg(int), __lg(long), __lg(long long)): Add, overloads
exploiting __builtin_clz*.
2007-10-24 Paolo Carlini <pcarlini@suse.de>
* include/tr1_impl/array (_M_instance): Align naturally.

18
libstdc++-v3/include/bits/stl_algo.h
View File

@ -2085,7 +2085,7 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
/**
* @if maint
* This is a helper function for the sort routines.
* This is a helper function for the sort routines. Precondition: __n > 0.
* @endif
*/
template<typename _Size>
@ -2093,11 +2093,23 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
__lg(_Size __n)
{
_Size __k;
for (__k = 0; __n != 1; __n >>= 1)
for (__k = 0; __n != 0; __n >>= 1)
++__k;
return __k;
return __k - 1;
}
inline int
__lg(int __n)
{ return sizeof(int) * __CHAR_BIT__ - 1 - __builtin_clz(__n); }
inline long
__lg(long __n)
{ return sizeof(long) * __CHAR_BIT__ - 1 - __builtin_clzl(__n); }
inline long long
__lg(long long __n)
{ return sizeof(long long) * __CHAR_BIT__ - 1 - __builtin_clzll(__n); }
// sort
template<typename _RandomAccessIterator, typename _Size>