libstdc++-v3 PATCH: _Count_ones<> should meet the zero-overhead rule

[Gabriel Dos Reis]

This patch turns the static integral data members of _Count_ones<>
into enumerators -- that makes it possible to avoid emission of
useless variables.  _Count_ones<> should be costless.

-- Gaby
CodeSourcery, LLC            http://www.codesourcery.com
     http://www.codesourcery.com/gcc-compile.shtml

Index: ChangeLog
===================================================================
RCS file: /cvs/gcc/egcs/libstdc++-v3/ChangeLog,v
retrieving revision 1.251
diff -p -r1.251 ChangeLog
*** ChangeLog	2000/11/09 02:57:23	1.251
--- ChangeLog	2000/11/10 17:33:37
***************
*** 1,3 ****
--- 1,8 ----
+ 2000-11-10  Gabriel Dos Reis  <gdr@codesourcery.com>
+ 
+ 	* include/bits/localefwd.h (_Count_ones<>::_S_halfcount,
+ 	_Count_ones<>::_S_count): Turn into enumerators.
+ 
  2000-11-08  Mark Mitchell  <mark@codesourcery.com>
  
  	* include/bits/codecvt.h (codecvt::do_out): Make it const-correct.
Index: include/bits/localefwd.h
===================================================================
RCS file: /cvs/gcc/egcs/libstdc++-v3/include/bits/localefwd.h,v
retrieving revision 1.3
diff -p -r1.3 localefwd.h
*** localefwd.h	2000/10/20 06:51:59	1.3
--- localefwd.h	2000/11/10 17:33:38
*************** namespace std
*** 49,75 ****
             unsigned int _Mask = (~0u >> _Shift) >
      struct _Count_ones;
  
    template<unsigned int _Num, unsigned int _Mask>
      struct _Count_ones<_Num, 0, _Mask> 
!     { static const unsigned int _S_count = _Num; };
! 
!   template<unsigned int _Num, unsigned int _Mask>
!     const unsigned int _Count_ones<_Num, 0, _Mask>::_S_count;
  
    template<unsigned int _Num, int _Shift, unsigned int _Mask>
      struct _Count_ones 
      {
!       static const unsigned int _S_halfcount =
!         _Count_ones<_Num, _Shift/2, (_Mask^((~_Mask)>>(_Shift/2))) >::_S_count;
!       static const unsigned int _S_count
!       = (_S_halfcount&_Mask) + ((_S_halfcount>>_Shift)&_Mask);
      };
- 
-   template<unsigned int _Num, int _Shift, unsigned int _Mask>
-     const unsigned int _Count_ones<_Num, _Shift, _Mask>::_S_count;
- 
-   template<unsigned int _Num, int _Shift, unsigned int _Mask>
-     const unsigned int _Count_ones<_Num, _Shift, _Mask>::_S_halfcount;
  
    // 22.1.1 Locale
    template<typename _Tp> class allocator;
--- 49,75 ----
             unsigned int _Mask = (~0u >> _Shift) >
      struct _Count_ones;
  
+   // It is preferable to use enumerators instead of integral static data
+   // members to avoid emission of superflous variables -- gdr.
    template<unsigned int _Num, unsigned int _Mask>
      struct _Count_ones<_Num, 0, _Mask> 
!     {
!       enum
!       {
!         _S_count = _Num
!       };
!     };
  
    template<unsigned int _Num, int _Shift, unsigned int _Mask>
      struct _Count_ones 
      {
!       enum
!       {
!         _S_halfcount = _Count_ones<_Num, _Shift/2,
!                                    (_Mask^((~_Mask)>>(_Shift/2))) >::_S_count,
!         _S_count = (_S_halfcount&_Mask) + ((_S_halfcount>>_Shift)&_Mask)
!       };
      };
  
    // 22.1.1 Locale
    template<typename _Tp> class allocator;