[Bug target/32605] New: massive moves instead of bswap{l,q}

["pluto at agmk dot net" <gcc-bugzilla at gcc dot gnu dot org>]

#include <algorithm>
#include <iterator>
template < typename T >
void reverse( T& t )
{
    unsigned char* bytes = reinterpret_cast< unsigned char* >( &t );
    std::swap_ranges( bytes, bytes + sizeof( T ) / 2,
        std::reverse_iterator< unsigned char* >( bytes + sizeof( T ) ) );
}
template void reverse( std::size_t& );

attached testcase produces massive byte-moves instead of bswap.

$ g++ -Wall swap_ranges.cpp -fomit-frame-pointer -m32 -O3 -c

00000000 <void reverse<unsigned int>(unsigned int&)>:
   0:   8b 44 24 04             mov    0x4(%esp),%eax
   4:   0f b6 08                movzbl (%eax),%ecx
   7:   0f b6 50 03             movzbl 0x3(%eax),%edx
   b:   88 48 03                mov    %cl,0x3(%eax)
   e:   0f b6 48 01             movzbl 0x1(%eax),%ecx
  12:   88 10                   mov    %dl,(%eax)
  14:   0f b6 50 02             movzbl 0x2(%eax),%edx
  18:   88 48 02                mov    %cl,0x2(%eax)
  1b:   88 50 01                mov    %dl,0x1(%eax)
  1e:   c3                      ret

0000000000000000 <void reverse<unsigned long>(unsigned long&)>:
   0:   0f b6 17                movzbl (%rdi),%edx
   3:   0f b6 47 07             movzbl 0x7(%rdi),%eax
   7:   88 57 07                mov    %dl,0x7(%rdi)
   a:   88 07                   mov    %al,(%rdi)
   c:   0f b6 57 01             movzbl 0x1(%rdi),%edx
  10:   0f b6 47 06             movzbl 0x6(%rdi),%eax
  14:   88 57 06                mov    %dl,0x6(%rdi)
  17:   88 47 01                mov    %al,0x1(%rdi)
  1a:   0f b6 57 02             movzbl 0x2(%rdi),%edx
  1e:   0f b6 47 05             movzbl 0x5(%rdi),%eax
  22:   88 57 05                mov    %dl,0x5(%rdi)
  25:   88 47 02                mov    %al,0x2(%rdi)
  28:   0f b6 57 03             movzbl 0x3(%rdi),%edx
  2c:   0f b6 47 04             movzbl 0x4(%rdi),%eax
  30:   88 57 04                mov    %dl,0x4(%rdi)
  33:   88 47 03                mov    %al,0x3(%rdi)
  36:   c3                      retq


-- 
           Summary: massive moves instead of bswap{l,q}
           Product: gcc
           Version: 4.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pluto at agmk dot net
GCC target triplet: x86_64-*-*, i?86-*-*


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32605