[Bug rtl-optimization/21329] New: optimize i386 block copy

[vda at port dot imtp dot ilyichevsk dot odessa dot ua]

gcc generates suboptimal i386 block copy code, like this:
        movl    $9, %ecx
        rep
        movsb
or this:
        movl    $2, %ecx
        rep
        movsl
        movsw

Such short copies can be done with few movsl's instead.
Patch is attached. Note that I am not familiar with gcc
internals at all, so take it with reasonable suspicion.

-- 
           Summary: optimize i386 block copy
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: vda at port dot imtp dot ilyichevsk dot odessa dot ua
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i386-pc-linux-gnu
  GCC host triplet: i386-pc-linux-gnu
GCC target triplet: i386-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21329