I've attached two copies of a simple function. They are identical except for
the type of the internal variable (one uses 'int64_t', the other uses 'int').
When compiled with GCC 4.4.3 on a x64 platform using -O3 optimizations, the
assembly code for the first version will contain a conditional move instruction
'cmov', the second version will contain a branch. Since branches are extremely
slow, the second version ends up two times slower than the first version.

           Summary: GCC optimizer for Intel x64 generates inefficient code
           Product: gcc
           Version: 4.4.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: ekuznetsov at divxcorp dot com


Reply via email to