[Bug tree-optimization/31040] New: unroll/peel loops not aggressive enough

["jv244 at cam dot ac dot uk" <gcc-bugzilla at gcc dot gnu dot org>]

Looking at the asm for the program below, there plenty of loops left after
compiling with

> gfortran  -S -march=native -O3 -funroll-loops -funroll-all-loops -fpeel-loops test.f90

or any combination of these options. A full unrolling (and in that case a
return of the value 3) would be possible and much faster.

> cat test.f90

INTEGER FUNCTION lxy()
   lxy=0
   DO lxa=0,1
   DO lxb=0,0
     DO lya=0,1-lxa
     DO lyb=0,0-lxb
       lxy=lxy+1
     ENDDO
     ENDDO
   ENDDO
   ENDDO
END FUNCTION
write(6,*) lxy()
END


-- 
           Summary: unroll/peel loops not aggressive enough
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jv244 at cam dot ac dot uk


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31040