> Am 17.12.2025 um 00:57 schrieb Steve Kargl via Gcc <[email protected]>:
>
> On Tue, Dec 16, 2025 at 11:31:13PM +0100, Florian Weimer wrote:
>> * Steve Kargl via Gcc:
>>
>>> So, my question is "Does -flto simply suppress reporting from
>>> -fopt-info-optall or does -flto actually suppress unrolling,
>>> tree vectorization, and tree auto parallization.
>>
>> Do you supply -fopt-info-optall during linking?
>>
>
> To simplify things,
>
> % cat xxx.f90
> module xxx
> implicit none
> contains
> subroutine bar(n, dx, x, y)
> integer, intent(in) :: n
> real, intent(in) :: dx, x(n)
> real, intent(out) :: y(n)
> integer i
> y = x + dx * [(i, i = 0, n-1)]
> end subroutine bar
> end module xxx
>
>
> % gfcx --version
> GNU Fortran (GCC) 16.0.0 20251119 (experimental)
> % gfcx -c -O3 -ftree-vectorize -fopt-info-optall xxx.f90
> xxx.f90:9:39: optimized: loop vectorized using 16 byte vectors and unroll
> factor 4
> xxx.f90:9:39: optimized: epilogue loop vectorized using 8 byte vectors and
> unroll factor 2
> xxx.f90:9:39: optimized: loop vectorized using 16 byte vectors and unroll
> factor 4
> xxx.f90:9:39: optimized: loop turned into non-loop; it never loops
> xxx.f90:9:39: optimized: loop turned into non-loop; it never loops
> xxx.f90:9:39: optimized: loop with 2 iterations completely unrolled (header
> execution count 7569051)
> % gfcx -c -O3 -ftree-vectorize -fopt-info-optall -flto=auto xxx.f90
> (nothing?)
Vectorization only happens at the link stage with -flto so here it is working
as expected.
If you have a single translation unit a LTO-like effect can be produced by
compiling with -fwhole-program
Richard
>
> --
> Steve
