On Thu, Sep 07, 2017 at 04:35:17PM +0800, Xiaoyun Li wrote:
> GCC thinks target atom doesn't support SSE4.2 and SSE4 is now part of
> minimum requirements for DPDK on x86. So there are compiling errors when
> cross-compiling for target atom. And in fact, the atom supports SSE4 now.
> This patch fixes this issue.
>
> Fixes: 5ea4d4688dce ("net/ixgbe: remove fallback code for x86 non-SSE4")
> Cc: sta...@dpdk.org
>
> Signed-off-by: Xiaoyun Li <xiaoyun...@intel.com>
The -march=atom flag is for older atom CPUs, and is no longer advertised
by gcc, since all -march flags now correspond to the actual core
microarchitecture used. [man gcc on Fedora 26, no longer lists atom as a
valid march value, though it's probably still accepted for backward
compatibility]. The direct replacement for atom is "bonnell", which does
not have SSE4.2 support, so we should not use. What we do support is
later atoms, so the architecture targets for atom should be
"-march=silvermont". This automatically includes sse4 support so no
additional flags needed.
Note: I previously had this discussion with Neil on-list, but forgot to
do the follow-up work agreed on. See:
https://www.mail-archive.com/dev@dpdk.org/msg72629.html
The agreed plan was to remove atom as a target for DPDK builds and add a
"silvermont" replacement instead. If you have time, perhaps you could
look at doing that instead of this fix?
/Bruce
> ---
> mk/machine/atm/rte.vars.mk | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/mk/machine/atm/rte.vars.mk b/mk/machine/atm/rte.vars.mk
> index cfed110..a6899d9 100644
> --- a/mk/machine/atm/rte.vars.mk
> +++ b/mk/machine/atm/rte.vars.mk
> @@ -56,3 +56,5 @@
> # CPU_ASFLAGS =
>
> MACHINE_CFLAGS = -march=atom
> +
> +MACHINE_CFLAGS += -msse4.2
> --
> 2.7.4
>
