On Thu, 2023-08-10 at 09:11 +0800, liuhongt via Gcc-patches wrote:
> Currently we have 3 different independent tunes for gather
> "use_gather,use_gather_2parts,use_gather_4parts",
> similar for scatter, there're
> "use_scatter,use_scatter_2parts,use_scatter_4parts"
>
> The patch support 2 standardizing options to enable/disable
> vectorization for all gather/scatter instructions. The options is
> interpreted by driver to 3 tunes.
>
> bootstrapped and regtested on x86_64-pc-linux-gnu.
> Ok for trunk?
And should we set -mno-gather as the default for GDS affected
processors? We'll likely apply the ucode update for them, and then the
gathering instructions will be much slower.
> gcc/ChangeLog:
>
> * config/i386/i386.h (DRIVER_SELF_SPECS): Add
> GATHER_SCATTER_DRIVER_SELF_SPECS.
> (GATHER_SCATTER_DRIVER_SELF_SPECS): New macro.
> * config/i386/i386.opt (mgather): New option.
> (mscatter): Ditto.
> ---
> gcc/config/i386/i386.h | 12 +++++++++++-
> gcc/config/i386/i386.opt | 8 ++++++++
> 2 files changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
> index ef342fcee9b..d9ac2c29bde 100644
> --- a/gcc/config/i386/i386.h
> +++ b/gcc/config/i386/i386.h
> @@ -565,7 +565,17 @@ extern GTY(()) tree x86_mfence;
> # define SUBTARGET_DRIVER_SELF_SPECS ""
> #endif
>
> -#define DRIVER_SELF_SPECS SUBTARGET_DRIVER_SELF_SPECS
> +#ifndef GATHER_SCATTER_DRIVER_SELF_SPECS
> +# define GATHER_SCATTER_DRIVER_SELF_SPECS \
> + "%{mno-gather:-mtune-
> ctrl=^use_gather_2parts,^use_gather_4parts,^use_gather} \
> + %{mgather:-mtune-
> ctrl=use_gather_2parts,use_gather_4parts,use_gather} \
> + %{mno-scatter:-mtune-
> ctrl=^use_scatter_2parts,^use_scatter_4parts,^use_scatter} \
> + %{mscatter:-mtune-
> ctrl=use_scatter_2parts,use_scatter_4parts,use_scatter}"
> +#endif
> +
> +#define DRIVER_SELF_SPECS \
> + SUBTARGET_DRIVER_SELF_SPECS " " \
> + GATHER_SCATTER_DRIVER_SELF_SPECS
>
> /* -march=native handling only makes sense with compiler running on
> an x86 or x86_64 chip. If changing this condition, also change
> diff --git a/gcc/config/i386/i386.opt b/gcc/config/i386/i386.opt
> index ddb7f110aa2..99948644a8d 100644
> --- a/gcc/config/i386/i386.opt
> +++ b/gcc/config/i386/i386.opt
> @@ -424,6 +424,14 @@ mdaz-ftz
> Target
> Set the FTZ and DAZ Flags.
>
> +mgather
> +Target
> +Enable vectorization for gather instruction.
> +
> +mscatter
> +Target
> +Enable vectorization for scatter instruction.
> +
> mpreferred-stack-boundary=
> Target RejectNegative Joined UInteger
> Var(ix86_preferred_stack_boundary_arg)
> Attempt to keep stack aligned to this power of 2.
--
Xi Ruoyao <[email protected]>
School of Aerospace Science and Technology, Xidian University
