Richard Biener <rguent...@suse.de> writes:
> The following adds a target hook to specify whether regs of MODE can be
> used to transfer bits. The hook is supposed to be used for value-numbering
> to decide whether a value loaded in such mode can be punned to another
> mode instead of re-loading the value in the other mode and for SRA to
> decide whether MODE is suitable as container holding a value to be
> used in different modes.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu, OK this way?
LGTM FWIW.
Richard
>
> Thanks,
> Richard.
>
> * target.def (mode_can_transfer_bits): New target hook.
> * target.h (mode_can_transfer_bits): New function wrapping the
> hook and providing default behavior.
> * doc/tm.texi.in: Update.
> * doc/tm.texi: Re-generate.
> ---
> gcc/doc/tm.texi | 6 ++++++
> gcc/doc/tm.texi.in | 2 ++
> gcc/target.def | 8 ++++++++
> gcc/target.h | 16 ++++++++++++++++
> 4 files changed, 32 insertions(+)
>
> diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
> index c7535d07f4d..fa53c23f1de 100644
> --- a/gcc/doc/tm.texi
> +++ b/gcc/doc/tm.texi
> @@ -4545,6 +4545,12 @@ is either a declaration of type int or accessed by
> dereferencing
> a pointer to int.
> @end deftypefn
>
> +@deftypefn {Target Hook} bool TARGET_MODE_CAN_TRANSFER_BITS (machine_mode
> @var{mode})
> +Define this to return false if the mode @var{mode} cannot be used
> +for memory copying. The default is to assume modes with the same
> +precision as size are fine to be used.
> +@end deftypefn
> +
> @deftypefn {Target Hook} machine_mode TARGET_TRANSLATE_MODE_ATTRIBUTE
> (machine_mode @var{mode})
> Define this hook if during mode attribute processing, the port should
> translate machine_mode @var{mode} to another mode. For example, rs6000's
> diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
> index 64cea3b1eda..8af3f414505 100644
> --- a/gcc/doc/tm.texi.in
> +++ b/gcc/doc/tm.texi.in
> @@ -3455,6 +3455,8 @@ stack.
>
> @hook TARGET_REF_MAY_ALIAS_ERRNO
>
> +@hook TARGET_MODE_CAN_TRANSFER_BITS
> +
> @hook TARGET_TRANSLATE_MODE_ATTRIBUTE
>
> @hook TARGET_SCALAR_MODE_SUPPORTED_P
> diff --git a/gcc/target.def b/gcc/target.def
> index 3de1aad4c84..4356ef2f974 100644
> --- a/gcc/target.def
> +++ b/gcc/target.def
> @@ -3363,6 +3363,14 @@ a pointer to int.",
> bool, (ao_ref *ref),
> default_ref_may_alias_errno)
>
> +DEFHOOK
> +(mode_can_transfer_bits,
> + "Define this to return false if the mode @var{mode} cannot be used\n\
> +for memory copying. The default is to assume modes with the same\n\
> +precision as size are fine to be used.",
> + bool, (machine_mode mode),
> + NULL)
> +
> /* Support for named address spaces. */
> #undef HOOK_PREFIX
> #define HOOK_PREFIX "TARGET_ADDR_SPACE_"
> diff --git a/gcc/target.h b/gcc/target.h
> index c1f99b97b86..837651d273a 100644
> --- a/gcc/target.h
> +++ b/gcc/target.h
> @@ -312,6 +312,22 @@ estimated_poly_value (poly_int64 x,
> return targetm.estimated_poly_value (x, kind);
> }
>
> +/* Return true when MODE can be used to copy GET_MODE_BITSIZE bits
> + unchanged. */
> +
> +inline bool
> +mode_can_transfer_bits (machine_mode mode)
> +{
> + if (mode == BLKmode)
> + return true;
> + if (maybe_ne (GET_MODE_BITSIZE (mode),
> + GET_MODE_UNIT_PRECISION (mode) * GET_MODE_NUNITS (mode)))
> + return false;
> + if (targetm.mode_can_transfer_bits)
> + return targetm.mode_can_transfer_bits (mode);
> + return true;
> +}
> +
> #ifdef GCC_TM_H
>
> #ifndef CUMULATIVE_ARGS_MAGIC
