Re: [PATCH v5] dse: Remove partial load after full store for high part access[PR71309]

[luoxhu via Gcc-patches]

Hi Richard,

On 2020/8/3 22:01, Richard Sandiford wrote:

        /* Try a wider mode if truncating the store mode to NEW_MODE
         requires a real instruction.  */
        if (maybe_lt (GET_MODE_SIZE (new_mode), GET_MODE_SIZE (store_mode))
@@ -1779,6 +1780,25 @@ find_shift_sequence (poly_int64 access_size,
          && !targetm.modes_tieable_p (new_mode, store_mode))
        continue;

+ if (multiple_p (GET_MODE_BITSIZE (new_mode), shift)

Like I mentioned before, this should be the other way around:

     multiple_p (shift, GET_MODE_BITSIZE (new_mode))

i.e. for the subreg to be valid, the shift amount must be a multiple
of the outer mode size in bits.

OK with that change, thanks, and sorry for the multiple review cycles.

Just had another question is do we want to backport this patch to gcc-10
and gcc-9 branches? :)


Xionghu

Richard