Re: [PATCH] middle-end/102682 - avoid invalid subreg on the LHS

[Jeff Law via Gcc-patches]

On 10/11/2021 7:39 AM, Richard Biener wrote:

The following avoids generating

(insn 6 5 7 2 (set (subreg:OI (concatn/v:TI [
                     (reg:DI 92 [ buffer ])
                     (reg:DI 93 [ buffer+8 ])
                 ]) 0)
         (subreg:OI (reg/v:V8SI 85 [ __x ]) 0)) "t.ii":76:21 74 
{*movoi_internal_avx}
      (nil))

via store_bit_field_1 when we try to store excess data into
a register allocated temporary.  The case was supposed to

       /* Use the subreg machinery either to narrow OP0 to the required
          words...

but the check ensured only an register-aligned but not a large
enough piece.  The following adds such missed check which ends up
decomposing the set to

(insn 6 5 7 (set (subreg:DI (reg/v:TI 84 [ buffer ]) 0)
         (subreg:DI (reg/v:V8SI 85 [ __x ]) 0)) "t.ii":76:21 -1
      (nil))

(insn 7 6 0 (set (subreg:DI (reg/v:TI 84 [ buffer ]) 8)
         (subreg:DI (reg/v:V8SI 85 [ __x ]) 8)) "t.ii":76:21 -1
      (nil))


Bootstrapped and tested on x86_64-unknown-linux-gnu, OK for trunk?

Thanks,
Richard.

2021-10-11  Richard Biener  <rguent...@suse.de>

        PR middle-end/102682
        * expmed.c (store_bit_field_1): Ensure a LHS subreg would
        not create a paradoxical subreg.

OK.

Jeff