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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/105463] [12/13 Regression] MVE: Wrong code, incorrect
 alignment assumption
Date: Tue, 03 May 2022 11:31:58 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105463

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |12.0

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
We vectorize correctly using a 1-byte aligned load:

void __GIMPLE (ssa,guessed_local(1073741824))
bar (const unsigned char * block)
{
  vector(4) unsigned int vect__3.5;
  unsigned int buf[4];

  __BB(2,guessed_local(1073741824)):
  vect__3.5_14 =3D __MEM <vector(4) unsigned int, 8> ((char *
{ref-all})block_2(D));
  __MEM <vector(4) unsigned int> ((char * {ref-all})&buf) =3D vect__3.5_14;
  foo (&buf);
  buf =3D{v} _Literal (unsigned int[4]) {CLOBBER(eol)};
  return;

and expand to

(insn 9 8 10 (set (reg:V4SI 118 [ vect__3.5 ])
        (unspec:V4SI [
                (mem:V4SI (reg/v/f:SI 114 [ block ]) [0 MEM <vector(4) unsi=
gned
int> [(char * {ref-all})block_2(D)]+0 S16 A8])
            ] UNSPEC_MISALIGNED_ACCESS)) "t.c":5:3 -1
     (nil))

which also looks OK.  'buf' is appropriately aligned:

(insn 10 9 0 (set (mem/c:V4SI (reg/f:SI 117) [0 MEM <vector(4) unsigned int>
[(char * {ref-all})&buf]+0 S16 A64])
        (reg:V4SI 118 [ vect__3.5 ])) "t.c":5:3 -1

and it's OK till the very end:

(insn 9 12 10 2 (set (reg:V4SI 28 s12 [orig:118 vect__3.5 ] [118])
        (unspec:V4SI [
                (mem:V4SI (reg:SI 3 r3 [120]) [0 MEM <vector(4) unsigned in=
t>
[(char * {ref-all})block_2(D)]+0 S16 A8])
            ] UNSPEC_MISALIGNED_ACCESS)) "t.c":5:3 4951
{*movmisalignv4si_mve_load}
     (expr_list:REG_DEAD (reg:SI 3 r3 [120])
        (nil)))

so it's a bug in the machine description somehow.=