[Bug target/89226] codegen for copying a 512-bit object fails to use avx instructions

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89226

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
That is because in copy1 it is a normal memcpy expansion.
And, the generic move_by_pieces case is done in preference to target specific
one.  In i386.h we have:
/* Max number of bytes we can move from memory to memory
   in one reasonably fast instruction.  */
#define MOVE_MAX 16

/* MOVE_MAX_PIECES is the number of bytes at a time which we can
   move efficiently, as opposed to  MOVE_MAX which is the maximum
   number of bytes we can move with a single instruction.

   ??? We should use TImode in 32-bit mode and use OImode or XImode
   if they are available.  But since by_pieces_ninsns determines the
   widest mode with MAX_FIXED_MODE_SIZE, we can only use TImode in
   64-bit mode.  */
#define MOVE_MAX_PIECES \
  ((TARGET_64BIT \
    && TARGET_SSE2 \
    && TARGET_SSE_UNALIGNED_LOAD_OPTIMAL \
    && TARGET_SSE_UNALIGNED_STORE_OPTIMAL) \
   ? GET_MODE_SIZE (TImode) : UNITS_PER_WORD)

and in defaults.h
/* MOVE_MAX_PIECES is the number of bytes at a time which we can
   move efficiently, as opposed to  MOVE_MAX which is the maximum
   number of bytes we can move with a single instruction.  */

#ifndef MOVE_MAX_PIECES
#define MOVE_MAX_PIECES   MOVE_MAX
#endif

/* STORE_MAX_PIECES is the number of bytes at a time that we can
   store efficiently.  Due to internal GCC limitations, this is
   MOVE_MAX_PIECES limited by the number of bytes GCC can represent
   for an immediate constant.  */

#ifndef STORE_MAX_PIECES
#define STORE_MAX_PIECES  MIN (MOVE_MAX_PIECES, 2 * sizeof (HOST_WIDE_INT))
#endif

/* Likewise for block comparisons.  */
#ifndef COMPARE_MAX_PIECES
#define COMPARE_MAX_PIECES  MOVE_MAX_PIECES
#endif

#ifndef MAX_MOVE_MAX
#define MAX_MOVE_MAX MOVE_MAX
#endif