[Bug target/108599] [12/13 Regression] Incorrect code generation newer intel architectures

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108599

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:963315a922e228c4f6853826666151fc540f111a

commit r13-5529-g963315a922e228c4f6853826666151fc540f111a
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Jan 31 10:12:19 2023 +0100

    i386: Fix up ix86_convert_const_wide_int_to_broadcast [PR108599]

    The following testcase is miscompiled.  The problem is that during
    RTL DSE we see a V4DI register is being loaded { 16, 16, 0, 0 }
    value and DSE mostly works in terms of scalar modes, so it calls
    movoi to set an OImode REG to (const_wide_int 0x100000000000000010)
    and ix86_convert_const_wide_int_to_broadcast thinks it can compute
    that value by broadcasting DImode 0x10.  While it is true that
    for TImode result the broadcast could be used, for OImode/XImode
    it can't be, because all but the lowest 2 HOST_WIDE_INTs aren't
    present (so are 0 or -1 depending on sign), not 0x10 in this case.
    The function checks if the least significant HOST_WIDE_INT elt
    of the CONST_WIDE_INT is broadcastable from QI/HI/SI/DImode and then
      /* Check if OP can be broadcasted from VAL.  */
      for (int i = 1; i < CONST_WIDE_INT_NUNITS (op); i++)
        if (val != CONST_WIDE_INT_ELT (op, i))
          return nullptr;
    That is needed of course, but nothing checks that
    CONST_WIDE_INT_NUNITS (op) isn't too small for the mode in question.
    I think if op would be 0 or -1, it ought to be never CONST_WIDE_INT,
    but CONST_INT and so we can just punt whenever the number of
    CONST_WIDE_INT elts is not the expected one.

    2023-01-31  Jakub Jelinek  <jakub@redhat.com>

            PR target/108599
            * config/i386/i386-expand.cc
            (ix86_convert_const_wide_int_to_broadcast): Return nullptr if
            CONST_WIDE_INT_NUNITS (op) times HOST_BITS_PER_WIDE_INT isn't
            equal to bitsize of mode.

            * gcc.target/i386/avx2-pr108599.c: New test.