[Bug target/106278] [13 Regression] ICE on valid code at -Os and above on x86_64-linux-gnu: in ix86_output_ssemov, at config/i386/i386.cc:5555 since r13-1607-gc3ed9e0d6e96d869

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106278

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Roger Sayle <sayle@gcc.gnu.org>:

https://gcc.gnu.org/g:2fd215b03e88baae4e047dcb8dac5daa145dc3b4

commit r13-1707-g2fd215b03e88baae4e047dcb8dac5daa145dc3b4
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Fri Jul 15 14:39:28 2022 +0100

    PR target/106278: Keep REG_EQUAL notes consistent during TImode STV on
x86_64.

    This patch resolves PR target/106278 a regression on x86_64 caused by my
    recent TImode STV improvements.  Now that TImode STV can handle comparisons
    such as "(set (regs:CC) (compare:CC (reg:TI) ...))" the convert_insn method
    sensibly checks that the mode of the SET_DEST is TImode before setting
    it to V1TImode [to avoid V1TImode appearing on the hard reg CC_FLAGS.

    Hence the current code looks like:

          if (GET_MODE (dst) == TImode)
            {
              tmp = find_reg_equal_equiv_note (insn);
              if (tmp && GET_MODE (XEXP (tmp, 0)) == TImode)
                PUT_MODE (XEXP (tmp, 0), V1TImode);
              PUT_MODE (dst, V1TImode);
              fix_debug_reg_uses (dst);
            }
          break;

    which checks GET_MODE (dst) before calling PUT_MODE, and when a
    change is made updating the REG_EQUAL_NOTE tmp if it exists.

    The logical flaw (oversight) is that due to RTL sharing, the destination
    of this set may already have been updated to V1TImode, as this chain is
    being converted, but we still need to update any REG_EQUAL_NOTE that
    still has TImode.  Hence the correct code is actually:

          if (GET_MODE (dst) == TImode)
            {
              PUT_MODE (dst, V1TImode);
              fix_debug_reg_uses (dst);
            }
          if (GET_MODE (dst) == V1TImode)
            {
              tmp = find_reg_equal_equiv_note (insn);
              if (tmp && GET_MODE (XEXP (tmp, 0)) == TImode)
                PUT_MODE (XEXP (tmp, 0), V1TImode);
            }
          break;

    While fixing this behavior, I noticed I had some indentation whitespace
    issues and some vestigial dead code in this function/method that I've
    taken the liberty of cleaning up (as obvious) in this patch.

    2022-07-15  Roger Sayle  <roger@nextmovesoftware.com>

    gcc/ChangeLog
            PR target/106278
            * config/i386/i386-features.cc
(general_scalar_chain::convert_insn):
            Fix indentation whitespace.
            (timode_scalar_chain::fix_debug_reg_uses): Likewise.
            (timode_scalar_chain::convert_insn): Delete dead code.
            Update TImode REG_EQUAL_NOTE even if the SET_DEST is already V1TI.
            Fix indentation whitespace.
            (convertible_comparison_p): Likewise.
            (timode_scalar_to_vector_candidate_p): Likewise.

    gcc/testsuite/ChangeLog
            * gcc.dg/pr106278.c: New test case.