[Bug target/95713] [10/11 Regression] ICE in emit_move_insn when converting int2 vector to short2 vector for -march=skylake-avx512 since r10-5031-g78307657cf9675bc

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95713

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|i?86-*-*                    |x86_64-*-* i?86-*-*
   Target Milestone|---                         |10.2
                 CC|                            |hjl.tools at gmail dot com,
                   |                            |kyukhin at gcc dot gnu.org

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
So the expansion of

  b_4 = VEC_PACK_TRUNC_EXPR <_2, _7>;

with two V1SI operands results in a DImode rtx (reg:DI 93) but RTL
expansion wants to see it in (reg:SI 84) (that is b).  But the
simplistic code doing that doesn't work (obviously):

                temp = force_operand (temp, target);
                if (temp != target)
                  emit_move_insn (target, temp);

I guess the expansion of VEC_PACK_TRUNC_EXPR is "wrong".  We do have
CODE_FOR_vec_pack_trunc_si but that maps to

(define_expand "vec_pack_trunc_<mode>"
  [(set (match_operand:<DOUBLEMASKMODE> 0 "register_operand")
        (ior:<DOUBLEMASKMODE>
          (ashift:<DOUBLEMASKMODE>
            (zero_extend:<DOUBLEMASKMODE>
              (match_operand:SWI24 2 "register_operand"))
            (match_dup 3))
          (zero_extend:<DOUBLEMASKMODE>
            (match_operand:SWI24 1 "register_operand"))))]
  "TARGET_AVX512BW"

where expand_binop_directly does

1098      if (binoptab == vec_pack_trunc_optab
...
1106          /* The mode of the result is different then the mode of the
1107             arguments.  */
1108          tmp_mode = insn_data[(int) icode].operand[0].mode;

and tmp_mode ends up as DImode.  Shouldn't the pattern use HALFMASKMODE?

Are those patterns supposed to only trigger for VECTOR_BOOLEAN and not
"generic" vectors mapping to integer modes?