[Bug target/109855] [14 Regression] ICE: in curr_insn_transform, at lra-constraints.cc:4231 unable to generate reloads for {aarch64_mlav4hi_vec_concatz_le} at -O1

[ktkachov at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109855

ktkachov at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2023-05-22
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

--- Comment #2 from ktkachov at gcc dot gnu.org ---
Confirmed.
The ICE in LRA happens very early on:
********** Local #1: **********

           Spilling non-eliminable hard regs: 31
            alt=0: Bad operand -- refuse


The pattern matches:
 [(set (match_operand:VDQ_BHSI 0 "register_operand" "=w")
       (plus:VDQ_BHSI (mult:VDQ_BHSI
                        (match_operand:VDQ_BHSI 2 "register_operand" "w")
                        (match_operand:VDQ_BHSI 3 "register_operand" "w"))
                      (match_operand:VDQ_BHSI 1 "register_operand" "0")))]

I wonder whether the substitution breaks something on the constraint in operand
1, which is tied to 0. The define_subst rule adds another operand to the
pattern to match the zero vector, but I would have expected the substitution
machinery to handle it all transparently...