If linker relaxation enabled, relaxable code sequence expanded from
pseudos should avoid being separated by instruction scheduling. This
commit tags scheduling boundary for them to avoid being scheduled.
(Except for `tls_le/tls_ie` and `call36/tail36`. Because `tls_le/tls_ie`
can be scheduled and have no influence to relax, `call36/tail36` are
expanded later in `LoongArchExpandPseudo` pass.)
A new mask target-flag is added to attach relax relocs to the relaxable
code sequence. (No need to add it for `tls_le` and `call36/tail36`
because we can simply add relax relocs for them according to their
relocs. But for other code sequence, such as `PCALA_{HI20/LO12}`, we
must use the mask flag, mainly because relax should not be added when
code model is large.)
Because of the new mask target-flag, get "direct" flags is necessary
when using their target-flags. In addition, code sequence after being
optimized by `MergeBaseOffset` pass may not relaxable any more, so the
relax "bitmask" flag should be removed.
0288d065ee