According to the description of the psABI v2.30:
https://github.com/loongson/la-abi-specs/releases/tag/v2.30, moved the
expansion of relevant pseudo-instructions from
`LoongArchPreRAExpandPseudo` pass to `LoongArchExpandPseudo` pass, to
ensure that the code sequences of `PseudoLA*_LARGE` instructions and
Medium code model's function call are not scheduled.
According to the description of the psABI v2.20:
https://github.com/loongson/la-abi-specs/releases/tag/v2.20, adjustments
are made to the function call instructions under the medium code model.
At the same time, AsmParser has already supported parsing the call36 and
tail36 macro instructions.
This is intended to behave like GCC's `-mcmodel=extreme`.
Technically the true GCC equivalent would be `-mcmodel=large` which is
not yet implemented there, and we probably do not want to take the
"Large" name until things settle in GCC side, but:
* LLVM does not have a `CodeModel::Extreme`, and it seems too early to
have such a variant added just for enabling LoongArch; and
* `CodeModel::Small` is already being used for GCC `-mcmodel=normal`
which is already a case of divergent naming.
Regarding the codegen, loads/stores immediately after a PC-relative
large address load (that ends with something like `add.d $addr, $addr,
$tmp`) should get merged with the addition into corresponding `ldx/stx`
ops, but is currently not done. This is because pseudo-instructions are
expanded after instruction selection, and is best fixed with a separate
change.
Reviewed By: SixWeining
Differential Revision: https://reviews.llvm.org/D150522
