cmd/internal/obj/loong64: add the PCALAU12I instruction for reloc use
The LoongArch ELF psABI v2.00 revamped the relocation design, largely
moving to using the `pcalau12i + addi/ld/st` pair for PC-relative
addressing within +/- 32 bits. The "pcala" in `pcalau12i` stands for
"PC-aligned add"; the instruction's semantics happen to coincide with
arm64's `adrp`.
Add support for emitting this instruction as part of the relevant
addressing ops, for use with new reloc types later.
Updates #58784
Change-Id: Ic1747cd9745aad0d1abb9bd78400cd5ff5978bc8
Reviewed-on: https://go-review.googlesource.com/c/go/+/455016 Reviewed-by: abner chenc <chenguoqi@loongson.cn>
Auto-Submit: Wayne Zuo <wdvxdr@golangcn.org> Reviewed-by: Ian Lance Taylor <iant@google.com>
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