R_LARCH_CALL36 was designed for function call on medium code model where
the 2 instructions (pcaddu18i + jirl) must be adjacent. This is expected
to replace current medium code model implementation, i.e.
R_LARCH_PCALA_{HI20,LO12} on pcalau12i + jirl.
See https://github.com/loongson/la-abi-specs/pull/3 for more details.
The R_LARCH_{ADD,SUB}6 relocation type are usually used by DwarfCFA to
calculate a tiny offset. They appear after binutils 2.41, with GAS
enabling relaxation by default.
`R_LARCH_PCREL20_S2` is a new added relocation type in LoongArch ELF
psABI v2.10 [1] which is not corvered by D138135 except `R_LARCH_64_PCREL`.
A motivation to support `R_LARCH_PCREL20_S2` in lld is to build the
runtime of .NET core (a.k.a `CoreCLR`) in which strict PC-relative
semantics need to be guaranteed [2]. The normal `pcalau12i + addi.d`
approach doesn't work because the code will be copied to other places
with different "page" and offsets. To achieve this, we can use `pcaddi`
with explicit `R_LARCH_PCREL20_S2` reloc to address +-2MB PC-relative
range with 4-bytes aligned.
[1]: https://github.com/loongson/la-abi-specs/releases/tag/v2.10
[2]: https://github.com/dotnet/runtime/blob/release/7.0/src/coreclr/vm/loongarch64/asmhelpers.S#L307
Reviewed By: xen0n, MaskRay
Differential Revision: https://reviews.llvm.org/D156772
This adds support for the LoongArch ELF psABI v2.00 [1] relocation
model to LLD. The deprecated stack-machine-based psABI v1 relocs are not
supported.
The code is tested by successfully bootstrapping a Gentoo/LoongArch
stage3, complete with common GNU userland tools and both the LLVM and
GNU toolchains (GNU toolchain is present only for building glibc,
LLVM+Clang+LLD are used for the rest). Large programs like QEMU are
tested to work as well.
[1]: https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html
Reviewed By: MaskRay, SixWeining
Differential Revision: https://reviews.llvm.org/D138135
