Several SPARC lld issues in compiler-rt tests

[rorth]

When running an LLVM build on Debian/sparc64, several compiler-rt tests FAIL with linker errors. Although the primary linker is ld.bfd 2.42.50.20240625, some tests are specificially run with ld.lld. Admittedly this is currenty lld 16.0.6, AFAICS most if not all of the issues remain:

ld.lld: error: unknown emulation: elf32_sparc

ld.lld: error: /lib/sparc64-linux-gnu/Scrt1.o:(function _start: .text+0x1c): unknown relocation (82) against symbol main
ld.lld: error: /lib/sparc64-linux-gnu/Scrt1.o:(function _start: .text+0x20): unknown relocation (83) against symbol main
ld.lld: error: /lib/sparc64-linux-gnu/Scrt1.o:(function _start: .text+0x24): unknown relocation (84) against symbol main

which is

#define R_SPARC_GOTDATA_OP_HIX22	82
#define R_SPARC_GOTDATA_OP_LOX10	83
#define R_SPARC_GOTDATA_OP	84

ld.lld: error: /tmp/lit-tmp-gq6t5qs1/coverage-linkage-35e2a3.o:(__llvm_prf_data+0x10): unknown relocation (46) against symbol 

which is

#define R_SPARC_DISP64		46	/* PC relative 64 bit */

ld.lld: error: relocation R_SPARC_64 cannot be used against local symbol; recompile with -fPIC

I'm still looking how to properly disable use of -fuse-lld on this target; maybe it should be done in compiler-rt for now.

[llvmbot]

@llvm/issue-subscribers-lld-elf

Author: Rainer Orth (rorth)

When running an LLVM build on Debian/sparc64, several `compiler-rt` tests `FAIL` with linker errors. Although the primary linker is `ld.bfd` 2.42.50.20240625, some tests are specificially run with `ld.lld`. Admittedly this is currenty `lld` 16.0.6, AFAICS most if not all of the issues remain: ``` ld.lld: error: unknown emulation: elf32_sparc ``` ``` ld.lld: error: /lib/sparc64-linux-gnu/Scrt1.o:(function _start: .text+0x1c): unknown relocation (82) against symbol main ld.lld: error: /lib/sparc64-linux-gnu/Scrt1.o:(function _start: .text+0x20): unknown relocation (83) against symbol main ld.lld: error: /lib/sparc64-linux-gnu/Scrt1.o:(function _start: .text+0x24): unknown relocation (84) against symbol main ``` which is ``` #define R_SPARC_GOTDATA_OP_HIX22 82 #define R_SPARC_GOTDATA_OP_LOX10 83 #define R_SPARC_GOTDATA_OP 84 ``` ``` ld.lld: error: /tmp/lit-tmp-gq6t5qs1/coverage-linkage-35e2a3.o:(__llvm_prf_data+0x10): unknown relocation (46) against symbol ``` which is ``` #define R_SPARC_DISP64 46 /* PC relative 64 bit */ ``` ``` ld.lld: error: relocation R_SPARC_64 cannot be used against local symbol; recompile with -fPIC ``` I'm still looking how to properly disable use of `-fuse-lld` on this target; maybe it should be done in `compiler-rt` for now.

[MaskRay]

I believe the Sparc port of lld for the 64-bit architecture was contributed by enthusiasts without long-term maintenance plans.
The 32-bit architecture was never seriously considered.
Due to the complexity of older architectures and potential ABI issues requiring significant changes to the core codebase, maintaining the 32-bit version poses challenges and risks to the project's overall health.
Given the limited user base and the availability of GNU ld as a functional alternative, I think it is reasonable to consider the 32-bit Sparc architecture unsupported for lld.

[rorth]

Thanks for the explanation. I've just had a look: after the initial code drop back in 2017 there were barely any non-mechanical changes to the file.

Given that situation (no 32-bit support at all, incomplete 64-bit reloc support, ...), I guess it's reasonable to disable the -fuse-ld=lld tests in compiler-rt as I've proposed in PR #100533?