[all-commits] [llvm/llvm-project] 4b91af: [lld][LoongArch] Implement TLSDESC GD/LD to IE/LE.

[Zhaoxin Yang via All-commits]

  Branch: refs/heads/users/ylzsx/r-tlsdesc-to-iele-norelax
  Home:   https://github.com/llvm/llvm-project
  Commit: 4b91af1232fe7a18b4fca4329d0c916cbfa59dc9
      https://github.com/llvm/llvm-project/commit/4b91af1232fe7a18b4fca4329d0c916cbfa59dc9
  Author: yangzhaoxin <yangzhaoxin at loongson.cn>
  Date:   2025-04-11 (Fri, 11 Apr 2025)

  Changed paths:
    M lld/ELF/Arch/LoongArch.cpp
    M lld/ELF/InputSection.cpp
    M lld/ELF/Relocations.cpp
    M lld/ELF/Relocations.h

  Log Message:
  -----------
  [lld][LoongArch] Implement TLSDESC GD/LD to IE/LE.

Support TLSDESC to initial-exec or local-exec optimizations. Introduce a new hook
RE_LOONGARCH_RELAX_TLS_GD_TO_IE_PAGE_PC and use existing R_RELAX_TLS_GD_TO_IE_ABS
to support TLSDESC => IE, while use existing R_RELAX_TLS_GD_TO_LE to support
TLSDESC => LE.

In normal or medium code model, there are two forms of code sequences:
 * pcalau12i  $a0, %desc_pc_hi20(sym_desc)
 * addi.d     $a0, $a0, %desc_pc_lo12(sym_desc)
 * ld.d       $ra, $a0, %desc_ld(sym_desc)
 * jirl       $ra, $ra, %desc_call(sym_desc)
 ------
 * pcaddi     $a0, %desc_pcrel_20(sym_desc)
 * ld.d       $ra, $a0, %desc_ld(sym_desc)
 * jirl       $ra, $ra, %desc_call(sym_desc)

The code sequence obtained is as follows:
 * pcalau12i $a0, %ie_pc_hi20(sym_ie)
 * ld.[wd]   $a0, $a0, %ie_pc_lo12(sym_ie)

Simplicity, whether tlsdescToIe or tlsdescToLe, we always tend to convert the preceding
instructions to NOPs, due to both forms of code sequence (corresponding to relocation
combinations: R_LARCH_TLS_DESC_PC_HI20+R_LARCH_TLS_DESC_PC_LO12 and R_LARCH_TLS_DESC_PCREL20_S2)
have same process.

FIXME: When relaxation enables, redundant NOPs can be removed. It will
be implemented in a future patch.

Note: All forms of TLSDESC code sequences should not appear interleaved in the normal,
medium or extreme code model, which compilers do not generate and lld is unsupported.
This is thanks to the guard in PostRASchedulerList.cpp in llvm.
```
Calls are not scheduling boundaries before register allocation, but
post-ra we don't gain anything by scheduling across calls since we
don't need to worry about register pressure.
```


  Commit: 99c1a4eaaad1e71aab45861aa48da768e8868d0b
      https://github.com/llvm/llvm-project/commit/99c1a4eaaad1e71aab45861aa48da768e8868d0b
  Author: yangzhaoxin <yangzhaoxin at loongson.cn>
  Date:   2025-04-11 (Fri, 11 Apr 2025)

  Changed paths:
    M lld/test/ELF/loongarch-relax-tlsdesc.s
    M lld/test/ELF/loongarch-tlsdesc-pcrel20-s2.s
    M lld/test/ELF/loongarch-tlsdesc.s

  Log Message:
  -----------
  Modify loongarch-tlsdesc.s and loongarch-tlsdesc-pcrel20-s2.s

Add loongarch-relax-tlsdesc.s


  Commit: baee006a50c14536f2e60ad4300458458ee67d6c
      https://github.com/llvm/llvm-project/commit/baee006a50c14536f2e60ad4300458458ee67d6c
  Author: yangzhaoxin <yangzhaoxin at loongson.cn>
  Date:   2025-04-11 (Fri, 11 Apr 2025)

  Changed paths:
    M lld/ELF/Relocations.cpp
    M lld/ELF/Symbols.h

  Log Message:
  -----------
  Delete the wrong flag NEEDS_TLSGD_TO_IE in the extreme code model.


Compare: https://github.com/llvm/llvm-project/compare/0c6ba1de86e3...baee006a50c1

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