[PATCH] D138135: [lld][ELF] Support LoongArch

Fri Jul 7 14:41:10 PDT 2023

MaskRay added inline comments.

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Comment at: lld/ELF/Arch/LoongArch.cpp:360
+  case R_LARCH_PCALA_LO12:
+    // This may well be just R_ABS and nothing more, but unfortunately some
+    // people had the brilliant idea of reusing the R_LARCH_PCALA_LO12 reloc on
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This wording may sound irony for a public project. Also, the paragraph is too long.

We could just R_ABS, but the JIRL instruction reuses the relocation type for a different purpose.
This questionable use case is part of glibc 2.37 Scrt1.o (is it true?), which is linked into user programs, so we have to work around it for a while, even if a new relocation type may be introduced in the future.

I wonder why the medium code model designer decides to use pcalau12i+jirl. Range extension thunks are much better.

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Comment at: lld/ELF/Arch/LoongArch.cpp:370
+    //
+    // * R_LARCH_PCALA_LO12 just places its computed value unmodified, but JIRL
+    //   expects its immediate to be pre-shifted by 2 bits, making the reloc
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The long description about "* R_LARCH_PCALA_LO12 just places its computed value unmodified" can be simplified to just mention that the computation is different.  How it is different is the job of the comment in `relocate`.

Repository:
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  https://reviews.llvm.org/D138135/new/

https://reviews.llvm.org/D138135