[PATCH] D25833: [ELF][MIPS] Put local GOT entries accessed via a 16-bit index first

[Simon Atanasyan via llvm-commits]

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Some MIPS relocations used to access GOT entries are able to manipulate 16-bit index. The other ones like R_MIPS_CALL_HI16/LO16 can handle 32-bit indexes. 16-bit relocations are generated by default. The 32-bit relocations are generated by -mxgot flag passed to compiler. Usually these relocation are not mixed in the same code but files like crt*.o contain 16-bit relocations so even if all "user's" code compiled with -mxgot flag a few 16-bit relocations might come to the linking phase.

Now LLD does not differentiate local GOT entries accessed via a 16-bit and 32-bit indexes. That might lead to relocation's overflow if 16-bit entries are allocated to far from the beginning of the GOT.

The patch introduces new "part" of MIPS GOT dedicated to the local GOT entries accessed by 32-bit relocations. That allows to put local GOT entries accessed via a 16-bit index first and escape relocation's overflow.


Repository:
  rL LLVM

https://reviews.llvm.org/D25833

Files:
  ELF/InputSection.cpp
  ELF/OutputSections.cpp
  ELF/OutputSections.h
  ELF/Relocations.cpp
  ELF/Relocations.h
  ELF/Symbols.cpp
  ELF/Symbols.h
  ELF/Target.cpp
  test/ELF/mips-xgot-order.s

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