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[ELF][MIPS] Add comments to describe __gnu_local_gp magic symbol 

NFC. Follow-up to r259781.

llvm-svn: 260027
This commit is contained in:
Simon Atanasyan 2016-02-07 12:09:40 +00:00
parent ece55b045b
commit b76108a63a
2 changed files with 8 additions and 4 deletions
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7
lld/ELF/Driver.cpp
View File

@ -325,9 +325,12 @@ template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
if (Config->EMachine == EM_MIPS) {
// On MIPS O32 ABI, _gp_disp is a magic symbol designates offset between
// start of function and gp pointer into GOT. Use 'strong' variant of
// the addIgnored to prevent '_gp_disp' substitution.
// start of function and 'gp' pointer into GOT.
Config->MipsGpDisp = Symtab.addIgnored("_gp_disp");
// The __gnu_local_gp is a magic symbol equal to the current value of 'gp'
// pointer. This symbol is used in the code generated by .cpload pseudo-op
// in case of using -mno-shared option.
// https://sourceware.org/ml/binutils/2004-12/msg00094.html
Config->MipsLocalGp = Symtab.addIgnored("__gnu_local_gp");
// Define _gp for MIPS. st_value of _gp symbol will be updated by Writer

5
lld/ELF/Writer.cpp
View File

@ -397,8 +397,9 @@ void Writer<ELFT>::scanRelocs(
// linking only.
continue;
if (Body == Config->MipsGpDisp || Body == Config->MipsLocalGp)
// MIPS _gp_disp designates offset between start of function and gp
// pointer into GOT therefore any relocations against it do not require
// MIPS _gp_disp designates offset between start of function and 'gp'
// pointer into GOT. __gnu_local_gp is equal to the current value of
// the 'gp'. Therefore any relocations against them do not require
// dynamic relocation.
continue;
}