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

NFC. Follow-up to r259781.

llvm-svn: 260027

diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index 3bb9053..9a14228 100644 (file)
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -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

diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 20a1dfb..2c362e7 100644 (file)
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -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;
     }