[ELF][MIPS] Make _gp, _gp_disp, __gnu_local_gp global symbols

These MIPS specific symbols should be global because in general they can
have an arbitrary value. By default this value is a fixed offset from .got
section.

This patch adds more checks to the mips-gp-local.s test case but marks
it as XFAIL because LLD does not allow redefinition of absolute symbols
value by a linker script. This should be fixed by D27276.

Differential revision: https://reviews.llvm.org/D27524

llvm-svn: 289025

1 files changed, 5 insertions, 0 deletions

diff --git a/lld/ELF/Relocations.cpp b/lld/ELF/Relocations.cpp
index 4f39f3c06b5..a3945690a45 100644
--- a/lld/ELF/Relocations.cpp
+++ b/lld/ELF/Relocations.cpp
@@ -348,9 +348,14 @@ static bool isStaticLinkTimeConstant(RelExpr E, uint32_t Type,
   // resolve to the image base. This is a little strange, but it allows us to
   // link function calls to such symbols. Normally such a call will be guarded
   // with a comparison, which will load a zero from the GOT.
+  // Another special case is MIPS _gp_disp symbol which represents offset
+  // between start of a function and '_gp' value and defined as absolute just
+  // to simplify the code.
   if (AbsVal && RelE) {
     if (Body.isUndefined() && !Body.isLocal() && Body.symbol()->isWeak())
       return true;
+    if (&Body == ElfSym<ELFT>::MipsGpDisp)
+      return true;
     error(S.getLocation(RelOff) + ": relocation " + toString(Type) +
           " cannot refer to absolute symbol '" + toString(Body) +
           "' defined in " + toString(Body.File));