Add comment on AMDGPU that the difference has no obvious reason.

llvm-svn: 262026
diff --git a/lld/ELF/Symbols.cpp b/lld/ELF/Symbols.cpp
index bd6f6b4..125e6c7 100644
--- a/lld/ELF/Symbols.cpp
+++ b/lld/ELF/Symbols.cpp
@@ -44,10 +44,12 @@
       return D->Sym.st_value;
     assert(SC->Live);
 
-    // Symbol offsets for AMDGPU need to be the offset in bytes of the symbol
-    // from the beginning of the section.
+    // Symbol offsets for AMDGPU are the offsets in bytes of the symbols
+    // from the beginning of the section. Note that this part of AMDGPU's
+    // ELF spec is odd and not in line with the standard ELF.
     if (Config->EMachine == EM_AMDGPU)
       return SC->getOffset(D->Sym);
+
     if (D->Sym.getType() == STT_TLS)
       return SC->OutSec->getVA() + SC->getOffset(D->Sym) -
              Out<ELFT>::TlsPhdr->p_vaddr;