[ELF] - Do not collect SHT_REL[A] sections unconditionally when --gc-sections and --emit-relocs used together.

This is "Bug 34836 - --gc-sections remove relocations from --emit-relocs",

When --emit-relocs is used, LLD currently always drops SHT_REL[A] sections from
output if --gc-sections is present. Patch fixes the issue.

Differential revision: https://reviews.llvm.org/D38724

1 files changed, 3 insertions, 9 deletions

diff --git a/lld/ELF/MarkLive.cpp b/lld/ELF/MarkLive.cpp
index 62a0039ef01..05fe3a494c7 100644
--- a/lld/ELF/MarkLive.cpp
+++ b/lld/ELF/MarkLive.cpp
@@ -162,9 +162,9 @@ scanEhFrameSection(EhInputSection &EH,
     scanEhFrameSection<ELFT>(EH, EH.template rels<ELFT>(), Fn);
 }
 
-// We do not garbage-collect two types of sections:
-// 1) Sections used by the loader (.init, .fini, .ctors, .dtors or .jcr)
-// 2) Non-allocatable sections which typically contain debugging information
+// Some sections are used directly by the loader, so they should never be
+// garbage-collected. This function returns true if a given section is such
+// section.
 template <class ELFT> static bool isReserved(InputSectionBase *Sec) {
   switch (Sec->Type) {
   case SHT_FINI_ARRAY:
@@ -173,9 +173,6 @@ template <class ELFT> static bool isReserved(InputSectionBase *Sec) {
   case SHT_PREINIT_ARRAY:
     return true;
   default:
-    if (!(Sec->Flags & SHF_ALLOC))
-      return true;
-
     StringRef S = Sec->Name;
     return S.startswith(".ctors") || S.startswith(".dtors") ||
            S.startswith(".init") || S.startswith(".fini") ||
@@ -198,9 +195,6 @@ template <class ELFT> static void doGcSections() {
     if (Sec == &InputSection::Discarded)
       return;
 
-    // We don't gc non alloc sections.
-    if (!(Sec->Flags & SHF_ALLOC))
-      return;
 
     // Usually, a whole section is marked as live or dead, but in mergeable
     // (splittable) sections, each piece of data has independent liveness bit.