1 files changed, 58 insertions, 12 deletions

diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index fdf935a30856..43978cd66c61 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/lld/ELF/InputFiles.cpp
@@ -13,6 +13,7 @@
 #include "SymbolTable.h"
 #include "Symbols.h"
 #include "SyntheticSections.h"
+#include "lld/Common/DWARF.h"
 #include "lld/Common/ErrorHandler.h"
 #include "lld/Common/Memory.h"
 #include "llvm/ADT/STLExtras.h"
@@ -295,7 +296,7 @@ Optional<DILineInfo> ObjFile<ELFT>::getDILineInfo(InputSectionBase *s,
     }
   }
 
-  // Use fake address calcuated by adding section file offset and offset in
+  // Use fake address calculated by adding section file offset and offset in
   // section. See comments for ObjectInfo class.
   return dwarf->getDILineInfo(s->getOffsetInFile() + offset, sectionIndex);
 }
@@ -496,6 +497,44 @@ static void addDependentLibrary(StringRef specifier, const InputFile *f) {
           specifier);
 }
 
+// Record the membership of a section group so that in the garbage collection
+// pass, section group members are kept or discarded as a unit.
+template <class ELFT>
+static void handleSectionGroup(ArrayRef<InputSectionBase *> sections,
+                               ArrayRef<typename ELFT::Word> entries) {
+  bool hasAlloc = false;
+  for (uint32_t index : entries.slice(1)) {
+    if (index >= sections.size())
+      return;
+    if (InputSectionBase *s = sections[index])
+      if (s != &InputSection::discarded && s->flags & SHF_ALLOC)
+        hasAlloc = true;
+  }
+
+  // If any member has the SHF_ALLOC flag, the whole group is subject to garbage
+  // collection. See the comment in markLive(). This rule retains .debug_types
+  // and .rela.debug_types.
+  if (!hasAlloc)
+    return;
+
+  // Connect the members in a circular doubly-linked list via
+  // nextInSectionGroup.
+  InputSectionBase *head;
+  InputSectionBase *prev = nullptr;
+  for (uint32_t index : entries.slice(1)) {
+    InputSectionBase *s = sections[index];
+    if (!s || s == &InputSection::discarded)
+      continue;
+    if (prev)
+      prev->nextInSectionGroup = s;
+    else
+      head = s;
+    prev = s;
+  }
+  if (prev)
+    prev->nextInSectionGroup = head;
+}
+
 template <class ELFT>
 void ObjFile<ELFT>::initializeSections(bool ignoreComdats) {
   const ELFFile<ELFT> &obj = this->getObj();
@@ -506,6 +545,8 @@ void ObjFile<ELFT>::initializeSections(bool ignoreComdats) {
   this->sectionStringTable =
       CHECK(obj.getSectionStringTable(objSections), this);
 
+  std::vector<ArrayRef<Elf_Word>> selectedGroups;
+
   for (size_t i = 0, e = objSections.size(); i < e; ++i) {
     if (this->sections[i] == &InputSection::discarded)
       continue;
@@ -563,6 +604,7 @@ void ObjFile<ELFT>::initializeSections(bool ignoreComdats) {
       if (isNew) {
         if (config->relocatable)
           this->sections[i] = createInputSection(sec);
+        selectedGroups.push_back(entries);
         continue;
       }
 
@@ -587,6 +629,7 @@ void ObjFile<ELFT>::initializeSections(bool ignoreComdats) {
     }
   }
 
+  // This block handles SHF_LINK_ORDER.
   for (size_t i = 0, e = objSections.size(); i < e; ++i) {
     if (this->sections[i] == &InputSection::discarded)
       continue;
@@ -609,6 +652,9 @@ void ObjFile<ELFT>::initializeSections(bool ignoreComdats) {
             " with SHF_LINK_ORDER should not refer a non-regular section: " +
             toString(linkSec));
   }
+
+  for (ArrayRef<Elf_Word> entries : selectedGroups)
+    handleSectionGroup<ELFT>(this->sections, entries);
 }
 
 // For ARM only, to set the EF_ARM_ABI_FLOAT_SOFT or EF_ARM_ABI_FLOAT_HARD
@@ -741,7 +787,7 @@ static uint32_t readAndFeatures(ObjFile<ELFT> *obj, ArrayRef<uint8_t> data) {
 
       if (type == featureAndType) {
         // We found a FEATURE_1_AND field. There may be more than one of these
-        // in a .note.gnu.propery section, for a relocatable object we
+        // in a .note.gnu.property section, for a relocatable object we
         // accumulate the bits set.
         featuresSet |= read32le(desc.data() + 8);
       }
@@ -838,6 +884,16 @@ InputSectionBase *ObjFile<ELFT>::createInputSection(const Elf_Shdr &sec) {
     if (!target)
       return nullptr;
 
+    // ELF spec allows mergeable sections with relocations, but they are
+    // rare, and it is in practice hard to merge such sections by contents,
+    // because applying relocations at end of linking changes section
+    // contents. So, we simply handle such sections as non-mergeable ones.
+    // Degrading like this is acceptable because section merging is optional.
+    if (auto *ms = dyn_cast<MergeInputSection>(target)) {
+      target = toRegularSection(ms);
+      this->sections[sec.sh_info] = target;
+    }
+
     // This section contains relocation information.
     // If -r is given, we do not interpret or apply relocation
     // but just copy relocation sections to output.
@@ -856,16 +912,6 @@ InputSectionBase *ObjFile<ELFT>::createInputSection(const Elf_Shdr &sec) {
       fatal(toString(this) +
             ": multiple relocation sections to one section are not supported");
 
-    // ELF spec allows mergeable sections with relocations, but they are
-    // rare, and it is in practice hard to merge such sections by contents,
-    // because applying relocations at end of linking changes section
-    // contents. So, we simply handle such sections as non-mergeable ones.
-    // Degrading like this is acceptable because section merging is optional.
-    if (auto *ms = dyn_cast<MergeInputSection>(target)) {
-      target = toRegularSection(ms);
-      this->sections[sec.sh_info] = target;
-    }
-
     if (sec.sh_type == SHT_RELA) {
       ArrayRef<Elf_Rela> rels = CHECK(getObj().relas(&sec), this);
       target->firstRelocation = rels.begin();