[lld] r352218 - Merging r352068:

[Hans Wennborg via llvm-commits]

Author: hans
Date: Fri Jan 25 09:01:21 2019
New Revision: 352218

URL: http://llvm.org/viewvc/llvm-project?rev=352218&view=rev
Log:
Merging r352068:
------------------------------------------------------------------------
r352068 | serge_sans_paille | 2019-01-24 18:56:08 +0100 (Thu, 24 Jan 2019) | 7 lines

Partial support of SHT_GROUP without flag

This does *not* implement full SHT_GROUP semantic, yet it is a simple step forward:
Sections within a group are still considered valid, but they do not behave as
specified by the standard in case of garbage collection.

Differential Revision: https://reviews.llvm.org/D56437
------------------------------------------------------------------------

Added:
    lld/branches/release_80/test/ELF/sht-group-empty.test
      - copied unchanged from r352068, lld/trunk/test/ELF/sht-group-empty.test
Modified:
    lld/branches/release_80/   (props changed)
    lld/branches/release_80/ELF/InputFiles.cpp

Propchange: lld/branches/release_80/
------------------------------------------------------------------------------
--- svn:mergeinfo (original)
+++ svn:mergeinfo Fri Jan 25 09:01:21 2019
@@ -1 +1 @@
-/lld/trunk:351326,351335,351898-351899,352082
+/lld/trunk:351326,351335,351898-351899,352068,352082

Modified: lld/branches/release_80/ELF/InputFiles.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/branches/release_80/ELF/InputFiles.cpp?rev=352218&r1=352217&r2=352218&view=diff
==============================================================================
--- lld/branches/release_80/ELF/InputFiles.cpp (original)
+++ lld/branches/release_80/ELF/InputFiles.cpp Fri Jan 25 09:01:21 2019
@@ -320,17 +320,6 @@ StringRef ObjFile<ELFT>::getShtGroupSign
   return Signature;
 }
 
-template <class ELFT>
-ArrayRef<typename ObjFile<ELFT>::Elf_Word>
-ObjFile<ELFT>::getShtGroupEntries(const Elf_Shdr &Sec) {
-  const ELFFile<ELFT> &Obj = this->getObj();
-  ArrayRef<Elf_Word> Entries =
-      CHECK(Obj.template getSectionContentsAsArray<Elf_Word>(&Sec), this);
-  if (Entries.empty() || Entries[0] != GRP_COMDAT)
-    fatal(toString(this) + ": unsupported SHT_GROUP format");
-  return Entries.slice(1);
-}
-
 template <class ELFT> bool ObjFile<ELFT>::shouldMerge(const Elf_Shdr &Sec) {
   // On a regular link we don't merge sections if -O0 (default is -O1). This
   // sometimes makes the linker significantly faster, although the output will
@@ -440,26 +429,34 @@ void ObjFile<ELFT>::initializeSections(
     case SHT_GROUP: {
       // De-duplicate section groups by their signatures.
       StringRef Signature = getShtGroupSignature(ObjSections, Sec);
-      bool IsNew = ComdatGroups.insert(CachedHashStringRef(Signature)).second;
       this->Sections[I] = &InputSection::Discarded;
 
-      // We only support GRP_COMDAT type of group. Get the all entries of the
-      // section here to let getShtGroupEntries to check the type early for us.
-      ArrayRef<Elf_Word> Entries = getShtGroupEntries(Sec);
-
-      // If it is a new section group, we want to keep group members.
-      // Group leader sections, which contain indices of group members, are
-      // discarded because they are useless beyond this point. The only
-      // exception is the -r option because in order to produce re-linkable
-      // object files, we want to pass through basically everything.
+
+      ArrayRef<Elf_Word> Entries =
+          CHECK(Obj.template getSectionContentsAsArray<Elf_Word>(&Sec), this);
+      if (Entries.empty())
+        fatal(toString(this) + ": empty SHT_GROUP");
+
+      // The first word of a SHT_GROUP section contains flags. Currently,
+      // the standard defines only "GRP_COMDAT" flag for the COMDAT group.
+      // An group with the empty flag doesn't define anything; such sections
+      // are just skipped.
+      if (Entries[0] == 0)
+        continue;
+
+      if (Entries[0] != GRP_COMDAT)
+        fatal(toString(this) + ": unsupported SHT_GROUP format");
+
+      bool IsNew = ComdatGroups.insert(CachedHashStringRef(Signature)).second;
       if (IsNew) {
         if (Config->Relocatable)
           this->Sections[I] = createInputSection(Sec);
-        continue;
+	continue;
       }
 
+
       // Otherwise, discard group members.
-      for (uint32_t SecIndex : Entries) {
+      for (uint32_t SecIndex : Entries.slice(1)) {
         if (SecIndex >= Size)
           fatal(toString(this) +
                 ": invalid section index in group: " + Twine(SecIndex));