Revert r358069 "Discard debuginfo for object files empty after GC"

The change broke some scenarios where debug information is still
needed, although MarkLive cannot see it, including the
Chromium/Android build. Reverting to unbreak that build.

llvm-svn: 360955

lld/ELF/Driver.cpp

@@ -1670,8 +1670,11 @@ template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
 
   // We do not want to emit debug sections if --strip-all
   // or -strip-debug are given.
-  if (Config->Strip != StripPolicy::None)
-    llvm::erase_if(InputSections, [](InputSectionBase *S) { return S->Debug; });
+  if (Config->Strip != StripPolicy::None) {
+    llvm::erase_if(InputSections, [](InputSectionBase *S) {
+      return S->Name.startswith(".debug") || S->Name.startswith(".zdebug");
+    });
+  }
 
   Config->EFlags = Target->calcEFlags();
   // MaxPageSize (sometimes called abi page size) is the maximum page size that

lld/ELF/InputFiles.h

@@ -237,10 +237,6 @@ public:
   // but had one or more functions with the no_split_stack attribute.
   bool SomeNoSplitStack = false;
 
-  // True if the file has any live Regular or Merge sections that aren't
-  // the LDSA section.
-  bool HasLiveCodeOrData = false;
-
   // Pointer to this input file's .llvm_addrsig section, if it has one.
   const Elf_Shdr *AddrsigSec = nullptr;
 

lld/ELF/InputSection.cpp

@@ -71,7 +71,6 @@ InputSectionBase::InputSectionBase(InputFile *File, uint64_t Flags,
 
   NumRelocations = 0;
   AreRelocsRela = false;
-  Debug = Name.startswith(".debug") || Name.startswith(".zdebug");
 
   // The ELF spec states that a value of 0 means the section has
   // no alignment constraits.

lld/ELF/InputSection.h

@@ -51,7 +51,7 @@ public:
 
   unsigned SectionKind : 3;
 
-  // The next four bit fields are only used by InputSectionBase, but we
+  // The next three bit fields are only used by InputSectionBase, but we
   // put them here so the struct packs better.
 
   // The garbage collector sets sections' Live bits.
@@ -73,9 +73,6 @@ public:
 
   unsigned Bss : 1;
 
-  // True if this is a debuginfo section.
-  unsigned Debug : 1;
-
   // Set for sections that should not be folded by ICF.
   unsigned KeepUnique : 1;
 
@@ -103,9 +100,8 @@ protected:
               uint64_t Entsize, uint64_t Alignment, uint32_t Type,
               uint32_t Info, uint32_t Link)
       : Name(Name), Repl(this), SectionKind(SectionKind), Live(false),
-        Assigned(false), Bss(false), Debug(false), KeepUnique(false),
-        Alignment(Alignment), Flags(Flags), Entsize(Entsize), Type(Type),
-        Link(Link), Info(Info) {}
+        Assigned(false), Bss(false), KeepUnique(false), Alignment(Alignment),
+        Flags(Flags), Entsize(Entsize), Type(Type), Link(Link), Info(Info) {}
 };
 
 // This corresponds to a section of an input file.

lld/ELF/MarkLive.cpp

@@ -47,7 +47,7 @@ public:
   void run();
 
 private:
-  void enqueue(InputSectionBase *Sec, uint64_t Offset, bool IsLSDA);
+  void enqueue(InputSectionBase *Sec, uint64_t Offset);
   void markSymbol(Symbol *Sym);
 
   template <class RelTy>
@@ -97,7 +97,7 @@ void MarkLive<ELFT>::resolveReloc(InputSectionBase &Sec, RelTy &Rel,
       Offset += getAddend<ELFT>(Sec, Rel);
 
     if (!IsLSDA || !(RelSec->Flags & SHF_EXECINSTR))
-      enqueue(RelSec, Offset, IsLSDA);
+      enqueue(RelSec, Offset);
     return;
   }
 
@@ -106,7 +106,7 @@ void MarkLive<ELFT>::resolveReloc(InputSectionBase &Sec, RelTy &Rel,
       SS->getFile().IsNeeded = true;
 
   for (InputSectionBase *Sec : CNamedSections.lookup(Sym.getName()))
-    enqueue(Sec, 0, IsLSDA);
+    enqueue(Sec, 0);
 }
 
 // The .eh_frame section is an unfortunate special case.
@@ -169,8 +169,7 @@ static bool isReserved(InputSectionBase *Sec) {
 }
 
 template <class ELFT>
-void MarkLive<ELFT>::enqueue(InputSectionBase *Sec, uint64_t Offset,
-                             bool IsLSDA) {
+void MarkLive<ELFT>::enqueue(InputSectionBase *Sec, uint64_t Offset) {
   // Skip over discarded sections. This in theory shouldn't happen, because
   // the ELF spec doesn't allow a relocation to point to a deduplicated
   // COMDAT section directly. Unfortunately this happens in practice (e.g.
@@ -184,26 +183,19 @@ void MarkLive<ELFT>::enqueue(InputSectionBase *Sec, uint64_t Offset,
   if (auto *MS = dyn_cast<MergeInputSection>(Sec))
     MS->getSectionPiece(Offset)->Live = true;
 
-  InputSection *S = dyn_cast<InputSection>(Sec);
-  // LSDA does not count as "live code or data" in the object file.
-  // The section may already have been marked live for LSDA in which
-  // case we still need to mark the file.
-  if (S && !IsLSDA && Sec->File)
-    Sec->getFile<ELFT>()->HasLiveCodeOrData = true;
-
   if (Sec->Live)
     return;
-
   Sec->Live = true;
+
   // Add input section to the queue.
-  if (S)
+  if (InputSection *S = dyn_cast<InputSection>(Sec))
     Queue.push_back(S);
 }
 
 template <class ELFT> void MarkLive<ELFT>::markSymbol(Symbol *Sym) {
   if (auto *D = dyn_cast_or_null<Defined>(Sym))
     if (auto *IS = dyn_cast_or_null<InputSectionBase>(D->Section))
-      enqueue(IS, D->Value, false);
+      enqueue(IS, D->Value);
 }
 
 // This is the main function of the garbage collector.
@@ -247,7 +239,7 @@ template <class ELFT> void MarkLive<ELFT>::run() {
       continue;
 
     if (isReserved(Sec) || Script->shouldKeep(Sec)) {
-      enqueue(Sec, 0, false);
+      enqueue(Sec, 0);
     } else if (isValidCIdentifier(Sec->Name)) {
       CNamedSections[Saver.save("__start_" + Sec->Name)].push_back(Sec);
       CNamedSections[Saver.save("__stop_" + Sec->Name)].push_back(Sec);
@@ -267,7 +259,7 @@ template <class ELFT> void MarkLive<ELFT>::run() {
     }
 
     for (InputSectionBase *IS : Sec.DependentSections)
-      enqueue(IS, 0, false);
+      enqueue(IS, 0);
   }
 }
 
@@ -293,7 +285,7 @@ template <class ELFT> void elf::markLive() {
   // The -gc-sections option works only for SHF_ALLOC sections
   // (sections that are memory-mapped at runtime). So we can
   // unconditionally make non-SHF_ALLOC sections alive except
-  // SHF_LINK_ORDER and SHT_REL/SHT_RELA sections and .debug sections.
+  // SHF_LINK_ORDER and SHT_REL/SHT_RELA sections.
   //
   // Usually, SHF_ALLOC sections are not removed even if they are
   // unreachable through relocations because reachability is not
@@ -314,19 +306,13 @@ template <class ELFT> void elf::markLive() {
     bool IsLinkOrder = (Sec->Flags & SHF_LINK_ORDER);
     bool IsRel = (Sec->Type == SHT_REL || Sec->Type == SHT_RELA);
 
-    if (!IsAlloc && !IsLinkOrder && !IsRel && !Sec->Debug)
+    if (!IsAlloc && !IsLinkOrder && !IsRel)
       Sec->Live = true;
   }
 
   // Follow the graph to mark all live sections.
   MarkLive<ELFT>().run();
 
-  // Mark debug sections as live in any object file that has a live
-  // Regular or Merge section.
-  for (InputSectionBase *Sec : InputSections)
-    if (Sec->Debug && Sec->getFile<ELFT>()->HasLiveCodeOrData)
-      Sec->Live = true;
-
   // Report garbage-collected sections.
   if (Config->PrintGcSections)
     for (InputSectionBase *Sec : InputSections)

lld/test/ELF/linkerscript/comdat-gc.s

@@ -8,9 +8,6 @@
 
 # GC1:     Name: .debug_line
 
-# Add .ctors section so all debuginfo isn't GCed
-.section  .ctors,"ax",@progbits
-
 .file 1 "test/ELF/linkerscript/comdat_gc.s"
 .section  .text._Z3fooIiEvv,"axG",@progbits,_Z3fooIiEvv,comdat
 .loc 1 14

lld/test/ELF/linkerscript/debuginfo-gc.s

@@ -1,14 +0,0 @@
-# REQUIRES: x86
-
-# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
-# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/comdat-gc.s -o %t1
-# RUN: echo "SECTIONS { .text : { *(.text*) } }" > %t.script
-# RUN: ld.lld --gc-sections --script %t.script %t %t1 -o %t2
-# RUN: llvm-readobj --sections --symbols %t2 | FileCheck %s
-
-# CHECK-NOT: Name: .debug_line
-
-.file 1 "test/ELF/linkerscript/comdat_gc.s"
-.section  .text._Z3fooIiEvv,"axG",@progbits,_Z3fooIiEvv,comdat
-.loc 1 14
-  ret