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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
This commit is contained in:
Bob Haarman 2019-05-16 23:33:06 +00:00
parent add7ed2281
commit 5ff1eb6418
7 changed files with 19 additions and 56 deletions
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7
lld/ELF/Driver.cpp
View File

@ -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

4
lld/ELF/InputFiles.h
View File

@ -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;

1
lld/ELF/InputSection.cpp
View File

@ -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.

10
lld/ELF/InputSection.h
View File

@ -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.

36
lld/ELF/MarkLive.cpp
View File

@ -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)

3
lld/test/ELF/linkerscript/comdat-gc.s
View File

@ -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

14
lld/test/ELF/linkerscript/debuginfo-gc.s
View File

@ -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