rocallahan updated this revision to Diff 194244.
rocallahan added a comment.
Addressed all comments AFAIK. I'll post some performance numbers in a moment.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D54747/new/
https://reviews.llvm.org/D54747
Files:
lld/ELF/Driver.cpp
lld/ELF/InputFiles.h
lld/ELF/InputSection.cpp
lld/ELF/InputSection.h
lld/ELF/MarkLive.cpp
lld/test/ELF/linkerscript/comdat-gc.s
lld/test/ELF/linkerscript/debuginfo-gc.s
Index: lld/test/ELF/linkerscript/debuginfo-gc.s
===================================================================
--- /dev/null
+++ lld/test/ELF/linkerscript/debuginfo-gc.s
@@ -0,0 +1,14 @@
+# 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
Index: lld/test/ELF/linkerscript/comdat-gc.s
===================================================================
--- lld/test/ELF/linkerscript/comdat-gc.s
+++ lld/test/ELF/linkerscript/comdat-gc.s
@@ -8,6 +8,9 @@
# 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
Index: lld/ELF/MarkLive.cpp
===================================================================
--- lld/ELF/MarkLive.cpp
+++ lld/ELF/MarkLive.cpp
@@ -47,7 +47,7 @@
void run();
private:
- void enqueue(InputSectionBase *Sec, uint64_t Offset);
+ void enqueue(InputSectionBase *Sec, uint64_t Offset, bool IsLSDA);
void markSymbol(Symbol *Sym);
template <class RelTy>
@@ -97,7 +97,7 @@
Offset += getAddend<ELFT>(Sec, Rel);
if (!IsLSDA || !(RelSec->Flags & SHF_EXECINSTR))
- enqueue(RelSec, Offset);
+ enqueue(RelSec, Offset, IsLSDA);
return;
}
@@ -106,7 +106,7 @@
SS->getFile().IsNeeded = true;
for (InputSectionBase *Sec : CNamedSections.lookup(Sym.getName()))
- enqueue(Sec, 0);
+ enqueue(Sec, 0, IsLSDA);
}
// The .eh_frame section is an unfortunate special case.
@@ -169,7 +169,7 @@
}
template <class ELFT>
-void MarkLive<ELFT>::enqueue(InputSectionBase *Sec, uint64_t Offset) {
+void MarkLive<ELFT>::enqueue(InputSectionBase *Sec, uint64_t Offset, bool IsLSDA) {
// 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.
@@ -183,19 +183,28 @@
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)
+ if (isa<InputSection>(Sec) || isa<MergeInputSection>(Sec))
+ Sec->getFile<ELFT>()->HasLiveCodeOrData = true;
+
if (Sec->Live)
return;
- Sec->Live = true;
+ Sec->Live = true;
// Add input section to the queue.
- if (InputSection *S = dyn_cast<InputSection>(Sec))
+ if (S) {
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);
+ enqueue(IS, D->Value, false);
}
// This is the main function of the garbage collector.
@@ -239,7 +248,7 @@
continue;
if (isReserved(Sec) || Script->shouldKeep(Sec)) {
- enqueue(Sec, 0);
+ enqueue(Sec, 0, false);
} else if (isValidCIdentifier(Sec->Name)) {
CNamedSections[Saver.save("__start_" + Sec->Name)].push_back(Sec);
CNamedSections[Saver.save("__stop_" + Sec->Name)].push_back(Sec);
@@ -259,7 +268,7 @@
}
for (InputSectionBase *IS : Sec.DependentSections)
- enqueue(IS, 0);
+ enqueue(IS, 0, false);
}
}
@@ -285,7 +294,7 @@
// 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.
+ // SHF_LINK_ORDER and SHT_REL/SHT_RELA sections and .debug sections.
//
// Usually, SHF_ALLOC sections are not removed even if they are
// unreachable through relocations because reachability is not
@@ -301,7 +310,12 @@
// or -emit-reloc were given. And they are subject of garbage
// collection because, if we remove a text section, we also
// remove its relocation section.
+ bool AnyDebugSections = false;
for (InputSectionBase *Sec : InputSections) {
+ if (Sec->Debug) {
+ AnyDebugSections = true;
+ continue;
+ }
bool IsAlloc = (Sec->Flags & SHF_ALLOC);
bool IsLinkOrder = (Sec->Flags & SHF_LINK_ORDER);
bool IsRel = (Sec->Type == SHT_REL || Sec->Type == SHT_RELA);
@@ -313,6 +327,13 @@
// Follow the graph to mark all live sections.
MarkLive<ELFT>().run();
+ if (AnyDebugSections)
+ // 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)
Index: lld/ELF/InputSection.h
===================================================================
--- lld/ELF/InputSection.h
+++ lld/ELF/InputSection.h
@@ -51,7 +51,7 @@
unsigned SectionKind : 3;
- // The next three bit fields are only used by InputSectionBase, but we
+ // The next four bit fields are only used by InputSectionBase, but we
// put them here so the struct packs better.
// The garbage collector sets sections' Live bits.
@@ -73,6 +73,9 @@
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;
@@ -100,7 +103,7 @@
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), KeepUnique(false), Alignment(Alignment),
+ Assigned(false), Bss(false), Debug(false), KeepUnique(false), Alignment(Alignment),
Flags(Flags), Entsize(Entsize), Type(Type), Link(Link), Info(Info) {}
};
Index: lld/ELF/InputSection.cpp
===================================================================
--- lld/ELF/InputSection.cpp
+++ lld/ELF/InputSection.cpp
@@ -71,6 +71,7 @@
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.
Index: lld/ELF/InputFiles.h
===================================================================
--- lld/ELF/InputFiles.h
+++ lld/ELF/InputFiles.h
@@ -234,6 +234,10 @@
// 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;
Index: lld/ELF/Driver.cpp
===================================================================
--- lld/ELF/Driver.cpp
+++ lld/ELF/Driver.cpp
@@ -1613,11 +1613,8 @@
// 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->Name.startswith(".debug") || S->Name.startswith(".zdebug");
- });
- }
+ if (Config->Strip != StripPolicy::None)
+ llvm::erase_if(InputSections, [](InputSectionBase *S) { return S->Debug; });
// The Target instance handles target-specific stuff, such as applying
// relocations or writing a PLT section. It also contains target-dependent
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