[lld] r267233 - Bring r267164 back with a fix.
Rafael Espindola via llvm-commits
llvm-commits at lists.llvm.org
Fri Apr 22 15:09:35 PDT 2016
Author: rafael
Date: Fri Apr 22 17:09:35 2016
New Revision: 267233
URL: http://llvm.org/viewvc/llvm-project?rev=267233&view=rev
Log:
Bring r267164 back with a fix.
The fix is to handle local symbols referring to SHF_MERGE sections.
Original message:
GC entries of SHF_MERGE sections.
It is a fairly direct extension of the gc algorithm. For merge sections
instead of remembering just a live bit, we remember which offsets
were used.
This reduces the .rodata sections in chromium from 9648861 to 9477472
bytes.
Added:
lld/trunk/test/ELF/gc-sections-merge-addend.s
lld/trunk/test/ELF/gc-sections-merge-implicit-addend.s
lld/trunk/test/ELF/gc-sections-merge.s
Modified:
lld/trunk/ELF/InputSection.cpp
lld/trunk/ELF/InputSection.h
lld/trunk/ELF/MarkLive.cpp
lld/trunk/ELF/OutputSections.cpp
lld/trunk/ELF/Writer.cpp
lld/trunk/test/ELF/gc-merge-local-sym.s
Modified: lld/trunk/ELF/InputSection.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputSection.cpp?rev=267233&r1=267232&r2=267233&view=diff
==============================================================================
--- lld/trunk/ELF/InputSection.cpp (original)
+++ lld/trunk/ELF/InputSection.cpp Fri Apr 22 17:09:35 2016
@@ -77,23 +77,41 @@ InputSectionBase<ELFT>::getOffset(const
return getOffset(Sym.Value);
}
-// Returns a section that Rel relocation is pointing to.
template <class ELFT>
-InputSectionBase<ELFT> *
-InputSectionBase<ELFT>::getRelocTarget(const Elf_Rel &Rel) const {
- // Global symbol
+static DefinedRegular<ELFT> *getRelocTargetSym(elf::ObjectFile<ELFT> *File,
+ const typename ELFT::Rel &Rel) {
uint32_t SymIndex = Rel.getSymbol(Config->Mips64EL);
SymbolBody &B = File->getSymbolBody(SymIndex).repl();
if (auto *D = dyn_cast<DefinedRegular<ELFT>>(&B))
if (D->Section)
- return D->Section->Repl;
+ return D;
return nullptr;
}
+// Returns a section that Rel relocation is pointing to.
+template <class ELFT>
+std::pair<InputSectionBase<ELFT> *, typename ELFT::uint>
+InputSectionBase<ELFT>::getRelocTarget(const Elf_Rel &Rel) const {
+ auto *D = getRelocTargetSym(File, Rel);
+ if (!D)
+ return std::make_pair(nullptr, 0);
+ if (!D->isSection())
+ return std::make_pair(D->Section->Repl, D->Value);
+ const uint8_t *BufLoc = getSectionData().begin() + Rel.r_offset;
+ uintX_t Addend =
+ Target->getImplicitAddend(BufLoc, Rel.getType(Config->Mips64EL));
+ return std::make_pair(D->Section->Repl, D->Value + Addend);
+}
+
template <class ELFT>
-InputSectionBase<ELFT> *
+std::pair<InputSectionBase<ELFT> *, typename ELFT::uint>
InputSectionBase<ELFT>::getRelocTarget(const Elf_Rela &Rel) const {
- return getRelocTarget(reinterpret_cast<const Elf_Rel &>(Rel));
+ auto *D = getRelocTargetSym(File, Rel);
+ if (!D)
+ return std::make_pair(nullptr, 0);
+ if (!D->isSection())
+ return std::make_pair(D->Section->Repl, D->Value);
+ return std::make_pair(D->Section->Repl, D->Value + Rel.r_addend);
}
template <class ELFT>
@@ -368,10 +386,49 @@ typename ELFT::uint EHInputSection<ELFT>
return Base + Addend;
}
+static size_t findNull(StringRef S, size_t EntSize) {
+ // Optimize the common case.
+ if (EntSize == 1)
+ return S.find(0);
+
+ for (unsigned I = 0, N = S.size(); I != N; I += EntSize) {
+ const char *B = S.begin() + I;
+ if (std::all_of(B, B + EntSize, [](char C) { return C == 0; }))
+ return I;
+ }
+ return StringRef::npos;
+}
+
template <class ELFT>
MergeInputSection<ELFT>::MergeInputSection(elf::ObjectFile<ELFT> *F,
const Elf_Shdr *Header)
- : SplitInputSection<ELFT>(F, Header, InputSectionBase<ELFT>::Merge) {}
+ : SplitInputSection<ELFT>(F, Header, InputSectionBase<ELFT>::Merge) {
+ uintX_t EntSize = Header->sh_entsize;
+ ArrayRef<uint8_t> D = this->getSectionData();
+ StringRef Data((const char *)D.data(), D.size());
+ std::vector<std::pair<uintX_t, uintX_t>> &Offsets = this->Offsets;
+
+ uintX_t V = Config->GcSections ? -1 : 0;
+ if (Header->sh_flags & SHF_STRINGS) {
+ uintX_t Offset = 0;
+ while (!Data.empty()) {
+ size_t End = findNull(Data, EntSize);
+ if (End == StringRef::npos)
+ fatal("string is not null terminated");
+ Offsets.push_back(std::make_pair(Offset, V));
+ uintX_t Size = End + EntSize;
+ Data = Data.substr(Size);
+ Offset += Size;
+ }
+ return;
+ }
+
+ // If this is not of type string, every entry has the same size.
+ size_t Size = Data.size();
+ assert((Size % EntSize) == 0);
+ for (unsigned I = 0, N = Size; I != N; I += EntSize)
+ Offsets.push_back(std::make_pair(I, V));
+}
template <class ELFT>
bool MergeInputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
Modified: lld/trunk/ELF/InputSection.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputSection.h?rev=267233&r1=267232&r2=267233&view=diff
==============================================================================
--- lld/trunk/ELF/InputSection.h (original)
+++ lld/trunk/ELF/InputSection.h Fri Apr 22 17:09:35 2016
@@ -124,8 +124,10 @@ public:
ArrayRef<uint8_t> getSectionData() const;
// Returns a section that Rel is pointing to. Used by the garbage collector.
- InputSectionBase<ELFT> *getRelocTarget(const Elf_Rel &Rel) const;
- InputSectionBase<ELFT> *getRelocTarget(const Elf_Rela &Rel) const;
+ std::pair<InputSectionBase<ELFT> *, uintX_t>
+ getRelocTarget(const Elf_Rel &Rel) const;
+ std::pair<InputSectionBase<ELFT> *, uintX_t>
+ getRelocTarget(const Elf_Rela &Rel) const;
void relocate(uint8_t *Buf, uint8_t *BufEnd);
std::vector<Relocation> Relocations;
Modified: lld/trunk/ELF/MarkLive.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/MarkLive.cpp?rev=267233&r1=267232&r2=267233&view=diff
==============================================================================
--- lld/trunk/ELF/MarkLive.cpp (original)
+++ lld/trunk/ELF/MarkLive.cpp Fri Apr 22 17:09:35 2016
@@ -40,20 +40,29 @@ using namespace lld::elf;
// Calls Fn for each section that Sec refers to via relocations.
template <class ELFT>
-static void forEachSuccessor(InputSection<ELFT> *Sec,
- std::function<void(InputSectionBase<ELFT> *)> Fn) {
+static void forEachSuccessor(
+ InputSection<ELFT> *Sec,
+ std::function<void(InputSectionBase<ELFT> *, typename ELFT::uint Offset)>
+ Fn) {
typedef typename ELFT::Rel Elf_Rel;
typedef typename ELFT::Rela Elf_Rela;
typedef typename ELFT::Shdr Elf_Shdr;
+ typedef typename ELFT::uint uintX_t;
ELFFile<ELFT> &Obj = Sec->getFile()->getObj();
for (const Elf_Shdr *RelSec : Sec->RelocSections) {
if (RelSec->sh_type == SHT_RELA) {
- for (const Elf_Rela &RI : Obj.relas(RelSec))
- Fn(Sec->getRelocTarget(RI));
+ for (const Elf_Rela &RI : Obj.relas(RelSec)) {
+ std::pair<InputSectionBase<ELFT> *, uintX_t> P =
+ Sec->getRelocTarget(RI);
+ Fn(P.first, P.second);
+ }
} else {
- for (const Elf_Rel &RI : Obj.rels(RelSec))
- Fn(Sec->getRelocTarget(RI));
+ for (const Elf_Rel &RI : Obj.rels(RelSec)) {
+ std::pair<InputSectionBase<ELFT> *, uintX_t> P =
+ Sec->getRelocTarget(RI);
+ Fn(P.first, P.second);
+ }
}
}
}
@@ -85,10 +94,18 @@ template <class ELFT> static bool isRese
// Starting from GC-root sections, this function visits all reachable
// sections to set their "Live" bits.
template <class ELFT> void elf::markLive(SymbolTable<ELFT> *Symtab) {
+ typedef typename ELFT::uint uintX_t;
SmallVector<InputSection<ELFT> *, 256> Q;
- auto Enqueue = [&](InputSectionBase<ELFT> *Sec) {
- if (!Sec || Sec->Live)
+ auto Enqueue = [&](InputSectionBase<ELFT> *Sec, uintX_t Offset) {
+ if (!Sec)
+ return;
+ if (auto *MS = dyn_cast<MergeInputSection<ELFT>>(Sec)) {
+ std::pair<std::pair<uintX_t, uintX_t> *, uintX_t> T =
+ MS->getRangeAndSize(Offset);
+ T.first->second = 0;
+ }
+ if (Sec->Live)
return;
Sec->Live = true;
if (InputSection<ELFT> *S = dyn_cast<InputSection<ELFT>>(Sec))
@@ -98,7 +115,7 @@ template <class ELFT> void elf::markLive
auto MarkSymbol = [&](SymbolBody *Sym) {
if (Sym)
if (auto *D = dyn_cast<DefinedRegular<ELFT>>(Sym))
- Enqueue(D->Section);
+ Enqueue(D->Section, D->Value);
};
// Add GC root symbols.
@@ -122,7 +139,7 @@ template <class ELFT> void elf::markLive
for (InputSectionBase<ELFT> *Sec : F->getSections())
if (Sec && Sec != &InputSection<ELFT>::Discarded)
if (isReserved(Sec) || Script<ELFT>::X->shouldKeep(Sec))
- Enqueue(Sec);
+ Enqueue(Sec, 0);
// Mark all reachable sections.
while (!Q.empty())
Modified: lld/trunk/ELF/OutputSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.cpp?rev=267233&r1=267232&r2=267233&view=diff
==============================================================================
--- lld/trunk/ELF/OutputSections.cpp (original)
+++ lld/trunk/ELF/OutputSections.cpp Fri Apr 22 17:09:35 2016
@@ -1132,7 +1132,7 @@ void EHOutputSection<ELFT>::addSectionAu
} else {
if (!HasReloc)
fatal("FDE doesn't reference another section");
- InputSectionBase<ELFT> *Target = S->getRelocTarget(*RelI);
+ InputSectionBase<ELFT> *Target = S->getRelocTarget(*RelI).first;
if (Target && Target->Live) {
uint32_t CieOffset = Offset + 4 - ID;
auto I = OffsetToIndex.find(CieOffset);
@@ -1227,19 +1227,6 @@ template <class ELFT> void MergeOutputSe
}
}
-static size_t findNull(StringRef S, size_t EntSize) {
- // Optimize the common case.
- if (EntSize == 1)
- return S.find(0);
-
- for (unsigned I = 0, N = S.size(); I != N; I += EntSize) {
- const char *B = S.begin() + I;
- if (std::all_of(B, B + EntSize, [](char C) { return C == 0; }))
- return I;
- }
- return StringRef::npos;
-}
-
template <class ELFT>
void MergeOutputSection<ELFT>::addSection(InputSectionBase<ELFT> *C) {
auto *S = cast<MergeInputSection<ELFT>>(C);
@@ -1250,31 +1237,32 @@ void MergeOutputSection<ELFT>::addSectio
StringRef Data((const char *)D.data(), D.size());
uintX_t EntSize = S->getSectionHdr()->sh_entsize;
this->Header.sh_entsize = EntSize;
+ MutableArrayRef<std::pair<uintX_t, uintX_t>> Offsets = S->Offsets;
// If this is of type string, the contents are null-terminated strings.
if (this->Header.sh_flags & SHF_STRINGS) {
- uintX_t Offset = 0;
- while (!Data.empty()) {
- size_t End = findNull(Data, EntSize);
- if (End == StringRef::npos)
- fatal("string is not null terminated");
- StringRef Entry = Data.substr(0, End + EntSize);
+ for (unsigned I = 0, N = Offsets.size(); I != N; ++I) {
+ auto &P = Offsets[I];
+ if (P.second == (uintX_t)-1)
+ continue;
+
+ uintX_t Start = P.first;
+ uintX_t End = (I == N - 1) ? Data.size() : Offsets[I + 1].first;
+ StringRef Entry = Data.substr(Start, End - Start);
uintX_t OutputOffset = Builder.add(Entry);
if (shouldTailMerge())
OutputOffset = -1;
- S->Offsets.push_back(std::make_pair(Offset, OutputOffset));
- uintX_t Size = End + EntSize;
- Data = Data.substr(Size);
- Offset += Size;
+ P.second = OutputOffset;
}
return;
}
// If this is not of type string, every entry has the same size.
- for (unsigned I = 0, N = Data.size(); I != N; I += EntSize) {
- StringRef Entry = Data.substr(I, EntSize);
- size_t OutputOffset = Builder.add(Entry);
- S->Offsets.push_back(std::make_pair(I, OutputOffset));
+ for (auto &P : Offsets) {
+ if (P.second == (uintX_t)-1)
+ continue;
+ StringRef Entry = Data.substr(P.first, EntSize);
+ P.second = Builder.add(Entry);
}
}
Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=267233&r1=267232&r2=267233&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Fri Apr 22 17:09:35 2016
@@ -790,8 +790,19 @@ template <class ELFT> void Writer<ELFT>:
InputSectionBase<ELFT> *Sec = DR->Section;
if (!shouldKeepInSymtab<ELFT>(Sec, SymName, *B))
continue;
- if (Sec && !Sec->Live)
- continue;
+ if (Sec) {
+ if (!Sec->Live)
+ continue;
+
+ // Garbage collection is normally able to remove local symbols if they
+ // point to gced sections. In the case of SHF_MERGE sections, we want it
+ // to also be able to drop them if part of the section is gced.
+ // We could look at the section offset map to keep some of these
+ // symbols, but almost all local symbols are .L* symbols, so it
+ // is probably not worth the complexity.
+ if (Config->GcSections && isa<MergeInputSection<ELFT>>(Sec))
+ continue;
+ }
++Out<ELFT>::SymTab->NumLocals;
if (Config->Relocatable)
B->DynsymIndex = Out<ELFT>::SymTab->NumLocals;
Modified: lld/trunk/test/ELF/gc-merge-local-sym.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/gc-merge-local-sym.s?rev=267233&r1=267232&r2=267233&view=diff
==============================================================================
--- lld/trunk/test/ELF/gc-merge-local-sym.s (original)
+++ lld/trunk/test/ELF/gc-merge-local-sym.s Fri Apr 22 17:09:35 2016
@@ -11,24 +11,18 @@
// CHECK-NEXT: ]
// CHECK-NEXT: Address: 0x1C8
// CHECK-NEXT: Offset:
-// CHECK-NEXT: Size: 8
+// CHECK-NEXT: Size: 4
// CHECK-NEXT: Link: 0
// CHECK-NEXT: Info: 0
// CHECK-NEXT: AddressAlignment: 1
// CHECK-NEXT: EntrySize: 1
// CHECK-NEXT: SectionData (
-// CHECK-NEXT: 0000: 64656600 61626300 |def.abc.|
+// CHECK-NEXT: 0000: 61626300 |abc.|
// CHECK-NEXT: )
// CHECK: Symbols [
// CHECK: Symbol {
-// CHECK: Name: bar
-// CHECK-NEXT: Value: 0x1C8
-// CHECK-NEXT: Size: 0
-// CHECK-NEXT: Binding: Local
-// CHECK-NEXT: Type: None
-// CHECK-NEXT: Other: 0
-// CHECK-NEXT: Section: .rodata
+// CHECK-NOT: Name: bar
.global foo
foo:
Added: lld/trunk/test/ELF/gc-sections-merge-addend.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/gc-sections-merge-addend.s?rev=267233&view=auto
==============================================================================
--- lld/trunk/test/ELF/gc-sections-merge-addend.s (added)
+++ lld/trunk/test/ELF/gc-sections-merge-addend.s Fri Apr 22 17:09:35 2016
@@ -0,0 +1,39 @@
+// RUN: llvm-mc %s -o %t.o -filetype=obj -triple=x86_64-pc-linux
+// RUN: ld.lld %t.o -o %t.so -shared --gc-sections
+// RUN: llvm-readobj -s -section-data %t.so | FileCheck %s
+
+
+// CHECK: Name: .rodata
+// CHECK-NEXT: Type: SHT_PROGBITS
+// CHECK-NEXT: Flags [
+// CHECK-NEXT: SHF_ALLOC
+// CHECK-NEXT: SHF_MERGE
+// CHECK-NEXT: SHF_STRINGS
+// CHECK-NEXT: ]
+// CHECK-NEXT: Address:
+// CHECK-NEXT: Offset:
+// CHECK-NEXT: Size: 4
+// CHECK-NEXT: Link: 0
+// CHECK-NEXT: Info: 0
+// CHECK-NEXT: AddressAlignment: 1
+// CHECK-NEXT: EntrySize: 1
+// CHECK-NEXT: SectionData (
+// CHECK-NEXT: 0000: 62617200 |bar.|
+// CHECK-NEXT: )
+
+ .section .data.f,"aw", at progbits
+ .globl f
+f:
+ .quad .rodata.str1.1 + 4
+
+ .section .data.g,"aw", at progbits
+ .hidden g
+ .globl g
+g:
+ .quad .rodata.str1.1
+
+ .section .rodata.str1.1,"aMS", at progbits,1
+.L.str:
+ .asciz "foo"
+.L.str.1:
+ .asciz "bar"
Added: lld/trunk/test/ELF/gc-sections-merge-implicit-addend.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/gc-sections-merge-implicit-addend.s?rev=267233&view=auto
==============================================================================
--- lld/trunk/test/ELF/gc-sections-merge-implicit-addend.s (added)
+++ lld/trunk/test/ELF/gc-sections-merge-implicit-addend.s Fri Apr 22 17:09:35 2016
@@ -0,0 +1,39 @@
+// RUN: llvm-mc %s -o %t.o -filetype=obj -triple=i386-pc-linux
+// RUN: ld.lld %t.o -o %t.so -shared --gc-sections
+// RUN: llvm-readobj -s -section-data %t.so | FileCheck %s
+
+
+// CHECK: Name: .rodata
+// CHECK-NEXT: Type: SHT_PROGBITS
+// CHECK-NEXT: Flags [
+// CHECK-NEXT: SHF_ALLOC
+// CHECK-NEXT: SHF_MERGE
+// CHECK-NEXT: SHF_STRINGS
+// CHECK-NEXT: ]
+// CHECK-NEXT: Address:
+// CHECK-NEXT: Offset:
+// CHECK-NEXT: Size: 4
+// CHECK-NEXT: Link: 0
+// CHECK-NEXT: Info: 0
+// CHECK-NEXT: AddressAlignment: 1
+// CHECK-NEXT: EntrySize: 1
+// CHECK-NEXT: SectionData (
+// CHECK-NEXT: 0000: 62617200 |bar.|
+// CHECK-NEXT: )
+
+ .section .data.f,"aw", at progbits
+ .globl f
+f:
+ .long .rodata.str1.1 + 4
+
+ .section .data.g,"aw", at progbits
+ .hidden g
+ .globl g
+g:
+ .long .rodata.str1.1
+
+ .section .rodata.str1.1,"aMS", at progbits,1
+.L.str:
+ .asciz "foo"
+.L.str.1:
+ .asciz "bar"
Added: lld/trunk/test/ELF/gc-sections-merge.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/gc-sections-merge.s?rev=267233&view=auto
==============================================================================
--- lld/trunk/test/ELF/gc-sections-merge.s (added)
+++ lld/trunk/test/ELF/gc-sections-merge.s Fri Apr 22 17:09:35 2016
@@ -0,0 +1,61 @@
+// RUN: llvm-mc %s -o %t.o -filetype=obj -triple=x86_64-pc-linux
+// RUN: ld.lld %t.o -o %t.so -shared
+// RUN: ld.lld %t.o -o %t.gc.so -shared --gc-sections
+// RUN: llvm-readobj -s -section-data %t.so | FileCheck %s
+// RUN: llvm-readobj -s -section-data %t.gc.so | FileCheck --check-prefix=GC %s
+
+
+// CHECK: Name: .rodata
+// CHECK-NEXT: Type: SHT_PROGBITS
+// CHECK-NEXT: Flags [
+// CHECK-NEXT: SHF_ALLOC
+// CHECK-NEXT: SHF_MERGE
+// CHECK-NEXT: SHF_STRINGS
+// CHECK-NEXT: ]
+// CHECK-NEXT: Address:
+// CHECK-NEXT: Offset:
+// CHECK-NEXT: Size: 8
+// CHECK-NEXT: Link: 0
+// CHECK-NEXT: Info: 0
+// CHECK-NEXT: AddressAlignment: 1
+// CHECK-NEXT: EntrySize: 1
+// CHECK-NEXT: SectionData (
+// CHECK-NEXT: 0000: 666F6F00 62617200 |foo.bar.|
+// CHECK-NEXT: )
+
+// GC: Name: .rodata
+// GC-NEXT: Type: SHT_PROGBITS
+// GC-NEXT: Flags [
+// GC-NEXT: SHF_ALLOC
+// GC-NEXT: SHF_MERGE
+// GC-NEXT: SHF_STRINGS
+// GC-NEXT: ]
+// GC-NEXT: Address:
+// GC-NEXT: Offset:
+// GC-NEXT: Size: 4
+// GC-NEXT: Link: 0
+// GC-NEXT: Info: 0
+// GC-NEXT: AddressAlignment: 1
+// GC-NEXT: EntrySize: 1
+// GC-NEXT: SectionData (
+// GC-NEXT: 0000: 666F6F00 |foo.|
+// GC-NEXT: )
+
+ .section .text.f,"ax", at progbits
+ .globl f
+f:
+ leaq .L.str(%rip), %rax
+ retq
+
+ .section .text.g,"ax", at progbits
+ .hidden g
+ .globl g
+g:
+ leaq .L.str.1(%rip), %rax
+ retq
+
+ .section .rodata.str1.1,"aMS", at progbits,1
+.L.str:
+ .asciz "foo"
+.L.str.1:
+ .asciz "bar"
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