[lld] r267164 - GC entries of SHF_MERGE sections.
Rafael Espíndola via llvm-commits
llvm-commits at lists.llvm.org
Fri Apr 22 12:22:20 PDT 2016
Debugging.
Do you want me to revert for now?
Cheers,
Rafael
On 22 April 2016 at 15:14, Peter Collingbourne <peter at pcc.me.uk> wrote:
> This change appears to break the bootstrap when using the steps given in
> PR27482.
>
> I get:
>
> ld.lld: ../lib/MC/StringTableBuilder.cpp:180: size_t
> llvm::StringTableBuilder::getOffset(llvm::StringRef) const: Assertion `I !=
> StringIndexMap.end() && "String is not in table!"' failed.
>
> when linking llvm-profdata during stage 2.
>
> Peter
>
> On Fri, Apr 22, 2016 at 9:46 AM, Rafael Espindola via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
>>
>> Author: rafael
>> Date: Fri Apr 22 11:46:08 2016
>> New Revision: 267164
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=267164&view=rev
>> Log:
>> 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
>>
>> Modified: lld/trunk/ELF/InputSection.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputSection.cpp?rev=267164&r1=267163&r2=267164&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/ELF/InputSection.cpp (original)
>> +++ lld/trunk/ELF/InputSection.cpp Fri Apr 22 11:46:08 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(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=267164&r1=267163&r2=267164&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/ELF/InputSection.h (original)
>> +++ lld/trunk/ELF/InputSection.h Fri Apr 22 11:46:08 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=267164&r1=267163&r2=267164&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/ELF/MarkLive.cpp (original)
>> +++ lld/trunk/ELF/MarkLive.cpp Fri Apr 22 11:46:08 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.
>> @@ -125,7 +142,7 @@ 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=267164&r1=267163&r2=267164&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/ELF/OutputSections.cpp (original)
>> +++ lld/trunk/ELF/OutputSections.cpp Fri Apr 22 11:46:08 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);
>> }
>> }
>>
>>
>> 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=267164&view=auto
>>
>> ==============================================================================
>> --- lld/trunk/test/ELF/gc-sections-merge-addend.s (added)
>> +++ lld/trunk/test/ELF/gc-sections-merge-addend.s Fri Apr 22 11:46:08 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=267164&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
>> 11:46:08 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=267164&view=auto
>>
>> ==============================================================================
>> --- lld/trunk/test/ELF/gc-sections-merge.s (added)
>> +++ lld/trunk/test/ELF/gc-sections-merge.s Fri Apr 22 11:46:08 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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>> llvm-commits at lists.llvm.org
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>
>
>
>
> --
> --
> Peter
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