[lld] r303225 - Garbage collect dllimported symbols.
Hans Wennborg via llvm-commits
llvm-commits at lists.llvm.org
Wed May 17 09:35:31 PDT 2017
Looks like this broke the sanitizer-windows bot:
http://lab.llvm.org:8011/builders/sanitizer-windows/builds/11427
I've reverted in r303270.
On Tue, May 16, 2017 at 5:35 PM, Rui Ueyama via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: ruiu
> Date: Tue May 16 19:35:50 2017
> New Revision: 303225
>
> URL: http://llvm.org/viewvc/llvm-project?rev=303225&view=rev
> Log:
> Garbage collect dllimported symbols.
>
> Summary:
> Previously, the garbage collector (enabled by default or by explicitly
> passing /opt:ref) did not kill dllimported symbols. As a result,
> dllimported symbols could be added to resulting executables' dllimport
> list even if no one was actually using them.
>
> This patch implements dllexported symbol garbage collection. Just like
> COMDAT sections, dllimported symbols now have Live bits to manage their
> liveness, and MarkLive marks reachable dllimported symbols.
>
> Fixes https://bugs.llvm.org/show_bug.cgi?id=32950
>
> Reviewers: pcc
>
> Subscribers: llvm-commits
>
> Differential Revision: https://reviews.llvm.org/D33264
>
> Added:
> lld/trunk/test/COFF/dllimport-gc.test
> Modified:
> lld/trunk/COFF/InputFiles.cpp
> lld/trunk/COFF/MarkLive.cpp
> lld/trunk/COFF/Symbols.cpp
> lld/trunk/COFF/Symbols.h
> lld/trunk/COFF/Writer.cpp
> lld/trunk/test/COFF/Inputs/import.yaml
>
> Modified: lld/trunk/COFF/InputFiles.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/InputFiles.cpp?rev=303225&r1=303224&r2=303225&view=diff
> ==============================================================================
> --- lld/trunk/COFF/InputFiles.cpp (original)
> +++ lld/trunk/COFF/InputFiles.cpp Tue May 16 19:35:50 2017
> @@ -325,12 +325,21 @@ void ImportFile::parse() {
> this->Hdr = Hdr;
> ExternalName = ExtName;
>
> + // Instantiate symbol objects.
> ImpSym = cast<DefinedImportData>(
> Symtab->addImportData(ImpName, this)->body());
> - if (Hdr->getType() == llvm::COFF::IMPORT_CONST)
> +
> + if (Hdr->getType() == llvm::COFF::IMPORT_CONST) {
> ConstSym =
> cast<DefinedImportData>(Symtab->addImportData(Name, this)->body());
>
> + // A __imp_ and non-__imp_ symbols for the same dllimport'ed symbol
> + // should be gc'ed as a group. Add a bidirectional edge.
> + // Used by MarkLive.cpp.
> + ImpSym->Sibling = ConstSym;
> + ConstSym->Sibling = ImpSym;
> + }
> +
> // If type is function, we need to create a thunk which jump to an
> // address pointed by the __imp_ symbol. (This allows you to call
> // DLL functions just like regular non-DLL functions.)
>
> Modified: lld/trunk/COFF/MarkLive.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/MarkLive.cpp?rev=303225&r1=303224&r2=303225&view=diff
> ==============================================================================
> --- lld/trunk/COFF/MarkLive.cpp (original)
> +++ lld/trunk/COFF/MarkLive.cpp Tue May 16 19:35:50 2017
> @@ -15,16 +15,16 @@
> namespace lld {
> namespace coff {
>
> -// Set live bit on for each reachable chunk. Unmarked (unreachable)
> -// COMDAT chunks will be ignored by Writer, so they will be excluded
> -// from the final output.
> +// Set live bit for each reachable COMDAT chunk and dllimported symbol.
> +// Unmarked (or unreachable) chunks or symbols are ignored by Writer,
> +// so they are not included in the final output.
> void markLive(const std::vector<Chunk *> &Chunks) {
> // We build up a worklist of sections which have been marked as live. We only
> // push into the worklist when we discover an unmarked section, and we mark
> // as we push, so sections never appear twice in the list.
> SmallVector<SectionChunk *, 256> Worklist;
>
> - // COMDAT section chunks are dead by default. Add non-COMDAT chunks.
> + // Non-COMDAT chunks are never be gc'ed, so they are gc-root.
> for (Chunk *C : Chunks)
> if (auto *SC = dyn_cast<SectionChunk>(C))
> if (SC->isLive())
> @@ -37,19 +37,37 @@ void markLive(const std::vector<Chunk *>
> Worklist.push_back(C);
> };
>
> - // Add GC root chunks.
> + // Mark a given symbol as reachable.
> + std::function<void(SymbolBody * B)> AddSym = [&](SymbolBody *B) {
> + if (auto *Sym = dyn_cast<DefinedRegular>(B)) {
> + Enqueue(Sym->getChunk());
> + } else if (auto *Sym = dyn_cast<DefinedImportData>(B)) {
> + if (Sym->Live)
> + return;
> + Sym->Live = true;
> + if (Sym->Sibling)
> + Sym->Sibling->Live = true;
> + } else if (auto *Sym = dyn_cast<DefinedImportThunk>(B)) {
> + if (Sym->Live)
> + return;
> + Sym->Live = true;
> + AddSym(Sym->WrappedSym);
> + } else if (auto *Sym = dyn_cast<DefinedLocalImport>(B)) {
> + AddSym(Sym->WrappedSym);
> + }
> + };
> +
> + // Add gc-root symbols.
> for (SymbolBody *B : Config->GCRoot)
> - if (auto *D = dyn_cast<DefinedRegular>(B))
> - Enqueue(D->getChunk());
> + AddSym(B);
>
> while (!Worklist.empty()) {
> SectionChunk *SC = Worklist.pop_back_val();
> assert(SC->isLive() && "We mark as live when pushing onto the worklist!");
>
> // Mark all symbols listed in the relocation table for this section.
> - for (SymbolBody *S : SC->symbols())
> - if (auto *D = dyn_cast<DefinedRegular>(S))
> - Enqueue(D->getChunk());
> + for (SymbolBody *B : SC->symbols())
> + AddSym(B);
>
> // Mark associative sections if any.
> for (SectionChunk *C : SC->children())
>
> Modified: lld/trunk/COFF/Symbols.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Symbols.cpp?rev=303225&r1=303224&r2=303225&view=diff
> ==============================================================================
> --- lld/trunk/COFF/Symbols.cpp (original)
> +++ lld/trunk/COFF/Symbols.cpp Tue May 16 19:35:50 2017
> @@ -63,7 +63,8 @@ COFFSymbolRef DefinedCOFF::getCOFFSymbol
>
> DefinedImportThunk::DefinedImportThunk(StringRef Name, DefinedImportData *S,
> uint16_t Machine)
> - : Defined(DefinedImportThunkKind, Name) {
> + : Defined(DefinedImportThunkKind, Name), Live(!Config->DoGC),
> + WrappedSym(S) {
> switch (Machine) {
> case AMD64: Data = make<ImportThunkChunkX64>(S); return;
> case I386: Data = make<ImportThunkChunkX86>(S); return;
>
> Modified: lld/trunk/COFF/Symbols.h
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Symbols.h?rev=303225&r1=303224&r2=303225&view=diff
> ==============================================================================
> --- lld/trunk/COFF/Symbols.h (original)
> +++ lld/trunk/COFF/Symbols.h Tue May 16 19:35:50 2017
> @@ -287,19 +287,29 @@ public:
> class DefinedImportData : public Defined {
> public:
> DefinedImportData(StringRef N, ImportFile *F)
> - : Defined(DefinedImportDataKind, N), File(F) {
> - }
> + : Defined(DefinedImportDataKind, N), Live(!Config->DoGC), File(F) {}
>
> static bool classof(const SymbolBody *S) {
> return S->kind() == DefinedImportDataKind;
> }
>
> uint64_t getRVA() { return File->Location->getRVA(); }
> +
> StringRef getDLLName() { return File->DLLName; }
> StringRef getExternalName() { return File->ExternalName; }
> void setLocation(Chunk *AddressTable) { File->Location = AddressTable; }
> uint16_t getOrdinal() { return File->Hdr->OrdinalHint; }
>
> + // If all sections referring a dllimported symbol become dead by gc,
> + // we want to kill the symbol as well, so that a resulting binary has
> + // fewer number of dependencies to DLLs. "Live" bit manages reachability.
> + bool Live;
> +
> + // For a dllimported data symbol, we create two symbols.
> + // They should be considered as a unit by gc. This pointer points
> + // to the other symbol.
> + DefinedImportData *Sibling = nullptr;
> +
> private:
> ImportFile *File;
> };
> @@ -320,6 +330,10 @@ public:
> uint64_t getRVA() { return Data->getRVA(); }
> Chunk *getChunk() { return Data; }
>
> + // For GC.
> + bool Live;
> + DefinedImportData *WrappedSym;
> +
> private:
> Chunk *Data;
> };
> @@ -332,7 +346,8 @@ private:
> class DefinedLocalImport : public Defined {
> public:
> DefinedLocalImport(StringRef N, Defined *S)
> - : Defined(DefinedLocalImportKind, N), Data(make<LocalImportChunk>(S)) {}
> + : Defined(DefinedLocalImportKind, N), WrappedSym(S),
> + Data(make<LocalImportChunk>(S)) {}
>
> static bool classof(const SymbolBody *S) {
> return S->kind() == DefinedLocalImportKind;
> @@ -341,6 +356,9 @@ public:
> uint64_t getRVA() { return Data->getRVA(); }
> Chunk *getChunk() { return Data; }
>
> + // For GC.
> + Defined *WrappedSym;
> +
> private:
> LocalImportChunk *Data;
> };
>
> Modified: lld/trunk/COFF/Writer.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Writer.cpp?rev=303225&r1=303224&r2=303225&view=diff
> ==============================================================================
> --- lld/trunk/COFF/Writer.cpp (original)
> +++ lld/trunk/COFF/Writer.cpp Tue May 16 19:35:50 2017
> @@ -376,18 +376,24 @@ void Writer::createImportTables() {
> OutputSection *Text = createSection(".text");
> for (ImportFile *File : Symtab->ImportFiles) {
> if (DefinedImportThunk *Thunk = File->ThunkSym)
> - Text->addChunk(Thunk->getChunk());
> + if (Thunk->Live)
> + Text->addChunk(Thunk->getChunk());
> +
> if (Config->DelayLoads.count(StringRef(File->DLLName).lower())) {
> - DelayIdata.add(File->ImpSym);
> + if (File->ImpSym->Live)
> + DelayIdata.add(File->ImpSym);
> } else {
> - Idata.add(File->ImpSym);
> + if (File->ImpSym->Live)
> + Idata.add(File->ImpSym);
> }
> }
> +
> if (!Idata.empty()) {
> OutputSection *Sec = createSection(".idata");
> for (Chunk *C : Idata.getChunks())
> Sec->addChunk(C);
> }
> +
> if (!DelayIdata.empty()) {
> Defined *Helper = cast<Defined>(Config->DelayLoadHelper);
> DelayIdata.create(Helper);
>
> Modified: lld/trunk/test/COFF/Inputs/import.yaml
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/Inputs/import.yaml?rev=303225&r1=303224&r2=303225&view=diff
> ==============================================================================
> --- lld/trunk/test/COFF/Inputs/import.yaml (original)
> +++ lld/trunk/test/COFF/Inputs/import.yaml Tue May 16 19:35:50 2017
> @@ -7,6 +7,13 @@ sections:
> Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
> Alignment: 4
> SectionData: 0000000000000000
> + Relocations:
> + - VirtualAddress: 0
> + SymbolName: exportfn1
> + Type: IMAGE_REL_AMD64_ADDR32NB
> + - VirtualAddress: 4
> + SymbolName: exportfn2
> + Type: IMAGE_REL_AMD64_ADDR32NB
> symbols:
> - Name: .text
> Value: 0
> @@ -16,7 +23,7 @@ symbols:
> StorageClass: IMAGE_SYM_CLASS_STATIC
> SectionDefinition:
> Length: 8
> - NumberOfRelocations: 0
> + NumberOfRelocations: 2
> NumberOfLinenumbers: 0
> CheckSum: 0
> Number: 0
>
> Added: lld/trunk/test/COFF/dllimport-gc.test
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/dllimport-gc.test?rev=303225&view=auto
> ==============================================================================
> --- lld/trunk/test/COFF/dllimport-gc.test (added)
> +++ lld/trunk/test/COFF/dllimport-gc.test Tue May 16 19:35:50 2017
> @@ -0,0 +1,51 @@
> +# REQUIRES: winres
> +
> +# RUN: yaml2obj < %p/Inputs/export.yaml > %t-lib.obj
> +# RUN: lld-link /out:%t.dll /dll %t-lib.obj /implib:%t.lib /export:exportfn1
> +
> +# RUN: yaml2obj < %s > %t.obj
> +
> +# RUN: lld-link /out:%t1.exe /entry:main %t.obj %t.lib
> +# RUN: llvm-readobj -coff-imports %t1.exe | FileCheck -check-prefix=REF %s
> +# REF-NOT: Symbol: exportfn1
> +
> +# RUN: lld-link /out:%t2.exe /entry:main %t.obj %t.lib /opt:noref
> +# RUN: llvm-readobj -coff-imports %t2.exe | FileCheck -check-prefix=NOREF %s
> +# NOREF: Symbol: exportfn1
> +
> +--- !COFF
> +header:
> + Machine: IMAGE_FILE_MACHINE_AMD64
> + Characteristics: []
> +sections:
> + - Name: .text
> + Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
> + Alignment: 4
> + SectionData: 0000000000000000
> + Relocations:
> +symbols:
> + - Name: .text
> + Value: 0
> + SectionNumber: 1
> + SimpleType: IMAGE_SYM_TYPE_NULL
> + ComplexType: IMAGE_SYM_DTYPE_NULL
> + StorageClass: IMAGE_SYM_CLASS_STATIC
> + SectionDefinition:
> + Length: 8
> + NumberOfRelocations: 2
> + NumberOfLinenumbers: 0
> + CheckSum: 0
> + Number: 0
> + - Name: main
> + Value: 0
> + SectionNumber: 1
> + SimpleType: IMAGE_SYM_TYPE_NULL
> + ComplexType: IMAGE_SYM_DTYPE_FUNCTION
> + StorageClass: IMAGE_SYM_CLASS_EXTERNAL
> + - Name: exportfn1
> + Value: 0
> + SectionNumber: 0
> + SimpleType: IMAGE_SYM_TYPE_NULL
> + ComplexType: IMAGE_SYM_DTYPE_NULL
> + StorageClass: IMAGE_SYM_CLASS_EXTERNAL
> +...
>
>
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