[lld] r303304 - Re-submit r303225: Garbage collect dllimported symbols.
Rui Ueyama via llvm-commits
llvm-commits at lists.llvm.org
Wed May 17 14:36:08 PDT 2017
Author: ruiu
Date: Wed May 17 16:36:08 2017
New Revision: 303304
URL: http://llvm.org/viewvc/llvm-project?rev=303304&view=rev
Log:
Re-submit r303225: Garbage collect dllimported symbols.
This reverts re-submits r303225 which was reverted in r303270 because it
broke the sanitizer-windows bot.
The reason of the failure is that we were writing dead symbols to the
symbol table. I fixed the issue.
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=303304&r1=303303&r2=303304&view=diff
==============================================================================
--- lld/trunk/COFF/InputFiles.cpp (original)
+++ lld/trunk/COFF/InputFiles.cpp Wed May 17 16:36:08 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=303304&r1=303303&r2=303304&view=diff
==============================================================================
--- lld/trunk/COFF/MarkLive.cpp (original)
+++ lld/trunk/COFF/MarkLive.cpp Wed May 17 16:36:08 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=303304&r1=303303&r2=303304&view=diff
==============================================================================
--- lld/trunk/COFF/Symbols.cpp (original)
+++ lld/trunk/COFF/Symbols.cpp Wed May 17 16:36:08 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=303304&r1=303303&r2=303304&view=diff
==============================================================================
--- lld/trunk/COFF/Symbols.h (original)
+++ lld/trunk/COFF/Symbols.h Wed May 17 16:36:08 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=303304&r1=303303&r2=303304&view=diff
==============================================================================
--- lld/trunk/COFF/Writer.cpp (original)
+++ lld/trunk/COFF/Writer.cpp Wed May 17 16:36:08 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);
@@ -494,14 +500,24 @@ void Writer::createSymbolAndStringTable(
Sec->setStringTableOff(addEntryToStringTable(Name));
}
- for (lld::coff::ObjectFile *File : Symtab->ObjectFiles)
- for (SymbolBody *B : File->getSymbols())
- if (auto *D = dyn_cast<Defined>(B))
- if (!D->WrittenToSymtab) {
- D->WrittenToSymtab = true;
- if (Optional<coff_symbol16> Sym = createSymbol(D))
- OutputSymtab.push_back(*Sym);
- }
+ for (lld::coff::ObjectFile *File : Symtab->ObjectFiles) {
+ for (SymbolBody *B : File->getSymbols()) {
+ auto *D = dyn_cast<Defined>(B);
+ if (!D || D->WrittenToSymtab)
+ continue;
+
+ if (auto *S = dyn_cast<DefinedImportData>(D))
+ if (!S->Live)
+ continue;
+ if (auto *S = dyn_cast<DefinedImportThunk>(D))
+ if (!S->Live)
+ continue;
+
+ D->WrittenToSymtab = true;
+ if (Optional<coff_symbol16> Sym = createSymbol(D))
+ OutputSymtab.push_back(*Sym);
+ }
+ }
OutputSection *LastSection = OutputSections.back();
// We position the symbol table to be adjacent to the end of the last section.
Modified: lld/trunk/test/COFF/Inputs/import.yaml
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/Inputs/import.yaml?rev=303304&r1=303303&r2=303304&view=diff
==============================================================================
--- lld/trunk/test/COFF/Inputs/import.yaml (original)
+++ lld/trunk/test/COFF/Inputs/import.yaml Wed May 17 16:36:08 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=303304&view=auto
==============================================================================
--- lld/trunk/test/COFF/dllimport-gc.test (added)
+++ lld/trunk/test/COFF/dllimport-gc.test Wed May 17 16:36:08 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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