[lld] r360782 - [WebAssembly] LTO: Honor comdat groups when loading bitcode files
Sam Clegg via llvm-commits
llvm-commits at lists.llvm.org
Wed May 15 09:03:29 PDT 2019
Author: sbc
Date: Wed May 15 09:03:28 2019
New Revision: 360782
URL: http://llvm.org/viewvc/llvm-project?rev=360782&view=rev
Log:
[WebAssembly] LTO: Honor comdat groups when loading bitcode files
But don't apply comdat groups when loading the LTO object files.
This is basically the same logic used by the ELF linker.
Differential Revision: https://reviews.llvm.org/D61924
Added:
lld/trunk/test/wasm/lto/comdat.ll
Modified:
lld/trunk/wasm/InputFiles.cpp
lld/trunk/wasm/InputFiles.h
lld/trunk/wasm/SymbolTable.cpp
lld/trunk/wasm/SymbolTable.h
Added: lld/trunk/test/wasm/lto/comdat.ll
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/wasm/lto/comdat.ll?rev=360782&view=auto
==============================================================================
--- lld/trunk/test/wasm/lto/comdat.ll (added)
+++ lld/trunk/test/wasm/lto/comdat.ll Wed May 15 09:03:28 2019
@@ -0,0 +1,15 @@
+; Verify that comdat symbols can be defined in LTO objects. We had a
+; regression where the comdat handling code was causing symbol in the lto object
+; to be ignored.
+; RUN: llvm-as %s -o %t.o
+; RUN: wasm-ld %t.o %t.o -o %t.wasm
+
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown"
+
+$foo = comdat any
+
+define linkonce_odr void @_start() comdat($foo) {
+entry:
+ ret void
+}
Modified: lld/trunk/wasm/InputFiles.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/InputFiles.cpp?rev=360782&r1=360781&r2=360782&view=diff
==============================================================================
--- lld/trunk/wasm/InputFiles.cpp (original)
+++ lld/trunk/wasm/InputFiles.cpp Wed May 15 09:03:28 2019
@@ -60,7 +60,7 @@ InputFile *lld::wasm::createObjectFile(M
}
void ObjFile::dumpInfo() const {
- log("info for: " + getName() +
+ log("info for: " + toString(this) +
"\n Symbols : " + Twine(Symbols.size()) +
"\n Function Imports : " + Twine(WasmObj->getNumImportedFunctions()) +
"\n Global Imports : " + Twine(WasmObj->getNumImportedGlobals()) +
@@ -232,7 +232,7 @@ static void setRelocs(const std::vector<
}
}
-void ObjFile::parse() {
+void ObjFile::parse(bool IgnoreComdats) {
// Parse a memory buffer as a wasm file.
LLVM_DEBUG(dbgs() << "Parsing object: " << toString(this) << "\n");
std::unique_ptr<Binary> Bin = CHECK(createBinary(MB), toString(this));
@@ -283,9 +283,11 @@ void ObjFile::parse() {
TypeIsUsed.resize(getWasmObj()->types().size(), false);
ArrayRef<StringRef> Comdats = WasmObj->linkingData().Comdats;
- UsedComdats.resize(Comdats.size());
for (unsigned I = 0; I < Comdats.size(); ++I)
- UsedComdats[I] = Symtab->addComdat(Comdats[I]);
+ if (IgnoreComdats)
+ KeptComdats.push_back(true);
+ else
+ KeptComdats.push_back(Symtab->addComdat(Comdats[I]));
// Populate `Segments`.
for (const WasmSegment &S : WasmObj->dataSegments())
@@ -326,7 +328,7 @@ bool ObjFile::isExcludedByComdat(InputCh
uint32_t C = Chunk->getComdat();
if (C == UINT32_MAX)
return false;
- return !UsedComdats[C];
+ return !KeptComdats[C];
}
FunctionSymbol *ObjFile::getFunctionSymbol(uint32_t Index) const {
@@ -427,7 +429,7 @@ Symbol *ObjFile::createUndefined(const W
llvm_unreachable("unknown symbol kind");
}
-void ArchiveFile::parse() {
+void ArchiveFile::parse(bool IgnoreComdats) {
// Parse a MemoryBufferRef as an archive file.
LLVM_DEBUG(dbgs() << "Parsing library: " << toString(this) << "\n");
File = CHECK(Archive::create(MB), toString(this));
@@ -474,14 +476,18 @@ static uint8_t mapVisibility(GlobalValue
llvm_unreachable("unknown visibility");
}
-static Symbol *createBitcodeSymbol(const lto::InputFile::Symbol &ObjSym,
+static Symbol *createBitcodeSymbol(const std::vector<bool> &KeptComdats,
+ const lto::InputFile::Symbol &ObjSym,
BitcodeFile &F) {
StringRef Name = Saver.save(ObjSym.getName());
uint32_t Flags = ObjSym.isWeak() ? WASM_SYMBOL_BINDING_WEAK : 0;
Flags |= mapVisibility(ObjSym.getVisibility());
- if (ObjSym.isUndefined()) {
+ int C = ObjSym.getComdatIndex();
+ bool ExcludedByComdat = C != -1 && !KeptComdats[C];
+
+ if (ObjSym.isUndefined() || ExcludedByComdat) {
if (ObjSym.isExecutable())
return Symtab->addUndefinedFunction(Name, Name, DefaultModule, Flags, &F,
nullptr);
@@ -493,7 +499,7 @@ static Symbol *createBitcodeSymbol(const
return Symtab->addDefinedData(Name, Flags, &F, nullptr, 0, 0);
}
-void BitcodeFile::parse() {
+void BitcodeFile::parse(bool IgnoreComdats) {
Obj = check(lto::InputFile::create(MemoryBufferRef(
MB.getBuffer(), Saver.save(ArchiveName + MB.getBufferIdentifier()))));
Triple T(Obj->getTargetTriple());
@@ -501,9 +507,15 @@ void BitcodeFile::parse() {
error(toString(MB.getBufferIdentifier()) + ": machine type must be wasm32");
return;
}
+ std::vector<bool> KeptComdats;
+ for (StringRef S : Obj->getComdatTable())
+ if (IgnoreComdats)
+ KeptComdats.push_back(true);
+ else
+ KeptComdats.push_back(Symtab->addComdat(S));
for (const lto::InputFile::Symbol &ObjSym : Obj->symbols())
- Symbols.push_back(createBitcodeSymbol(ObjSym, *this));
+ Symbols.push_back(createBitcodeSymbol(KeptComdats, ObjSym, *this));
}
// Returns a string in the format of "foo.o" or "foo.a(bar.o)".
Modified: lld/trunk/wasm/InputFiles.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/InputFiles.h?rev=360782&r1=360781&r2=360782&view=diff
==============================================================================
--- lld/trunk/wasm/InputFiles.h (original)
+++ lld/trunk/wasm/InputFiles.h Wed May 15 09:03:28 2019
@@ -44,7 +44,7 @@ public:
StringRef getName() const { return MB.getBufferIdentifier(); }
// Reads a file (the constructor doesn't do that).
- virtual void parse() = 0;
+ virtual void parse(bool IgnoreComdats = false) = 0;
Kind kind() const { return FileKind; }
@@ -72,7 +72,7 @@ public:
void addMember(const llvm::object::Archive::Symbol *Sym);
- void parse() override;
+ void parse(bool IgnoreComdats) override;
private:
std::unique_ptr<llvm::object::Archive> File;
@@ -88,7 +88,7 @@ public:
}
static bool classof(const InputFile *F) { return F->kind() == ObjectKind; }
- void parse() override;
+ void parse(bool IgnoreComdats) override;
// Returns the underlying wasm file.
const WasmObjectFile *getWasmObj() const { return WasmObj.get(); }
@@ -111,7 +111,7 @@ public:
std::vector<bool> TypeIsUsed;
// Maps function indices to table indices
std::vector<uint32_t> TableEntries;
- std::vector<bool> UsedComdats;
+ std::vector<bool> KeptComdats;
std::vector<InputSegment *> Segments;
std::vector<InputFunction *> Functions;
std::vector<InputGlobal *> Globals;
@@ -141,7 +141,7 @@ public:
explicit SharedFile(MemoryBufferRef M) : InputFile(SharedKind, M) {}
static bool classof(const InputFile *F) { return F->kind() == SharedKind; }
- void parse() override {}
+ void parse(bool IgnoreComdats) override {}
};
// .bc file
@@ -153,7 +153,7 @@ public:
}
static bool classof(const InputFile *F) { return F->kind() == BitcodeKind; }
- void parse() override;
+ void parse(bool IgnoreComdats) override;
std::unique_ptr<llvm::lto::InputFile> Obj;
};
Modified: lld/trunk/wasm/SymbolTable.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/SymbolTable.cpp?rev=360782&r1=360781&r2=360782&view=diff
==============================================================================
--- lld/trunk/wasm/SymbolTable.cpp (original)
+++ lld/trunk/wasm/SymbolTable.cpp Wed May 15 09:03:28 2019
@@ -59,7 +59,7 @@ void SymbolTable::addCombinedLTOObject()
for (StringRef Filename : LTO->compile()) {
auto *Obj = make<ObjFile>(MemoryBufferRef(Filename, "lto.tmp"), "");
- Obj->parse();
+ Obj->parse(true);
ObjectFiles.push_back(Obj);
}
}
@@ -476,7 +476,7 @@ void SymbolTable::addLazy(ArchiveFile *F
}
bool SymbolTable::addComdat(StringRef Name) {
- return Comdats.insert(CachedHashStringRef(Name)).second;
+ return ComdatGroups.insert(CachedHashStringRef(Name)).second;
}
// The new signature doesn't match. Create a variant to the symbol with the
Modified: lld/trunk/wasm/SymbolTable.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/SymbolTable.h?rev=360782&r1=360781&r2=360782&view=diff
==============================================================================
--- lld/trunk/wasm/SymbolTable.h (original)
+++ lld/trunk/wasm/SymbolTable.h Wed May 15 09:03:28 2019
@@ -104,7 +104,10 @@ private:
// variants of the same symbol with different signatures.
llvm::DenseMap<llvm::CachedHashStringRef, std::vector<Symbol *>> SymVariants;
- llvm::DenseSet<llvm::CachedHashStringRef> Comdats;
+ // Comdat groups define "link once" sections. If two comdat groups have the
+ // same name, only one of them is linked, and the other is ignored. This set
+ // is used to uniquify them.
+ llvm::DenseSet<llvm::CachedHashStringRef> ComdatGroups;
// For LTO.
std::unique_ptr<BitcodeCompiler> LTO;
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