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Remember if a weakref of a symbol has been used.

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This avoids yet another last minute patching of the binding.

While at it, also simplify the weakref implementation a bit by not walking
past it in the expression evaluation.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238982 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola 2015-06-03 21:52:06 +00:00
parent f3857c334f
commit 5eb7481d03
4 changed files with 33 additions and 27 deletions
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7
include/llvm/MC/MCSymbolELF.h
View File

@ -19,11 +19,13 @@ class MCSymbolELF : public MCSymbol {
mutable unsigned BindingSet : 1;
mutable unsigned UsedInReloc : 1;
mutable unsigned WeakrefUsedInReloc : 1;
mutable unsigned IsSignature : 1;
public:
MCSymbolELF(const StringMapEntry<bool> *Name, bool isTemporary)
: MCSymbol(true, Name, isTemporary), BindingSet(false) {}
: MCSymbol(true, Name, isTemporary), BindingSet(false),
UsedInReloc(false), WeakrefUsedInReloc(false), IsSignature(false) {}
void setSize(const MCExpr *SS) { SymbolSize = SS; }
const MCExpr *getSize() const { return SymbolSize; }
@ -45,6 +47,9 @@ public:
void setUsedInReloc() const;
bool isUsedInReloc() const;
void setIsWeakrefUsedInReloc() const;
bool isWeakrefUsedInReloc() const;
void setIsSignature() const;
bool isSignature() const;

40
lib/MC/ELFObjectWriter.cpp
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@ -98,7 +98,6 @@ class ELFObjectWriter : public MCObjectWriter {
/// The target specific ELF writer instance.
std::unique_ptr<MCELFObjectTargetWriter> TargetObjectWriter;
SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc;
DenseMap<const MCSymbolELF *, const MCSymbolELF *> Renames;
llvm::DenseMap<const MCSectionELF *, std::vector<ELFRelocationEntry>>
@ -141,7 +140,6 @@ class ELFObjectWriter : public MCObjectWriter {
: MCObjectWriter(OS, IsLittleEndian), TargetObjectWriter(MOTW) {}
void reset() override {
WeakrefUsedInReloc.clear();
Renames.clear();
Relocations.clear();
StrTabBuilder.clear();
@ -589,25 +587,6 @@ bool ELFObjectWriter::shouldRelocateWithSymbol(const MCAssembler &Asm,
return false;
}
static const MCSymbol *getWeakRef(const MCSymbolRefExpr &Ref) {
const MCSymbol &Sym = Ref.getSymbol();
if (Ref.getKind() == MCSymbolRefExpr::VK_WEAKREF)
return &Sym;
if (!Sym.isVariable())
return nullptr;
const MCExpr *Expr = Sym.getVariableValue();
const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr);
if (!Inner)
return nullptr;
if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF)
return &Inner->getSymbol();
return nullptr;
}
// True if the assembler knows nothing about the final value of the symbol.
// This doesn't cover the comdat issues, since in those cases the assembler
// can at least know that all symbols in the section will move together.
@ -681,6 +660,17 @@ void ELFObjectWriter::RecordRelocation(MCAssembler &Asm,
const MCSymbolRefExpr *RefA = Target.getSymA();
const auto *SymA = RefA ? cast<MCSymbolELF>(&RefA->getSymbol()) : nullptr;
bool ViaWeakRef = false;
if (SymA && SymA->isVariable()) {
const MCExpr *Expr = SymA->getVariableValue();
if (const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr)) {
if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) {
SymA = cast<MCSymbolELF>(&Inner->getSymbol());
ViaWeakRef = true;
}
}
}
unsigned Type = GetRelocType(Target, Fixup, IsPCRel);
bool RelocateWithSymbol = shouldRelocateWithSymbol(Asm, RefA, SymA, C, Type);
if (!RelocateWithSymbol && SymA && !SymA->isUndefined())
@ -709,8 +699,8 @@ void ELFObjectWriter::RecordRelocation(MCAssembler &Asm,
if (const MCSymbolELF *R = Renames.lookup(SymA))
SymA = R;
if (const MCSymbol *WeakRef = getWeakRef(*RefA))
WeakrefUsedInReloc.insert(WeakRef);
if (ViaWeakRef)
SymA->setIsWeakrefUsedInReloc();
else
SymA->setUsedInReloc();
}
@ -785,7 +775,7 @@ void ELFObjectWriter::computeSymbolTable(
for (const MCSymbol &S : Asm.symbols()) {
const auto &Symbol = cast<MCSymbolELF>(S);
bool Used = Symbol.isUsedInReloc();
bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol);
bool WeakrefUsed = Symbol.isWeakrefUsedInReloc();
bool isSignature = Symbol.isSignature();
if (!isInSymtab(Layout, Symbol, Used || WeakrefUsed || isSignature,
@ -809,8 +799,6 @@ void ELFObjectWriter::computeSymbolTable(
} else {
MSD.SectionIndex = ELF::SHN_UNDEF;
}
if (!Used && WeakrefUsed)
Symbol.setBinding(ELF::STB_WEAK);
} else {
const MCSectionELF &Section =
static_cast<const MCSectionELF &>(Symbol.getSection());

7
lib/MC/MCExpr.cpp
View File

@ -601,6 +601,13 @@ bool MCExpr::evaluateAsValue(MCValue &Res, const MCAsmLayout &Layout) const {
}
static bool canExpand(const MCSymbol &Sym, const MCAssembler *Asm, bool InSet) {
const MCExpr *Expr = Sym.getVariableValue();
const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr);
if (Inner) {
if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF)
return false;
}
if (InSet)
return true;
if (!Asm)

6
lib/MC/MCSymbolELF.cpp
View File

@ -35,6 +35,8 @@ unsigned MCSymbolELF::getBinding() const {
return ELF::STB_LOCAL;
if (isUsedInReloc())
return ELF::STB_GLOBAL;
if (isWeakrefUsedInReloc())
return ELF::STB_WEAK;
if (isSignature())
return ELF::STB_LOCAL;
return ELF::STB_GLOBAL;
@ -96,6 +98,10 @@ bool MCSymbolELF::isUsedInReloc() const {
return UsedInReloc;
}
void MCSymbolELF::setIsWeakrefUsedInReloc() const { WeakrefUsedInReloc = true; }
bool MCSymbolELF::isWeakrefUsedInReloc() const { return WeakrefUsedInReloc; }
void MCSymbolELF::setIsSignature() const { IsSignature = true; }
bool MCSymbolELF::isSignature() const { return IsSignature; }