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Don't create an unused _GLOBAL_OFFSET_TABLE_.

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This was a bug for bug compatibility with gas that is completely unnecessary.
If a _GLOBAL_OFFSET_TABLE_ symbol is used, it will already be created by
the time we get to the ELF writer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238432 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola 2015-05-28 15:20:00 +00:00
parent 6952e75aa5
commit c4e38f605e
3 changed files with 6 additions and 81 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

44
lib/MC/ELFObjectWriter.cpp
View File

@ -71,7 +71,6 @@ public:
class ELFObjectWriter : public MCObjectWriter {
static bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind);
static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant);
static uint64_t SymbolValue(const MCSymbol &Sym, const MCAsmLayout &Layout);
static bool isInSymtab(const MCAsmLayout &Layout, const MCSymbol &Symbol,
bool Used, bool Renamed);
@ -120,8 +119,6 @@ class ELFObjectWriter : public MCObjectWriter {
/// @}
bool NeedsGOT;
// This holds the symbol table index of the last local symbol.
unsigned LastLocalSymbolIndex;
// This holds the .strtab section index.
@ -148,8 +145,7 @@ class ELFObjectWriter : public MCObjectWriter {
public:
ELFObjectWriter(MCELFObjectTargetWriter *MOTW, raw_pwrite_stream &OS,
bool IsLittleEndian)
: MCObjectWriter(OS, IsLittleEndian), TargetObjectWriter(MOTW),
NeedsGOT(false) {}
: MCObjectWriter(OS, IsLittleEndian), TargetObjectWriter(MOTW) {}
void reset() override {
UsedInReloc.clear();
@ -161,7 +157,6 @@ class ELFObjectWriter : public MCObjectWriter {
LocalSymbolData.clear();
ExternalSymbolData.clear();
UndefinedSymbolData.clear();
NeedsGOT = false;
SectionTable.clear();
MCObjectWriter::reset();
}
@ -319,27 +314,6 @@ bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel;
}
bool ELFObjectWriter::RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) {
switch (Variant) {
default:
return false;
case MCSymbolRefExpr::VK_GOT:
case MCSymbolRefExpr::VK_PLT:
case MCSymbolRefExpr::VK_GOTPCREL:
case MCSymbolRefExpr::VK_GOTOFF:
case MCSymbolRefExpr::VK_TPOFF:
case MCSymbolRefExpr::VK_TLSGD:
case MCSymbolRefExpr::VK_GOTTPOFF:
case MCSymbolRefExpr::VK_INDNTPOFF:
case MCSymbolRefExpr::VK_NTPOFF:
case MCSymbolRefExpr::VK_GOTNTPOFF:
case MCSymbolRefExpr::VK_TLSLDM:
case MCSymbolRefExpr::VK_DTPOFF:
case MCSymbolRefExpr::VK_TLSLD:
return true;
}
}
ELFObjectWriter::~ELFObjectWriter()
{}
@ -811,12 +785,6 @@ void ELFObjectWriter::RecordRelocation(MCAssembler &Asm,
FixedValue = C;
// FIXME: What is this!?!?
MCSymbolRefExpr::VariantKind Modifier =
RefA ? RefA->getKind() : MCSymbolRefExpr::VK_None;
if (RelocNeedsGOT(Modifier))
NeedsGOT = true;
if (!RelocateWithSymbol) {
const MCSection *SecA =
(SymA && !SymA->isUndefined()) ? &SymA->getSection() : nullptr;
@ -915,16 +883,6 @@ void ELFObjectWriter::computeSymbolTable(
SymtabSection->setAlignment(is64Bit() ? 8 : 4);
SymbolTableIndex = addToSectionTable(SymtabSection);
// FIXME: Is this the correct place to do this?
// FIXME: Why is an undefined reference to _GLOBAL_OFFSET_TABLE_ needed?
if (NeedsGOT) {
StringRef Name = "_GLOBAL_OFFSET_TABLE_";
MCSymbol *Sym = Asm.getContext().getOrCreateSymbol(Name);
MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym);
Data.setExternal(true);
MCELF::SetBinding(Data, ELF::STB_GLOBAL);
}
// Add the data for the symbols.
bool HasLargeSectionIndex = false;
for (const MCSymbol &Symbol : Asm.symbols()) {

11
test/MC/ELF/got.s
View File

@ -1,7 +1,7 @@
// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | llvm-readobj -r -t | FileCheck %s
// Test that this produces a R_X86_64_GOT32 and that we have an undefined
// reference to _GLOBAL_OFFSET_TABLE_.
// Test that this produces the correct relocations R_X86_64_GOT32 and that we,
// unlike gas, don't create a _GLOBAL_OFFSET_TABLE_ symbol as a side effect.
movl foo@GOT, %eax
movl foo@GOTPCREL(%rip), %eax
@ -13,8 +13,5 @@
// CHECK-NEXT: }
// CHECK-NEXT: ]
// CHECK: Symbol {
// CHECK: Name: _GLOBAL_OFFSET_TABLE_
// CHECK-NEXT: Value:
// CHECK-NEXT: Size:
// CHECK-NEXT: Binding: Global
// CHECK: Symbols [
// CHECK-NOT: _GLOBAL_OFFSET_TABLE_

32
test/MC/ELF/weakref-reloc.s
View File

@ -1,7 +1,6 @@
// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | llvm-readobj -r -t | FileCheck %s
// Test that the relocations point to the correct symbols. We used to get the
// symbol index wrong for weakrefs when creating _GLOBAL_OFFSET_TABLE_.
// Test that the relocations point to the correct symbols.
.weakref bar,foo
call zed@PLT
@ -13,32 +12,3 @@
// CHECK-NEXT: 0x6 R_X86_64_PC32 foo 0xFFFFFFFFFFFFFFFC
// CHECK-NEXT: }
// CHECK-NEXT: ]
// CHECK: Symbols [
// CHECK: Symbol {
// CHECK: Name: _GLOBAL_OFFSET_TABLE_
// CHECK-NEXT: Value: 0x0
// CHECK-NEXT: Size: 0
// CHECK-NEXT: Binding: Global
// CHECK-NEXT: Type: None
// CHECK-NEXT: Other: 0
// CHECK-NEXT: Section: Undefined (0x0)
// CHECK-NEXT: }
// CHECK-NEXT: Symbol {
// CHECK-NEXT: Name: foo
// CHECK-NEXT: Value: 0x0
// CHECK-NEXT: Size: 0
// CHECK-NEXT: Binding: Weak
// CHECK-NEXT: Type: None
// CHECK-NEXT: Other: 0
// CHECK-NEXT: Section: Undefined (0x0)
// CHECK-NEXT: }
// CHECK-NEXT: Symbol {
// CHECK-NEXT: Name: zed
// CHECK-NEXT: Value: 0x0
// CHECK-NEXT: Size: 0
// CHECK-NEXT: Binding: Global
// CHECK-NEXT: Type: None
// CHECK-NEXT: Other: 0
// CHECK-NEXT: Section: Undefined (0x0)
// CHECK-NEXT: }