Don't create an unused _GLOBAL_OFFSET_TABLE_.

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

diff --git a/lib/MC/ELFObjectWriter.cpp b/lib/MC/ELFObjectWriter.cpp
index 8061f691064529b7b952dd3c4eaab66dea116fc3..37762a40874b88f34d9420ff528e6172f9f2d8e6 100644 (file)
--- a/lib/MC/ELFObjectWriter.cpp
+++ b/lib/MC/ELFObjectWriter.cpp
@@ -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()) {

diff --git a/test/MC/ELF/got.s b/test/MC/ELF/got.s
index 30114b75d84daf60c22e127715283f2b8e408233..3fe3e4a62b1a559870e0bbd2e773f43a6589020c 100644 (file)
--- a/test/MC/ELF/got.s
+++ b/test/MC/ELF/got.s
@@ -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_

diff --git a/test/MC/ELF/weakref-reloc.s b/test/MC/ELF/weakref-reloc.s
index 484167f0434ea67eca817783c54ba025059a01cc..baf80060c433629b010a140390e1ff9113d4f252 100644 (file)
--- a/test/MC/ELF/weakref-reloc.s
+++ b/test/MC/ELF/weakref-reloc.s
@@ -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:   }