Add r224985 back with a fix.

The issues was that AArch64 has additional restrictions on when local
relocations can be used. We have to take those into consideration when
deciding to put a L symbol in the symbol table or not.

Original message:

Remove doesSectionRequireSymbols.

In an assembly expression like

bar:
.long L0 + 1

the intended semantics is that bar will contain a pointer one byte past L0.

In sections that are merged by content (strings, 4 byte constants, etc), a
single position in the section doesn't give the linker enough information.
For example, it would not be able to tell a relocation must point to the
end of a string, since that would look just like the start of the next.

The solution used in ELF to use relocation with symbols if there is a non-zero
addend.

In MachO before this patch we would just keep all symbols in some sections.

This would miss some cases (only cstrings on x86_64 were implemented) and was
inefficient since most relocations have an addend of 0 and can be represented
without the symbol.

This patch implements the non-zero addend logic for MachO too.

llvm-svn: 225048

1 files changed, 4 insertions, 6 deletions

diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index e4442e10a05..83a76dc2256 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -219,7 +219,7 @@ class ELFObjectWriter : public MCObjectWriter {
                                   const MCSymbolData *SD, uint64_t C,
                                   unsigned Type) const;
 
-    void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
+    void RecordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
                           const MCFragment *Fragment, const MCFixup &Fixup,
                           MCValue Target, bool &IsPCRel,
                           uint64_t &FixedValue) override;
@@ -789,13 +789,11 @@ static const MCSymbol *getWeakRef(const MCSymbolRefExpr &Ref) {
   return nullptr;
 }
 
-void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
+void ELFObjectWriter::RecordRelocation(MCAssembler &Asm,
                                        const MCAsmLayout &Layout,
                                        const MCFragment *Fragment,
-                                       const MCFixup &Fixup,
-                                       MCValue Target,
-                                       bool &IsPCRel,
-                                       uint64_t &FixedValue) {
+                                       const MCFixup &Fixup, MCValue Target,
+                                       bool &IsPCRel, uint64_t &FixedValue) {
   const MCSectionData *FixupSection = Fragment->getParent();
   uint64_t C = Target.getConstant();
   uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();