llvm-mc/Mach-O: Support symbol attributes.
- This is mostly complete, the main thing missing is .indirect_symbol support
(which would be straight-forward, except that the way it is implemented in
'as' makes getting an exact .o match interesting).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@79899 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCMachOStreamer.cpp b/lib/MC/MCMachOStreamer.cpp
index caff125..9d60e3e 100644
--- a/lib/MC/MCMachOStreamer.cpp
+++ b/lib/MC/MCMachOStreamer.cpp
@@ -19,6 +19,27 @@
namespace {
class MCMachOStreamer : public MCStreamer {
+ /// SymbolFlags - We store the value for the 'desc' symbol field in the lowest
+ /// 16 bits of the implementation defined flags.
+ enum SymbolFlags { // See <mach-o/nlist.h>.
+ SF_DescFlagsMask = 0xFFFF,
+
+ // Reference type flags.
+ SF_ReferenceTypeMask = 0x0007,
+ SF_ReferenceTypeUndefinedNonLazy = 0x0000,
+ SF_ReferenceTypeUndefinedLazy = 0x0001,
+ SF_ReferenceTypeDefined = 0x0002,
+ SF_ReferenceTypePrivateDefined = 0x0003,
+ SF_ReferenceTypePrivateUndefinedNonLazy = 0x0004,
+ SF_ReferenceTypePrivateUndefinedLazy = 0x0005,
+
+ // Other 'desc' flags.
+ SF_NoDeadStrip = 0x0020,
+ SF_WeakReference = 0x0040,
+ SF_WeakDefinition = 0x0080
+ };
+
+private:
MCAssembler Assembler;
MCSectionData *CurSectionData;
@@ -121,6 +142,9 @@
assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
SD.setFragment(F);
SD.setOffset(F->getContents().size());
+
+ // This causes the reference type and weak reference flags to be cleared.
+ SD.setFlags(SD.getFlags() & ~(SF_WeakReference | SF_ReferenceTypeMask));
Symbol->setSection(*CurSection);
}
@@ -141,18 +165,71 @@
void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
SymbolAttr Attribute) {
+ // Adding a symbol attribute always introduces the symbol, note that an
+ // important side effect of calling getSymbolData here is to register the
+ // symbol with the assembler.
+ MCSymbolData &SD = getSymbolData(*Symbol);
+
+ // The implementation of symbol attributes is designed to match 'as', but it
+ // leaves much to desired. It doesn't really make sense to arbitrarily add and
+ // remove flags, but 'as' allows this (in particular, see .desc).
+ //
+ // In the future it might be worth trying to make these operations more well
+ // defined.
switch (Attribute) {
- default:
- llvm_unreachable("FIXME: Not yet implemented!");
+ case MCStreamer::Hidden:
+ case MCStreamer::Internal:
+ case MCStreamer::Protected:
+ case MCStreamer::Weak:
+ assert(0 && "Invalid symbol attribute for Mach-O!");
+ break;
case MCStreamer::Global:
getSymbolData(*Symbol).setExternal(true);
break;
+
+ case MCStreamer::LazyReference:
+ // FIXME: This requires -dynamic.
+ SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
+ if (Symbol->isUndefined())
+ SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
+ break;
+
+ case MCStreamer::IndirectSymbol:
+ llvm_unreachable("FIXME: Not yet implemented!");
+ break;
+
+ // Since .reference sets the no dead strip bit, it is equivalent to
+ // .no_dead_strip in practice.
+ case MCStreamer::Reference:
+ case MCStreamer::NoDeadStrip:
+ SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
+ break;
+
+ case MCStreamer::PrivateExtern:
+ SD.setExternal(true);
+ SD.setPrivateExtern(true);
+ break;
+
+ case MCStreamer::WeakReference:
+ // FIXME: This requires -dynamic.
+ if (Symbol->isUndefined())
+ SD.setFlags(SD.getFlags() | SF_WeakReference);
+ break;
+
+ case MCStreamer::WeakDefinition:
+ // FIXME: 'as' enforces that this is defined and global. The manual claims
+ // it has to be in a coalesced section, but this isn't enforced.
+ SD.setFlags(SD.getFlags() | SF_WeakDefinition);
+ break;
}
}
void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
- llvm_unreachable("FIXME: Not yet implemented!");
+ // Encode the 'desc' value into the lowest implementation defined bits.
+ assert(DescValue == (DescValue & SF_DescFlagsMask) &&
+ "Invalid .desc value!");
+ getSymbolData(*Symbol).setFlags(DescValue & SF_DescFlagsMask);
}
void MCMachOStreamer::EmitLocalSymbol(MCSymbol *Symbol, const MCValue &Value) {