Set the thumb flag for thumb symbols coming from an ELF file

[tberghammer]

Summary

Set the thumb flag for thumb symbols coming from an ELF file

Without setting the flag there is no way to determine if a symbol
points to an arm or to a thumb function as the LSB of the address
masked out in all getter function.

[tberghammer]

Friendly ping

[• rafael]

testcase?

[tberghammer]

Currently I don't see any easy way to test this as the thumb flag is only used by llvm-objdump when dumping a MachO file. The ELF dumping code in llvm-objdump should be fixed to use this flag as well as it currently fails to disassemble thumb code but doing it requires a significant amount of refactor. I plan to create a fix for that issue but I don't know when I will have time for doing it. If you have any suggestion about how can I write a standalone test for this change I would appreciate any suggestion.

P.S. I detected the issue while working on an external library using the object file parsing logic from llvm.

[• rafael]

LGTM.

Please say in the commit message why it is not tested.

llvm/trunk/include/llvm/Object/ELFObjectFile.h

uint32_t ELFObjectFile<ELFT>::getSymbolFlags(DataRefImpl Sym) const {
 
   if (EF.getHeader()->e_machine == ELF::EM_ARM) {
     if (ErrorOr<StringRef> NameOrErr = getSymbolName(Sym)) {
       StringRef Name = *NameOrErr;
       if (Name.startswith("$d") || Name.startswith("$t") ||
           Name.startswith("$a"))
         Result |= SymbolRef::SF_FormatSpecific;
     }
+    if (ESym->getType() == ELF::STT_FUNC && (ESym->st_value & 1) == 1)
+      Result |= SymbolRef::SF_Thumb;
   }
 
   if (ESym->st_shndx == ELF::SHN_UNDEF)
     Result |= SymbolRef::SF_Undefined;
 
   if (ESym->getType() == ELF::STT_COMMON || ESym->st_shndx == ELF::SHN_COMMON)
     Result |= SymbolRef::SF_Common;