[llvm-nm] Display defined weak STT_GNU_IFUNC symbols as 'i'

[MaskRay]

Summary

This patch makes the behavior match GNU nm.
Note: undefined STT_GNU_IFUNC symbols use 'U'.

[MaskRay]

Display Mach-O WeakRef as 'U'

Mach-O is poorly tested. CC @lhames in case he wants to add Mach-O tests:)

$ echo '__attribute__((weak)) void ref();  __attribute__((weak)) void def() { ref(); };' > test.c && clang -c test.c
$ nm test.o
0000000000000000 T _def
                 U _ref

[grimar]

llvm/tools/llvm-nm/llvm-nm.cpp

1150–1154

I'd reorder. The isa<MachOObjectFile>(Obj) condition looks a bit too burried.

if (Symflags & object::SymbolRef::SF_Undefined) {
  if (isa<MachOObjectFile>(Obj) || !(Symflags & object::SymbolRef::SF_Weak))
    return 'U';
  return isObject(Obj, I) ? 'v' : 'w';
}

1155

No need to have curly bracers here.

1156

The same comment about reordering applies here.
I think checking the object type first is cleaner.

if (!isa<MachOObjectFile>(Obj) && (Symflags & object::SymbolRef::SF_Weak))

[MaskRay]

comments

[jhenderson]

Frankly, the llvm-nm code in this area feels like a bit of a mess, but this is at least an improvement. Just one test suggestion. Otherwise, this looks good.

llvm/test/tools/llvm-nm/ifunc.test

34–36

Maybe worth a weak undefined case too.

[MaskRay]

Add undef weak

[jhenderson]

LGTM.

llvm/test/tools/llvm-nm/ifunc.test

 ## Test that the symbol type of STT_GNU_IFUNC is 'i'.
 
 # RUN: yaml2obj %s -o %t
 # RUN: llvm-nm --no-sort %t | FileCheck %s
 
 # CHECK:      i ifunc_local
 # CHECK-NEXT: i ifunc_global
+# CHECK-NEXT: i ifunc_weak
+# CHECK-NEXT: U ifunc_undef
 
 !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_REL
   Machine: EM_X86_64
 Sections:
   - Name:  .text
     Type:  SHT_PROGBITS
     Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
 Symbols:
   - Name:    ifunc_local
     Type:    STT_GNU_IFUNC
     Binding: STB_LOCAL
     Section: .text
   - Name:    ifunc_global
     Type:    STT_GNU_IFUNC
     Binding: STB_GLOBAL
     Section: .text
+  - Name:    ifunc_weak
+    Type:    STT_GNU_IFUNC
+    Binding: STB_WEAK
+    Section: .text
+  - Name:    ifunc_undef
+    Type:    STT_GNU_IFUNC
+    Binding: STB_GLOBAL

llvm/tools/llvm-nm/llvm-nm.cpp

else {
       if (!NameOrErr) {
         consumeError(NameOrErr.takeError());
         return '?';
       }
       SecName = *NameOrErr;
     }
   }
 
-  if ((Symflags & object::SymbolRef::SF_Weak) && !isa<MachOObjectFile>(Obj)) {
-    char Ret = isObject(Obj, I) ? 'v' : 'w';
-    return (!(Symflags & object::SymbolRef::SF_Undefined)) ? toupper(Ret) : Ret;
-  }
-
-  if (Symflags & object::SymbolRef::SF_Undefined)
+  if (Symflags & object::SymbolRef::SF_Undefined) {
+    if (isa<MachOObjectFile>(Obj) || !(Symflags & object::SymbolRef::SF_Weak))
       return 'U';
+    return isObject(Obj, I) ? 'v' : 'w';
+  }
+  if (ELFObjectFileBase *ELF = dyn_cast<ELFObjectFileBase>(&Obj))
+    if (ELFSymbolRef(*I).getELFType() == ELF::STT_GNU_IFUNC)
+      return 'i';
+  if (!isa<MachOObjectFile>(Obj) && (Symflags & object::SymbolRef::SF_Weak))
+    return isObject(Obj, I) ? 'V' : 'W';
 
   if (Symflags & object::SymbolRef::SF_Common)
     return 'C';
 
   char Ret = '?';
   if (Symflags & object::SymbolRef::SF_Absolute)
     Ret = 'a';
   else if (IRObjectFile *IR = dyn_cast<IRObjectFile>(&Obj))
     Ret = getSymbolNMTypeChar(*IR, I);
   else if (COFFObjectFile *COFF = dyn_cast<COFFObjectFile>(&Obj))
     Ret = getSymbolNMTypeChar(*COFF, I);
   else if (COFFImportFile *COFFImport = dyn_cast<COFFImportFile>(&Obj))
     Ret = getSymbolNMTypeChar(*COFFImport);
   else if (MachOObjectFile *MachO = dyn_cast<MachOObjectFile>(&Obj))
     Ret = getSymbolNMTypeChar(*MachO, I);
   else if (WasmObjectFile *Wasm = dyn_cast<WasmObjectFile>(&Obj))
     Ret = getSymbolNMTypeChar(*Wasm, I);
   else if (TapiFile *Tapi = dyn_cast<TapiFile>(&Obj))
     Ret = getSymbolNMTypeChar(*Tapi, I);
   else if (ELFObjectFileBase *ELF = dyn_cast<ELFObjectFileBase>(&Obj)) {
-    if (ELFSymbolRef(*I).getELFType() == ELF::STT_GNU_IFUNC)
-      return 'i';
     Ret = getSymbolNMTypeChar(*ELF, I);
     if (ELFSymbolRef(*I).getBinding() == ELF::STB_GNU_UNIQUE)
       return Ret;
   } else
     llvm_unreachable("unknown binary format");
 
   if (!(Symflags & object::SymbolRef::SF_Global))
     return Ret;