[llvm-nm] Display STT_GNU_IFUNC as 'i'

[grimar]

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

2

Add a file comment?

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

1136

Why not to place the new logic inside getSymbolNMTypeChar ?
It would be consistent with STB_GNU_UNIQUE I think.

[MaskRay]

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

1136

Place the new logic inside getSymbolNMTypeChar will be more complex.

For both global and local symbols, the key is the lower case i...

[grimar]

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

1136

Ok, that behavior makes sence I think.
What about handling the STB_GNU_UNIQUE here too?
(Because at this point this looks like it solves the same thing as STB_GNU_UNIQUE,
but in the different way, what looks inconsistent).

Also, would it be better to do the following?

else if (WasmObjectFile *Wasm = dyn_cast<WasmObjectFile>(&Obj))
  Ret = getSymbolNMTypeChar(*Wasm, I);
else if (ELFObjectFileBase *ELF = dyn_cast<ELFObjectFileBase>(&Obj)) {
 ...
}
else
 llvm_unreachable(...);

(for me it wasn't obvious that is is OK to use elf_symbol_iterator(I) before
cast<ELFObjectFileBase>(Obj). It was not clear that iterator have the same safe cast
inside).

[MaskRay]

Add llvm_unreachable

[MaskRay]

Simplify

[grimar]

LGTM

[MaskRay]

Add a file-level comment to ifunc.test

[jhenderson]

I guess this isn't a real-world use case, but did you consider testing the interaction between STB_GNU_UNIQUE and STT_GNU_IFUNC? For all other types, the unique binding trumped the type, so seeing it different is a little odd.

[MaskRay]

In D71803#1801067, @jhenderson wrote:

I guess this isn't a real-world use case, but did you consider testing the interaction between STB_GNU_UNIQUE and STT_GNU_IFUNC? For all other types, the unique binding trumped the type, so seeing it different is a little odd.

binutils-gdb/bfd/syms.c:bfd_decode_symclass

  if (symbol->flags & BSF_GNU_INDIRECT_FUNCTION)
    return 'i';
  if (symbol->flags & BSF_WEAK)
    {
      /* If weak, determine if it's specifically an object
	 or non-object weak.  */
      if (symbol->flags & BSF_OBJECT)
	return 'V';
      else
	return 'W';
    }
  if (symbol->flags & BSF_GNU_UNIQUE)
    return 'u';

Our rule matches GNU nm.

With regard to the interaction, STB_GNU_UNIQUE describes a property of a data symbol, while STT_GNU_IFUNC describes a property of a function symbol. So they cannot be mixed.

lld/test/ELF/ppc64-ifunc.s

 # RUN: llvm-mc -filetype=obj -triple=powerpc64-unknown-linux %s -o %t.o
 # RUN: ld.lld %t.o -o %t
 # RUN: llvm-nm %t | FileCheck --check-prefix=NM %s
 # RUN: llvm-readelf -S %t | FileCheck --check-prefix=SECTIONS %s
 # RUN: llvm-objdump -d --no-show-raw-insn %t | FileCheck %s
 # RUN: llvm-readobj -r %t | FileCheck --check-prefix=REL %s
 
 # NM-DAG: 0000000010028248 d .TOC.
-# NM-DAG: 00000000100101f8 T ifunc
-# NM-DAG: 00000000100101fc T ifunc2
+# NM-DAG: 00000000100101f8 i ifunc
+# NM-DAG: 00000000100101fc i ifunc2
 
 # SECTIONS: .plt NOBITS 0000000010030250 000250 000010 00 WA 0 0 8
 
 # __plt_ifunc - . = 0x10010218 - 0x10010208 = 16
 # __plt_ifunc2 - . = 0x1001022c - 0x10010210 = 28
 # CHECK: _start:
 # CHECK-NEXT:                 addis 2, 12, 2
 # CHECK-NEXT:                 addi 2, 2, -32696

llvm/test/LTO/Resolution/X86/ifunc.ll

 ; RUN: opt -module-summary -o %t.bc %s
 ; RUN: llvm-lto2 run %t.bc -r %t.bc,foo,pl -o %t2
 ; RUN: llvm-nm %t2.1 | FileCheck %s
-; CHECK: T foo
+; CHECK: i foo
 ; CHECK: t foo_ifunc
 
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 @foo = ifunc i32 (i32), i64 ()* @foo_ifunc
 
 define internal i64 @foo_ifunc() {
 entry:
   ret i64 0
 }

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
+
+!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

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

static char getNMSectionTagAndName(SymbolicFile &Obj, basic_symbol_iterator 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
-    Ret = getSymbolNMTypeChar(cast<ELFObjectFileBase>(Obj), I);
-
-  if (!(Symflags & object::SymbolRef::SF_Global))
+  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 (Obj.isELF() && ELFSymbolRef(*I).getBinding() == ELF::STB_GNU_UNIQUE)
+  if (!(Symflags & object::SymbolRef::SF_Global))
     return Ret;
 
   return toupper(Ret);
 }
 
 // getNsectForSegSect() is used to implement the Mach-O "-s segname sectname"
 // option to dump only those symbols from that section in a Mach-O file.
 // It is called once for each Mach-O file from dumpSymbolNamesFromObject()