[llvm-nm] add a new option -X to specify the type of object file llvm-nm should examine

[DiggerLin]

Summary

Added a new option "-X" to specify, which type of object file should be examine.
for example ,

1. "llvm-nm -X64 archive.a" only deal with the 64bit object files in the archive.a ,ignore the all 32bit object files in the archive.a

2 "llvm-nm -X32 xcoffobj32.o xcoffobj64.o " only deal with the 32bit object file "xcoffobj32.o" , 64bit object file "xcoffobj64.o" will be ignored

[MaskRay]

llvm-nm is a multi-target binary. It doesn't need --triple=aarch64-linux-gnu to work with an aarch64 object file.
Can't llvm-nm infer the bit mode from the object file automatically?

[MaskRay]

So I just found https://www.ibm.com/docs/en/aix/7.1?topic=n-nm-command

If the intention is to support AIX nm -X, I think it is fine because GNU nm's manpage says -X This option is ignored for compatibility with the AIX version of nm. It takes one parameter which must be the string 32_64. The default mode of AIX nm corresponds to -X 32, which is not supported by GNU nm.
For other short options I would be concerned if there could be a potential conflict with GNU nm.

For the long option --bit-mode, I don't know whether it is necessary.

[hubert.reinterpretcast]

In D118193#3271117, @MaskRay wrote:

Can't llvm-nm infer the bit mode from the object file automatically?

llvm-nm also works on archives, which, on AIX, can contain both 32-bit and 64-bit members. The option performs a filtering operation in such cases.

[DiggerLin]

In D118193#3271123, @MaskRay wrote:

So I just found https://www.ibm.com/docs/en/aix/7.1?topic=n-nm-command

If the intention is to support AIX nm -X, I think it is fine because GNU nm's manpage says -X This option is ignored for compatibility with the AIX version of nm. It takes one parameter which must be the string 32_64. The default mode of AIX nm corresponds to -X 32, which is not supported by GNU nm.
For other short options I would be concerned if there could be a potential conflict with GNU nm.

For the long option --bit-mode, I don't know whether it is necessary.

I will remove long option --bit-mode ,

Since the llvm-nm can dump a 64bit object file without any errror prompt.

bash> llvm-nm option-bit-mode.test.tmp64.o
0000000000000000 D var64

but in aix nm, if we dump symbol of 64bit object file, it will have

bash> nm option-bit-mode.test.tmp64.o
0654-210 option-bit-mode.test.tmp64.o is not valid in the current object file mode.

Use the -X option to specify the desired object mode

I think it maybe better to keep the default -X Value to "any" for llvm-nm , setting default value of -X to "any" will keep llvm-nm current behavior without -X option.

[MaskRay]

llvm/test/tools/llvm-nm/XCOFF/option-bit-mode.test

20 ↗

(On Diff #403032)

Without FileCheck --match-full-lines, 0000000000000000 D var32 will be matched as well.

llvm/tools/llvm-nm/Opts.td

16

Ensure the space separators are consistently used: 32, 64, (default) any or 32, 64, any (default)

The leading message can be "(AIX specific) Specify the type of object file to examine". Note that other messages are imperative sentences and don't use the third-person singular. The tool is called llvm-nm, so it is unneeded to repeat llvm-nm in individual option messages.

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

86

enum class

1630

Avoid a negative function/variable name which holds a boolean that tells of whether we should not do something. Use the positive form: shouldDump

if (BitMode == Any)
  return true;
return isSymbolList64Bit(Obj) ? BitMode == Bit64 : BitMode == Bit32

2173

perhaps use this message

[DiggerLin]

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

1630

thanks

[DiggerLin]

added a new test case

[MaskRay]

llvm/docs/CommandGuide/llvm-nm.rst

131

Use imperative sentences like other options

132

Align

133

Can you run ninja docs-llvm-html and inspect whether the .rst renders properly?

Ensure sphinx-build exists. Configure your build with -DLLVM_ENABLE_SPHINX=ON.

llvm/test/tools/llvm-nm/XCOFF/option-X.test

12 ↗

(On Diff #404647)

If you use --implicit-check-not={{.}}, the NOT pattern should be unneeded.

25 ↗

(On Diff #404647)

It's worth testing the intermediate lines between the [[FILE32]]: stanza and the [[FILE64]]: stanza, to ensure the formatting is intended.

I didn't verify:

# BOTH:        [[FILE32]]:
# BOTH-NEXT:   00000000 D var32
# BOTH-EMPTY:
# BOTH-NEXT:   [[FILE64]]:
# BOTH-NEXT:   0000000000000000 D var64

37 ↗

(On Diff #404647)

replace --allow-empty usage with count 0 (there is zero line, i.e. empty)

llvm/test/tools/llvm-nm/option-X-elf-bitcode.test

6 ↗

(On Diff #404647)

Because of project layering, llvm tests cannot use clang. You need to use llc to generate the test.

Consider split-file. There are quite few tests in llvm/test/tools/

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

86

If Any is not that different from Bit32_64, just remove Any.

[DiggerLin]

llvm/docs/CommandGuide/llvm-nm.rst

133

thanks

llvm/test/tools/llvm-nm/XCOFF/option-X.test

12 ↗

(On Diff #404647)

the BIT32-NOT is for
RUN: llvm-nm -X32 %t.a | FileCheck --check-prefixes=BIT32 %s

llvm/test/tools/llvm-nm/option-X-elf-bitcode.test

6 ↗

(On Diff #404647)

thanks

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

86

yes, we have maybe has to support "the old pre-AIX v5 XCOFF64." later.

[jhenderson]

Added a new option "-X" to specify,which type of object file should be examined.
For example,

1. "llvm-nm -X64 archive.a" only deals with the 64-bit object files in archive.a, ignoring all 32-bit object files.

I'm not sure what this second sentence is actually saying. Please fix it.

2. "llvm-nm -X32 xcoffobj32.o xcoffobj64.o " only deal with the 32bit , 64bit object files input from command line

llvm/docs/CommandGuide/llvm-nm.rst

131

[jhenderson]

llvm/docs/CommandGuide/llvm-nm.rst

132

Use the proper-noun form to make it stand out that this is a specific file format and doesn't simply mean "large regular archives".

135–141

In all cases: "Processes" -> "Process"

Also "all of" -> "all"

llvm/test/tools/llvm-nm/XCOFF/option-X.test

1 ↗

(On Diff #404966)

This comment can be simplified, since you are a) inside the llvm-nm testsuite, and b) inside the XCOFF subdirectory.

4–5 ↗

(On Diff #404966)

Here and for all references, delete _xcoff from the file names: we're in the XCOFF subdirectory, so there's no need to provide that disambiguation.

10–12 ↗

(On Diff #404966)

You should be able to do this here too. You also will need to add an extra check for a filename, I believe (which will also help show that only the desired object is dumped). Prefer the catch-all --implicit-check-not={{.}} to a pattern that could go stale if the test is modified slightly

14–17 ↗

(On Diff #404966)

Same sort of comments as above.

19–21 ↗

(On Diff #404966)

These lines are all very long. Split them over multiple lines as shown.

llvm/test/tools/llvm-nm/option-X-elf-bitcode.test

30–34 ↗

(On Diff #404966)

Split all these lines into two lines each. Same below.

6 ↗

(On Diff #404647)

You've marked as done, but you haven't used split-file to provide multiple inputs within the file instead of using echo. Please adderss this point.

llvm/tools/llvm-nm/Opts.td

16

Marked as done, but not addressed?

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

1630

Obvious question: why does it only work for those kinds of files, and not COFF or Mach-O files (for example)?

2216

[DiggerLin]

In D118193#3289498, @jhenderson wrote:

Added a new option "-X" to specify,which type of object file should be examined.
For example,

1. "llvm-nm -X64 archive.a" only deals with the 64-bit object files in archive.a, ignoring all 32-bit object files.

I'm not sure what this second sentence is actually saying. Please fix it.

2. "llvm-nm -X32 xcoffobj32.o xcoffobj64.o " only deal with the 32bit , 64bit object files input from command line

it should be 
  "llvm-nm -X32  xcoffobj32.o xcoffobj64.o " only deal with the 32bit object file "xcoffobj32.o" ,  64bit object file "xcoffobj64.o" will be ignored.

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

1630

based the our requirement , we need the the option for XCOFF, llvmbit code and ELF object file, I am not sure about the whether it is COFF and Mach-O need the functionality or not, if the COFF and Mach-O need the functionality, we can a new separate patch later.

[DiggerLin]

llvm/docs/CommandGuide/llvm-nm.rst

132

we can create gnu archive file which contain xcoff object file, bit code, elf object file, etc with llvm-ar technically.(it is perfectly valid, just not particularly useful) .
all the llvm tools can support decode the xcoff object file in gnu archive(if there is) or elf object file in big archive(if there is) now.
so we do not need to a specific archive format here.

llvm/tools/llvm-nm/Opts.td

16

-X is not only AIX specific now. it work for llvm bit code, elf object file,xcoff object file from gnu archive and big archive or from command line input .

[jhenderson]

llvm/test/tools/llvm-nm/XCOFF/option-X.test

9–15 ↗

(On Diff #405400)

Possible simplification, as it removes the duplicate 00000000 D var32.

20–23 ↗

(On Diff #405400)

45–48 ↗

(On Diff #405400)

Indent to align.

I'd also change ARCHIVE to ARCBOTH or something equivalent, so that it is consistent with the 32-bit and 64-bit cases.

llvm/test/tools/llvm-nm/option-X-elf-bitcode.test

1 ↗

(On Diff #405400)

Nit: the file format should be all caps.

It's not clear to me why this test contains test cases for two formats (ELF and bitcode), but not all formats supported by this option. In other words, could you please explain why your XCOFF case is in a separate test file to these two (and why you've kept ELF and bitcode in the same one)?

3–4 ↗

(On Diff #405400)

These files don't exist. Did you forget to add them?

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

1630–1631

I think you can simplify this comment, and also clarify that the option isn't fundamentally impossible with other formats, just isn't implemented.

1632–1634

It's fine not to add support for COFF and Mach-O in this patch, but something to consider is what might happen if a user attempted to use that option with an object in that format. The option would be silently ignored, but it wouldn't be clear why to them. I'd consider adding a warning here, if the option has been specified, but the input object is not a supported format.

Alternatively, just add support for all supported formats up-front.

2216

Please add a test-case for this.

[DiggerLin]

llvm/test/tools/llvm-nm/option-X-elf-bitcode.test

1 ↗

(On Diff #405400)

As I mention before, the -X only support for XCOFF, bitcode, ELF object file, not support for other object file in the patch.
xcoff is test on the llvm/test/tools/llvm-nm/XCOFF/option-X.test,

you suggestion moving the content of test llvm/test/tools/llvm-nm/XCOFF/option-X.test into the file too?

3–4 ↗

(On Diff #405400)

the two files are in the patch "--export-symbols" ,

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

1632–1634

I think we have some description in the command guide.

.. option:: -X

Specify the type of XCOFF object file, ELF object file, or IR object file input
from command line or from archive files that llvm-nm should examine.

if I change the code to

 if (!isa<XCOFFObjectFile>(Obj) && !isa<ELFObjectFileBase>(Obj) &&
      !isa<IRObjectFile>(Obj)) {
    if(BitMode !=BitModeTy::Any)
     error("-X option is currently only implemented for XCOFF, ELF, and IR object files");
    return true;
}

it will print out a warning info for each object files in a archive file, there many a lot of same warning print out. It do not look reasonable.

[MaskRay]

llvm/test/tools/llvm-nm/option-X-invalid-arg.test

1 ↗

(On Diff #405763)

Not necessary to use a separate file for errors. It can be placed at the end of option-X.test. I usually place error tests at the end.

I'd avoid -invalid-arg in the filename since I may test more than one types of errors and -invalid-arg restricts the types of errors the file can test.

5 ↗

(On Diff #405763)

7 ↗

(On Diff #405763)

It's not necessary to test the filename part.

Is there a stray colon in : : ?

llvm/tools/llvm-nm/Opts.td

16

Imperative: Specifies -> Specify

The value must be one of : => The value must be one of:

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

2205–2206

Remove // XCOFF specific options. since it's no longer XCOFF specific.

[jhenderson]

llvm/test/tools/llvm-nm/option-X-elf-bitcode.test

1 ↗

(On Diff #405400)

I'm suggesting one of either:

Putting the XCOFF case in this test.

OR

Splitting the bitcode and ELF cases into separate files.

I don't have a particular preference as to which.

3–4 ↗

(On Diff #405400)

This patch doesn't need to rely on the --export-symbols patch though, so it shouldn't really be rebased on top of it. Preferable would be making it an independent patch, and just have the new test inputs duplicated between the two patches (obviously when landing the two patches, you only need one version of the test inputs, so the second-to-land patch won't have them in).

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

1632–1634

People won't routinely look at the command guide, so documenting the limitation there is insufficient.

I do agree with your comment about not wanting to duplicate the error multiple times though. I don't have a good solution, but a small improvement would be to add the limitation to the --help text.

[DiggerLin]

llvm/test/tools/llvm-nm/option-X-invalid-arg.test

7 ↗

(On Diff #405763)

yes, there is ": : " output

[jhenderson]

llvm/test/tools/llvm-nm/option-X.test

8

A thought: I wonder if it would be simpler for all positive inptus to be tested in a single set of llvm-nm invocations. In other words, ratehr than having near-identical bitcode, ELF, and XCOFF cases, you could have them all combined into one, e.g.

# RUN: llvm-nm --format=just-symbols -X32 %t32.bc %t64.bc %t32.elf %t64.elf %t_xcoff.a | \
# RUN:   FileCheck %s ...

Not sure how easy it would be to craft the FileCheck line, so this may not work.

54

The Machine key probably isn't needed for this test case. You should be able to omit it.

58

Flags aren't important for this test case. Delete them.

60–61

The default binding is Local. This is sufficient for this test case, so delete the explicit binding and rename the symbol.

64

You don't need a second YAML document here. You can use -D YAML macros to configure the Class field for the specific variety you want. There are plenty of examples in other ELF tests. You don't need a unique symbol name either, though you can if you want (if you want one, I'd reuse the Class macro in the symbol name, so you don't need an additional macro).

81

No need for the r in -rf, since %t.a isn't a directory.

126

Nit: no double blank line.

131

Similar comment to the two ELF inputs. I think you can reduce duplication by using a single YAML input for XCOFF and using yaml2obj's -D option to customise it accordingly.

134–139

Do you actually need all these fields? Do any of them have defaults that are sufficient for our needs?

141–144

Why do you have two sections? Won't one do, like the ELF case?

148–153

Same comment as above: are all of these required fields, or are the defaults sufficient?

[DiggerLin]

llvm/test/tools/llvm-nm/option-X.test

8

I think a separate test , it is easy to understand, and if someone want to add a new object format support support in some day, for example, MachO support, they just need to add one new test line, do not need to change current test line.

64

thanks.

134–139

thanks

141–144

thanks

148–153

thanks

[jhenderson]

llvm/test/tools/llvm-nm/option-X.test

58

Ping. You've not deleted the flag field, despite this being marked as done. Please don't mark things as done unless you've uploaded a diff with the comment addressed.

59

As suggested in my earlier comment, you can reuse the class macro, to avoid needing an extra variable. The fact that the symbol is both "global" and "data" is irrelevant to the test.

60–61

Ping. You've not deleted the binding field, despite this being marked as done. Please don't mark things as done unless you've uploaded a diff with the comment addressed.

[DiggerLin]

reduce test case

[jhenderson]

Looks good, barring a couple of suggestions. You might want to confirm with @MaskRay too.

llvm/test/tools/llvm-nm/option-X.test

63–65

Here and below for the 64-bit equivalent, I'd make the BIT32 prefix XCOFF32, since it's specifically testing XCOFF, and not other formats (ARC32 can stay the same if you want, or change it as you feel is appropriate).

67

FWIW, in this particular case, I'd be okay if you wanted to use a second -D option to name the variable, so that it is a little more explicit. Up to you either way, whichever you prefer.

105

I'm pretty sure the double colon is a bug, but I guess it's a bug elsewhere in the code not touched by this patch. You might want to fix it in a separate patch, if you have time.

[MaskRay]

Looks great!

llvm/tools/llvm-nm/Opts.td

16

Just to keep the binary formats sorted alphabetically.

[DiggerLin]

llvm/test/tools/llvm-nm/option-X.test

63–65

thanks, I keep ARC as it is.

67

I keep as it. thanks

105

yes, I think so. I will do it when I am available.

llvm/tools/llvm-nm/Opts.td

16

thanks

llvm/docs/CommandGuide/llvm-nm.rst

 -------
 
 .. program:: llvm-nm
 
 .. option:: -B
 
  Use BSD output format. Alias for ``--format=bsd``.
 
+.. option:: -X
+
+ Specify the type of XCOFF object file, ELF object file, or IR object file input
+ from command line or from archive files that llvm-nm should examine. The
+ mode must be one of the following:
+   32
+         Process only 32-bit object files.
+   64
+         Process only 64-bit object files.
+   32_64
+         Process both 32-bit and 64-bit object files.
+   any
+         Process all the supported object files.
+
 .. option:: --debug-syms, -a
 
  Show all symbols, even those usually suppressed.
 
 .. option:: --defined-only
 
  Print only symbols defined in this file.
 

llvm/test/tools/llvm-nm/Inputs/bitcode-sym32.ll

+target triple = "powerpcle-unknown-linux-gnu"
+
+@C32 = dso_local global i32 5, align 4
+@undef_var32 = external dso_local global i32, align 4
+
+define dso_local i32 @foo32(i32 %i) #0 {
+entry:
+  %i.addr = alloca i32, align 4
+  store i32 %i, i32* %i.addr, align 4
+  %0 = load i32, i32* %i.addr, align 4
+  %1 = load i32, i32* @undef_var32, align 4
+  %add = add nsw i32 %0, %1
+  ret i32 %add
+}

llvm/test/tools/llvm-nm/Inputs/bitcode-sym64.ll

+target triple = "powerpc64le-unknown-linux-gnu"
+
+@C64 = dso_local global i32 5, align 4
+@static_var64 = internal global i32 2, align 4
+
+define dso_local signext i32 @bar64() #0 {
+entry:
+  %0 = load i32, i32* @static_var64, align 4
+  %1 = load i32, i32* @C64, align 4
+  %add = add nsw i32 %0, %1
+  ret i32 %add
+}

llvm/test/tools/llvm-nm/option-X.test

+## Test the "-X" option.
+## The option specifies the type of object file to examine.
+
+# RUN: llvm-as -o %t32.bc %p/Inputs/bitcode-sym32.ll
+# RUN: llvm-as -o %t64.bc %p/Inputs/bitcode-sym64.ll
+
+# RUN: llvm-nm --format=just-symbols -X32 %t32.bc %t64.bc | \
+# RUN:   FileCheck %s -DFILE1=%t32.bc --check-prefixes=BITCODE32 --implicit-check-not={{.}}
+# RUN: llvm-nm --format=just-symbols -X64 %t32.bc %t64.bc | \
+# RUN:   FileCheck %s -DFILE2=%t64.bc --check-prefixes=BITCODE64 --implicit-check-not={{.}}
+# RUN: llvm-nm --format=just-symbols %t32.bc %t64.bc | \
+# RUN:   FileCheck %s -DFILE1=%t32.bc -DFILE2=%t64.bc --check-prefixes=BITCODE32,BITCODE64
+# RUN: llvm-nm --format=just-symbols -X32_64 %t32.bc %t64.bc | \
+# RUN:   FileCheck %s -DFILE1=%t32.bc -DFILE2=%t64.bc --check-prefixes=BITCODE32,BITCODE64
+# RUN: llvm-nm --format=just-symbols -Xany %t32.bc %t64.bc | \
+# RUN:   FileCheck %s -DFILE1=%t32.bc -DFILE2=%t64.bc --check-prefixes=BITCODE32,BITCODE64
+
+# BITCODE32:      [[FILE1]]:
+# BITCODE32-NEXT: C32
+# BITCODE32-NEXT: foo32
+# BITCODE32-NEXT: undef_var32
+
+# BITCODE64:      [[FILE2]]:
+# BITCODE64-NEXT: C64
+# BITCODE64-NEXT: bar64
+# BITCODE64-NEXT: static_var64
+
+# RUN: yaml2obj --docnum=1 -DCLASS=ELFCLASS32 %s -o %t_elf32.o
+# RUN: yaml2obj --docnum=1 -DCLASS=ELFCLASS64 %s -o %t_elf64.o
+
+# RUN: llvm-nm --format=just-symbols -X32 %t_elf32.o %t_elf64.o | \
+# RUN:   FileCheck %s -DFILE32=%t_elf32.o --check-prefixes=ELF32 --implicit-check-not={{.}}
+# RUN: llvm-nm --format=just-symbols -X64 %t_elf32.o %t_elf64.o | \
+# RUN:   FileCheck %s -DFILE64=%t_elf64.o --check-prefixes=ELF64 --implicit-check-not={{.}}
+# RUN: llvm-nm --format=just-symbols %t_elf32.o %t_elf64.o | \
+# RUN:   FileCheck %s -DFILE32=%t_elf32.o -DFILE64=%t_elf64.o --check-prefixes=ELF32,ELF64
+# RUN: llvm-nm --format=just-symbols -X32_64 %t_elf32.o %t_elf64.o | \
+# RUN:   FileCheck %s -DFILE32=%t_elf32.o -DFILE64=%t_elf64.o --check-prefixes=ELF32,ELF64
+# RUN: llvm-nm --format=just-symbols -Xany %t_elf32.o %t_elf64.o | \
+# RUN:   FileCheck %s -DFILE32=%t_elf32.o -DFILE64=%t_elf64.o --check-prefixes=ELF32,ELF64
+
+# ELF32:      [[FILE32]]:
+# ELF32-NEXT: ELFCLASS32_var
+
+# ELF64:      [[FILE64]]:
+# ELF64-NEXT: ELFCLASS64_var
+
+--- !ELF
+FileHeader:
+  Class:   [[CLASS]]
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+Symbols:
+  - Name:    [[CLASS]]_var
+
+# RUN: yaml2obj --docnum=2 -DFLAG=0x1DF %s -o %t_xcoff32.o
+# RUN: yaml2obj --docnum=2 -DFLAG=0x1F7 %s -o %t_xcoff64.o
+# RUN: rm -f %t.a
+# RUN: llvm-ar -q -c %t.a %t_xcoff32.o %t_xcoff64.o
+
+# RUN: llvm-nm --format=just-symbols -X32 %t_xcoff32.o | \
+# RUN:   FileCheck --check-prefixes=XCOFF32 %s --implicit-check-not={{.}}
+# RUN: llvm-nm --format=just-symbols -X32 %t.a | \
+# RUN:   FileCheck --check-prefixes=ARC32,XCOFF32 %s -DFILE=%basename_t --implicit-check-not={{.}}
+# ARC32:      [[FILE]].tmp_xcoff32.o:
+# XCOFF32:      var_0x1DF
+
+# RUN: llvm-nm --format=just-symbols -X64 %t_xcoff64.o | \
+# RUN:   FileCheck --check-prefixes=XCOFF64 %s --implicit-check-not={{.}}
+# RUN: llvm-nm --format=just-symbols -X64 %t.a | \
+# RUN:   FileCheck --check-prefixes=ARC64,XCOFF64 -DFILE=%basename_t %s --implicit-check-not={{.}}
+# ARC64:       [[FILE]].tmp_xcoff64.o:
+# XCOFF64:       var_0x1F7
+
+# RUN: llvm-nm --format=just-symbols %t_xcoff32.o %t_xcoff64.o | \
+# RUN:   FileCheck --check-prefixes=BOTH %s -DFILE32=%t_xcoff32.o -DFILE64=%t_xcoff64.o --match-full-lines
+# RUN: llvm-nm --format=just-symbols -X32_64 %t_xcoff32.o %t_xcoff64.o | \
+# RUN:   FileCheck --check-prefixes=BOTH %s -DFILE32=%t_xcoff32.o -DFILE64=%t_xcoff64.o --match-full-lines
+# RUN: llvm-nm --format=just-symbols -Xany %t_xcoff32.o %t_xcoff64.o | \
+# RUN:   FileCheck --check-prefixes=BOTH %s -DFILE32=%t_xcoff32.o -DFILE64=%t_xcoff64.o --match-full-lines
+
+# BOTH:        [[FILE32]]:
+# BOTH-NEXT:   var_0x1DF
+# BOTH-EMPTY:
+# BOTH-NEXT:   [[FILE64]]:
+# BOTH-NEXT:   var_0x1F7
+
+# RUN: llvm-nm --format=just-symbols %t.a | \
+# RUN:   FileCheck --check-prefixes=ARCHIVE-BOTH -DFILE=%basename_t --match-full-lines %s
+# RUN: llvm-nm --format=just-symbols -X32_64 %t.a | \
+# RUN:   FileCheck --check-prefixes=ARCHIVE-BOTH -DFILE=%basename_t --match-full-lines %s
+# RUN: llvm-nm --format=just-symbols -Xany %t.a | \
+# RUN:   FileCheck --check-prefixes=ARCHIVE-BOTH -DFILE=%basename_t --match-full-lines %s
+
+# ARCHIVE-BOTH:      [[FILE]].tmp_xcoff32.o:
+# ARCHIVE-BOTH-NEXT: var_0x1DF{{[[:space:]]}}
+# ARCHIVE-BOTH-NEXT: [[FILE]].tmp_xcoff64.o:
+# ARCHIVE-BOTH-NEXT: var_0x1F7
+
+# RUN: llvm-nm --format=just-symbols -X64 %t_xcoff32.o | count 0
+# RUN: llvm-nm --format=just-symbols -X32 %t_xcoff64.o | count 0
+
+# RUN: not llvm-nm --format=just-symbols -X33 %t_xcoff32.o 2>&1 |  FileCheck %s --check-prefixes=ERR
+# ERR:      error: : -X value should be one of: 32, 64, 32_64, (default) any
+# ERR-NEXT: var_0x1DF
+
+--- !XCOFF
+FileHeader:
+  MagicNumber:       [[FLAG]]
+Symbols:
+  - Name:            var_[[FLAG]]

llvm/tools/llvm-nm/Opts.td

 include "llvm/Option/OptParser.td"
 
 class F<string letter, string help> : Flag<["-"], letter>, HelpText<help>;
 class FF<string name, string help> : Flag<["--"], name>, HelpText<help>;
 
 multiclass BB<string name, string help1, string help2> {
   def NAME: Flag<["--"], name>, HelpText<help1>;
   def no_ # NAME: Flag<["--"], "no-" # name>, HelpText<help2>;
 }
 
 multiclass Eq<string name, string help> {
   def NAME #_EQ : Joined<["--"], name #"=">, HelpText<help>;
   def : Separate<["--"], name>, Alias<!cast<Joined>(NAME #_EQ)>;
 }
 
+def X : JoinedOrSeparate<["-"], "X">, HelpText<"Specifies the type of ELF, XCOFF, or IR object file to examine. The value must be one of: 32, 64, 32_64, any (default)">;
 def debug_syms : FF<"debug-syms", "Show all symbols, even debugger only">;
 def defined_only : FF<"defined-only", "Show only defined symbols">;
 defm demangle : BB<"demangle", "Demangle C++ symbol names", "Don't demangle symbol names">;
 def dynamic : FF<"dynamic", "Display dynamic symbols instead of normal symbols">;
 def extern_only : FF<"extern-only", "Show only external symbols">;
 defm format : Eq<"format", "Specify output format: bsd (default), posix, sysv, darwin, just-symbols">, MetaVarName<"<format>">;
 def help : FF<"help", "Display this help">;
 def no_llvm_bc : FF<"no-llvm-bc", "Disable LLVM bitcode reader">;

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

 };
 
 class NmOptTable : public opt::OptTable {
 public:
   NmOptTable() : OptTable(InfoTable) { setGroupedShortOptions(true); }
 };
 
 enum OutputFormatTy { bsd, sysv, posix, darwin, just_symbols };
+enum class BitModeTy { Bit32, Bit64, Bit32_64, Any };
 } // namespace
 
 static bool ArchiveMap;
+static BitModeTy BitMode;
 static bool DebugSyms;
 static bool DefinedOnly;
 static bool Demangle;
 static bool DynamicSyms;
 static bool ExternalOnly;
 static OutputFormatTy OutputFormat;
 static bool NoLLVMBitcode;
 static bool NoSort;
if (FunctionStartsAdded) {
           Q += strlen(Q) + 1;
         }
         I++;
       }
     }
   }
 }
 
+static bool shouldDump(SymbolicFile &Obj) {
+  // The -X option is currently only implemented for XCOFF, ELF, and IR object
+  // files. The option isn't fundamentally impossible with other formats, just
+  // isn't implemented.
+  if (!isa<XCOFFObjectFile>(Obj) && !isa<ELFObjectFileBase>(Obj) &&
+      !isa<IRObjectFile>(Obj))
+    return true;
+
+  return isSymbolList64Bit(Obj) ? BitMode != BitModeTy::Bit32
+                                : BitMode != BitModeTy::Bit64;
+}
+
 static void dumpSymbolNamesFromObject(SymbolicFile &Obj, bool printName,
                                       StringRef ArchiveName = {},
                                       StringRef ArchitectureName = {}) {
+  if (!shouldDump(Obj))
+    return;
   auto Symbols = Obj.symbols();
   std::vector<VersionEntry> SymbolVersions;
   if (DynamicSyms) {
     const auto *E = dyn_cast<ELFObjectFileBase>(&Obj);
     if (!E) {
       error("File format has no dynamic symbol table", Obj.getFileName());
       return;
     }
if (ArchiveMap) {
         if (SymbolicFile *O = dyn_cast<SymbolicFile>(&*ChildOrErr.get())) {
           if (!MachOPrintSizeWarning && PrintSize &&  isa<MachOObjectFile>(O)) {
             WithColor::warning(errs(), ToolName)
                 << "sizes with -print-size for Mach-O files are always zero.\n";
             MachOPrintSizeWarning = true;
           }
           if (!checkMachOAndArchFlags(O, Filename))
             return;
-          if (!PrintFileName) {
+          if (!PrintFileName && shouldDump(*O)) {
             outs() << "\n";
             if (isa<MachOObjectFile>(O)) {
               outs() << Filename << "(" << O->getFileName() << ")";
             } else
               outs() << O->getFileName();
             outs() << ":\n";
           }
           dumpSymbolNamesFromObject(*O, false, Filename);
int main(int argc, char **argv) {
   NoWeakSymbols = Args.hasArg(OPT_no_weak);
   NumericSort = Args.hasArg(OPT_numeric_sort);
   ArchiveMap = Args.hasArg(OPT_print_armap);
   PrintFileName = Args.hasArg(OPT_print_file_name);
   PrintSize = Args.hasArg(OPT_print_size);
   ReverseSort = Args.hasArg(OPT_reverse_sort);
   Quiet = Args.hasArg(OPT_quiet);
   V = Args.getLastArgValue(OPT_radix_EQ, "x");
   if (V == "o")
     AddressRadix = Radix::o;
   else if (V == "d")
     AddressRadix = Radix::d;
   else if (V == "x")
     AddressRadix = Radix::x;
   else
     error("--radix value should be one of: 'o' (octal), 'd' (decimal), 'x' "
           "(hexadecimal)");
   SizeSort = Args.hasArg(OPT_size_sort);
   SpecialSyms = Args.hasArg(OPT_special_syms);
   UndefinedOnly = Args.hasArg(OPT_undefined_only);
   WithoutAliases = Args.hasArg(OPT_without_aliases);
 
+  StringRef Mode = Args.getLastArgValue(OPT_X, "any");
+  if (Mode == "32")
+    BitMode = BitModeTy::Bit32;
+  else if (Mode == "64")
+    BitMode = BitModeTy::Bit64;
+  else if (Mode == "32_64")
+    BitMode = BitModeTy::Bit32_64;
+  else if (Mode == "any")
+    BitMode = BitModeTy::Any;
+  else
+    error("-X value should be one of: 32, 64, 32_64, (default) any");
+
   // Mach-O specific options.
   FormatMachOasHex = Args.hasArg(OPT_x);
   AddDyldInfo = Args.hasArg(OPT_add_dyldinfo);
   AddInlinedInfo = Args.hasArg(OPT_add_inlinedinfo);
   DyldInfoOnly = Args.hasArg(OPT_dyldinfo_only);
   NoDyldInfo = Args.hasArg(OPT_no_dyldinfo);
 
   // llvm-nm only reads binary files.
   if (error(sys::ChangeStdinToBinary()))
     return 1;
 
   // These calls are needed so that we can read bitcode correctly.
   llvm::InitializeAllTargetInfos();
   llvm::InitializeAllTargetMCs();
   llvm::InitializeAllAsmParsers();
 
   // The relative order of these is important. If you pass --size-sort it should
   // only print out the size. However, if you pass -S --size-sort, it should
   // print out both the size and address.
   if (SizeSort && !PrintSize)
     PrintAddress = false;
   if (OutputFormat == sysv || SizeSort)
     PrintSize = true;
 
   for (const auto *A : Args.filtered(OPT_arch_EQ)) {
     SmallVector<StringRef, 2> Values;