[llvm-bugs] [Bug 39762] New: OCaml binding Llvm.value_name always returns empty string

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=39762

            Bug ID: 39762
           Summary: OCaml binding Llvm.value_name always returns empty
                    string
           Product: libraries
           Version: 6.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: taquangtrungvn at gmail.com
                CC: craig.topper at gmail.com, llvm-bugs at lists.llvm.org,
                    llvm-dev at redking.me.uk, spatel+llvm at rotateright.com

I followed the tutorial https://www.wzdftpd.net/blog/ocaml-llvm-02.html to
build an analyzer for LLVM bitcode. 

However, the OCaml binding function Llvm.value_name always returns an empty
string. This is unexpected since the function Llvm.string_of_llvalue returns
the correct string-representation of an Llvm value.

I'm using LLVM 6.0 and test with two versions of OCaml: 4.06.1 and 4.07.0.

Here are the steps to reproduce the bug:

1. Create a file hello.c

      #include<stdio.h>

      int main(int arg) {
          int x = arg;
          if (x>1)
              return 1;
          else
              return 2;
          assert(1>2);
      }

2. Compile it to bitcode: clang -c hello.c -emit-llvm

3. Here is my OCaml code to print the value name of the bitcode file hello.bc

      let print_bitcode file =
        let llctx = Llvm.global_context () in
        let llmem = Llvm.MemoryBuffer.of_file file in
        let llm = Llvm_bitreader.parse_bitcode llctx llmem in
        Llvm.iter_functions (fun func ->
          Llvm.iter_blocks (fun blk ->
            Llvm.iter_instrs(fun inst ->
              print_endline ("Value Name: '" ^ (Llvm.value_name inst) ^ "'");
              print_endline ("Value Str: '" ^ (Llvm.string_of_llvalue inst) ^
"'\n");
            ) blk
          ) func
        ) llm

4. Here is the output:

      Value Name: ''
      Value Str: '  %2 = alloca i32, align 4'

      Value Name: ''
      Value Str: '  %3 = alloca i32, align 4'

      Value Name: ''
      Value Str: '  %4 = alloca i32, align 4'

      Value Name: ''
      Value Str: '  store i32 0, i32* %2, align 4'

      Value Name: ''
      Value Str: '  store i32 %0, i32* %3, align 4'

      Value Name: ''
      Value Str: '  %5 = load i32, i32* %3, align 4'

      Value Name: ''
      Value Str: '  store i32 %5, i32* %4, align 4'

      Value Name: ''
      Value Str: '  %6 = load i32, i32* %4, align 4'

      Value Name: ''
      Value Str: '  %7 = icmp sgt i32 %6, 1'

      Value Name: ''
      Value Str: '  br i1 %7, label %8, label %9'

      Value Name: ''
      Value Str: '  store i32 1, i32* %2, align 4'

      Value Name: ''
      Value Str: '  br label %10'

      Value Name: ''
      Value Str: '  store i32 2, i32* %2, align 4'

      Value Name: ''
      Value Str: '  br label %10'

      Value Name: ''
      Value Str: '  %11 = load i32, i32* %2, align 4'

      Value Name: ''
      Value Str: '  ret i32 %11'

5. As can be seen above, all the Value Name is empty.

So, I wonder if this is a bug of the binding function Llvm.value_name, 
or did I make some mistakes in my code?

Thank you!

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20181123/11f54a3a/attachment-0001.html>