[llvm-bugs] [Bug 36168] New: [DebugInfo] Wrong representation of enumerator values in debug info metadata

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=36168

            Bug ID: 36168
           Summary: [DebugInfo] Wrong representation of enumerator values
                    in debug info metadata
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: LLVM Codegen
          Assignee: unassignedclangbugs at nondot.org
          Reporter: momchil.velikov at arm.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 19780
  --> https://bugs.llvm.org/attachment.cgi?id=19780&action=edit
C language test case

There are a few issue with the representation of enumeration types in the debug
info metadata as well as in DWARF.

The representation of enumerator values uses a single `int64_t`, which does not
convey enough information about the enumerator value.  For example, when
compiling
the attached `e.c`, `clang` encodes  the values of `A5` and `A7` wrong in the
DWARF debug info:
```
$ clang -c -g e.c && llvm-dwarfdump --debug-info e.o | grep -A1 A[0-9]       
                  DW_AT_name    ("A0")
                  DW_AT_const_value     (-128)
--
                  DW_AT_name    ("A1")
                  DW_AT_const_value     (255)
--
                  DW_AT_name    ("A2")
                  DW_AT_const_value     (-32768)
--
                  DW_AT_name    ("A3")
                  DW_AT_const_value     (65535)
--
                  DW_AT_name    ("A4")
                  DW_AT_const_value     (-2147483648)
--
                  DW_AT_name    ("A5")
                  DW_AT_const_value     (-1)
--
                  DW_AT_name    ("A6")
                  DW_AT_const_value     (-9223372036854775808)
--
                  DW_AT_name    ("A7")
                  DW_AT_const_value     (-9223372036854775808)

```

Compiling the same program as C++ and using the `-fshort-enums` gets wrong the
value of A3 as well:

> $ clang -fshort-enums -x c++ -c -g e.c && llvm-dwarfdump --debug-info e.o | grep -A1 A3
>                   DW_AT_name	("A3")
>                   DW_AT_const_value	(-1)
> 

Similar issues are present with C++11 enumerations with  a fixed underlying
type, e.g. compiling the attached `e.cc`, yields wrong values for `A1`, `A3`,
`A5`, and `A7`:
```
$ clang -c -g e.cc && llvm-dwarfdump --debug-info e.o | grep -A1 A[0-9]
                  DW_AT_name    ("A0")
                  DW_AT_const_value     (-128)
--
                  DW_AT_name    ("A1")
                  DW_AT_const_value     (-1)
--
                  DW_AT_name    ("A2")
                  DW_AT_const_value     (-32768)
--
                  DW_AT_name    ("A3")
                  DW_AT_const_value     (-1)
--
                  DW_AT_name    ("A4")
                  DW_AT_const_value     (-2147483648)
--
                  DW_AT_name    ("A5")
                  DW_AT_const_value     (-1)
--
                  DW_AT_name    ("A6")
                  DW_AT_const_value     (-9223372036854775808)
--
                  DW_AT_name    ("A7")
                  DW_AT_const_value     (-9223372036854775808)
```

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