Support demangling in llvm-cxxfilt for fixed point types

[PiJoules]

Tools like llvm-cxxfilt or other llvm tools that support demangling like llvm-readelf won't demangle fixed point types. Clang supports mangling them but it would be really helpful for llvm tools to demangle them. The mangling rules under the Itanium C++ ABI for fixed point types are at https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling-builtin.

PiJoules#1 is a WIP patch that someone can ressurect and land but it'll need some tests before landing.

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Check that no other contributor has already been assigned to this issue. If you believe that no one is actually working on it despite an assignment, ping the person. After one week without a response, the assignee may be changed.
2. In the comments of this issue, request for it to be assigned to you, or just create a pull request after following the steps below. Mention this issue in the description of the pull request.
3. Fix the issue locally.
4. Run the test suite locally. Remember that the subdirectories under test/ create fine-grained testing targets, so you can e.g. use make check-clang-ast to only run Clang's AST tests.
5. Create a Git commit.
6. Run git clang-format HEAD~1 to format your changes.
7. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation. Mention this issue in the description of the pull request.

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: None (PiJoules)

Tools like `llvm-cxxfilt` or other llvm tools that support demangling like `llvm-readelf` won't demangle fixed point types. Clang supports mangling them but it would be really helpful for llvm tools to demangle them. The mangling rules under the Itanium C++ ABI for fixed point types are at https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling-builtin.

PiJoules#1 is a WIP patch that someone can ressurect and land but it'll need some tests before landing.

[llvmbot]

@llvm/issue-subscribers-tools-llvm-cxxfilt

Author: None (PiJoules)

Tools like `llvm-cxxfilt` or other llvm tools that support demangling like `llvm-readelf` won't demangle fixed point types. Clang supports mangling them but it would be really helpful for llvm tools to demangle them. The mangling rules under the Itanium C++ ABI for fixed point types are at https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling-builtin.

PiJoules#1 is a WIP patch that someone can ressurect and land but it'll need some tests before landing.

[Kalomidin]

can I take this issue?