[llvm] [ValueTracking] Return `poison` for zero-sized types (PR #122647)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `lldb-remote-linux-win` running on `as-builder-10` while building `llvm` at step 17 "test-check-lldb-api".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/197/builds/728

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 17 (test-check-lldb-api) failure: Test just built components: check-lldb-api completed (failure)
******************** TEST 'lldb-api :: commands/thread/backtrace/TestThreadBacktraceRepeat.py' FAILED ********************
Script:
--
C:/Python312/python.exe C:/buildbot/as-builder-10/lldb-x-aarch64/llvm-project/lldb\test\API\dotest.py -u CXXFLAGS -u CFLAGS --env LLVM_LIBS_DIR=C:/buildbot/as-builder-10/lldb-x-aarch64/build/./lib --env LLVM_INCLUDE_DIR=C:/buildbot/as-builder-10/lldb-x-aarch64/build/include --env LLVM_TOOLS_DIR=C:/buildbot/as-builder-10/lldb-x-aarch64/build/./bin --arch aarch64 --build-dir C:/buildbot/as-builder-10/lldb-x-aarch64/build/lldb-test-build.noindex --lldb-module-cache-dir C:/buildbot/as-builder-10/lldb-x-aarch64/build/lldb-test-build.noindex/module-cache-lldb\lldb-api --clang-module-cache-dir C:/buildbot/as-builder-10/lldb-x-aarch64/build/lldb-test-build.noindex/module-cache-clang\lldb-api --executable C:/buildbot/as-builder-10/lldb-x-aarch64/build/./bin/lldb.exe --compiler C:/buildbot/as-builder-10/lldb-x-aarch64/build/./bin/clang.exe --dsymutil C:/buildbot/as-builder-10/lldb-x-aarch64/build/./bin/dsymutil.exe --make C:/ninja/make.exe --llvm-tools-dir C:/buildbot/as-builder-10/lldb-x-aarch64/build/./bin --lldb-obj-root C:/buildbot/as-builder-10/lldb-x-aarch64/build/tools/lldb --lldb-libs-dir C:/buildbot/as-builder-10/lldb-x-aarch64/build/./lib --platform-url connect://jetson-agx-0086.lab.llvm.org:1234 --platform-working-dir /home/ubuntu/lldb-tests --sysroot c:/buildbot/fs/jetson-agx-ubuntu --env ARCH_CFLAGS=-mcpu=cortex-a78 --platform-name remote-linux --skip-category=lldb-server C:\buildbot\as-builder-10\lldb-x-aarch64\llvm-project\lldb\test\API\commands\thread\backtrace -p TestThreadBacktraceRepeat.py
--
Exit Code: 1

Command Output (stdout):
--
lldb version 20.0.0git (https://github.com/llvm/llvm-project.git revision d89751240206dafcbc138829d9d7aad137aa2e04)
  clang revision d89751240206dafcbc138829d9d7aad137aa2e04
  llvm revision d89751240206dafcbc138829d9d7aad137aa2e04
Setting up remote platform 'remote-linux'

Connecting to remote platform 'remote-linux' at 'connect://jetson-agx-0086.lab.llvm.org:1234'...

Connected.

Setting remote platform working directory to '/home/ubuntu/lldb-tests'...

Skipping the following test categories: ['lldb-server', 'dsym', 'gmodules', 'debugserver', 'objc', 'lldb-dap']


--
Command Output (stderr):
--
PASS: LLDB (C:\buildbot\as-builder-10\lldb-x-aarch64\build\bin\clang.exe-aarch64) :: test_thread_backtrace_one_thread (TestThreadBacktraceRepeat.TestThreadBacktracePage.test_thread_backtrace_one_thread)

FAIL: LLDB (C:\buildbot\as-builder-10\lldb-x-aarch64\build\bin\clang.exe-aarch64) :: test_thread_backtrace_two_threads (TestThreadBacktraceRepeat.TestThreadBacktracePage.test_thread_backtrace_two_threads)

======================================================================

FAIL: test_thread_backtrace_two_threads (TestThreadBacktraceRepeat.TestThreadBacktracePage.test_thread_backtrace_two_threads)

   Test that repeat works even when backtracing on more than one thread.

----------------------------------------------------------------------

Traceback (most recent call last):

  File "C:\buildbot\as-builder-10\lldb-x-aarch64\llvm-project\lldb\test\API\commands\thread\backtrace\TestThreadBacktraceRepeat.py", line 142, in test_thread_backtrace_two_threads

    ) = lldbutil.run_to_source_breakpoint(

        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  File "C:\buildbot\as-builder-10\lldb-x-aarch64\llvm-project\lldb\packages\Python\lldbsuite\test\lldbutil.py", line 1016, in run_to_source_breakpoint

    return run_to_breakpoint_do_run(

...

```

</details>

https://github.com/llvm/llvm-project/pull/122647