[llvm] [X86] Don't clobber x87 return values when zeroing call-used registers (PR #211129)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `sanitizer-x86_64-linux` running on `sanitizer-buildbot1` while building `llvm` at step 2 "annotate".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/66/builds/34530

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

```
Step 2 (annotate) failure: 'python ../sanitizer_buildbot/sanitizers/zorg/buildbot/builders/sanitizers/buildbot_selector.py' (failure) (timed out)
...
[0/1] Install the project...
-- Install configuration: "Release"
[418/424] Generating MSAN_INST_GTEST.gtest-all.cc.x86_64-with-call.o
[419/424] Generating MSAN_INST_GTEST.gtest-all.cc.x86_64.o
[420/424] Generating MSAN_INST_TEST_OBJECTS.msan_test.cpp.x86_64-with-call.o
[421/424] Generating Msan-x86_64-with-call-Test
[422/424] Generating MSAN_INST_TEST_OBJECTS.msan_test.cpp.x86_64.o
[423/424] Generating Msan-x86_64-Test
[423/424] Running compiler_rt regression tests
-- Testing: 11702 tests, 64 workers --
command timed out: 1200 seconds without output running [b'python', b'../sanitizer_buildbot/sanitizers/zorg/buildbot/builders/sanitizers/buildbot_selector.py'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=1973.056506
Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..
Step 9 (test compiler-rt symbolizer) failure: test compiler-rt symbolizer (failure)
...
[1874/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/filesystem/filesystem_error.cpp.o
[1875/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/barrier.cpp.o
[1876/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/ios.cpp.o
[1877/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/print.cpp.o
[1878/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/condition_variable.cpp.o
[1879/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/memory.cpp.o
[1880/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/strstream.cpp.o
[1881/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/thread.cpp.o
[1882/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/random_shuffle.cpp.o
[1883/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/atomic.cpp.o
[1884/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/charconv.cpp.o
[1885/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/regex.cpp.o
[1886/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/chrono.cpp.o
[1887/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/iostream.cpp.o
[1888/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/ostream.cpp.o
[1889/1905] Building CXX object libcxx/src/CMakeFiles/cxx_experimental.dir/experimental/chrono_exception.cpp.o
[1890/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/filesystem/path.cpp.o
[1891/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/filesystem/filesystem_clock.cpp.o
[1892/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/filesystem/directory_entry.cpp.o
[1893/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/string.cpp.o
[1894/1905] Building CXX object libcxx/src/CMakeFiles/cxx_experimental.dir/experimental/tzdb_list.cpp.o
[1895/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/filesystem/directory_iterator.cpp.o
[1896/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/ios.instantiations.cpp.o
[1897/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/filesystem/operations.cpp.o
[1898/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/algorithm.cpp.o
[1899/1905] Building CXX object libcxxabi/src/CMakeFiles/cxxabi_static_objects.dir/cxa_demangle.cpp.o
[1900/1905] Linking CXX static library lib/libc++abi.a
[1901/1905] Building CXX object libcxx/src/CMakeFiles/cxx_experimental.dir/experimental/tzdb.cpp.o
[1902/1905] Building CXX object libcxx/src/CMakeFiles/cxx_experimental.dir/experimental/time_zone.cpp.o
[1903/1905] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/locale.cpp.o
[1904/1905] Linking CXX static library lib/libc++.a
[1905/1905] Linking CXX static library lib/libc++experimental.a
[415/424] Generating FuzzerUtils-x86_64-Test
[416/424] Installing libcxx_tsan_x86_64...
[0/1] Install the project...
-- Install configuration: "Release"
[418/424] Generating MSAN_INST_GTEST.gtest-all.cc.x86_64-with-call.o
[419/424] Generating MSAN_INST_GTEST.gtest-all.cc.x86_64.o
[420/424] Generating MSAN_INST_TEST_OBJECTS.msan_test.cpp.x86_64-with-call.o
[421/424] Generating Msan-x86_64-with-call-Test
[422/424] Generating MSAN_INST_TEST_OBJECTS.msan_test.cpp.x86_64.o
[423/424] Generating Msan-x86_64-Test
[423/424] Running compiler_rt regression tests
-- Testing: 11702 tests, 64 workers --

command timed out: 1200 seconds without output running [b'python', b'../sanitizer_buildbot/sanitizers/zorg/buildbot/builders/sanitizers/buildbot_selector.py'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=1973.056506
Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..

```

</details>

https://github.com/llvm/llvm-project/pull/211129