[llvm] [X86] Don't use `rbp` when it's reserved (PR #146638)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `flang-arm64-windows-msvc` running on `linaro-armv8-windows-msvc-01` while building `llvm` at step 7 "test-build-unified-tree-check-flang".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/207/builds/3511

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

```
Step 7 (test-build-unified-tree-check-flang) failure: test (failure)
******************** TEST 'Flang :: Parser/OpenMP/declare-reduction-operator.f90' FAILED ********************
Exit Code: 2

Command Output (stdout):
--
# RUN: at line 1
c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe -fc1 -fdebug-unparse -fopenmp C:\Users\tcwg\llvm-worker\flang-arm64-windows-msvc\llvm-project\flang\test\Parser\OpenMP\declare-reduction-operator.f90 | c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\filecheck.exe --ignore-case C:\Users\tcwg\llvm-worker\flang-arm64-windows-msvc\llvm-project\flang\test\Parser\OpenMP\declare-reduction-operator.f90
# executed command: 'c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe' -fc1 -fdebug-unparse -fopenmp 'C:\Users\tcwg\llvm-worker\flang-arm64-windows-msvc\llvm-project\flang\test\Parser\OpenMP\declare-reduction-operator.f90'
# .---command stderr------------
# | PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
# | Stack dump:
# | 0.	Program arguments: c:\\users\\tcwg\\llvm-worker\\flang-arm64-windows-msvc\\build\\bin\\flang.exe -fc1 -fdebug-unparse -fopenmp C:\\Users\\tcwg\\llvm-worker\\flang-arm64-windows-msvc\\llvm-project\\flang\\test\\Parser\\OpenMP\\declare-reduction-operator.f90
# | Exception Code: 0xC0000005
# |  #0 0x00007ff7e1472c7c (c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe+0x1a92c7c)
# |  #1 0x00007ff7e1470964 (c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe+0x1a90964)
# |  #2 0x00007ff7e146e7f8 (c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe+0x1a8e7f8)
# |  #3 0x00007ff7e147450c (c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe+0x1a9450c)
# |  #4 0x00007ff7e146e360 (c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe+0x1a8e360)
# |  #5 0x00007ff7e028c808 (c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe+0x8ac808)
# |  #6 0x00007ff7e02d5c68 (c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe+0x8f5c68)
# |  #7 0x00007ff7e037eb24 (c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe+0x99eb24)
# |  #8 0x00007ff7e02d50a4 (c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe+0x8f50a4)
# |  #9 0x00007ff7dfa78ac8 (c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe+0x98ac8)
# | #10 0x00007ff7dfa8ea90 (c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe+0xaea90)
# | #11 0x00007ff7df9e34e8 (c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe+0x34e8)
# | #12 0x00007ff7df9e20a4 (c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe+0x20a4)
# | #13 0x00007ff7e46a0db8 mlir::detail::FallbackTypeIDResolver::registerImplicitTypeID(class llvm::StringRef) (c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\flang.exe+0x4cc0db8)
# | #14 0x225ffff7e46a0e54
# `-----------------------------
# error: command failed with exit status: 0xc0000005
# executed command: 'c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\filecheck.exe' --ignore-case 'C:\Users\tcwg\llvm-worker\flang-arm64-windows-msvc\llvm-project\flang\test\Parser\OpenMP\declare-reduction-operator.f90'
# .---command stderr------------
# | FileCheck error: '<stdin>' is empty.
# | FileCheck command line:  c:\users\tcwg\llvm-worker\flang-arm64-windows-msvc\build\bin\filecheck.exe --ignore-case C:\Users\tcwg\llvm-worker\flang-arm64-windows-msvc\llvm-project\flang\test\Parser\OpenMP\declare-reduction-operator.f90
# `-----------------------------
# error: command failed with exit status: 2

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/146638