[llvm] [profcheck] Add unknown branch weights to expanded cmpxchg loop. (PR #165841)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-sie-ubuntu-fast` running on `sie-linux-worker` while building `llvm` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/144/builds/39438

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

```
Step 5 (build-unified-tree) failure: build (failure)
...
4.703 [48/13/88] Linking CXX executable bin/clang-reorder-fields
4.761 [48/12/89] Linking CXX executable bin/find-all-symbols
4.790 [48/11/90] Linking CXX executable bin/clang-installapi
4.854 [48/10/91] Linking CXX executable bin/clang-refactor
4.946 [48/9/92] Linking CXX executable bin/clang-move
4.990 [48/8/93] Linking CXX executable bin/pp-trace
5.006 [48/7/94] Linking CXX executable bin/clang-include-cleaner
5.011 [48/6/95] Linking CXX executable bin/clang-query
5.034 [48/5/96] Linking CXX executable bin/tool-template
5.039 [48/4/97] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/AtomicExpandPass.cpp.o
FAILED: lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/AtomicExpandPass.cpp.o 
CCACHE_CPP2=yes CCACHE_HASHDIR=yes CCACHE_SLOPPINESS=pch_defines,time_macros /usr/bin/ccache /usr/bin/g++ -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GLIBCXX_USE_CXX11_ABI=1 -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/lib/CodeGen -I/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/lib/CodeGen -I/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/include -I/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-uninitialized -Wno-nonnull -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-array-bounds -Wno-stringop-overread -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wno-misleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -std=c++17 -MD -MT lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/AtomicExpandPass.cpp.o -MF lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/AtomicExpandPass.cpp.o.d -o lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/AtomicExpandPass.cpp.o -c /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/lib/CodeGen/AtomicExpandPass.cpp
In file included from /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/include/llvm/CodeGen/TargetLowering.h:32,
                 from /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/lib/CodeGen/AtomicExpandPass.cpp:24:
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/include/llvm/CodeGen/LibcallLoweringInfo.h:15:46: warning: ‘visibility’ attribute ignored [-Wattributes]
   15 |   LLVM_ABI const RTLIB::RuntimeLibcallsInfo &RTLCI;
      |                                              ^~~~~
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/include/llvm/CodeGen/LibcallLoweringInfo.h:18:25: warning: ‘visibility’ attribute ignored [-Wattributes]
   18 |       RTLIB::Unsupported};
      |                         ^
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/lib/CodeGen/AtomicExpandPass.cpp: In static member function ‘static llvm::Value* {anonymous}::AtomicExpandImpl::insertRMWCmpXchgLoop(llvm::IRBuilderBase&, llvm::Type*, llvm::Value*, llvm::Align, llvm::AtomicOrdering, llvm::SyncScope::ID, llvm::function_ref<llvm::Value*(llvm::IRBuilderBase&, llvm::Value*)>, llvm::CreateCmpXchgInstFun, llvm::Instruction*)’:
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/lib/CodeGen/AtomicExpandPass.cpp:1694:56: error: could not convert ‘* F’ from ‘llvm::Function’ to ‘llvm::StringRef’
 1694 |   setExplicitlyUnknownBranchWeightsIfProfiled(*CondBr, *F, DEBUG_TYPE);
      |                                                        ^~
      |                                                        |
      |                                                        llvm::Function
6.883 [48/3/98] Linking CXX executable bin/clang-tidy
13.376 [48/2/99] Building CXX object lib/CodeGen/AsmPrinter/CMakeFiles/LLVMAsmPrinter.dir/AsmPrinter.cpp.o
In file included from /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/include/llvm/CodeGen/TargetLowering.h:32,
                 from /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp:62:
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/include/llvm/CodeGen/LibcallLoweringInfo.h:15:46: warning: ‘visibility’ attribute ignored [-Wattributes]
   15 |   LLVM_ABI const RTLIB::RuntimeLibcallsInfo &RTLCI;
      |                                              ^~~~~
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/include/llvm/CodeGen/LibcallLoweringInfo.h:18:25: warning: ‘visibility’ attribute ignored [-Wattributes]
   18 |       RTLIB::Unsupported};
      |                         ^
14.532 [48/1/100] Building CXX object lib/LTO/CMakeFiles/LLVMLTO.dir/LTO.cpp.o
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/165841