[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 `ppc64le-mlir-rhel-clang` running on `ppc64le-mlir-rhel-test` while building `llvm` at step 5 "build-check-mlir-build-only".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/129/builds/32530

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

```
Step 5 (build-check-mlir-build-only) failure: build (failure)
...
9.171 [115/12/4349] Linking CXX static library lib/libMLIRTestIR.a
9.183 [115/11/4350] Linking CXX executable tools/mlir/unittests/Dialect/OpenACC/MLIROpenACCTests
9.192 [115/10/4351] Linking CXX executable tools/mlir/unittests/Dialect/SPIRV/MLIRSPIRVImportExportTests
9.203 [115/9/4352] Linking CXX executable tools/mlir/unittests/Dialect/SparseTensor/MLIRSparseTensorTests
9.353 [115/8/4353] Linking CXX executable tools/mlir/unittests/Dialect/ArmSME/MLIRArmSMETests
9.366 [115/7/4354] Building CXX object lib/Object/CMakeFiles/LLVMObject.dir/IRSymtab.cpp.o
9.447 [115/6/4355] Linking CXX executable tools/mlir/unittests/IR/MLIRIRTests
9.448 [115/5/4356] Linking CXX executable tools/mlir/unittests/TableGen/MLIRTableGenTests
9.509 [115/4/4357] Linking CXX executable tools/mlir/unittests/Parser/MLIRParserTests
11.732 [115/3/4358] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/AtomicExpandPass.cpp.o
FAILED: lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/AtomicExpandPass.cpp.o 
ccache /home/buildbots/llvm-external-buildbots/clang.19.1.7/bin/clang++ -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/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/build/lib/CodeGen -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/llvm-project/llvm/lib/CodeGen -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/build/include -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/llvm-project/llvm/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wno-pass-failed -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG -std=c++17  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -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/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/llvm-project/llvm/lib/CodeGen/AtomicExpandPass.cpp
/home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/llvm-project/llvm/lib/CodeGen/AtomicExpandPass.cpp:1694:3: error: no matching function for call to 'setExplicitlyUnknownBranchWeightsIfProfiled'
 1694 |   setExplicitlyUnknownBranchWeightsIfProfiled(*CondBr, *F, DEBUG_TYPE);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/llvm-project/llvm/include/llvm/IR/ProfDataUtils.h:200:1: note: candidate function not viable: no known conversion from 'Function' to 'StringRef' for 2nd argument
  200 | setExplicitlyUnknownBranchWeightsIfProfiled(Instruction &I, StringRef PassName,
      | ^                                                           ~~~~~~~~~~~~~~~~~~
1 error generated.
13.413 [115/2/4359] Building CXX object lib/MC/MCParser/CMakeFiles/LLVMMCParser.dir/AsmParser.cpp.o
22.313 [115/1/4360] Building CXX object lib/CodeGen/AsmPrinter/CMakeFiles/LLVMAsmPrinter.dir/AsmPrinter.cpp.o
ninja: build stopped: subcommand failed.

```

</details>

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