[llvm] [CFIFixup] Factor logic into helpers and use range-based loops (NFC) (PR #125137)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `bolt-x86_64-ubuntu-nfc` running on `bolt-worker` while building `llvm` at step 7 "build-bolt".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/92/builds/12982

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

```
Step 7 (build-bolt) failure: build (failure)
...
ninja: no work to do.
0.014 [14/3/2] Generating VCSRevision.h
0.023 [8/4/3] No install step for 'bolt_rt'
0.024 [7/4/4] Generating VCSVersion.inc
0.039 [6/4/5] Completed 'bolt_rt'
0.050 [6/3/6] Building CXX object lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/SLPVectorizer.cpp.o
0.211 [5/3/7] Linking CXX static library lib/libLLVMVectorize.a
1.013 [5/2/8] Building CXX object tools/bolt/lib/Utils/CMakeFiles/LLVMBOLTUtils.dir/CommandLineOpts.cpp.o
1.051 [4/2/9] Linking CXX static library lib/libLLVMBOLTUtils.a
2.676 [4/1/10] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/CFIFixup.cpp.o
FAILED: lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/CFIFixup.cpp.o 
ccache /usr/bin/c++ -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/lib/CodeGen -I/home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/llvm-project/llvm/lib/CodeGen -I/home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/build/include -I/home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/llvm-project/llvm/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -fno-lifetime-dse -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-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/CFIFixup.cpp.o -MF lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/CFIFixup.cpp.o.d -o lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/CFIFixup.cpp.o -c /home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/llvm-project/llvm/lib/CodeGen/CFIFixup.cpp
/home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/llvm-project/llvm/lib/CodeGen/CFIFixup.cpp: In function ‘llvm::SmallVector<BlockFlags> computeBlockInfo(const llvm::MachineFunction&, const llvm::MachineBasicBlock*)’:
/home/worker/bolt-worker2/bolt-x86_64-ubuntu-nfc/llvm-project/llvm/lib/CodeGen/CFIFixup.cpp:174:10: error: could not convert ‘BlockInfo’ from ‘SmallVector<[...],32>’ to ‘SmallVector<[...],40>’
  174 |   return BlockInfo;
      |          ^~~~~~~~~
      |          |
      |          SmallVector<[...],32>
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/125137