[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 `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/17106

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

```
Step 5 (build-unified-tree) failure: build (failure)
...
3.028 [49/30/54] Copying llvm-locstats into /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/./bin
3.032 [49/29/55] Linking CXX executable bin/llvm-objdump
3.036 [48/29/56] Generating ../../bin/llvm-otool
3.054 [48/28/57] Linking CXX executable bin/llvm-debuginfo-analyzer
3.055 [48/27/58] Linking CXX executable bin/llvm-xray
3.075 [48/26/59] Linking CXX executable bin/clang-apply-replacements
3.087 [48/25/60] Linking CXX executable bin/nvptx-arch
3.092 [48/24/61] Linking CXX executable bin/clang-offload-bundler
3.284 [48/23/62] Linking CXX executable bin/llvm-profgen
3.407 [48/22/63] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/CFIFixup.cpp.o
FAILED: lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/CFIFixup.cpp.o 
CCACHE_CPP2=yes CCACHE_HASHDIR=yes /usr/bin/ccache /usr/bin/g++ -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/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 -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/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/lib/CodeGen/CFIFixup.cpp
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/lib/CodeGen/CFIFixup.cpp: In function ‘llvm::SmallVector<BlockFlags> computeBlockInfo(const llvm::MachineFunction&, const llvm::MachineBasicBlock*)’:
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/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>
3.851 [48/21/64] Linking CXX executable bin/diagtool
3.977 [48/20/65] Linking CXX shared module lib/SampleAnalyzerPlugin.so
4.120 [48/19/66] Linking CXX shared module lib/CheckerOptionHandlingAnalyzerPlugin.so
4.200 [48/18/67] Linking CXX shared module lib/CheckerDependencyHandlingAnalyzerPlugin.so
4.388 [48/17/68] Linking CXX executable bin/clang-reorder-fields
4.461 [48/16/69] Linking CXX executable bin/find-all-symbols
4.463 [48/15/70] Linking CXX executable bin/clang-change-namespace
4.463 [48/14/71] Linking CXX executable bin/clang-installapi
4.464 [48/13/72] Linking CXX executable bin/clang-refactor
4.467 [48/12/73] Linking CXX executable bin/pp-trace
4.507 [48/11/74] Linking CXX executable bin/tool-template
4.551 [48/10/75] Linking CXX executable bin/clang-doc
4.692 [48/9/76] Linking CXX executable bin/modularize
4.701 [48/8/77] Linking CXX executable bin/clang-include-fixer
4.705 [48/7/78] Linking CXX executable bin/clang-diff
4.748 [48/6/79] Linking CXX executable bin/clang-include-cleaner
4.802 [48/5/80] Linking CXX executable bin/clang-query
4.825 [48/4/81] Linking CXX executable bin/clang-move
6.152 [48/3/82] Linking CXX executable bin/clang-tidy
12.459 [48/2/83] Building CXX object lib/CodeGen/AsmPrinter/CMakeFiles/LLVMAsmPrinter.dir/AsmPrinter.cpp.o
13.115 [48/1/84] Building CXX object lib/LTO/CMakeFiles/LLVMLTO.dir/LTO.cpp.o
ninja: build stopped: subcommand failed.

```

</details>

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