Reapply "[utils][UpdateLLCTestChecks] Add MIR support to update_llc_test_checks.py." (#164965) (#166575)

This change enables update_llc_test_checks.py to automatically generate
MIR checks for RUN lines that use `-stop-before` or `-stop-after` flags
allowing tests to verify intermediate compilation stages (e.g., after
instruction selection but before peephole optimizations) alongside the
final assembly output. If `-debug-only` flag is present in the run line it's
considered as the main point of interest for testing and stop flags above
are ignored (that is no MIR checks are generated).

This resulted from the scenario, when I needed to test two instruction
matching patterns where the later pattern in the peepholer reverts the
earlier pattern in the instruction selector and distinguish it from the
case when the earlier pattern didn't worked at all.

Initially created by Claude Sonnet 4.5 it was improved later to handle
conflicts in MIR <-> ASM prefixes and formatting.
9 files changed
tree: 8d69cef820c5e17b6a280ce04f5ab39c75def98f
  1. .ci/
  2. .github/
  3. bolt/
  4. clang/
  5. clang-tools-extra/
  6. cmake/
  7. compiler-rt/
  8. cross-project-tests/
  9. flang/
  10. flang-rt/
  11. libc/
  12. libclc/
  13. libcxx/
  14. libcxxabi/
  15. libsycl/
  16. libunwind/
  17. lld/
  18. lldb/
  19. llvm/
  20. llvm-libgcc/
  21. mlir/
  22. offload/
  23. openmp/
  24. orc-rt/
  25. polly/
  26. runtimes/
  27. third-party/
  28. utils/
  29. .clang-format
  30. .clang-format-ignore
  31. .clang-tidy
  32. .git-blame-ignore-revs
  33. .gitattributes
  34. .gitignore
  35. .mailmap
  36. CODE_OF_CONDUCT.md
  37. CONTRIBUTING.md
  38. LICENSE.TXT
  39. pyproject.toml
  40. README.md
  41. SECURITY.md
README.md

The LLVM Compiler Infrastructure

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Welcome to the LLVM project!

This repository contains the source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and run-time environments.

The LLVM project has multiple components. The core of the project is itself called “LLVM”. This contains all of the tools, libraries, and header files needed to process intermediate representations and convert them into object files. Tools include an assembler, disassembler, bitcode analyzer, and bitcode optimizer.

C-like languages use the Clang frontend. This component compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode -- and from there into object files, using LLVM.

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