-ftime-report: reorganize timers

The code generation time is unclear in the -ftime-report output:

* The two clang timers "Code Generation Time" and "LLVM IR Generation
  Time" are in the default group "Miscellaneous Ungrouped Timers".
* There is also a "Clang front-end time" group, which actually includes
  code generation time.

```
===-------------------------------------------------------------------------===
                         Miscellaneous Ungrouped Timers
===-------------------------------------------------------------------------===

   ---User Time---   --System Time--   --User+System--   ---Wall Time---  --- Name ---
   0.0611 (  1.7%)   0.0099 (  4.4%)   0.0710 (  1.9%)   0.0713 (  1.9%)  LLVM IR Generation Time
   3.5140 ( 98.3%)   0.2165 ( 95.6%)   3.7306 ( 98.1%)   3.7342 ( 98.1%)  Code Generation Time
   3.5751 (100.0%)   0.2265 (100.0%)   3.8016 (100.0%)   3.8055 (100.0%)  Total
...
===-------------------------------------------------------------------------===
                          Clang front-end time report
===-------------------------------------------------------------------------===
  Total Execution Time: 3.9108 seconds (3.9146 wall clock)

   ---User Time---   --System Time--   --User+System--   ---Wall Time---  --- Name ---
   3.6802 (100.0%)   0.2306 (100.0%)   3.9108 (100.0%)   3.9146 (100.0%)  Clang front-end timer
   3.6802 (100.0%)   0.2306 (100.0%)   3.9108 (100.0%)   3.9146 (100.0%)  Total
```

This patch

* renames "Clang front-end time report" (FrontendAction time) to "Clang
  time report",
* renames "Clang front-end" to "Front end",
* moves "LLVM IR Generation" into the group,
* replaces "Code Generation time" with "Optimizer" (middle end) and
  "Machine code generation" (back end).

```
% clang -c sqlite3.i -w -ftime-report -mllvm -sort-timers=0
...
===-------------------------------------------------------------------------===
                               Clang time report
===-------------------------------------------------------------------------===
  Total Execution Time: 1.5922 seconds (1.5972 wall clock)

   ---User Time---   --System Time--   --User+System--   ---Wall Time---  --- Name ---
   0.5107 ( 35.9%)   0.0105 (  6.2%)   0.5211 ( 32.7%)   0.5222 ( 32.7%)  Front end
   0.2464 ( 17.3%)   0.0340 ( 20.0%)   0.2804 ( 17.6%)   0.2814 ( 17.6%)  LLVM IR generation
   0.6240 ( 43.9%)   0.1235 ( 72.7%)   0.7475 ( 47.0%)   0.7503 ( 47.0%)  Machine code generation
   0.0413 (  2.9%)   0.0018 (  1.0%)   0.0431 (  2.7%)   0.0433 (  2.7%)  Optimizer
   1.4224 (100.0%)   0.1698 (100.0%)   1.5922 (100.0%)   1.5972 (100.0%)  Total
```

Pull Request: https://github.com/llvm/llvm-project/pull/122225
8 files changed
tree: 573b0ec23d72e7765236a997d963ebe797a2c8ef
  1. .ci/
  2. .github/
  3. bolt/
  4. clang/
  5. clang-tools-extra/
  6. cmake/
  7. compiler-rt/
  8. cross-project-tests/
  9. flang/
  10. libc/
  11. libclc/
  12. libcxx/
  13. libcxxabi/
  14. libunwind/
  15. lld/
  16. lldb/
  17. llvm/
  18. llvm-libgcc/
  19. mlir/
  20. offload/
  21. openmp/
  22. polly/
  23. pstl/
  24. runtimes/
  25. third-party/
  26. utils/
  27. .clang-format
  28. .clang-tidy
  29. .git-blame-ignore-revs
  30. .gitattributes
  31. .gitignore
  32. .mailmap
  33. CODE_OF_CONDUCT.md
  34. CONTRIBUTING.md
  35. LICENSE.TXT
  36. pyproject.toml
  37. README.md
  38. SECURITY.md
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