[InstCombine] Fold redundant FP clamp selects; relax min-max-pattern bailout in visitFCmp (#173452)

visitFCmp() previously bailed out when a following select matched a
clamp pattern. This blocks simplifications when the clamp is provably
redundant.

This PR allows simplification for clamp selects of flavor SPF_FMAXNUM/
SPF_FMINNUM when one arm is a constant and the other is a sitofp/uitofp
of an integer value, and the constant equals the exact min/max of that
integer domain:
* SPF_FMAXNUM (pattern max(X,C)): redundant if C is the minimum integer
mapped exactly to FP (e.g. X = sitofp i8, C = -128.0f).
* SPF_FMINNUM (pattern min(X,C)): redundant if C is the maximum integer
mapped exactly to FP (e.g. X = uitofp i8, C = 255.0f).

This fixes a regression in #173454

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Yingwei Zheng <dtcxzyw@qq.com>
2 files changed
tree: 80456419f3904173f6b415a27fa342e8b78f57a9
  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
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