[SelectionDAG] Use Magic Algorithm for Splitting UDIV/UREM by Constant (#154968)

For integer types twice as large as a legal type, we have previously
generated a library call if another splitting technique was not
applicable.
    
With this change, we use an adaption of the Magic algorithm. This
algorithm is also used for UDIV/UREM by constants on legal types. The
implementation introduced here is a simple port of the already existing
implementation to types twice the size of a legal type. The core idea of
this algorithm is to replace (udiv x c) for a constant c with the bits
higher or equal to the s-th bit of the multiplication of x by (2^s +
o)/c
for some s and o. More details are available in Henry S. Warren, Jr.:
"Hacker's Delight", chapter 10.
    
An efficient handling of UDIV/UREM by constants on types twice as large
as a legal type is mostly relevant for 32-bit platforms. But some
projects may also benefit on 64-bit platforms. For example, the `fmt`
library for C++ uses 128-bit unsigned divisions by 100 and 10000, which
have not been covered by the previously existing optimizations.
    
Closes #137514.
6 files changed
tree: 900135aaca62160e446aae7e79a3fad33af99c8f
  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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