[RISCV] Fix i64 gather/scatter cost on rv32 (#176105)

Fixes #175909

We compute the cost of a gather/scatter by multiplying the cost of the
scalar element type memory op by the estimated number of elements. On
rv32 though a scalar i64 load costs 2, even if we have zve64x.

This causes the cost to diverge between a vector of f64 and vector of
i64, even though both are the same. This fixes it by just using
TTI::TCC_Basic as the scalar memory op cost. The element type is checked
to be legal at this point.

I think we have the same issue for the strided op cost, but we don't
have test coverage for it yet.

(cherry picked from commit 0c1257cd46456513016b106d964dc5ad47c6289b)
3 files changed
tree: 41642c26cc64de6f7f206cab7cb200c819c4b639
  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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