[RISCV] Accept c.slli/c.srli/c.srli with a 0 immediate as hints. (#150689)

These encodings were previously assigned to c.slli64/srli64/srai64, and
designated as hints for RV32 and RV64. Those mnemonics no longer appear
in the ISA manual after RV128 was removed. The spec now says that
c.slli/c.srli/c.srai with an immediate of 0 is a hint.

This patch updates the assembler to accept this. I've left the old
spelling for backwards compatibility but we disassemble a shift with a
zero immediate. The C_SLLI64_HINT/C_SRLI_HINT/C_SRAI_HINT instructions
are removed and the predicates for C_SLLI/C_SRLI/C_SRAI not accept a 0
immediate.

Fixes #150304
6 files changed
tree: 7a1d21973bf721a6393f54684a5fce38f6e997bb
  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. libunwind/
  16. lld/
  17. lldb/
  18. llvm/
  19. llvm-libgcc/
  20. mlir/
  21. offload/
  22. openmp/
  23. polly/
  24. runtimes/
  25. third-party/
  26. utils/
  27. .clang-format
  28. .clang-format-ignore
  29. .clang-tidy
  30. .git-blame-ignore-revs
  31. .gitattributes
  32. .gitignore
  33. .mailmap
  34. CODE_OF_CONDUCT.md
  35. CONTRIBUTING.md
  36. LICENSE.TXT
  37. pyproject.toml
  38. README.md
  39. SECURITY.md
README.md

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