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llvm / llvm-project / 5d54a576fe0eecc37e318eb883bfbcc42f76ffb8
commit5d54a576fe0eecc37e318eb883bfbcc42f76ffb8[log] [tgz]
authorJim M. R. Teichgräber <Jim.Teichgraber@amd.com>Tue Aug 12 11:40:02 2025 +0100
committerGitHub <noreply@github.com>Tue Aug 12 19:40:02 2025 +0900
tree008163ba1977485ac169149777c14a9a0d97b181
parentca7ffaaeeb54bc350b8e48f4f35b68902dc9868c [diff]
[AMDGPU] AMDGPULateCodeGenPrepare Legacy PM: replace `setPreservesAll()` with `setPreservesCFG()` (#148167)

This PR depends on #148165; the first commit
(90f1d0a881a21a8b4f192622d798c290770fda63) belongs to that PR. The
changes are distinct, so separate PRs seemed like the best option. I
don't have commit access, so I couldn't use user-branches to mark the
dependency.

As AMDGPULateCodeGenPrepare actually performs changes that invalidate
Uniformity Analysis; use `setPreservesCFG()` to mark this, instead of
`setPreservesAll()` which wrongly includes preserving Uniformity
Analysis.

Note that before #148165, this would still have preserved Uniformity
Analysis, hence the dependency. In addition, `amdgpu/llc-pipeline.cc`
needs to be changed when both changes are in effect, but those changes
would make the test fail if the PRs weren't based on one another.

Note on why this hasn't caused issues so far:
It just so happens that AMDGPULateCodeGenPrepare is always immediately
followed by AMDGPUUnifyDivergentExitNodes, which *does* invalidate most
analyses, including Uniformity. And because UnifyDivergentExitNodes only
looks at terminators, and LateCGP seemingly does not replace uniform
values with divergent values, or divergent values with uniform values,
and it only *inserts new values that are not looked at by
UnifyDivergentExitNodes*, this bug remained hidden.

---

I ran `git-clang-format` on my changes. I tested them using the
`check-llvm` target; no unexpected failures occurred after I made the
change to `amdgpu/llc-pipeline.ll`.
2 files changed
tree: 008163ba1977485ac169149777c14a9a0d97b181
  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. polly/
  25. runtimes/
  26. third-party/
  27. utils/
  28. .clang-format
  29. .clang-format-ignore
  30. .clang-tidy
  31. .git-blame-ignore-revs
  32. .gitattributes
  33. .gitignore
  34. .mailmap
  35. CODE_OF_CONDUCT.md
  36. CONTRIBUTING.md
  37. LICENSE.TXT
  38. pyproject.toml
  39. README.md
  40. SECURITY.md
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