[MLIR][Affine] Fix null operands in simplifyConstrainedMinMaxOp (#189246)

`mlir::affine::simplifyConstrainedMinMaxOp` called
`canonicalizeMapAndOperands` with `newOperands` that could contain null
`Value()`s. These nulls came from
`unpackOptionalValues(constraints.getMaybeValues(), newOperands)` where
internal constraint variables added by `appendDimVar` (for `dimOp`,
`dimOpBound`, and `resultDimStart*`) have no associated SSA values.

Passing null Values to `canonicalizeMapAndOperands` risks undefined
behavior:
- `seenDims.find(null_value)` in the DenseMap causes all null operands
to collide at the same key, producing incorrect dim remapping.
- Any null operand that remains referenced in the result map would
propagate as a null Value into `AffineValueMap`, crashing callers that
try to use those operands to create ops.

Fix: Before calling `canonicalizeMapAndOperands`, filter null operands
from `newOperands` by replacing their dim/symbol positions in `newMap`
with constant 0 (safe because internal constraint dims should not appear
in the bound map expression) and compacting `newOperands` to contain
only non-null Values.

Fixes #127436

Assisted-by: Claude Code
2 files changed
tree: 96ae860852196d9557c4ddd72db72b86f0eb5490
  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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