[all-commits] [llvm/llvm-project] 456526: [mlir][SCF] `ValueBoundsConstraintSet`: Support pr...

[Matthias Springer via All-commits]

  Branch: refs/heads/users/matthias-springer/value_bounds_scf_if
  Home:   https://github.com/llvm/llvm-project
  Commit: 456526da09e835bb8f7f896a06b26da45a070cb8
      https://github.com/llvm/llvm-project/commit/456526da09e835bb8f7f896a06b26da45a070cb8
  Author: Matthias Springer <springerm at google.com>
  Date:   2024-03-20 (Wed, 20 Mar 2024)

  Changed paths:
    M mlir/include/mlir/Interfaces/ValueBoundsOpInterface.h
    M mlir/lib/Dialect/SCF/IR/ValueBoundsOpInterfaceImpl.cpp
    M mlir/lib/Interfaces/ValueBoundsOpInterface.cpp
    M mlir/test/Dialect/SCF/value-bounds-op-interface-impl.mlir

  Log Message:
  -----------
  [mlir][SCF] `ValueBoundsConstraintSet`: Support preliminary support for branches

This commit adds support for `scf.if` to `ValueBoundsConstraintSet`.

Example:
```
%0 = scf.if ... -> index {
  scf.yield %a : index
} else {
  scf.yield %b : index
}
```

The following constraints hold for %0:
* %0 >= min(%a, %b)
* %0 <= max(%a, %b)

Such constraints cannot be added to the constraint set; min/max is not supported by `IntegerRelation`. However, if we know which one of %a and %b is larger, we can add constraints for %0. E.g., if %a <= %b:
* %0 >= %a
* %0 <= %b

This commit required a few minor changes to the `ValueBoundsConstraintSet` infrastructure, so that values can be compared while we are still in the process of traversing the IR/adding constraints.



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