This commit fixes a crash in `-reconcile-unrealized-casts` when cast ops
have multiple operands:
```
DialectConversion.cpp:1583: virtual void mlir::ConversionPatternRewriter::replaceOp(mlir::Operation *, mlir::ValueRange): Assertion `op->getNumResults() == newValues.size() && "incorrect # of replacement values"' failed.
```
This commit also generalizes the pass such that more ops are folded. In
particular (letters indicate types):
```
A
/ \
B C
|
A
```
Previously, such IR was not folded at all. The `A -> B -> A` type cast
cycle is now folded away. (The `A -> C` cast stays in place.)
This commit also turns the pass from a dialect conversion into a simple
IR walk. The pattern and its `populate` function are removed. The
pattern was a (non-conversion) rewrite pattern, but used in a dialect
conversion, which is generally not safe. In particular, the rewrite
pattern may traverse IR that was already scheduled for erasure by the
dialect conversion.
Note: Some test cases changed slightly (NFC) because the new pass
implementation no longer attempts to fold ops.
Note for LLVM integration: If your pipeline uses the removed `populate`
function, try to simply remove that function call. Chances are you may
not need it at all. If it is in fact needed, run the
`-reconcile-unrealized-casts` pass right after the pass that used to
populate the pattern.
---------
Co-authored-by: Maksim Levental <maksim.levental@gmail.com>
Co-authored-by: Markus Böck <markus.boeck02@gmail.com>
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