[Mlir-commits] [mlir] [mlir] Add option to run CSE between greedy rewriter iterations (PR #193081)

[Hocky Yudhiono]

================
@@ -899,6 +901,15 @@ LogicalResult RegionPatternRewriteDriver::simplify(bool *changed) && {
           }
         },
         {&region}, iteration);
+
+    // Optionally run full CSE between iterations. If CSE changes the IR we
+    // iterate again so that patterns can fire on the deduplicated operations.
+    if (config.isCSEBetweenIterationsEnabled()) {
+      DominanceInfo domInfo(region.getParentOp());
+      bool cseChanged = false;
+      eliminateCommonSubExpressions(rewriter, domInfo, region, &cseChanged);
+      continueRewrites |= cseChanged;
+    }
----------------
hockyy wrote:

https://github.com/llvm/llvm-project/blob/main/mlir/include/mlir/Transforms/GreedyPatternRewriteDriver.h#L167

Based on this docs:
```
/// Only in-scope ops are added to the
/// worklist and only in-scope ops are allowed to be modified by the patterns.
```

Technically CSE'ing would remove and modify out-of-scope ops(?) Because CSE would call the replaced/erase notifier right?

https://github.com/llvm/llvm-project/pull/193081