[Mlir-commits] [mlir] [mlir][Affine] Fix loadCSE replacing a load with one already scheduled for erasure (PR #217511)

[Federico Bruzzone]

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@@ -1034,3 +1034,45 @@ func.func @vector_store_dead_elim_same_type(%arg0: memref<20x1xi64>) {
   affine.vector_store %cst2, %arg0[%c0, %c0] : memref<20x1xi64>, vector<5xi64>
   return
 }
+
+// Regression test for https://github.com/llvm/llvm-project/issues/216916:
+// loadCSE must not replace a load with a dominating, equivalent load that
+// has itself already been scheduled for erasure earlier in the same walk.
+// Doing so used to leave a load's uses pointing at an operation that was
+// about to be destroyed, which crashed with "operation destroyed but still
+// has uses". %a and %b below read the same, never-overwritten location
+// (%m[3]; the store only touches %m[0]) and dominate one another, so they
+// are redundant and must be CSE'd down to a single load without crashing.
+// %c reads the same location from inside the loop body: it does not
+// dominate (nor is dominated by) %a/%b in the same way, so loadCSE
+// conservatively leaves it as a separate load — this test only asserts
+// that doing so does not crash.
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FedericoBruzzone wrote:

AI tends to write very verbose comments for tests. Although a brief comment is sometimes necessary for tests as well, I don't think it is needed in this case.

Can we remove it?

https://github.com/llvm/llvm-project/pull/217511