[Mlir-commits] [mlir] [mlir][ArmSME] Use liveness information in the tile allocator (PR #90448)

[Benjamin Maxwell]

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@@ -116,4 +116,50 @@ VectorType getSMETileTypeForElement(Type elementType) {
   return VectorType::get({minNumElts, minNumElts}, elementType, {true, true});
 }
 
+void eraseTriviallyDeadTileOps(IRRewriter &rewriter,
+                               FunctionOpInterface function) {
+  SmallVector<Operation *> worklist;
+  function->walk([&](Operation *op) {
+    auto armSMEOp = dyn_cast<arm_sme::ArmSMETileOpInterface>(op);
+    if (armSMEOp && isOpTriviallyDead(armSMEOp))
+      worklist.push_back(armSMEOp);
+  });
+  while (!worklist.empty()) {
+    Operation *op = worklist.pop_back_val();
+    if (!isOpTriviallyDead(op))
+      continue;
+    for (Value value : op->getOperands()) {
+      if (auto armSMEOp = value.getDefiningOp<arm_sme::ArmSMETileOpInterface>())
+        worklist.push_back(armSMEOp);
+    }
+    rewriter.eraseOp(op);
+  }
+}
+
+bool isTriviallyCloneableTileOp(arm_sme::ArmSMETileOpInterface tileOp) {
+  return tileOp && tileOp->getNumResults() == 1 &&
+         tileOp->getNumOperands() == 0 && isPure(tileOp);
+}
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MacDue wrote:

It could have side-effects or inputs. 

- If it has inputs you may need to consider those too (and clone them)
- If it has side-effects you don't know how moving the operation could change the semantics of the program

Both cases seem non-trivial to me :)

https://github.com/llvm/llvm-project/pull/90448