[Mlir-commits] [mlir] [MLIR] Add single definition multiple regions for mem2reg (PR #89107)

[Christian Ulmann]

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@@ -297,14 +313,52 @@ LogicalResult MemorySlotPromotionAnalyzer::computeBlockingUses(
     }
   }
 
-  // Because this pass currently only supports analysing the parent region of
-  // the slot pointer, if a promotable memory op that needs promotion is outside
-  // of this region, promotion must fail because it will be impossible to
-  // provide a valid `reachingDef` for it.
-  for (auto &[toPromote, _] : userToBlockingUses)
+  // The define uses web only have one definition, It is the potential case.
+  totalStores != 1 ? singleDefining.setPointer(nullptr) : (void)0;
+
+  // The single definition can not dominate all of the uses, there are some
+  // uses need default value and block arguments. But current dominate
+  // frontier algorithms only support single region, so failed.
+  auto leagelSingleDefiningMultiRegions = [this](BlockingUsesMap &userMap) {
+    if (singleDefining.getPointer() == nullptr)
+      return failure();
+
+    // The single definition dominate all the uses, we can ignore whether
+    // all of the uses and definotion in a same region.
+    for (auto &[user, _] : userMap)
+      if (!dominance.dominates(singleDefining.getPointer(), user))
+        return failure();
+    // The same region case is fail in here we can konwn, clear the bool value
+    // of `singleDefing`, otherwise we may confuse weather same region or single
+    // define multiple region. Place this above return success() because when
+    // return failure() there is not any afterwards, will clear everything
+    // prepare the next slot.
+    singleDefining.setInt(false);
+    return success();
+  };
+
+  // Because we will first check weather def-uses at same region, if this
+  // success, we will missing the opportunity clear the pointer value
+  // of`singleDefinig`, so we need to known weather this is the same region case
+  // in the code afterward. If same region check fails, this value will been
+  // clear at the single defining multiple regions case.
+  singleDefining.setInt(true);
+  // Because this pass currently only supports has only one defining operation
+  // for the , slot or analysing the parent region of the slot pointer, if a
+  // promotable memory op that needs promotion is outside of this region,
+  // promotion must fail because it will be impossible to provide a valid
+  // `reachingDef` for it.
+  for (auto &[toPromote, _] : userToBlockingUses) {
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Dinistro wrote:

`llvm::make_first_range` helps with such things.

https://github.com/llvm/llvm-project/pull/89107