[Mlir-commits] [mlir] [MLIR] Prevent CF to SCF transform from erasing blocks still in use (PR #206310)

[Martin P]

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@@ -1234,10 +1234,24 @@ static ReturnLikeExitCombiner createSingleExitBlocksForReturnLike(
 /// Returns failure if any precondition is violated.
 static LogicalResult
 checkTransformationPreconditions(Region &region, CFGToSCFInterface &interface) {
-  for (Block &block : region.getBlocks())
-    if (block.hasNoPredecessors() && !block.isEntryBlock())
+  const auto reachableBlocks = [&region] {
+    SmallVector<Block *, 16> workList = {&region.front()};
+    SmallPtrSet<Block *, 16> visited = {&region.front()};
+    while (!workList.empty()) {
+      Block *current = workList.pop_back_val();
+      for (Block *succ : current->getSuccessors()) {
+        if (visited.insert(succ).second) {
+          workList.push_back(succ);
+        }
+      }
+    }
+    return visited;
+  }();
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pechy wrote:

neat

https://github.com/llvm/llvm-project/pull/206310