[Mlir-commits] [llvm] [mlir] [LoopInfo] Store blocks using Euler tour representation (PR #211485)

[Alexis Engelke]

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@@ -636,6 +648,49 @@ template <class BlockT, class LoopT> class LoopInfoBase {
     return Number < BBMap.size() ? BBMap[Number] : nullptr;
   }
 
+  /// AllocateLoop for analyze(): stash \p Header (see pendingHeader).
+  /// getHeader() only works once the layout carve has replaced the stash with
+  /// the loop's block list.
+  LoopT *allocateLoop(BlockT *Header) {
+    LoopT *L = AllocateLoop();
+    L->BlockData = reinterpret_cast<BlockT **>(Header);
+    return L;
+  }
+
+  /// The header of a loop under construction, stashed in BlockData until the
+  /// layout carve builds the block list.
+  static BlockT *pendingHeader(const LoopT *L) {
+    return reinterpret_cast<BlockT *>(L->BlockData);
+  }
+
+  void discoverAndMapSubloop(LoopT *L, BlockT *Header,
+                             ArrayRef<BlockT *> Backedges,
+                             const DominatorTreeBase<BlockT, false> &DomTree);
+
+  /// True if \p L's block list is a borrowed slice of BlockLayout rather than
+  /// a private allocation.
+  bool hasBorrowedBlocks(const LoopT &L) const {
+    return L.BlockData >= BlockLayout.get() &&
+           L.BlockData < BlockLayout.get() + BlockLayoutLen;
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aengelke wrote:

This comparison is UB if not borrowed?

https://github.com/llvm/llvm-project/pull/211485