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

[Alexis Engelke]

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@@ -600,14 +546,63 @@ void LoopInfoBase<BlockT, LoopT>::analyze(const DomTreeBase<BlockT> &DomTree) {
     }
     // Perform a backward CFG traversal to discover and map blocks in this loop.
     if (!Backedges.empty()) {
-      LoopT *L = AllocateLoop(Header);
-      discoverAndMapSubloop(L, ArrayRef<BlockT *>(Backedges), this, DomTree);
+      HasLoops = true;
+      LoopT *L = allocateLoop(Header);
+      discoverAndMapSubloop(L, Header, Backedges, DomTree);
+    }
+  }
+  // Most functions have no loops; skip the layout construction.
+  if (!HasLoops)
+    return;
+
+  // Record each in-loop block with its innermost loop in forward CFG postorder,
+  // and build the loop list in PO.
+  SmallVector<std::pair<BlockT *, LoopT *>, 32> PO;
+  SmallVector<LoopT *, 4> LoopsPO;
+  PO.reserve(BBMap.size());
+  for (BlockT *BB : post_order(DomRoot->getBlock())) {
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aengelke wrote:

Make ParentT a non const-derived pointer? (Not too important, but I personally hate that we have post_order<BasicBlock *>, post_order<const BasicBlock *>, post_order<Function *>, and post_order<const Function *> -- ending up in the binary doing 99.9% the same thing.)

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