[llvm] [Support] Store dominator tree nodes in a vector (PR #101705)

[Alexis Engelke via llvm-commits]

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@@ -0,0 +1,109 @@
+//===- unittests/Support/GenericDomTreeTest.cpp - GenericDomTree.h tests --===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/GenericDomTree.h"
+#include "llvm/ADT/GraphTraits.h"
+#include "llvm/Support/DataTypes.h"
+#include "gtest/gtest.h"
+using namespace llvm;
+
+namespace {
+
+// Very simple (fake) graph structure to test dominator tree on.
+struct NumberedGraph;
+
+struct NumberedNode {
+  NumberedGraph *Parent;
+  unsigned Number;
+
+  NumberedNode(NumberedGraph *Parent, unsigned Number)
+      : Parent(Parent), Number(Number) {}
+
+  NumberedGraph *getParent() const { return Parent; }
+};
+
+struct NumberedGraph {
+  SmallVector<std::unique_ptr<NumberedNode>> Nodes;
+  unsigned NumberEpoch = 0;
+
+  NumberedNode *addNode() {
+    unsigned Num = Nodes.size();
+    return Nodes.emplace_back(std::make_unique<NumberedNode>(this, Num)).get();
+  }
+};
+} // namespace
+
+namespace llvm {
+template <> struct GraphTraits<NumberedNode *> {
+  using NodeRef = NumberedNode *;
+  static unsigned getNumber(NumberedNode *Node) { return Node->Number; }
+};
+
+template <> struct GraphTraits<const NumberedNode *> {
+  using NodeRef = NumberedNode *;
+  static unsigned getNumber(const NumberedNode *Node) { return Node->Number; }
+};
+
+template <> struct GraphTraits<NumberedGraph *> {
+  using NodeRef = NumberedNode *;
+  static unsigned getMaxNumber(NumberedGraph *G) { return G->Nodes.size(); }
+  static unsigned getNumberEpoch(NumberedGraph *G) { return G->NumberEpoch; }
+};
+
+namespace DomTreeBuilder {
+// Dummy specialization. Only needed so that we can call recalculate(), which
+// sets DT.Parent -- but we can't access DT.Parent here.
+template <> void Calculate(DomTreeBase<NumberedNode> &DT) {}
+} // end namespace DomTreeBuilder
+} // end namespace llvm
+
+namespace {
+
+TEST(GenericDomTree, BlockNumbers) {
+  NumberedGraph G;
+  NumberedNode *N1 = G.addNode();
+  NumberedNode *N2 = G.addNode();
+
+  DomTreeBase<NumberedNode> DT;
+  DT.recalculate(G); // only sets parent
+  // Construct fake domtree: node 0 dominates all other nodes
+  DT.setNewRoot(N1);
+  DT.addNewBlock(N2, N1);
+
+  // Roundtrip is correct
+  for (auto &N : G.Nodes)
+    EXPECT_EQ(DT.getNode(N.get())->getBlock(), N.get());
+  // If we manually change a number, we should get a different node.
+  ASSERT_EQ(N1->Number, 0u);
+  ASSERT_EQ(N2->Number, 1u);
+  N1->Number = 1;
+  EXPECT_EQ(DT.getNode(N1)->getBlock(), N2);
+  EXPECT_EQ(DT.getNode(N2)->getBlock(), N2);
+  N2->Number = 0;
+  EXPECT_EQ(DT.getNode(N2)->getBlock(), N1);
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aengelke wrote:

It's the only test that actually makes sure that block numbers are used in the dominator tree...

https://github.com/llvm/llvm-project/pull/101705