Update prebuilt Clang to r416183b from Android.

https://android.googlesource.com/platform/prebuilts/clang/host/
linux-x86/+/06a71ddac05c22edb2d10b590e1769b3f8619bef

clang 12.0.5 (based on r416183b) from build 7284624.

Change-Id: I277a316abcf47307562d8b748b84870f31a72866
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
diff --git a/linux-x64/clang/include/llvm/Analysis/DependenceGraphBuilder.h b/linux-x64/clang/include/llvm/Analysis/DependenceGraphBuilder.h
new file mode 100644
index 0000000..6f4e1be
--- /dev/null
+++ b/linux-x64/clang/include/llvm/Analysis/DependenceGraphBuilder.h
@@ -0,0 +1,203 @@
+//===- llvm/Analysis/DependenceGraphBuilder.h -------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a builder interface that can be used to populate dependence
+// graphs such as DDG and PDG.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_DEPENDENCE_GRAPH_BUILDER_H
+#define LLVM_ANALYSIS_DEPENDENCE_GRAPH_BUILDER_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/EquivalenceClasses.h"
+#include "llvm/ADT/SmallVector.h"
+
+namespace llvm {
+
+class BasicBlock;
+class DependenceInfo;
+class Instruction;
+
+/// This abstract builder class defines a set of high-level steps for creating
+/// DDG-like graphs. The client code is expected to inherit from this class and
+/// define concrete implementation for each of the pure virtual functions used
+/// in the high-level algorithm.
+template <class GraphType> class AbstractDependenceGraphBuilder {
+protected:
+  using BasicBlockListType = SmallVectorImpl<BasicBlock *>;
+
+private:
+  using NodeType = typename GraphType::NodeType;
+  using EdgeType = typename GraphType::EdgeType;
+
+public:
+  using ClassesType = EquivalenceClasses<BasicBlock *>;
+  using NodeListType = SmallVector<NodeType *, 4>;
+
+  AbstractDependenceGraphBuilder(GraphType &G, DependenceInfo &D,
+                                 const BasicBlockListType &BBs)
+      : Graph(G), DI(D), BBList(BBs) {}
+  virtual ~AbstractDependenceGraphBuilder() {}
+
+  /// The main entry to the graph construction algorithm. It starts by
+  /// creating nodes in increasing order of granularity and then
+  /// adds def-use and memory edges. As one of the final stages, it
+  /// also creates pi-block nodes to facilitate codegen in transformations
+  /// that use dependence graphs.
+  ///
+  /// The algorithmic complexity of this implementation is O(V^2 * I^2), where V
+  /// is the number of vertecies (nodes) and I is the number of instructions in
+  /// each node. The total number of instructions, N, is equal to V * I,
+  /// therefore the worst-case time complexity is O(N^2). The average time
+  /// complexity is O((N^2)/2).
+  void populate() {
+    computeInstructionOrdinals();
+    createFineGrainedNodes();
+    createDefUseEdges();
+    createMemoryDependencyEdges();
+    simplify();
+    createAndConnectRootNode();
+    createPiBlocks();
+    sortNodesTopologically();
+  }
+
+  /// Compute ordinal numbers for each instruction and store them in a map for
+  /// future look up. These ordinals are used to compute node ordinals which are
+  /// in turn used to order nodes that are part of a cycle.
+  /// Instruction ordinals are assigned based on lexical program order.
+  void computeInstructionOrdinals();
+
+  /// Create fine grained nodes. These are typically atomic nodes that
+  /// consist of a single instruction.
+  void createFineGrainedNodes();
+
+  /// Analyze the def-use chains and create edges from the nodes containing
+  /// definitions to the nodes containing the uses.
+  void createDefUseEdges();
+
+  /// Analyze data dependencies that exist between memory loads or stores,
+  /// in the graph nodes and create edges between them.
+  void createMemoryDependencyEdges();
+
+  /// Create a root node and add edges such that each node in the graph is
+  /// reachable from the root.
+  void createAndConnectRootNode();
+
+  /// Apply graph abstraction to groups of nodes that belong to a strongly
+  /// connected component of the graph to create larger compound nodes
+  /// called pi-blocks. The purpose of this abstraction is to isolate sets of
+  /// program elements that need to stay together during codegen and turn
+  /// the dependence graph into an acyclic graph.
+  void createPiBlocks();
+
+  /// Go through all the nodes in the graph and collapse any two nodes
+  /// 'a' and 'b' if all of the following are true:
+  ///   - the only edge from 'a' is a def-use edge to 'b' and
+  ///   - the only edge to 'b' is a def-use edge from 'a' and
+  ///   - there is no cyclic edge from 'b' to 'a' and
+  ///   - all instructions in 'a' and 'b' belong to the same basic block and
+  ///   - both 'a' and 'b' are simple (single or multi instruction) nodes.
+  void simplify();
+
+  /// Topologically sort the graph nodes.
+  void sortNodesTopologically();
+
+protected:
+  /// Create the root node of the graph.
+  virtual NodeType &createRootNode() = 0;
+
+  /// Create an atomic node in the graph given a single instruction.
+  virtual NodeType &createFineGrainedNode(Instruction &I) = 0;
+
+  /// Create a pi-block node in the graph representing a group of nodes in an
+  /// SCC of the graph.
+  virtual NodeType &createPiBlock(const NodeListType &L) = 0;
+
+  /// Create a def-use edge going from \p Src to \p Tgt.
+  virtual EdgeType &createDefUseEdge(NodeType &Src, NodeType &Tgt) = 0;
+
+  /// Create a memory dependence edge going from \p Src to \p Tgt.
+  virtual EdgeType &createMemoryEdge(NodeType &Src, NodeType &Tgt) = 0;
+
+  /// Create a rooted edge going from \p Src to \p Tgt .
+  virtual EdgeType &createRootedEdge(NodeType &Src, NodeType &Tgt) = 0;
+
+  /// Given a pi-block node, return a vector of all the nodes contained within
+  /// it.
+  virtual const NodeListType &getNodesInPiBlock(const NodeType &N) = 0;
+
+  /// Deallocate memory of edge \p E.
+  virtual void destroyEdge(EdgeType &E) { delete &E; }
+
+  /// Deallocate memory of node \p N.
+  virtual void destroyNode(NodeType &N) { delete &N; }
+
+  /// Return true if creation of pi-blocks are supported and desired,
+  /// and false otherwise.
+  virtual bool shouldCreatePiBlocks() const { return true; }
+
+  /// Return true if graph simplification step is requested, and false
+  /// otherwise.
+  virtual bool shouldSimplify() const { return true; }
+
+  /// Return true if it's safe to merge the two nodes.
+  virtual bool areNodesMergeable(const NodeType &A,
+                                 const NodeType &B) const = 0;
+
+  /// Append the content of node \p B into node \p A and remove \p B and
+  /// the edge between \p A and \p B from the graph.
+  virtual void mergeNodes(NodeType &A, NodeType &B) = 0;
+
+  /// Given an instruction \p I return its associated ordinal number.
+  size_t getOrdinal(Instruction &I) {
+    assert(InstOrdinalMap.find(&I) != InstOrdinalMap.end() &&
+           "No ordinal computed for this instruction.");
+    return InstOrdinalMap[&I];
+  }
+
+  /// Given a node \p N return its associated ordinal number.
+  size_t getOrdinal(NodeType &N) {
+    assert(NodeOrdinalMap.find(&N) != NodeOrdinalMap.end() &&
+           "No ordinal computed for this node.");
+    return NodeOrdinalMap[&N];
+  }
+
+  /// Map types to map instructions to nodes used when populating the graph.
+  using InstToNodeMap = DenseMap<Instruction *, NodeType *>;
+
+  /// Map Types to map instruction/nodes to an ordinal number.
+  using InstToOrdinalMap = DenseMap<Instruction *, size_t>;
+  using NodeToOrdinalMap = DenseMap<NodeType *, size_t>;
+
+  /// Reference to the graph that gets built by a concrete implementation of
+  /// this builder.
+  GraphType &Graph;
+
+  /// Dependence information used to create memory dependence edges in the
+  /// graph.
+  DependenceInfo &DI;
+
+  /// The list of basic blocks to consider when building the graph.
+  const BasicBlockListType &BBList;
+
+  /// A mapping from instructions to the corresponding nodes in the graph.
+  InstToNodeMap IMap;
+
+  /// A mapping from each instruction to an ordinal number. This map is used to
+  /// populate the \p NodeOrdinalMap.
+  InstToOrdinalMap InstOrdinalMap;
+
+  /// A mapping from nodes to an ordinal number. This map is used to sort nodes
+  /// in a pi-block based on program order.
+  NodeToOrdinalMap NodeOrdinalMap;
+};
+
+} // namespace llvm
+
+#endif // LLVM_ANALYSIS_DEPENDENCE_GRAPH_BUILDER_H