1 files changed, 145 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/MachineDominators.cpp b/llvm/lib/CodeGen/MachineDominators.cpp
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index 000000000000..706c706d7527
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+++ b/llvm/lib/CodeGen/MachineDominators.cpp
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+//===- MachineDominators.cpp - Machine Dominator Calculation --------------===//
+//
+// 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 implements simple dominator construction algorithms for finding
+// forward dominators on machine functions.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/ADT/SmallBitVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Support/CommandLine.h"
+
+using namespace llvm;
+
+namespace llvm {
+// Always verify dominfo if expensive checking is enabled.
+#ifdef EXPENSIVE_CHECKS
+bool VerifyMachineDomInfo = true;
+#else
+bool VerifyMachineDomInfo = false;
+#endif
+} // namespace llvm
+
+static cl::opt<bool, true> VerifyMachineDomInfoX(
+    "verify-machine-dom-info", cl::location(VerifyMachineDomInfo), cl::Hidden,
+    cl::desc("Verify machine dominator info (time consuming)"));
+
+namespace llvm {
+template class DomTreeNodeBase<MachineBasicBlock>;
+template class DominatorTreeBase<MachineBasicBlock, false>; // DomTreeBase
+}
+
+char MachineDominatorTree::ID = 0;
+
+INITIALIZE_PASS(MachineDominatorTree, "machinedomtree",
+                "MachineDominator Tree Construction", true, true)
+
+char &llvm::MachineDominatorsID = MachineDominatorTree::ID;
+
+void MachineDominatorTree::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.setPreservesAll();
+  MachineFunctionPass::getAnalysisUsage(AU);
+}
+
+bool MachineDominatorTree::runOnMachineFunction(MachineFunction &F) {
+  CriticalEdgesToSplit.clear();
+  NewBBs.clear();
+  DT.reset(new DomTreeBase<MachineBasicBlock>());
+  DT->recalculate(F);
+  return false;
+}
+
+MachineDominatorTree::MachineDominatorTree()
+    : MachineFunctionPass(ID) {
+  initializeMachineDominatorTreePass(*PassRegistry::getPassRegistry());
+}
+
+void MachineDominatorTree::releaseMemory() {
+  CriticalEdgesToSplit.clear();
+  DT.reset(nullptr);
+}
+
+void MachineDominatorTree::verifyAnalysis() const {
+  if (DT && VerifyMachineDomInfo)
+    if (!DT->verify(DomTreeT::VerificationLevel::Basic)) {
+      errs() << "MachineDominatorTree verification failed\n";
+      abort();
+    }
+}
+
+void MachineDominatorTree::print(raw_ostream &OS, const Module*) const {
+  if (DT)
+    DT->print(OS);
+}
+
+void MachineDominatorTree::applySplitCriticalEdges() const {
+  // Bail out early if there is nothing to do.
+  if (CriticalEdgesToSplit.empty())
+    return;
+
+  // For each element in CriticalEdgesToSplit, remember whether or not element
+  // is the new immediate domminator of its successor. The mapping is done by
+  // index, i.e., the information for the ith element of CriticalEdgesToSplit is
+  // the ith element of IsNewIDom.
+  SmallBitVector IsNewIDom(CriticalEdgesToSplit.size(), true);
+  size_t Idx = 0;
+
+  // Collect all the dominance properties info, before invalidating
+  // the underlying DT.
+  for (CriticalEdge &Edge : CriticalEdgesToSplit) {
+    // Update dominator information.
+    MachineBasicBlock *Succ = Edge.ToBB;
+    MachineDomTreeNode *SuccDTNode = DT->getNode(Succ);
+
+    for (MachineBasicBlock *PredBB : Succ->predecessors()) {
+      if (PredBB == Edge.NewBB)
+        continue;
+      // If we are in this situation:
+      // FromBB1        FromBB2
+      //    +              +
+      //   + +            + +
+      //  +   +          +   +
+      // ...  Split1  Split2 ...
+      //           +   +
+      //            + +
+      //             +
+      //            Succ
+      // Instead of checking the domiance property with Split2, we check it with
+      // FromBB2 since Split2 is still unknown of the underlying DT structure.
+      if (NewBBs.count(PredBB)) {
+        assert(PredBB->pred_size() == 1 && "A basic block resulting from a "
+                                           "critical edge split has more "
+                                           "than one predecessor!");
+        PredBB = *PredBB->pred_begin();
+      }
+      if (!DT->dominates(SuccDTNode, DT->getNode(PredBB))) {
+        IsNewIDom[Idx] = false;
+        break;
+      }
+    }
+    ++Idx;
+  }
+
+  // Now, update DT with the collected dominance properties info.
+  Idx = 0;
+  for (CriticalEdge &Edge : CriticalEdgesToSplit) {
+    // We know FromBB dominates NewBB.
+    MachineDomTreeNode *NewDTNode = DT->addNewBlock(Edge.NewBB, Edge.FromBB);
+
+    // If all the other predecessors of "Succ" are dominated by "Succ" itself
+    // then the new block is the new immediate dominator of "Succ". Otherwise,
+    // the new block doesn't dominate anything.
+    if (IsNewIDom[Idx])
+      DT->changeImmediateDominator(DT->getNode(Edge.ToBB), NewDTNode);
+    ++Idx;
+  }
+  NewBBs.clear();
+  CriticalEdgesToSplit.clear();
+}