[TSAR, Transform] Add a pass to remove redundant edges in a CFG.

Author: yukatan1701

include/tsar/Transform/IR/RedundantEdgeElimination.h

@@ -0,0 +1,46 @@
+//===- RedundantEdgeElimination.h - Redundant Edge Elimination --*- C++ -*-===//
+//
+//                       Traits Static Analyzer (SAPFOR)
+//
+// Copyright 2018 DVM System Group
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a pass to replace the always true conditional branch
+// instructions with an unconditional branch instruction.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef TSAR_REDUNDANT_EDGE_ELIMINATION_H
+#define TSAR_REDUNDANT_EDGE_ELIMINATION_H
+
+#include "tsar/Transform/IR/Passes.h"
+#include <bcl/utility.h>
+#include <llvm/Pass.h>
+
+namespace llvm {
+class RedundantEdgeEliminationPass :
+    public FunctionPass, private bcl::Uncopyable {
+public:
+  static char ID;
+
+  RedundantEdgeEliminationPass() : FunctionPass(ID) {
+    initializeRedundantEdgeEliminationPassPass(*PassRegistry::getPassRegistry());
+  }
+
+  bool runOnFunction(Function &F) override;
+};
+}
+#endif//TSAR_REDUNDANT_EDGE_ELIMINATION_H

lib/Transform/IR/RedundantEdgeElimination.cpp

@@ -0,0 +1,67 @@
+//===-RedundantEdgeElimination.cpp - Redundant Edge Elimination -*- C++ -*-===//
+//
+//                       Traits Static Analyzer (SAPFOR)
+//
+// Copyright 2018 DVM System Group
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a pass to replace the always true conditional branch
+// instructions with an unconditional branch instruction.
+//
+//===----------------------------------------------------------------------===//
+
+#include "tsar/Transform/IR/RedundantEdgeElimination.h"
+#include <bcl/utility.h>
+#include <llvm/IR/Instructions.h>
+#include <llvm/Pass.h>
+#include <llvm/Support/Debug.h>
+#include <llvm/Transforms/Utils/BasicBlockUtils.h>
+
+#undef DEBUG_TYPE
+#define DEBUG_TYPE "red-edge"
+
+using namespace llvm;
+
+char RedundantEdgeEliminationPass::ID = 0;
+
+INITIALIZE_PASS_BEGIN(RedundantEdgeEliminationPass, "red-edge",
+  "Redundant Edge Elimination", true, false)
+INITIALIZE_PASS_END(RedundantEdgeEliminationPass, "red-edge",
+  "Redundant Edge Elimination", true, false)
+
+FunctionPass * llvm::createRedundantEdgeEliminationPass() {
+  return new RedundantEdgeEliminationPass;
+}
+
+bool RedundantEdgeEliminationPass::runOnFunction(Function &F) {
+  LLVM_DEBUG(dbgs() << "[REDUNDANT EDGE]: analyze " << F.getName() << "\n");
+  for (auto &BB : F.getBasicBlockList()) {
+    if (auto *TI = BB.getTerminator()) {
+      if (auto *BI = dyn_cast<BranchInst>(TI)) {
+        LLVM_DEBUG(dbgs() << "[REDUNDANT EDGE] instruction: "; BI->dump());
+        if (BI->isConditional() && isa<ConstantInt>(BI->getCondition())) {
+          ReplaceInstWithInst(
+              BI, cast<ConstantInt>(BI->getCondition())->equalsInt(0) ?
+                  BranchInst::Create(BI->getSuccessor(1)) :
+                  BranchInst::Create(BI->getSuccessor(0)));
+          LLVM_DEBUG(dbgs() << "[REDUNDANT EDGE] after: "; BB.dump());
+        }
+      }
+    }
+  }
+  LLVM_DEBUG(dbgs() << "[REDUNDANT EDGE]: leave " << F.getName() << "\n");
+  return true;
+}