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diff --git a/contrib/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp b/contrib/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
new file mode 100644
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+++ b/contrib/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
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+//===- SimplifyCFGPass.cpp - CFG Simplification Pass ----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements dead code elimination and basic block merging, along
+// with a collection of other peephole control flow optimizations.  For example:
+//
+//   * Removes basic blocks with no predecessors.
+//   * Merges a basic block into its predecessor if there is only one and the
+//     predecessor only has one successor.
+//   * Eliminates PHI nodes for basic blocks with a single predecessor.
+//   * Eliminates a basic block that only contains an unconditional branch.
+//   * Changes invoke instructions to nounwind functions to be calls.
+//   * Change things like "if (x) if (y)" into "if (x&y)".
+//   * etc..
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar/SimplifyCFG.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/GlobalsModRef.h"
+#include "llvm/Analysis/AssumptionCache.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/IR/Attributes.h"
+#include "llvm/IR/CFG.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Scalar.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "simplifycfg"
+
+static cl::opt<unsigned>
+UserBonusInstThreshold("bonus-inst-threshold", cl::Hidden, cl::init(1),
+   cl::desc("Control the number of bonus instructions (default = 1)"));
+
+STATISTIC(NumSimpl, "Number of blocks simplified");
+
+/// If we have more than one empty (other than phi node) return blocks,
+/// merge them together to promote recursive block merging.
+static bool mergeEmptyReturnBlocks(Function &F) {
+  bool Changed = false;
+
+  BasicBlock *RetBlock = nullptr;
+
+  // Scan all the blocks in the function, looking for empty return blocks.
+  for (Function::iterator BBI = F.begin(), E = F.end(); BBI != E; ) {
+    BasicBlock &BB = *BBI++;
+
+    // Only look at return blocks.
+    ReturnInst *Ret = dyn_cast<ReturnInst>(BB.getTerminator());
+    if (!Ret) continue;
+
+    // Only look at the block if it is empty or the only other thing in it is a
+    // single PHI node that is the operand to the return.
+    if (Ret != &BB.front()) {
+      // Check for something else in the block.
+      BasicBlock::iterator I(Ret);
+      --I;
+      // Skip over debug info.
+      while (isa<DbgInfoIntrinsic>(I) && I != BB.begin())
+        --I;
+      if (!isa<DbgInfoIntrinsic>(I) &&
+          (!isa<PHINode>(I) || I != BB.begin() || Ret->getNumOperands() == 0 ||
+           Ret->getOperand(0) != &*I))
+        continue;
+    }
+
+    // If this is the first returning block, remember it and keep going.
+    if (!RetBlock) {
+      RetBlock = &BB;
+      continue;
+    }
+
+    // Otherwise, we found a duplicate return block.  Merge the two.
+    Changed = true;
+
+    // Case when there is no input to the return or when the returned values
+    // agree is trivial.  Note that they can't agree if there are phis in the
+    // blocks.
+    if (Ret->getNumOperands() == 0 ||
+        Ret->getOperand(0) ==
+          cast<ReturnInst>(RetBlock->getTerminator())->getOperand(0)) {
+      BB.replaceAllUsesWith(RetBlock);
+      BB.eraseFromParent();
+      continue;
+    }
+
+    // If the canonical return block has no PHI node, create one now.
+    PHINode *RetBlockPHI = dyn_cast<PHINode>(RetBlock->begin());
+    if (!RetBlockPHI) {
+      Value *InVal = cast<ReturnInst>(RetBlock->getTerminator())->getOperand(0);
+      pred_iterator PB = pred_begin(RetBlock), PE = pred_end(RetBlock);
+      RetBlockPHI = PHINode::Create(Ret->getOperand(0)->getType(),
+                                    std::distance(PB, PE), "merge",
+                                    &RetBlock->front());
+
+      for (pred_iterator PI = PB; PI != PE; ++PI)
+        RetBlockPHI->addIncoming(InVal, *PI);
+      RetBlock->getTerminator()->setOperand(0, RetBlockPHI);
+    }
+
+    // Turn BB into a block that just unconditionally branches to the return
+    // block.  This handles the case when the two return blocks have a common
+    // predecessor but that return different things.
+    RetBlockPHI->addIncoming(Ret->getOperand(0), &BB);
+    BB.getTerminator()->eraseFromParent();
+    BranchInst::Create(RetBlock, &BB);
+  }
+
+  return Changed;
+}
+
+/// Call SimplifyCFG on all the blocks in the function,
+/// iterating until no more changes are made.
+static bool iterativelySimplifyCFG(Function &F, const TargetTransformInfo &TTI,
+                                   AssumptionCache *AC,
+                                   unsigned BonusInstThreshold) {
+  bool Changed = false;
+  bool LocalChange = true;
+  while (LocalChange) {
+    LocalChange = false;
+
+    // Loop over all of the basic blocks and remove them if they are unneeded.
+    for (Function::iterator BBIt = F.begin(); BBIt != F.end(); ) {
+      if (SimplifyCFG(&*BBIt++, TTI, BonusInstThreshold, AC)) {
+        LocalChange = true;
+        ++NumSimpl;
+      }
+    }
+    Changed |= LocalChange;
+  }
+  return Changed;
+}
+
+static bool simplifyFunctionCFG(Function &F, const TargetTransformInfo &TTI,
+                                AssumptionCache *AC, int BonusInstThreshold) {
+  bool EverChanged = removeUnreachableBlocks(F);
+  EverChanged |= mergeEmptyReturnBlocks(F);
+  EverChanged |= iterativelySimplifyCFG(F, TTI, AC, BonusInstThreshold);
+
+  // If neither pass changed anything, we're done.
+  if (!EverChanged) return false;
+
+  // iterativelySimplifyCFG can (rarely) make some loops dead.  If this happens,
+  // removeUnreachableBlocks is needed to nuke them, which means we should
+  // iterate between the two optimizations.  We structure the code like this to
+  // avoid rerunning iterativelySimplifyCFG if the second pass of
+  // removeUnreachableBlocks doesn't do anything.
+  if (!removeUnreachableBlocks(F))
+    return true;
+
+  do {
+    EverChanged = iterativelySimplifyCFG(F, TTI, AC, BonusInstThreshold);
+    EverChanged |= removeUnreachableBlocks(F);
+  } while (EverChanged);
+
+  return true;
+}
+
+SimplifyCFGPass::SimplifyCFGPass()
+    : BonusInstThreshold(UserBonusInstThreshold) {}
+
+SimplifyCFGPass::SimplifyCFGPass(int BonusInstThreshold)
+    : BonusInstThreshold(BonusInstThreshold) {}
+
+PreservedAnalyses SimplifyCFGPass::run(Function &F,
+                                       AnalysisManager<Function> *AM) {
+  auto &TTI = AM->getResult<TargetIRAnalysis>(F);
+  auto &AC = AM->getResult<AssumptionAnalysis>(F);
+
+  if (!simplifyFunctionCFG(F, TTI, &AC, BonusInstThreshold))
+    return PreservedAnalyses::none();
+
+  return PreservedAnalyses::all();
+}
+
+namespace {
+struct CFGSimplifyPass : public FunctionPass {
+  static char ID; // Pass identification, replacement for typeid
+  unsigned BonusInstThreshold;
+  std::function<bool(const Function &)> PredicateFtor;
+
+  CFGSimplifyPass(int T = -1,
+                  std::function<bool(const Function &)> Ftor = nullptr)
+      : FunctionPass(ID), PredicateFtor(Ftor) {
+    BonusInstThreshold = (T == -1) ? UserBonusInstThreshold : unsigned(T);
+    initializeCFGSimplifyPassPass(*PassRegistry::getPassRegistry());
+  }
+  bool runOnFunction(Function &F) override {
+    if (PredicateFtor && !PredicateFtor(F))
+      return false;
+
+    if (skipOptnoneFunction(F))
+      return false;
+
+    AssumptionCache *AC =
+        &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
+    const TargetTransformInfo &TTI =
+        getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
+    return simplifyFunctionCFG(F, TTI, AC, BonusInstThreshold);
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.addRequired<AssumptionCacheTracker>();
+    AU.addRequired<TargetTransformInfoWrapperPass>();
+    AU.addPreserved<GlobalsAAWrapperPass>();
+  }
+};
+}
+
+char CFGSimplifyPass::ID = 0;
+INITIALIZE_PASS_BEGIN(CFGSimplifyPass, "simplifycfg", "Simplify the CFG", false,
+                      false)
+INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
+INITIALIZE_PASS_END(CFGSimplifyPass, "simplifycfg", "Simplify the CFG", false,
+                    false)
+
+// Public interface to the CFGSimplification pass
+FunctionPass *
+llvm::createCFGSimplificationPass(int Threshold,
+                                  std::function<bool(const Function &)> Ftor) {
+  return new CFGSimplifyPass(Threshold, Ftor);
+}
+