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diff --git a/llvm/lib/Transforms/Scalar/LowerConstantIntrinsics.cpp b/llvm/lib/Transforms/Scalar/LowerConstantIntrinsics.cpp
new file mode 100644
index 00000000000..d0fcf38b5a7
--- /dev/null
+++ b/llvm/lib/Transforms/Scalar/LowerConstantIntrinsics.cpp
@@ -0,0 +1,170 @@
+//===- LowerConstantIntrinsics.cpp - Lower constant intrinsic calls -------===//
+//
+// 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 pass lowers all remaining 'objectsize' 'is.constant' intrinsic calls
+// and provides constant propagation and basic CFG cleanup on the result.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar/LowerConstantIntrinsics.h"
+#include "llvm/ADT/PostOrderIterator.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/MemoryBuiltins.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/PatternMatch.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/Local.h"
+
+using namespace llvm;
+using namespace llvm::PatternMatch;
+
+#define DEBUG_TYPE "lower-is-constant-intrinsic"
+
+STATISTIC(IsConstantIntrinsicsHandled,
+          "Number of 'is.constant' intrinsic calls handled");
+STATISTIC(ObjectSizeIntrinsicsHandled,
+          "Number of 'objectsize' intrinsic calls handled");
+
+static Value *lowerIsConstantIntrinsic(IntrinsicInst *II) {
+  Value *Op = II->getOperand(0);
+
+  return isa<Constant>(Op) ? ConstantInt::getTrue(II->getType())
+                           : ConstantInt::getFalse(II->getType());
+}
+
+static bool replaceConditionalBranchesOnConstant(Instruction *II,
+                                                 Value *NewValue) {
+  bool HasDeadBlocks = false;
+  SmallSetVector<Instruction *, 8> Worklist;
+  replaceAndRecursivelySimplify(II, NewValue, nullptr, nullptr, nullptr,
+                                &Worklist);
+  for (auto I : Worklist) {
+    BranchInst *BI = dyn_cast<BranchInst>(I);
+    if (!BI)
+      continue;
+    if (BI->isUnconditional())
+      continue;
+
+    BasicBlock *Target, *Other;
+    if (match(BI->getOperand(0), m_Zero())) {
+      Target = BI->getSuccessor(1);
+      Other = BI->getSuccessor(0);
+    } else if (match(BI->getOperand(0), m_One())) {
+      Target = BI->getSuccessor(0);
+      Other = BI->getSuccessor(1);
+    } else {
+      Target = nullptr;
+      Other = nullptr;
+    }
+    if (Target && Target != Other) {
+      BasicBlock *Source = BI->getParent();
+      Other->removePredecessor(Source);
+      BI->eraseFromParent();
+      BranchInst::Create(Target, Source);
+      if (pred_begin(Other) == pred_end(Other))
+        HasDeadBlocks = true;
+    }
+  }
+  return HasDeadBlocks;
+}
+
+static bool lowerConstantIntrinsics(Function &F, const TargetLibraryInfo *TLI) {
+  bool HasDeadBlocks = false;
+  const auto &DL = F.getParent()->getDataLayout();
+  SmallVector<WeakTrackingVH, 8> Worklist;
+
+  ReversePostOrderTraversal<Function *> RPOT(&F);
+  for (BasicBlock *BB : RPOT) {
+    for (Instruction &I: *BB) {
+      IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I);
+      if (!II)
+        continue;
+      switch (II->getIntrinsicID()) {
+      default:
+        break;
+      case Intrinsic::is_constant:
+      case Intrinsic::objectsize:
+        Worklist.push_back(WeakTrackingVH(&I));
+        break;
+      }
+    }
+  }
+  for (WeakTrackingVH &VH: Worklist) {
+    // Items on the worklist can be mutated by earlier recursive replaces.
+    // This can remove the intrinsic as dead (VH == null), but also replace
+    // the intrinsic in place.
+    if (!VH)
+      continue;
+    IntrinsicInst *II = dyn_cast<IntrinsicInst>(&*VH);
+    if (!II)
+      continue;
+    Value *NewValue;
+    switch (II->getIntrinsicID()) {
+    default:
+      continue;
+    case Intrinsic::is_constant:
+      NewValue = lowerIsConstantIntrinsic(II);
+      IsConstantIntrinsicsHandled++;
+      break;
+    case Intrinsic::objectsize:
+      NewValue = lowerObjectSizeCall(II, DL, TLI, true);
+      ObjectSizeIntrinsicsHandled++;
+      break;
+    }
+    HasDeadBlocks |= replaceConditionalBranchesOnConstant(II, NewValue);
+  }
+  if (HasDeadBlocks)
+    removeUnreachableBlocks(F);
+  return !Worklist.empty();
+}
+
+PreservedAnalyses
+LowerConstantIntrinsicsPass::run(Function &F, FunctionAnalysisManager &AM) {
+  if (lowerConstantIntrinsics(F, AM.getCachedResult<TargetLibraryAnalysis>(F)))
+    return PreservedAnalyses::none();
+
+  return PreservedAnalyses::all();
+}
+
+namespace {
+/// Legacy pass for lowering is.constant intrinsics out of the IR.
+///
+/// When this pass is run over a function it converts is.constant intrinsics
+/// into 'true' or 'false'. This is completements the normal constand folding
+/// to 'true' as part of Instruction Simplify passes.
+class LowerConstantIntrinsics : public FunctionPass {
+public:
+  static char ID;
+  LowerConstantIntrinsics() : FunctionPass(ID) {
+    initializeLowerConstantIntrinsicsPass(*PassRegistry::getPassRegistry());
+  }
+
+  bool runOnFunction(Function &F) override {
+    auto *TLIP = getAnalysisIfAvailable<TargetLibraryInfoWrapperPass>();
+    const TargetLibraryInfo *TLI = TLIP ? &TLIP->getTLI(F) : nullptr;
+    return lowerConstantIntrinsics(F, TLI);
+  }
+};
+} // namespace
+
+char LowerConstantIntrinsics::ID = 0;
+INITIALIZE_PASS(LowerConstantIntrinsics, "lower-constant-intrinsics",
+                "Lower constant intrinsics", false, false)
+
+FunctionPass *llvm::createLowerConstantIntrinsicsPass() {
+  return new LowerConstantIntrinsics();
+}