diff --git a/llvm/include/llvm/IR/BasicBlock.h b/llvm/include/llvm/IR/BasicBlock.h
--- a/llvm/include/llvm/IR/BasicBlock.h
+++ b/llvm/include/llvm/IR/BasicBlock.h
@@ -453,6 +453,27 @@
     return splitBasicBlockBefore(I->getIterator(), BBName);
   }
 
+  /// Transfer all instructions from \p FromBB to this basic block at \p ToIt.
+  void splice(BasicBlock::iterator ToIt, BasicBlock *FromBB) {
+    splice(ToIt, FromBB, FromBB->begin(), FromBB->end());
+  }
+
+  /// Transfer one instruction from \p FromBB at \p FromIt to this basic block
+  /// at \p ToIt.
+  void splice(BasicBlock::iterator ToIt, BasicBlock *FromBB,
+              BasicBlock::iterator FromIt) {
+    auto FromItLast = std::next(FromIt);
+    if (ToIt == FromIt || ToIt == FromItLast)
+      return;
+    splice(ToIt, FromBB, FromIt, FromItLast);
+  }
+
+  /// Transfer a range of instructions that belong to \p FromBB from \p
+  /// FromBeginIt to \p FromEndIt, to this basic block at \p ToIt.
+  void splice(BasicBlock::iterator ToIt, BasicBlock *FromBB,
+              BasicBlock::iterator FromBeginIt,
+              BasicBlock::iterator FromEndIt);
+
   /// Returns true if there are any uses of this basic block other than
   /// direct branches, switches, etc. to it.
   bool hasAddressTaken() const {
diff --git a/llvm/lib/IR/BasicBlock.cpp b/llvm/lib/IR/BasicBlock.cpp
--- a/llvm/lib/IR/BasicBlock.cpp
+++ b/llvm/lib/IR/BasicBlock.cpp
@@ -468,6 +468,18 @@
   return New;
 }
 
+void BasicBlock::splice(BasicBlock::iterator ToIt, BasicBlock *FromBB,
+                        BasicBlock::iterator FromBeginIt,
+                        BasicBlock::iterator FromEndIt) {
+#ifdef EXPENSIVE_CHECKS
+  // Check that FromBeginIt is befor FromEndIt.
+  auto FromBBEnd = FromBB->end();
+  for (auto It = FromBeginIt; It != FromEndIt; ++It)
+    assert(It != FromBBEnd && "FromBeginIt not before FromEndIt!");
+#endif // EXPENSIVE_CHECKS
+  getInstList().splice(ToIt, FromBB->getInstList(), FromBeginIt, FromEndIt);
+}
+
 void BasicBlock::replacePhiUsesWith(BasicBlock *Old, BasicBlock *New) {
   // N.B. This might not be a complete BasicBlock, so don't assume
   // that it ends with a non-phi instruction.
diff --git a/llvm/unittests/IR/BasicBlockTest.cpp b/llvm/unittests/IR/BasicBlockTest.cpp
--- a/llvm/unittests/IR/BasicBlockTest.cpp
+++ b/llvm/unittests/IR/BasicBlockTest.cpp
@@ -260,5 +260,249 @@
   EXPECT_EQ(std::next(I1->getIterator()), I3->getIterator());
 }
 
+static std::unique_ptr<Module> parseIR(LLVMContext &C, const char *IR) {
+  SMDiagnostic Err;
+  std::unique_ptr<Module> Mod = parseAssemblyString(IR, Err, C);
+  if (!Mod)
+    Err.print(__FILE__, errs());
+  return Mod;
+}
+
+TEST(BasicBlockTest, SpliceFromBB) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M = parseIR(Ctx, R"(
+    define void @f(i32 %a) {
+     from:
+       %fromInstr1 = add i32 %a, %a
+       %fromInstr2 = sub i32 %a, %a
+       br label %to
+
+     to:
+       %toInstr1 = mul i32 %a, %a
+       %toInstr2 = sdiv i32 %a, %a
+       ret void
+    }
+)");
+  Function *F = &*M->begin();
+  auto BBIt = F->begin();
+  BasicBlock *FromBB = &*BBIt++;
+  BasicBlock *ToBB = &*BBIt++;
+
+  auto FromBBIt = FromBB->begin();
+  Instruction *FromI1 = &*FromBBIt++;
+  Instruction *FromI2 = &*FromBBIt++;
+  Instruction *FromBr = &*FromBBIt++;
+
+  auto ToBBIt = ToBB->begin();
+  Instruction *ToI1 = &*ToBBIt++;
+  Instruction *ToI2 = &*ToBBIt++;
+  Instruction *ToRet = &*ToBBIt++;
+  ToBB->splice(ToI1->getIterator(), FromBB);
+
+  EXPECT_TRUE(FromBB->empty());
+
+  auto It = ToBB->begin();
+  EXPECT_EQ(&*It++, FromI1);
+  EXPECT_EQ(&*It++, FromI2);
+  EXPECT_EQ(&*It++, FromBr);
+  EXPECT_EQ(&*It++, ToI1);
+  EXPECT_EQ(&*It++, ToI2);
+  EXPECT_EQ(&*It++, ToRet);
+}
+
+TEST(BasicBlockTest, SpliceOneInstr) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M = parseIR(Ctx, R"(
+    define void @f(i32 %a) {
+     from:
+       %fromInstr1 = add i32 %a, %a
+       %fromInstr2 = sub i32 %a, %a
+       br label %to
+
+     to:
+       %toInstr1 = mul i32 %a, %a
+       %toInstr2 = sdiv i32 %a, %a
+       ret void
+    }
+)");
+  Function *F = &*M->begin();
+  auto BBIt = F->begin();
+  BasicBlock *FromBB = &*BBIt++;
+  BasicBlock *ToBB = &*BBIt++;
+
+  auto FromBBIt = FromBB->begin();
+  Instruction *FromI1 = &*FromBBIt++;
+  Instruction *FromI2 = &*FromBBIt++;
+  Instruction *FromBr = &*FromBBIt++;
+
+  auto ToBBIt = ToBB->begin();
+  Instruction *ToI1 = &*ToBBIt++;
+  Instruction *ToI2 = &*ToBBIt++;
+  Instruction *ToRet = &*ToBBIt++;
+  ToBB->splice(ToI1->getIterator(), FromBB, FromI2->getIterator());
+
+  EXPECT_EQ(FromBB->size(), 2u);
+  EXPECT_EQ(ToBB->size(), 4u);
+
+  auto It = FromBB->begin();
+  EXPECT_EQ(&*It++, FromI1);
+  EXPECT_EQ(&*It++, FromBr);
+
+  It = ToBB->begin();
+  EXPECT_EQ(&*It++, FromI2);
+  EXPECT_EQ(&*It++, ToI1);
+  EXPECT_EQ(&*It++, ToI2);
+  EXPECT_EQ(&*It++, ToRet);
+}
+
+TEST(BasicBlockTest, SpliceOneInstrWhenFromIsSameAsTo) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M = parseIR(Ctx, R"(
+    define void @f(i32 %a) {
+     bb:
+       %instr1 = add i32 %a, %a
+       %instr2 = sub i32 %a, %a
+       ret void
+    }
+)");
+  Function *F = &*M->begin();
+  auto BBIt = F->begin();
+  BasicBlock *BB = &*BBIt++;
+
+  auto It = BB->begin();
+  Instruction *Instr1 = &*It++;
+  Instruction *Instr2 = &*It++;
+  Instruction *Ret = &*It++;
+
+  BB->splice(Instr1->getIterator(), BB, Instr1->getIterator());
+
+  It = BB->begin();
+  EXPECT_EQ(&*It++, Instr1);
+  EXPECT_EQ(&*It++, Instr2);
+  EXPECT_EQ(&*It++, Ret);
+  EXPECT_EQ(BB->size(), 3u);
+}
+
+TEST(BasicBlockTest, SpliceLastInstr) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M = parseIR(Ctx, R"(
+    define void @f(i32 %a) {
+     from:
+       %fromInstr1 = add i32 %a, %a
+       %fromInstr2 = sub i32 %a, %a
+       br label %to
+
+     to:
+       %toInstr1 = mul i32 %a, %a
+       %toInstr2 = sdiv i32 %a, %a
+       ret void
+    }
+)");
+  Function *F = &*M->begin();
+  auto BBIt = F->begin();
+  BasicBlock *FromBB = &*BBIt++;
+  BasicBlock *ToBB = &*BBIt++;
+
+  auto FromBBIt = FromBB->begin();
+  Instruction *FromI1 = &*FromBBIt++;
+  Instruction *FromI2 = &*FromBBIt++;
+  Instruction *FromBr = &*FromBBIt++;
+
+  auto ToBBIt = ToBB->begin();
+  Instruction *ToI1 = &*ToBBIt++;
+  Instruction *ToI2 = &*ToBBIt++;
+  Instruction *ToRet = &*ToBBIt++;
+  ToBB->splice(ToI1->getIterator(), FromBB, FromI2->getIterator(),
+               FromBr->getIterator());
+
+  EXPECT_EQ(FromBB->size(), 2u);
+  auto It = FromBB->begin();
+  EXPECT_EQ(&*It++, FromI1);
+  EXPECT_EQ(&*It++, FromBr);
+
+  EXPECT_EQ(ToBB->size(), 4u);
+  It = ToBB->begin();
+  EXPECT_EQ(&*It++, FromI2);
+  EXPECT_EQ(&*It++, ToI1);
+  EXPECT_EQ(&*It++, ToI2);
+  EXPECT_EQ(&*It++, ToRet);
+}
+
+TEST(BasicBlockTest, SpliceInstrRange) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M = parseIR(Ctx, R"(
+    define void @f(i32 %a) {
+     from:
+       %fromInstr1 = add i32 %a, %a
+       %fromInstr2 = sub i32 %a, %a
+       br label %to
+
+     to:
+       %toInstr1 = mul i32 %a, %a
+       %toInstr2 = sdiv i32 %a, %a
+       ret void
+    }
+)");
+  Function *F = &*M->begin();
+  auto BBIt = F->begin();
+  BasicBlock *FromBB = &*BBIt++;
+  BasicBlock *ToBB = &*BBIt++;
+
+  auto FromBBIt = FromBB->begin();
+  Instruction *FromI1 = &*FromBBIt++;
+  Instruction *FromI2 = &*FromBBIt++;
+  Instruction *FromBr = &*FromBBIt++;
+
+  auto ToBBIt = ToBB->begin();
+  Instruction *ToI1 = &*ToBBIt++;
+  Instruction *ToI2 = &*ToBBIt++;
+  Instruction *ToRet = &*ToBBIt++;
+  ToBB->splice(ToI2->getIterator(), FromBB, FromBB->begin(), FromBB->end());
+
+  EXPECT_EQ(FromBB->size(), 0u);
+
+  EXPECT_EQ(ToBB->size(), 6u);
+  auto It = ToBB->begin();
+  EXPECT_EQ(&*It++, ToI1);
+  EXPECT_EQ(&*It++, FromI1);
+  EXPECT_EQ(&*It++, FromI2);
+  EXPECT_EQ(&*It++, FromBr);
+  EXPECT_EQ(&*It++, ToI2);
+  EXPECT_EQ(&*It++, ToRet);
+}
+
+TEST(BasicBlockTest, SpliceEndBeforeBegin) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M = parseIR(Ctx, R"(
+    define void @f(i32 %a) {
+     from:
+       %fromInstr1 = add i32 %a, %a
+       %fromInstr2 = sub i32 %a, %a
+       br label %to
+
+     to:
+       %toInstr1 = mul i32 %a, %a
+       %toInstr2 = sdiv i32 %a, %a
+       ret void
+    }
+)");
+  Function *F = &*M->begin();
+  auto BBIt = F->begin();
+  BasicBlock *FromBB = &*BBIt++;
+  BasicBlock *ToBB = &*BBIt++;
+
+  auto FromBBIt = FromBB->begin();
+  Instruction *FromI1 = &*FromBBIt++;
+  Instruction *FromI2 = &*FromBBIt++;
+
+  auto ToBBIt = ToBB->begin();
+  Instruction *ToI2 = &*ToBBIt++;
+#ifdef EXPENSIVE_CHECKS
+  EXPECT_DEATH(ToBB->splice(ToI2->getIterator(), FromBB, FromI2->getIterator(),
+                            FromI1->getIterator()),
+               "FromBeginIt not before FromEndIt!");
+#endif // EXPENSIVE_CHECKS
+}
+
 } // End anonymous namespace.
 } // End llvm namespace.