Index: unittests/CodeGen/BufferSourceTest.cpp
===================================================================
--- unittests/CodeGen/BufferSourceTest.cpp
+++ unittests/CodeGen/BufferSourceTest.cpp
@@ -6,7 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "clang/AST/ASTConsumer.h"
+#include "TestCompiler.h"
+
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/Basic/TargetInfo.h"
@@ -26,10 +27,11 @@
 
 namespace {
 
-// Emitting constructors for global objects involves looking
-// at the source file name. This makes sure that we don't crash
-// if the source file is a memory buffer.
-const char TestProgram[] =
+TEST(BufferSourceTest, EmitCXXGlobalInitFunc) {
+  // Emitting constructors for global objects involves looking
+  // at the source file name. This makes sure that we don't crash
+  // if the source file is a memory buffer.
+  const char TestProgram[] =
     "class EmitCXXGlobalInitFunc    "
     "{                              "
     "public:                        "
@@ -37,43 +39,13 @@
     "};                             "
     "EmitCXXGlobalInitFunc test;    ";
 
-TEST(BufferSourceTest, EmitCXXGlobalInitFunc) {
-    LLVMContext Context;
-    CompilerInstance compiler;
-
-    compiler.createDiagnostics();
-    compiler.getLangOpts().CPlusPlus = 1;
-    compiler.getLangOpts().CPlusPlus11 = 1;
-
-    compiler.getTargetOpts().Triple = llvm::Triple::normalize(
-        llvm::sys::getProcessTriple());
-    compiler.setTarget(clang::TargetInfo::CreateTargetInfo(
-      compiler.getDiagnostics(),
-      std::make_shared<clang::TargetOptions>(
-        compiler.getTargetOpts())));
-
-    compiler.createFileManager();
-    compiler.createSourceManager(compiler.getFileManager());
-    compiler.createPreprocessor(clang::TU_Prefix);
-
-    compiler.createASTContext();
-
-    compiler.setASTConsumer(std::unique_ptr<ASTConsumer>(
-        CreateLLVMCodeGen(
-            compiler.getDiagnostics(),
-            "EmitCXXGlobalInitFuncTest",
-            compiler.getHeaderSearchOpts(),
-            compiler.getPreprocessorOpts(),
-            compiler.getCodeGenOpts(),
-            Context)));
-
-    compiler.createSema(clang::TU_Prefix, nullptr);
-
-    clang::SourceManager &sm = compiler.getSourceManager();
-    sm.setMainFileID(sm.createFileID(
-        llvm::MemoryBuffer::getMemBuffer(TestProgram), clang::SrcMgr::C_User));
+  clang::LangOptions LO;
+  LO.CPlusPlus = 1;
+  LO.CPlusPlus11 = 1;
+  TestCompiler Compiler(LO);
+  Compiler.init(TestProgram);
 
-    clang::ParseAST(compiler.getSema(), false, false);
+  clang::ParseAST(Compiler.compiler.getSema(), false, false);
 }
 
 } // end anonymous namespace
Index: unittests/CodeGen/CodeGenExternalTest.cpp
===================================================================
--- unittests/CodeGen/CodeGenExternalTest.cpp
+++ unittests/CodeGen/CodeGenExternalTest.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "TestCompiler.h"
+
 #include "clang/AST/ASTConsumer.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/GlobalDecl.h"
@@ -50,11 +52,11 @@
 // before forwarding that function to the CodeGenerator.
 
 struct MyASTConsumer : public ASTConsumer {
-  std::unique_ptr<CodeGenerator> Builder;
+  CodeGenerator* Builder;
   std::vector<Decl*> toplevel_decls;
 
-  MyASTConsumer(std::unique_ptr<CodeGenerator> Builder_in)
-    : ASTConsumer(), Builder(std::move(Builder_in))
+  MyASTConsumer(CodeGenerator* Builder_in)
+    : ASTConsumer(), Builder(Builder_in)
   {
   }
 
@@ -257,45 +259,17 @@
 }
 
 TEST(CodeGenExternalTest, CodeGenExternalTest) {
-    LLVMContext Context;
-    CompilerInstance compiler;
-
-    compiler.createDiagnostics();
-    compiler.getLangOpts().CPlusPlus = 1;
-    compiler.getLangOpts().CPlusPlus11 = 1;
-
-    compiler.getTargetOpts().Triple = llvm::Triple::normalize(
-        llvm::sys::getProcessTriple());
-    compiler.setTarget(clang::TargetInfo::CreateTargetInfo(
-      compiler.getDiagnostics(),
-      std::make_shared<clang::TargetOptions>(
-        compiler.getTargetOpts())));
-
-    compiler.createFileManager();
-    compiler.createSourceManager(compiler.getFileManager());
-    compiler.createPreprocessor(clang::TU_Prefix);
-
-    compiler.createASTContext();
-
-
-    compiler.setASTConsumer(std::unique_ptr<ASTConsumer>(
-          new MyASTConsumer(std::unique_ptr<CodeGenerator>(
-             CreateLLVMCodeGen(compiler.getDiagnostics(),
-                               "MemoryTypesTest",
-                               compiler.getHeaderSearchOpts(),
-                               compiler.getPreprocessorOpts(),
-                               compiler.getCodeGenOpts(),
-                               Context)))));
-
-    compiler.createSema(clang::TU_Prefix, nullptr);
+  clang::LangOptions LO;
+  LO.CPlusPlus = 1;
+  LO.CPlusPlus11 = 1;
+  TestCompiler Compiler(LO);
+  auto CustomASTConsumer = llvm::make_unique<MyASTConsumer>(Compiler.CG);
 
-    clang::SourceManager &sm = compiler.getSourceManager();
-    sm.setMainFileID(sm.createFileID(
-        llvm::MemoryBuffer::getMemBuffer(TestProgram), clang::SrcMgr::C_User));
+  Compiler.init(TestProgram, std::move(CustomASTConsumer));
 
-    clang::ParseAST(compiler.getSema(), false, false);
+  clang::ParseAST(Compiler.compiler.getSema(), false, false);
 
-    ASSERT_TRUE(test_codegen_fns_ran);
+  ASSERT_TRUE(test_codegen_fns_ran);
 }
 
 } // end anonymous namespace
Index: unittests/CodeGen/IncrementalProcessingTest.cpp
===================================================================
--- unittests/CodeGen/IncrementalProcessingTest.cpp
+++ unittests/CodeGen/IncrementalProcessingTest.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "TestCompiler.h"
+
 #include "clang/AST/ASTConsumer.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/RecursiveASTVisitor.h"
@@ -108,52 +110,30 @@
 }
 
 TEST(IncrementalProcessing, EmitCXXGlobalInitFunc) {
-    LLVMContext Context;
-    CompilerInstance compiler;
-
-    compiler.createDiagnostics();
-    compiler.getLangOpts().CPlusPlus = 1;
-    compiler.getLangOpts().CPlusPlus11 = 1;
-
-    compiler.getTargetOpts().Triple = llvm::Triple::normalize(
-        llvm::sys::getProcessTriple());
-    compiler.setTarget(clang::TargetInfo::CreateTargetInfo(
-      compiler.getDiagnostics(),
-      std::make_shared<clang::TargetOptions>(
-        compiler.getTargetOpts())));
-
-    compiler.createFileManager();
-    compiler.createSourceManager(compiler.getFileManager());
-    compiler.createPreprocessor(clang::TU_Prefix);
-    compiler.getPreprocessor().enableIncrementalProcessing();
-
-    compiler.createASTContext();
-
-    CodeGenerator* CG =
-        CreateLLVMCodeGen(
-            compiler.getDiagnostics(),
-            "main-module",
-            compiler.getHeaderSearchOpts(),
-            compiler.getPreprocessorOpts(),
-            compiler.getCodeGenOpts(),
-            Context);
-    compiler.setASTConsumer(std::unique_ptr<ASTConsumer>(CG));
-    compiler.createSema(clang::TU_Prefix, nullptr);
-    Sema& S = compiler.getSema();
+    clang::LangOptions LO;
+    LO.CPlusPlus = 1;
+    LO.CPlusPlus11 = 1;
+    TestCompiler Compiler(LO);
+    clang::CompilerInstance &CI = Compiler.compiler;
+    CI.getPreprocessor().enableIncrementalProcessing();
+    CI.setASTConsumer(std::unique_ptr<ASTConsumer>(Compiler.CG));
+    CI.createSema(clang::TU_Prefix, nullptr);
+
+    Sema& S = CI.getSema();
 
     std::unique_ptr<Parser> ParseOP(new Parser(S.getPreprocessor(), S,
                                                /*SkipFunctionBodies*/ false));
     Parser &P = *ParseOP.get();
 
     std::array<std::unique_ptr<llvm::Module>, 3> M;
-    M[0] = IncrementalParseAST(compiler, P, *CG, nullptr);
+    M[0] = IncrementalParseAST(CI, P, *Compiler.CG, nullptr);
     ASSERT_TRUE(M[0]);
 
-    M[1] = IncrementalParseAST(compiler, P, *CG, TestProgram1);
+    M[1] = IncrementalParseAST(CI, P, *Compiler.CG, TestProgram1);
     ASSERT_TRUE(M[1]);
     ASSERT_TRUE(M[1]->getFunction("funcForProg1"));
 
-    M[2] = IncrementalParseAST(compiler, P, *CG, TestProgram2);
+    M[2] = IncrementalParseAST(CI, P, *Compiler.CG, TestProgram2);
     ASSERT_TRUE(M[2]);
     ASSERT_TRUE(M[2]->getFunction("funcForProg2"));
     // First code should not end up in second module:
Index: unittests/CodeGen/TBAAMetadataTest.cpp
===================================================================
--- unittests/CodeGen/TBAAMetadataTest.cpp
+++ unittests/CodeGen/TBAAMetadataTest.cpp
@@ -7,15 +7,10 @@
 //===----------------------------------------------------------------------===//
 
 #include "IRMatchers.h"
+#include "TestCompiler.h"
 #include "clang/AST/ASTConsumer.h"
 #include "clang/AST/ASTContext.h"
-#include "clang/CodeGen/ModuleBuilder.h"
-#include "clang/Frontend/CompilerInstance.h"
-#include "clang/Parse/ParseAST.h"
-#include "llvm/ADT/Triple.h"
-#include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Constants.h"
-#include "llvm/IR/Module.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "gtest/gtest.h"
 #include <memory>
@@ -24,82 +19,17 @@
 
 namespace {
 
-struct TestCompiler {
-  LLVMContext Context;
-  clang::CompilerInstance compiler;
-  clang::CodeGenerator *CG = nullptr;
-  llvm::Module *M = nullptr;
-  unsigned PtrSize = 0;
-
-  void init(const char *TestProgram) {
-    compiler.createDiagnostics();
-    compiler.getCodeGenOpts().StructPathTBAA = 1;
-    compiler.getCodeGenOpts().OptimizationLevel = 1;
-
-    std::string TrStr = llvm::Triple::normalize(llvm::sys::getProcessTriple());
-    llvm::Triple Tr(TrStr);
-    Tr.setOS(Triple::Linux);
-    Tr.setVendor(Triple::VendorType::UnknownVendor);
-    Tr.setEnvironment(Triple::EnvironmentType::UnknownEnvironment);
-    compiler.getTargetOpts().Triple = Tr.getTriple();
-    compiler.setTarget(clang::TargetInfo::CreateTargetInfo(
-        compiler.getDiagnostics(),
-        std::make_shared<clang::TargetOptions>(compiler.getTargetOpts())));
-
-    const clang::TargetInfo &TInfo = compiler.getTarget();
-    PtrSize = TInfo.getPointerWidth(0) / 8;
-
-    compiler.createFileManager();
-    compiler.createSourceManager(compiler.getFileManager());
-    compiler.createPreprocessor(clang::TU_Prefix);
-
-    compiler.createASTContext();
-
-    CG = CreateLLVMCodeGen(
-        compiler.getDiagnostics(),
-        "main-module",
-        compiler.getHeaderSearchOpts(),
-        compiler.getPreprocessorOpts(),
-        compiler.getCodeGenOpts(),
-        Context);
-    compiler.setASTConsumer(std::unique_ptr<clang::ASTConsumer>(CG));
-
-    compiler.createSema(clang::TU_Prefix, nullptr);
-
-    clang::SourceManager &sm = compiler.getSourceManager();
-    sm.setMainFileID(sm.createFileID(
-        llvm::MemoryBuffer::getMemBuffer(TestProgram), clang::SrcMgr::C_User));
-  }
-
-  const BasicBlock *compile() {
-    clang::ParseAST(compiler.getSema(), false, false);
-    M = CG->GetModule();
-
-    // Do not expect more than one function definition.
-    auto FuncPtr = M->begin();
-    for (; FuncPtr != M->end(); ++FuncPtr)
-      if (!FuncPtr->isDeclaration())
-        break;
-    assert(FuncPtr != M->end());
-    const llvm::Function &Func = *FuncPtr;
-    ++FuncPtr;
-    for (; FuncPtr != M->end(); ++FuncPtr)
-      if (!FuncPtr->isDeclaration())
-        break;
-    assert(FuncPtr == M->end());
-
-    // The function must consist of single basic block.
-    auto BBPtr = Func.begin();
-    assert(Func.begin() != Func.end());
-    const BasicBlock &BB = *BBPtr;
-    ++BBPtr;
-    assert(BBPtr == Func.end());
-
-    return &BB;
+struct TBAATestCompiler : public TestCompiler {
+  TBAATestCompiler(clang::LangOptions LO, clang::CodeGenOptions CGO)
+    : TestCompiler(LO, CGO) {}
+  static clang::CodeGenOptions getCommonCodeGenOpts() {
+    clang::CodeGenOptions CGOpts;
+    CGOpts.StructPathTBAA = 1;
+    CGOpts.OptimizationLevel = 1;
+    return CGOpts;
   }
 };
 
-
 auto OmnipotentCharC = MMTuple(
   MMString("omnipotent char"),
   MMTuple(
@@ -129,8 +59,8 @@
     }
   )**";
 
-  TestCompiler Compiler;
-  Compiler.compiler.getLangOpts().C11 = 1;
+  clang::LangOptions LO;
+  TBAATestCompiler Compiler(LO, TBAATestCompiler::getCommonCodeGenOpts());
   Compiler.init(TestProgram);
   const BasicBlock *BB = Compiler.compile();
 
@@ -225,8 +155,9 @@
     }
   )**";
 
-  TestCompiler Compiler;
-  Compiler.compiler.getLangOpts().C11 = 1;
+  clang::LangOptions LO;
+  LO.C11 = 1;
+  TBAATestCompiler Compiler(LO, TBAATestCompiler::getCommonCodeGenOpts());
   Compiler.init(TestProgram);
   const BasicBlock *BB = Compiler.compile();
 
@@ -346,8 +277,9 @@
     }
   )**";
 
-  TestCompiler Compiler;
-  Compiler.compiler.getLangOpts().C11 = 1;
+  clang::LangOptions LO;
+  LO.C11 = 1;
+  TBAATestCompiler Compiler(LO, TBAATestCompiler::getCommonCodeGenOpts());
   Compiler.init(TestProgram);
   const BasicBlock *BB = Compiler.compile();
 
@@ -438,8 +370,9 @@
     }
   )**";
 
-  TestCompiler Compiler;
-  Compiler.compiler.getLangOpts().C11 = 1;
+  clang::LangOptions LO;
+  LO.C11 = 1;
+  TBAATestCompiler Compiler(LO, TBAATestCompiler::getCommonCodeGenOpts());
   Compiler.init(TestProgram);
   const BasicBlock *BB = Compiler.compile();
 
@@ -531,8 +464,9 @@
     }
   )**";
 
-  TestCompiler Compiler;
-  Compiler.compiler.getLangOpts().C11 = 1;
+  clang::LangOptions LO;
+  LO.C11 = 1;
+  TBAATestCompiler Compiler(LO, TBAATestCompiler::getCommonCodeGenOpts());
   Compiler.init(TestProgram);
   const BasicBlock *BB = Compiler.compile();
 
@@ -632,9 +566,10 @@
     }
   )**";
 
-  TestCompiler Compiler;
-  Compiler.compiler.getLangOpts().CPlusPlus = 1;
-  Compiler.compiler.getLangOpts().CPlusPlus11 = 1;
+  clang::LangOptions LO;
+  LO.CPlusPlus = 1;
+  LO.CPlusPlus11 = 1;
+  TBAATestCompiler Compiler(LO, TBAATestCompiler::getCommonCodeGenOpts());
   Compiler.init(TestProgram);
   const BasicBlock *BB = Compiler.compile();
 
@@ -754,9 +689,10 @@
     }
   )**";
 
-  TestCompiler Compiler;
-  Compiler.compiler.getLangOpts().CPlusPlus = 1;
-  Compiler.compiler.getLangOpts().CPlusPlus11 = 1;
+  clang::LangOptions LO;
+  LO.CPlusPlus = 1;
+  LO.CPlusPlus11 = 1;
+  TBAATestCompiler Compiler(LO, TBAATestCompiler::getCommonCodeGenOpts());
   Compiler.init(TestProgram);
   const BasicBlock *BB = Compiler.compile();
 
@@ -854,9 +790,10 @@
     }
   )**";
 
-  TestCompiler Compiler;
-  Compiler.compiler.getLangOpts().CPlusPlus = 1;
-  Compiler.compiler.getLangOpts().CPlusPlus11 = 1;
+  clang::LangOptions LO;
+  LO.CPlusPlus = 1;
+  LO.CPlusPlus11 = 1;
+  TBAATestCompiler Compiler(LO, TBAATestCompiler::getCommonCodeGenOpts());
   Compiler.init(TestProgram);
   const BasicBlock *BB = Compiler.compile();
 
@@ -935,9 +872,10 @@
     }
   )**";
 
-  TestCompiler Compiler;
-  Compiler.compiler.getLangOpts().CPlusPlus = 1;
-  Compiler.compiler.getLangOpts().CPlusPlus11 = 1;
+  clang::LangOptions LO;
+  LO.CPlusPlus = 1;
+  LO.CPlusPlus11 = 1;
+  TBAATestCompiler Compiler(LO, TBAATestCompiler::getCommonCodeGenOpts());
   Compiler.init(TestProgram);
   const BasicBlock *BB = Compiler.compile();
 
@@ -1013,9 +951,10 @@
     }
   )**";
 
-  TestCompiler Compiler;
-  Compiler.compiler.getLangOpts().CPlusPlus = 1;
-  Compiler.compiler.getLangOpts().CPlusPlus11 = 1;
+  clang::LangOptions LO;
+  LO.CPlusPlus = 1;
+  LO.CPlusPlus11 = 1;
+  TBAATestCompiler Compiler(LO, TBAATestCompiler::getCommonCodeGenOpts());
   Compiler.init(TestProgram);
   const BasicBlock *BB = Compiler.compile();
 
@@ -1091,9 +1030,10 @@
     }
   )**";
 
-  TestCompiler Compiler;
-  Compiler.compiler.getLangOpts().CPlusPlus = 1;
-  Compiler.compiler.getLangOpts().CPlusPlus11 = 1;
+  clang::LangOptions LO;
+  LO.CPlusPlus = 1;
+  LO.CPlusPlus11 = 1;
+  TBAATestCompiler Compiler(LO, TBAATestCompiler::getCommonCodeGenOpts());
   Compiler.init(TestProgram);
   const BasicBlock *BB = Compiler.compile();
 
@@ -1167,9 +1107,10 @@
     }
   )**";
 
-  TestCompiler Compiler;
-  Compiler.compiler.getLangOpts().CPlusPlus = 1;
-  Compiler.compiler.getLangOpts().CPlusPlus11 = 1;
+  clang::LangOptions LO;
+  LO.CPlusPlus = 1;
+  LO.CPlusPlus11 = 1;
+  TBAATestCompiler Compiler(LO, TBAATestCompiler::getCommonCodeGenOpts());
   Compiler.init(TestProgram);
   const BasicBlock *BB = Compiler.compile();
 
@@ -1252,9 +1193,10 @@
     }
   )**";
 
-  TestCompiler Compiler;
-  Compiler.compiler.getLangOpts().CPlusPlus = 1;
-  Compiler.compiler.getLangOpts().CPlusPlus11 = 1;
+  clang::LangOptions LO;
+  LO.CPlusPlus = 1;
+  LO.CPlusPlus11 = 1;
+  TBAATestCompiler Compiler(LO, TBAATestCompiler::getCommonCodeGenOpts());
   Compiler.init(TestProgram);
   const BasicBlock *BB = Compiler.compile();
 
Index: unittests/CodeGen/TestCompiler.h
===================================================================
--- /dev/null
+++ unittests/CodeGen/TestCompiler.h
@@ -0,0 +1,111 @@
+//=== unittests/CodeGen/TestCompiler.h - Match on the LLVM IR ---*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef CLANG_UNITTESTS_CODEGEN_TESTCOMPILER_H
+#define CLANG_UNITTESTS_CODEGEN_TESTCOMPILER_H
+
+
+#include "clang/AST/ASTConsumer.h"
+#include "clang/Basic/TargetInfo.h"
+#include "clang/Basic/TargetOptions.h"
+#include "clang/CodeGen/ModuleBuilder.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Parse/ParseAST.h"
+
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+
+namespace llvm {
+
+struct TestCompiler {
+  LLVMContext Context;
+  clang::CompilerInstance compiler;
+  clang::CodeGenerator* CG;
+  llvm::Module *M = nullptr;
+  unsigned PtrSize = 0;
+
+  TestCompiler(clang::LangOptions LO,
+               clang::CodeGenOptions CGO = clang::CodeGenOptions()) {
+    compiler.getLangOpts() = LO;
+    compiler.getCodeGenOpts() = CGO;
+    compiler.createDiagnostics();
+
+    std::string TrStr = llvm::Triple::normalize(llvm::sys::getProcessTriple());
+    llvm::Triple Tr(TrStr);
+    Tr.setOS(Triple::Linux);
+    Tr.setVendor(Triple::VendorType::UnknownVendor);
+    Tr.setEnvironment(Triple::EnvironmentType::UnknownEnvironment);
+    compiler.getTargetOpts().Triple = Tr.getTriple();
+    compiler.setTarget(clang::TargetInfo::CreateTargetInfo(
+        compiler.getDiagnostics(),
+        std::make_shared<clang::TargetOptions>(compiler.getTargetOpts())));
+
+    const clang::TargetInfo &TInfo = compiler.getTarget();
+    PtrSize = TInfo.getPointerWidth(0) / 8;
+
+    compiler.createFileManager();
+    compiler.createSourceManager(compiler.getFileManager());
+    compiler.createPreprocessor(clang::TU_Prefix);
+
+    compiler.createASTContext();
+
+    CG = CreateLLVMCodeGen(compiler.getDiagnostics(),
+                           "main-module",
+                           compiler.getHeaderSearchOpts(),
+                           compiler.getPreprocessorOpts(),
+                           compiler.getCodeGenOpts(),
+                           Context);
+  }
+
+  void init(const char *TestProgram,
+            std::unique_ptr<clang::ASTConsumer> Consumer = nullptr) {
+    assert(CG);
+
+    if (!Consumer)
+      Consumer = std::unique_ptr<clang::ASTConsumer>(CG);
+
+    compiler.setASTConsumer(std::move(Consumer));
+
+    compiler.createSema(clang::TU_Prefix, nullptr);
+
+    clang::SourceManager &sm = compiler.getSourceManager();
+    sm.setMainFileID(sm.createFileID(
+        llvm::MemoryBuffer::getMemBuffer(TestProgram), clang::SrcMgr::C_User));
+  }
+
+  const BasicBlock *compile() {
+    clang::ParseAST(compiler.getSema(), false, false);
+    M = CG->GetModule();
+
+    // Do not expect more than one function definition.
+    auto FuncPtr = M->begin();
+    for (; FuncPtr != M->end(); ++FuncPtr)
+      if (!FuncPtr->isDeclaration())
+        break;
+    assert(FuncPtr != M->end());
+    const llvm::Function &Func = *FuncPtr;
+    ++FuncPtr;
+    for (; FuncPtr != M->end(); ++FuncPtr)
+      if (!FuncPtr->isDeclaration())
+        break;
+    assert(FuncPtr == M->end());
+
+    // The function must consist of single basic block.
+    auto BBPtr = Func.begin();
+    assert(Func.begin() != Func.end());
+    const BasicBlock &BB = *BBPtr;
+    ++BBPtr;
+    assert(BBPtr == Func.end());
+
+    return &BB;
+  }
+};
+
+} // namespace llvm
+#endif // CLANG_UNITTESTS_CODEGEN_TESTCOMPILER_H