unittests/ExecutionEngine/JIT/JITTest.cpp

//===- JITTest.cpp - Unit tests for the JIT -------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "gtest/gtest.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Assembly/Parser.h"
#include "llvm/BasicBlock.h"
#include "llvm/Constant.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/ExecutionEngine/JIT.h"
#include "llvm/ExecutionEngine/JITMemoryManager.h"
#include "llvm/Function.h"
#include "llvm/GlobalValue.h"
#include "llvm/GlobalVariable.h"
#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/ModuleProvider.h"
#include "llvm/Support/IRBuilder.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/TypeBuilder.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetSelect.h"
#include "llvm/Type.h"

#include <vector>
#include <string.h>

#if HAVE_ERRNO_H
#include <errno.h>
#endif
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#if _POSIX_MAPPED_FILES > 0
#include <sys/mman.h>
#endif

using namespace llvm;

namespace {

Function *makeReturnGlobal(std::string Name, GlobalVariable *G, Module *M) {
  std::vector<const Type*> params;
  const FunctionType *FTy = FunctionType::get(G->getType()->getElementType(),
                                              params, false);
  Function *F = Function::Create(FTy, GlobalValue::ExternalLinkage, Name, M);
  BasicBlock *Entry = BasicBlock::Create(M->getContext(), "entry", F);
  IRBuilder<> builder(Entry);
  Value *Load = builder.CreateLoad(G);
  const Type *GTy = G->getType()->getElementType();
  Value *Add = builder.CreateAdd(Load, ConstantInt::get(GTy, 1LL));
  builder.CreateStore(Add, G);
  builder.CreateRet(Add);
  return F;
}

std::string DumpFunction(const Function *F) {
  std::string Result;
  raw_string_ostream(Result) << "" << *F;
  return Result;
}

class RecordingJITMemoryManager : public JITMemoryManager {
  const OwningPtr<JITMemoryManager> Base;
public:
  RecordingJITMemoryManager()
    : Base(JITMemoryManager::CreateDefaultMemManager()) {
    stubsAllocated = 0;
  }

  virtual void setMemoryWritable() { Base->setMemoryWritable(); }
  virtual void setMemoryExecutable() { Base->setMemoryExecutable(); }
  virtual void setPoisonMemory(bool poison) { Base->setPoisonMemory(poison); }
  virtual void AllocateGOT() { Base->AllocateGOT(); }
  virtual uint8_t *getGOTBase() const { return Base->getGOTBase(); }
  struct StartFunctionBodyCall {
    StartFunctionBodyCall(uint8_t *Result, const Function *F,
                          uintptr_t ActualSize, uintptr_t ActualSizeResult)
      : Result(Result), F(F), F_dump(DumpFunction(F)),
        ActualSize(ActualSize), ActualSizeResult(ActualSizeResult) {}
    uint8_t *Result;
    const Function *F;
    std::string F_dump;
    uintptr_t ActualSize;
    uintptr_t ActualSizeResult;
  };
  std::vector<StartFunctionBodyCall> startFunctionBodyCalls;
  virtual uint8_t *startFunctionBody(const Function *F,
                                     uintptr_t &ActualSize) {
    uintptr_t InitialActualSize = ActualSize;
    uint8_t *Result = Base->startFunctionBody(F, ActualSize);
    startFunctionBodyCalls.push_back(
      StartFunctionBodyCall(Result, F, InitialActualSize, ActualSize));
    return Result;
  }
  int stubsAllocated;
  virtual uint8_t *allocateStub(const GlobalValue* F, unsigned StubSize,
                                unsigned Alignment) {
    stubsAllocated++;
    return Base->allocateStub(F, StubSize, Alignment);
  }
  struct EndFunctionBodyCall {
    EndFunctionBodyCall(const Function *F, uint8_t *FunctionStart,
                        uint8_t *FunctionEnd)
      : F(F), F_dump(DumpFunction(F)),
        FunctionStart(FunctionStart), FunctionEnd(FunctionEnd) {}
    const Function *F;
    std::string F_dump;
    uint8_t *FunctionStart;
    uint8_t *FunctionEnd;
  };
  std::vector<EndFunctionBodyCall> endFunctionBodyCalls;
  virtual void endFunctionBody(const Function *F, uint8_t *FunctionStart,
                               uint8_t *FunctionEnd) {
    endFunctionBodyCalls.push_back(
      EndFunctionBodyCall(F, FunctionStart, FunctionEnd));
    Base->endFunctionBody(F, FunctionStart, FunctionEnd);
  }
  virtual uint8_t *allocateSpace(intptr_t Size, unsigned Alignment) {
    return Base->allocateSpace(Size, Alignment);
  }
  virtual uint8_t *allocateGlobal(uintptr_t Size, unsigned Alignment) {
    return Base->allocateGlobal(Size, Alignment);
  }
  struct DeallocateFunctionBodyCall {
    DeallocateFunctionBodyCall(const void *Body) : Body(Body) {}
    const void *Body;
  };
  std::vector<DeallocateFunctionBodyCall> deallocateFunctionBodyCalls;
  virtual void deallocateFunctionBody(void *Body) {
    deallocateFunctionBodyCalls.push_back(DeallocateFunctionBodyCall(Body));
    Base->deallocateFunctionBody(Body);
  }
  struct DeallocateExceptionTableCall {
    DeallocateExceptionTableCall(const void *ET) : ET(ET) {}
    const void *ET;
  };
  std::vector<DeallocateExceptionTableCall> deallocateExceptionTableCalls;
  virtual void deallocateExceptionTable(void *ET) {
    deallocateExceptionTableCalls.push_back(DeallocateExceptionTableCall(ET));
    Base->deallocateExceptionTable(ET);
  }
  struct StartExceptionTableCall {
    StartExceptionTableCall(uint8_t *Result, const Function *F,
                            uintptr_t ActualSize, uintptr_t ActualSizeResult)
      : Result(Result), F(F), F_dump(DumpFunction(F)),
        ActualSize(ActualSize), ActualSizeResult(ActualSizeResult) {}
    uint8_t *Result;
    const Function *F;
    std::string F_dump;
    uintptr_t ActualSize;
    uintptr_t ActualSizeResult;
  };
  std::vector<StartExceptionTableCall> startExceptionTableCalls;
  virtual uint8_t* startExceptionTable(const Function* F,
                                       uintptr_t &ActualSize) {
    uintptr_t InitialActualSize = ActualSize;
    uint8_t *Result = Base->startExceptionTable(F, ActualSize);
    startExceptionTableCalls.push_back(
      StartExceptionTableCall(Result, F, InitialActualSize, ActualSize));
    return Result;
  }
  struct EndExceptionTableCall {
    EndExceptionTableCall(const Function *F, uint8_t *TableStart,
                          uint8_t *TableEnd, uint8_t* FrameRegister)
      : F(F), F_dump(DumpFunction(F)),
        TableStart(TableStart), TableEnd(TableEnd),
        FrameRegister(FrameRegister) {}
    const Function *F;
    std::string F_dump;
    uint8_t *TableStart;
    uint8_t *TableEnd;
    uint8_t *FrameRegister;
  };
  std::vector<EndExceptionTableCall> endExceptionTableCalls;
  virtual void endExceptionTable(const Function *F, uint8_t *TableStart,
                                 uint8_t *TableEnd, uint8_t* FrameRegister) {
      endExceptionTableCalls.push_back(
          EndExceptionTableCall(F, TableStart, TableEnd, FrameRegister));
    return Base->endExceptionTable(F, TableStart, TableEnd, FrameRegister);
  }
};

void LoadAssemblyInto(Module *M, const char *assembly) {
  SMDiagnostic Error;
  bool success = NULL != ParseAssemblyString(assembly, M, Error, M->getContext());
  std::string errMsg;
  raw_string_ostream os(errMsg);
  Error.Print("", os);
  ASSERT_TRUE(success) << os.str();
}

class JITTest : public testing::Test {
 protected:
  virtual void SetUp() {
    M = new Module("<main>", Context);
    MP = new ExistingModuleProvider(M);
    RJMM = new RecordingJITMemoryManager;
    std::string Error;
    TheJIT.reset(EngineBuilder(MP).setEngineKind(EngineKind::JIT)
                 .setJITMemoryManager(RJMM)
                 .setErrorStr(&Error).create());
    ASSERT_TRUE(TheJIT.get() != NULL) << Error;
  }

  void LoadAssembly(const char *assembly) {
    LoadAssemblyInto(M, assembly);
  }

  LLVMContext Context;
  Module *M;  // Owned by MP.
  ModuleProvider *MP;  // Owned by ExecutionEngine.
  RecordingJITMemoryManager *RJMM;
  OwningPtr<ExecutionEngine> TheJIT;
};

// Regression test for a bug.  The JIT used to allocate globals inside the same
// memory block used for the function, and when the function code was freed,
// the global was left in the same place.  This test allocates a function
// that uses and global, deallocates it, and then makes sure that the global
// stays alive after that.
TEST(JIT, GlobalInFunction) {
  LLVMContext context;
  Module *M = new Module("<main>", context);
  ExistingModuleProvider *MP = new ExistingModuleProvider(M);

  JITMemoryManager *MemMgr = JITMemoryManager::CreateDefaultMemManager();
  // Tell the memory manager to poison freed memory so that accessing freed
  // memory is more easily tested.
  MemMgr->setPoisonMemory(true);
  std::string Error;
  OwningPtr<ExecutionEngine> JIT(EngineBuilder(MP)
                                 .setEngineKind(EngineKind::JIT)
                                 .setErrorStr(&Error)
                                 .setJITMemoryManager(MemMgr)
                                 // The next line enables the fix:
                                 .setAllocateGVsWithCode(false)
                                 .create());
  ASSERT_EQ(Error, "");

  // Create a global variable.
  const Type *GTy = Type::getInt32Ty(context);
  GlobalVariable *G = new GlobalVariable(
      *M,
      GTy,
      false,  // Not constant.
      GlobalValue::InternalLinkage,
      Constant::getNullValue(GTy),
      "myglobal");

  // Make a function that points to a global.
  Function *F1 = makeReturnGlobal("F1", G, M);

  // Get the pointer to the native code to force it to JIT the function and
  // allocate space for the global.
  void (*F1Ptr)() =
      reinterpret_cast<void(*)()>((intptr_t)JIT->getPointerToFunction(F1));

  // Since F1 was codegen'd, a pointer to G should be available.
  int32_t *GPtr = (int32_t*)JIT->getPointerToGlobalIfAvailable(G);
  ASSERT_NE((int32_t*)NULL, GPtr);
  EXPECT_EQ(0, *GPtr);

  // F1() should increment G.
  F1Ptr();
  EXPECT_EQ(1, *GPtr);

  // Make a second function identical to the first, referring to the same
  // global.
  Function *F2 = makeReturnGlobal("F2", G, M);
  void (*F2Ptr)() =
      reinterpret_cast<void(*)()>((intptr_t)JIT->getPointerToFunction(F2));

  // F2() should increment G.
  F2Ptr();
  EXPECT_EQ(2, *GPtr);

  // Deallocate F1.
  JIT->freeMachineCodeForFunction(F1);

  // F2() should *still* increment G.
  F2Ptr();
  EXPECT_EQ(3, *GPtr);
}

int PlusOne(int arg) {
  return arg + 1;
}

TEST_F(JITTest, FarCallToKnownFunction) {
  // x86-64 can only make direct calls to functions within 32 bits of
  // the current PC.  To call anything farther away, we have to load
  // the address into a register and call through the register.  The
  // current JIT does this by allocating a stub for any far call.
  // There was a bug in which the JIT tried to emit a direct call when
  // the target was already in the JIT's global mappings and lazy
  // compilation was disabled.

  Function *KnownFunction = Function::Create(
      TypeBuilder<int(int), false>::get(Context),
      GlobalValue::ExternalLinkage, "known", M);
  TheJIT->addGlobalMapping(KnownFunction, (void*)(intptr_t)PlusOne);

  // int test() { return known(7); }
  Function *TestFunction = Function::Create(
      TypeBuilder<int(), false>::get(Context),
      GlobalValue::ExternalLinkage, "test", M);
  BasicBlock *Entry = BasicBlock::Create(Context, "entry", TestFunction);
  IRBuilder<> Builder(Entry);
  Value *result = Builder.CreateCall(
      KnownFunction,
      ConstantInt::get(TypeBuilder<int, false>::get(Context), 7));
  Builder.CreateRet(result);

  TheJIT->DisableLazyCompilation(true);
  int (*TestFunctionPtr)() = reinterpret_cast<int(*)()>(
      (intptr_t)TheJIT->getPointerToFunction(TestFunction));
  // This used to crash in trying to call PlusOne().
  EXPECT_EQ(8, TestFunctionPtr());
}

#if !defined(__arm__) && !defined(__powerpc__) && !defined(__ppc__)
// Test a function C which calls A and B which call each other.
TEST_F(JITTest, NonLazyCompilationStillNeedsStubs) {
  TheJIT->DisableLazyCompilation(true);

  const FunctionType *Func1Ty =
      cast<FunctionType>(TypeBuilder<void(void), false>::get(Context));
  std::vector<const Type*> arg_types;
  arg_types.push_back(Type::getInt1Ty(Context));
  const FunctionType *FuncTy = FunctionType::get(
      Type::getVoidTy(Context), arg_types, false);
  Function *Func1 = Function::Create(Func1Ty, Function::ExternalLinkage,
                                     "func1", M);
  Function *Func2 = Function::Create(FuncTy, Function::InternalLinkage,
                                     "func2", M);
  Function *Func3 = Function::Create(FuncTy, Function::InternalLinkage,
                                     "func3", M);
  BasicBlock *Block1 = BasicBlock::Create(Context, "block1", Func1);
  BasicBlock *Block2 = BasicBlock::Create(Context, "block2", Func2);
  BasicBlock *True2 = BasicBlock::Create(Context, "cond_true", Func2);
  BasicBlock *False2 = BasicBlock::Create(Context, "cond_false", Func2);
  BasicBlock *Block3 = BasicBlock::Create(Context, "block3", Func3);
  BasicBlock *True3 = BasicBlock::Create(Context, "cond_true", Func3);
  BasicBlock *False3 = BasicBlock::Create(Context, "cond_false", Func3);

  // Make Func1 call Func2(0) and Func3(0).
  IRBuilder<> Builder(Block1);
  Builder.CreateCall(Func2, ConstantInt::getTrue(Context));
  Builder.CreateCall(Func3, ConstantInt::getTrue(Context));
  Builder.CreateRetVoid();

  // void Func2(bool b) { if (b) { Func3(false); return; } return; }
  Builder.SetInsertPoint(Block2);
  Builder.CreateCondBr(Func2->arg_begin(), True2, False2);
  Builder.SetInsertPoint(True2);
  Builder.CreateCall(Func3, ConstantInt::getFalse(Context));
  Builder.CreateRetVoid();
  Builder.SetInsertPoint(False2);
  Builder.CreateRetVoid();

  // void Func3(bool b) { if (b) { Func2(false); return; } return; }
  Builder.SetInsertPoint(Block3);
  Builder.CreateCondBr(Func3->arg_begin(), True3, False3);
  Builder.SetInsertPoint(True3);
  Builder.CreateCall(Func2, ConstantInt::getFalse(Context));
  Builder.CreateRetVoid();
  Builder.SetInsertPoint(False3);
  Builder.CreateRetVoid();

  // Compile the function to native code
  void (*F1Ptr)() =
     reinterpret_cast<void(*)()>((intptr_t)TheJIT->getPointerToFunction(Func1));

  F1Ptr();
}

// Regression test for PR5162.  This used to trigger an AssertingVH inside the
// JIT's Function to stub mapping.
TEST_F(JITTest, NonLazyLeaksNoStubs) {
  TheJIT->DisableLazyCompilation(true);

  // Create two functions with a single basic block each.
  const FunctionType *FuncTy =
      cast<FunctionType>(TypeBuilder<int(), false>::get(Context));
  Function *Func1 = Function::Create(FuncTy, Function::ExternalLinkage,
                                     "func1", M);
  Function *Func2 = Function::Create(FuncTy, Function::InternalLinkage,
                                     "func2", M);
  BasicBlock *Block1 = BasicBlock::Create(Context, "block1", Func1);
  BasicBlock *Block2 = BasicBlock::Create(Context, "block2", Func2);

  // The first function calls the second and returns the result
  IRBuilder<> Builder(Block1);
  Value *Result = Builder.CreateCall(Func2);
  Builder.CreateRet(Result);

  // The second function just returns a constant
  Builder.SetInsertPoint(Block2);
  Builder.CreateRet(ConstantInt::get(TypeBuilder<int, false>::get(Context),42));

  // Compile the function to native code
  (void)TheJIT->getPointerToFunction(Func1);

  // Free the JIT state for the functions
  TheJIT->freeMachineCodeForFunction(Func1);
  TheJIT->freeMachineCodeForFunction(Func2);

  // Delete the first function (and show that is has no users)
  EXPECT_EQ(Func1->getNumUses(), 0u);
  Func1->eraseFromParent();

  // Delete the second function (and show that it has no users - it had one,
  // func1 but that's gone now)
  EXPECT_EQ(Func2->getNumUses(), 0u);
  Func2->eraseFromParent();
}
#endif

TEST_F(JITTest, ModuleDeletion) {
  TheJIT->DisableLazyCompilation(false);
  LoadAssembly("define void @main() { "
               "  call i32 @computeVal() "
               "  ret void "
               "} "
               " "
               "define internal i32 @computeVal()  { "
               "  ret i32 0 "
               "} ");
  Function *func = M->getFunction("main");
  TheJIT->getPointerToFunction(func);
  TheJIT->deleteModuleProvider(MP);

  SmallPtrSet<const void*, 2> FunctionsDeallocated;
  for (unsigned i = 0, e = RJMM->deallocateFunctionBodyCalls.size();
       i != e; ++i) {
    FunctionsDeallocated.insert(RJMM->deallocateFunctionBodyCalls[i].Body);
  }
  for (unsigned i = 0, e = RJMM->startFunctionBodyCalls.size(); i != e; ++i) {
    EXPECT_TRUE(FunctionsDeallocated.count(
                  RJMM->startFunctionBodyCalls[i].Result))
      << "Function leaked: \n" << RJMM->startFunctionBodyCalls[i].F_dump;
  }
  EXPECT_EQ(RJMM->startFunctionBodyCalls.size(),
            RJMM->deallocateFunctionBodyCalls.size());

  SmallPtrSet<const void*, 2> ExceptionTablesDeallocated;
  unsigned NumTablesDeallocated = 0;
  for (unsigned i = 0, e = RJMM->deallocateExceptionTableCalls.size();
       i != e; ++i) {
    ExceptionTablesDeallocated.insert(
        RJMM->deallocateExceptionTableCalls[i].ET);
    if (RJMM->deallocateExceptionTableCalls[i].ET != NULL) {
        // If JITEmitDebugInfo is off, we'll "deallocate" NULL, which doesn't
        // appear in startExceptionTableCalls.
        NumTablesDeallocated++;
    }
  }
  for (unsigned i = 0, e = RJMM->startExceptionTableCalls.size(); i != e; ++i) {
    EXPECT_TRUE(ExceptionTablesDeallocated.count(
                  RJMM->startExceptionTableCalls[i].Result))
      << "Function's exception table leaked: \n"
      << RJMM->startExceptionTableCalls[i].F_dump;
  }
  EXPECT_EQ(RJMM->startExceptionTableCalls.size(),
            NumTablesDeallocated);
}

#if !defined(__arm__) && !defined(__powerpc__) && !defined(__ppc__)
typedef int (*FooPtr) ();

TEST_F(JITTest, NoStubs) {
  LoadAssembly("define void @bar() {"
	       "entry: "
	       "ret void"
	       "}"
	       " "
	       "define i32 @foo() {"
	       "entry:"
	       "call void @bar()"
	       "ret i32 undef"
	       "}"
	       " "
	       "define i32 @main() {"
	       "entry:"
	       "%0 = call i32 @foo()"
	       "call void @bar()"
	       "ret i32 undef"
	       "}");
  Function *foo = M->getFunction("foo");
  uintptr_t tmp = (uintptr_t)(TheJIT->getPointerToFunction(foo));
  FooPtr ptr = (FooPtr)(tmp);

  (ptr)();

  // We should now allocate no more stubs, we have the code to foo
  // and the existing stub for bar.
  int stubsBefore = RJMM->stubsAllocated;
  Function *func = M->getFunction("main");
  TheJIT->getPointerToFunction(func);

  Function *bar = M->getFunction("bar");
  TheJIT->getPointerToFunction(bar);

  ASSERT_EQ(stubsBefore, RJMM->stubsAllocated);
}
#endif

#if _POSIX_MAPPED_FILES > 0 && (defined (__x86_64__) || defined (_M_AMD64) || defined (_M_X64))
class FarCallMemMgr : public RecordingJITMemoryManager {
  void *MmapRegion;
  size_t MmapSize;
  uint8_t *NextStub;
  uint8_t *NextFunction;

 public:
  FarCallMemMgr()
      : MmapSize(16ULL << 30) {  // 16GB
    MmapRegion = mmap(NULL, MmapSize, PROT_READ | PROT_WRITE | PROT_EXEC,
                      MAP_PRIVATE | MAP_ANON, -1, 0);
    if (MmapRegion == MAP_FAILED) {
      ADD_FAILURE() << "mmap failed: " << strerror(errno);
    }
    // Set up the 16GB mapped region in several chunks:
    // Stubs / ~5GB empty space / Function 1 / ~5GB empty space / Function 2
    // This way no two entities can use a 32-bit relative call to reach each other.
    NextStub = static_cast<uint8_t*>(MmapRegion);
    NextFunction = NextStub + (5ULL << 30);

    // Next, poison some of the memory so a wild call will eventually crash,
    // even if memory was initialized by the OS to 0.  We can't poison all of
    // the memory because we want to be able to run on systems with less than
    // 16GB of physical ram.
    int TrapInstr = 0xCC;  // INT 3
    memset(NextStub, TrapInstr, 1<<10);
    for (size_t Offset = 1<<30; Offset < MmapSize; Offset += 1<<30) {
      // Fill the 2KB around each GB boundary with trap instructions.  This
      // should ensure that we can't run into emitted functions without hitting
      // the trap.
      memset(NextStub + Offset - (1<<10), TrapInstr, 2<<10);
    }
  }

  ~FarCallMemMgr() {
    EXPECT_EQ(0, munmap(MmapRegion, MmapSize));
  }

  virtual void setMemoryWritable() {}
  virtual void setMemoryExecutable() {}
  virtual uint8_t *startFunctionBody(const Function *F,
                                     uintptr_t &ActualSize) {
    ActualSize = 1 << 30;
    uint8_t *Result = NextFunction;
    NextFunction += 5ULL << 30;
    return Result;
  }
  virtual void endFunctionBody(const Function*, uint8_t*, uint8_t*) {}
  virtual uint8_t *allocateStub(const GlobalValue* F, unsigned StubSize,
                                unsigned Alignment) {
    NextStub = reinterpret_cast<uint8_t*>(
        uintptr_t(NextStub + Alignment - 1) &~ uintptr_t(Alignment - 1));
    uint8_t *Result = NextStub;
    NextStub += StubSize;
    return Result;
  }
};

class FarTargetTest : public ::testing::TestWithParam<CodeGenOpt::Level> {
 protected:
  FarTargetTest() : SavedCodeModel(TargetMachine::getCodeModel()) {}
  ~FarTargetTest() {
    TargetMachine::setCodeModel(SavedCodeModel);
  }

  const CodeModel::Model SavedCodeModel;
};
INSTANTIATE_TEST_CASE_P(CodeGenOpt,
                        FarTargetTest,
                        ::testing::Values(CodeGenOpt::None,
                                          CodeGenOpt::Default));

TEST_P(FarTargetTest, CallToFarTarget) {
  // x86-64 can only make direct calls to functions within 32 bits of
  // the current PC.  To call anything farther away, we have to load
  // the address into a register and call through the register.  The
  // old JIT did this by allocating a stub for any far call.  However,
  // that stub needed to be within 32 bits of the callsite.  Here we
  // test that the JIT correctly deals with stubs and calls more than
  // 32 bits away from the callsite.

  // Make sure the code generator is assuming code might be far away.
  //TargetMachine::setCodeModel(CodeModel::Large);

  LLVMContext Context;
  Module *M = new Module("<main>", Context);
  ExistingModuleProvider *MP = new ExistingModuleProvider(M);

  JITMemoryManager *MemMgr = new FarCallMemMgr();
  std::string Error;
  OwningPtr<ExecutionEngine> JIT(EngineBuilder(MP)
                                 .setEngineKind(EngineKind::JIT)
                                 .setErrorStr(&Error)
                                 .setJITMemoryManager(MemMgr)
                                 .setOptLevel(GetParam())
                                 .create());
  ASSERT_EQ(Error, "");
  TargetMachine::setCodeModel(CodeModel::Large);

  LoadAssemblyInto(M,
                   "define i32 @test() { "
                   "  ret i32 7 "
                   "} "
                   " "
                   "define i32 @test_far() { "
                   "  %result = call i32 @test() "
                   "  ret i32 %result "
                   "} ");
  // First, lay out a function early in memory.
  Function *TestFunction = M->getFunction("test");
  int32_t (*TestFunctionPtr)() = reinterpret_cast<int32_t(*)()>(
      (intptr_t)JIT->getPointerToFunction(TestFunction));
  ASSERT_EQ(7, TestFunctionPtr());

  // We now lay out the far-away function. This should land >4GB away from test().
  Function *FarFunction = M->getFunction("test_far");
  int32_t (*FarFunctionPtr)() = reinterpret_cast<int32_t(*)()>(
      (intptr_t)JIT->getPointerToFunction(FarFunction));

  EXPECT_LT(1LL << 32, llabs(intptr_t(FarFunctionPtr) - intptr_t(TestFunctionPtr)))
      << "Functions must be >32 bits apart or the test is meaningless.";

  // This used to result in a segfault in FarFunction, when its call instruction
  // jumped to the wrong address.
  EXPECT_EQ(7, FarFunctionPtr());
}
#endif  // Platform has far-call problem.

// This code is copied from JITEventListenerTest, but it only runs once for all
// the tests in this directory.  Everything seems fine, but that's strange
// behavior.
class JITEnvironment : public testing::Environment {
  virtual void SetUp() {
    // Required to create a JIT.
    InitializeNativeTarget();
  }
};
testing::Environment* const jit_env =
  testing::AddGlobalTestEnvironment(new JITEnvironment);

}