llvm-project/llvm/tools/lli/lli.cpp

709 lines
24 KiB
C++

//===- lli.cpp - LLVM Interpreter / Dynamic compiler ----------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This utility provides a simple wrapper around the LLVM Execution Engines,
// which allow the direct execution of LLVM programs through a Just-In-Time
// compiler, or through an interpreter if no JIT is available for this platform.
//
//===----------------------------------------------------------------------===//
#include "OrcLazyJIT.h"
#include "RemoteJITUtils.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Bitcode/BitcodeReader.h"
#include "llvm/CodeGen/CommandFlags.h"
#include "llvm/CodeGen/LinkAllCodegenComponents.h"
#include "llvm/ExecutionEngine/GenericValue.h"
#include "llvm/ExecutionEngine/Interpreter.h"
#include "llvm/ExecutionEngine/JITEventListener.h"
#include "llvm/ExecutionEngine/MCJIT.h"
#include "llvm/ExecutionEngine/ObjectCache.h"
#include "llvm/ExecutionEngine/Orc/OrcRemoteTargetClient.h"
#include "llvm/ExecutionEngine/OrcMCJITReplacement.h"
#include "llvm/ExecutionEngine/SectionMemoryManager.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/TypeBuilder.h"
#include "llvm/IRReader/IRReader.h"
#include "llvm/Object/Archive.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/DynamicLibrary.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Memory.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/PluginLoader.h"
#include "llvm/Support/PrettyStackTrace.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/Signals.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Instrumentation.h"
#include <cerrno>
#ifdef __CYGWIN__
#include <cygwin/version.h>
#if defined(CYGWIN_VERSION_DLL_MAJOR) && CYGWIN_VERSION_DLL_MAJOR<1007
#define DO_NOTHING_ATEXIT 1
#endif
#endif
using namespace llvm;
#define DEBUG_TYPE "lli"
namespace {
enum class JITKind { MCJIT, OrcMCJITReplacement, OrcLazy };
cl::opt<std::string>
InputFile(cl::desc("<input bitcode>"), cl::Positional, cl::init("-"));
cl::list<std::string>
InputArgv(cl::ConsumeAfter, cl::desc("<program arguments>..."));
cl::opt<bool> ForceInterpreter("force-interpreter",
cl::desc("Force interpretation: disable JIT"),
cl::init(false));
cl::opt<JITKind> UseJITKind("jit-kind",
cl::desc("Choose underlying JIT kind."),
cl::init(JITKind::MCJIT),
cl::values(
clEnumValN(JITKind::MCJIT, "mcjit",
"MCJIT"),
clEnumValN(JITKind::OrcMCJITReplacement,
"orc-mcjit",
"Orc-based MCJIT replacement"),
clEnumValN(JITKind::OrcLazy,
"orc-lazy",
"Orc-based lazy JIT.")));
// The MCJIT supports building for a target address space separate from
// the JIT compilation process. Use a forked process and a copying
// memory manager with IPC to execute using this functionality.
cl::opt<bool> RemoteMCJIT("remote-mcjit",
cl::desc("Execute MCJIT'ed code in a separate process."),
cl::init(false));
// Manually specify the child process for remote execution. This overrides
// the simulated remote execution that allocates address space for child
// execution. The child process will be executed and will communicate with
// lli via stdin/stdout pipes.
cl::opt<std::string>
ChildExecPath("mcjit-remote-process",
cl::desc("Specify the filename of the process to launch "
"for remote MCJIT execution. If none is specified,"
"\n\tremote execution will be simulated in-process."),
cl::value_desc("filename"), cl::init(""));
// Determine optimization level.
cl::opt<char>
OptLevel("O",
cl::desc("Optimization level. [-O0, -O1, -O2, or -O3] "
"(default = '-O2')"),
cl::Prefix,
cl::ZeroOrMore,
cl::init(' '));
cl::opt<std::string>
TargetTriple("mtriple", cl::desc("Override target triple for module"));
cl::opt<std::string>
EntryFunc("entry-function",
cl::desc("Specify the entry function (default = 'main') "
"of the executable"),
cl::value_desc("function"),
cl::init("main"));
cl::list<std::string>
ExtraModules("extra-module",
cl::desc("Extra modules to be loaded"),
cl::value_desc("input bitcode"));
cl::list<std::string>
ExtraObjects("extra-object",
cl::desc("Extra object files to be loaded"),
cl::value_desc("input object"));
cl::list<std::string>
ExtraArchives("extra-archive",
cl::desc("Extra archive files to be loaded"),
cl::value_desc("input archive"));
cl::opt<bool>
EnableCacheManager("enable-cache-manager",
cl::desc("Use cache manager to save/load mdoules"),
cl::init(false));
cl::opt<std::string>
ObjectCacheDir("object-cache-dir",
cl::desc("Directory to store cached object files "
"(must be user writable)"),
cl::init(""));
cl::opt<std::string>
FakeArgv0("fake-argv0",
cl::desc("Override the 'argv[0]' value passed into the executing"
" program"), cl::value_desc("executable"));
cl::opt<bool>
DisableCoreFiles("disable-core-files", cl::Hidden,
cl::desc("Disable emission of core files if possible"));
cl::opt<bool>
NoLazyCompilation("disable-lazy-compilation",
cl::desc("Disable JIT lazy compilation"),
cl::init(false));
cl::opt<bool>
GenerateSoftFloatCalls("soft-float",
cl::desc("Generate software floating point library calls"),
cl::init(false));
ExitOnError ExitOnErr;
}
//===----------------------------------------------------------------------===//
// Object cache
//
// This object cache implementation writes cached objects to disk to the
// directory specified by CacheDir, using a filename provided in the module
// descriptor. The cache tries to load a saved object using that path if the
// file exists. CacheDir defaults to "", in which case objects are cached
// alongside their originating bitcodes.
//
class LLIObjectCache : public ObjectCache {
public:
LLIObjectCache(const std::string& CacheDir) : CacheDir(CacheDir) {
// Add trailing '/' to cache dir if necessary.
if (!this->CacheDir.empty() &&
this->CacheDir[this->CacheDir.size() - 1] != '/')
this->CacheDir += '/';
}
~LLIObjectCache() override {}
void notifyObjectCompiled(const Module *M, MemoryBufferRef Obj) override {
const std::string &ModuleID = M->getModuleIdentifier();
std::string CacheName;
if (!getCacheFilename(ModuleID, CacheName))
return;
if (!CacheDir.empty()) { // Create user-defined cache dir.
SmallString<128> dir(sys::path::parent_path(CacheName));
sys::fs::create_directories(Twine(dir));
}
std::error_code EC;
raw_fd_ostream outfile(CacheName, EC, sys::fs::F_None);
outfile.write(Obj.getBufferStart(), Obj.getBufferSize());
outfile.close();
}
std::unique_ptr<MemoryBuffer> getObject(const Module* M) override {
const std::string &ModuleID = M->getModuleIdentifier();
std::string CacheName;
if (!getCacheFilename(ModuleID, CacheName))
return nullptr;
// Load the object from the cache filename
ErrorOr<std::unique_ptr<MemoryBuffer>> IRObjectBuffer =
MemoryBuffer::getFile(CacheName, -1, false);
// If the file isn't there, that's OK.
if (!IRObjectBuffer)
return nullptr;
// MCJIT will want to write into this buffer, and we don't want that
// because the file has probably just been mmapped. Instead we make
// a copy. The filed-based buffer will be released when it goes
// out of scope.
return MemoryBuffer::getMemBufferCopy(IRObjectBuffer.get()->getBuffer());
}
private:
std::string CacheDir;
bool getCacheFilename(const std::string &ModID, std::string &CacheName) {
std::string Prefix("file:");
size_t PrefixLength = Prefix.length();
if (ModID.substr(0, PrefixLength) != Prefix)
return false;
std::string CacheSubdir = ModID.substr(PrefixLength);
#if defined(_WIN32)
// Transform "X:\foo" => "/X\foo" for convenience.
if (isalpha(CacheSubdir[0]) && CacheSubdir[1] == ':') {
CacheSubdir[1] = CacheSubdir[0];
CacheSubdir[0] = '/';
}
#endif
CacheName = CacheDir + CacheSubdir;
size_t pos = CacheName.rfind('.');
CacheName.replace(pos, CacheName.length() - pos, ".o");
return true;
}
};
// On Mingw and Cygwin, an external symbol named '__main' is called from the
// generated 'main' function to allow static initialization. To avoid linking
// problems with remote targets (because lli's remote target support does not
// currently handle external linking) we add a secondary module which defines
// an empty '__main' function.
static void addCygMingExtraModule(ExecutionEngine &EE, LLVMContext &Context,
StringRef TargetTripleStr) {
IRBuilder<> Builder(Context);
Triple TargetTriple(TargetTripleStr);
// Create a new module.
std::unique_ptr<Module> M = make_unique<Module>("CygMingHelper", Context);
M->setTargetTriple(TargetTripleStr);
// Create an empty function named "__main".
Function *Result;
if (TargetTriple.isArch64Bit()) {
Result = Function::Create(
TypeBuilder<int64_t(void), false>::get(Context),
GlobalValue::ExternalLinkage, "__main", M.get());
} else {
Result = Function::Create(
TypeBuilder<int32_t(void), false>::get(Context),
GlobalValue::ExternalLinkage, "__main", M.get());
}
BasicBlock *BB = BasicBlock::Create(Context, "__main", Result);
Builder.SetInsertPoint(BB);
Value *ReturnVal;
if (TargetTriple.isArch64Bit())
ReturnVal = ConstantInt::get(Context, APInt(64, 0));
else
ReturnVal = ConstantInt::get(Context, APInt(32, 0));
Builder.CreateRet(ReturnVal);
// Add this new module to the ExecutionEngine.
EE.addModule(std::move(M));
}
CodeGenOpt::Level getOptLevel() {
switch (OptLevel) {
default:
errs() << "lli: Invalid optimization level.\n";
exit(1);
case '0': return CodeGenOpt::None;
case '1': return CodeGenOpt::Less;
case ' ':
case '2': return CodeGenOpt::Default;
case '3': return CodeGenOpt::Aggressive;
}
llvm_unreachable("Unrecognized opt level.");
}
LLVM_ATTRIBUTE_NORETURN
static void reportError(SMDiagnostic Err, const char *ProgName) {
Err.print(ProgName, errs());
exit(1);
}
//===----------------------------------------------------------------------===//
// main Driver function
//
int main(int argc, char **argv, char * const *envp) {
sys::PrintStackTraceOnErrorSignal(argv[0]);
PrettyStackTraceProgram X(argc, argv);
atexit(llvm_shutdown); // Call llvm_shutdown() on exit.
if (argc > 1)
ExitOnErr.setBanner(std::string(argv[0]) + ": ");
// If we have a native target, initialize it to ensure it is linked in and
// usable by the JIT.
InitializeNativeTarget();
InitializeNativeTargetAsmPrinter();
InitializeNativeTargetAsmParser();
cl::ParseCommandLineOptions(argc, argv,
"llvm interpreter & dynamic compiler\n");
// If the user doesn't want core files, disable them.
if (DisableCoreFiles)
sys::Process::PreventCoreFiles();
LLVMContext Context;
// Load the bitcode...
SMDiagnostic Err;
std::unique_ptr<Module> Owner = parseIRFile(InputFile, Err, Context);
Module *Mod = Owner.get();
if (!Mod)
reportError(Err, argv[0]);
if (UseJITKind == JITKind::OrcLazy) {
std::vector<std::unique_ptr<Module>> Ms;
Ms.push_back(std::move(Owner));
for (auto &ExtraMod : ExtraModules) {
Ms.push_back(parseIRFile(ExtraMod, Err, Context));
if (!Ms.back())
reportError(Err, argv[0]);
}
std::vector<std::string> Args;
Args.push_back(InputFile);
for (auto &Arg : InputArgv)
Args.push_back(Arg);
return runOrcLazyJIT(std::move(Ms), Args);
}
if (EnableCacheManager) {
std::string CacheName("file:");
CacheName.append(InputFile);
Mod->setModuleIdentifier(CacheName);
}
// If not jitting lazily, load the whole bitcode file eagerly too.
if (NoLazyCompilation) {
// Use *argv instead of argv[0] to work around a wrong GCC warning.
ExitOnError ExitOnErr(std::string(*argv) +
": bitcode didn't read correctly: ");
ExitOnErr(Mod->materializeAll());
}
std::string ErrorMsg;
EngineBuilder builder(std::move(Owner));
builder.setMArch(MArch);
builder.setMCPU(MCPU);
builder.setMAttrs(MAttrs);
if (RelocModel.getNumOccurrences())
builder.setRelocationModel(RelocModel);
if (CMModel.getNumOccurrences())
builder.setCodeModel(CMModel);
builder.setErrorStr(&ErrorMsg);
builder.setEngineKind(ForceInterpreter
? EngineKind::Interpreter
: EngineKind::JIT);
builder.setUseOrcMCJITReplacement(UseJITKind == JITKind::OrcMCJITReplacement);
// If we are supposed to override the target triple, do so now.
if (!TargetTriple.empty())
Mod->setTargetTriple(Triple::normalize(TargetTriple));
// Enable MCJIT if desired.
RTDyldMemoryManager *RTDyldMM = nullptr;
if (!ForceInterpreter) {
if (RemoteMCJIT)
RTDyldMM = new ForwardingMemoryManager();
else
RTDyldMM = new SectionMemoryManager();
// Deliberately construct a temp std::unique_ptr to pass in. Do not null out
// RTDyldMM: We still use it below, even though we don't own it.
builder.setMCJITMemoryManager(
std::unique_ptr<RTDyldMemoryManager>(RTDyldMM));
} else if (RemoteMCJIT) {
errs() << "error: Remote process execution does not work with the "
"interpreter.\n";
exit(1);
}
builder.setOptLevel(getOptLevel());
TargetOptions Options;
if (FloatABIForCalls != FloatABI::Default)
Options.FloatABIType = FloatABIForCalls;
builder.setTargetOptions(Options);
std::unique_ptr<ExecutionEngine> EE(builder.create());
if (!EE) {
if (!ErrorMsg.empty())
errs() << argv[0] << ": error creating EE: " << ErrorMsg << "\n";
else
errs() << argv[0] << ": unknown error creating EE!\n";
exit(1);
}
std::unique_ptr<LLIObjectCache> CacheManager;
if (EnableCacheManager) {
CacheManager.reset(new LLIObjectCache(ObjectCacheDir));
EE->setObjectCache(CacheManager.get());
}
// Load any additional modules specified on the command line.
for (unsigned i = 0, e = ExtraModules.size(); i != e; ++i) {
std::unique_ptr<Module> XMod = parseIRFile(ExtraModules[i], Err, Context);
if (!XMod)
reportError(Err, argv[0]);
if (EnableCacheManager) {
std::string CacheName("file:");
CacheName.append(ExtraModules[i]);
XMod->setModuleIdentifier(CacheName);
}
EE->addModule(std::move(XMod));
}
for (unsigned i = 0, e = ExtraObjects.size(); i != e; ++i) {
Expected<object::OwningBinary<object::ObjectFile>> Obj =
object::ObjectFile::createObjectFile(ExtraObjects[i]);
if (!Obj) {
// TODO: Actually report errors helpfully.
consumeError(Obj.takeError());
reportError(Err, argv[0]);
}
object::OwningBinary<object::ObjectFile> &O = Obj.get();
EE->addObjectFile(std::move(O));
}
for (unsigned i = 0, e = ExtraArchives.size(); i != e; ++i) {
ErrorOr<std::unique_ptr<MemoryBuffer>> ArBufOrErr =
MemoryBuffer::getFileOrSTDIN(ExtraArchives[i]);
if (!ArBufOrErr)
reportError(Err, argv[0]);
std::unique_ptr<MemoryBuffer> &ArBuf = ArBufOrErr.get();
Expected<std::unique_ptr<object::Archive>> ArOrErr =
object::Archive::create(ArBuf->getMemBufferRef());
if (!ArOrErr) {
std::string Buf;
raw_string_ostream OS(Buf);
logAllUnhandledErrors(ArOrErr.takeError(), OS, "");
OS.flush();
errs() << Buf;
exit(1);
}
std::unique_ptr<object::Archive> &Ar = ArOrErr.get();
object::OwningBinary<object::Archive> OB(std::move(Ar), std::move(ArBuf));
EE->addArchive(std::move(OB));
}
// If the target is Cygwin/MingW and we are generating remote code, we
// need an extra module to help out with linking.
if (RemoteMCJIT && Triple(Mod->getTargetTriple()).isOSCygMing()) {
addCygMingExtraModule(*EE, Context, Mod->getTargetTriple());
}
// The following functions have no effect if their respective profiling
// support wasn't enabled in the build configuration.
EE->RegisterJITEventListener(
JITEventListener::createOProfileJITEventListener());
EE->RegisterJITEventListener(
JITEventListener::createIntelJITEventListener());
if (!NoLazyCompilation && RemoteMCJIT) {
errs() << "warning: remote mcjit does not support lazy compilation\n";
NoLazyCompilation = true;
}
EE->DisableLazyCompilation(NoLazyCompilation);
// If the user specifically requested an argv[0] to pass into the program,
// do it now.
if (!FakeArgv0.empty()) {
InputFile = static_cast<std::string>(FakeArgv0);
} else {
// Otherwise, if there is a .bc suffix on the executable strip it off, it
// might confuse the program.
if (StringRef(InputFile).endswith(".bc"))
InputFile.erase(InputFile.length() - 3);
}
// Add the module's name to the start of the vector of arguments to main().
InputArgv.insert(InputArgv.begin(), InputFile);
// Call the main function from M as if its signature were:
// int main (int argc, char **argv, const char **envp)
// using the contents of Args to determine argc & argv, and the contents of
// EnvVars to determine envp.
//
Function *EntryFn = Mod->getFunction(EntryFunc);
if (!EntryFn) {
errs() << '\'' << EntryFunc << "\' function not found in module.\n";
return -1;
}
// Reset errno to zero on entry to main.
errno = 0;
int Result = -1;
// Sanity check use of remote-jit: LLI currently only supports use of the
// remote JIT on Unix platforms.
if (RemoteMCJIT) {
#ifndef LLVM_ON_UNIX
errs() << "Warning: host does not support external remote targets.\n"
<< " Defaulting to local execution\n";
return -1;
#else
if (ChildExecPath.empty()) {
errs() << "-remote-mcjit requires -mcjit-remote-process.\n";
exit(1);
} else if (!sys::fs::can_execute(ChildExecPath)) {
errs() << "Unable to find usable child executable: '" << ChildExecPath
<< "'\n";
return -1;
}
#endif
}
if (!RemoteMCJIT) {
// If the program doesn't explicitly call exit, we will need the Exit
// function later on to make an explicit call, so get the function now.
Constant *Exit = Mod->getOrInsertFunction("exit", Type::getVoidTy(Context),
Type::getInt32Ty(Context));
// Run static constructors.
if (!ForceInterpreter) {
// Give MCJIT a chance to apply relocations and set page permissions.
EE->finalizeObject();
}
EE->runStaticConstructorsDestructors(false);
// Trigger compilation separately so code regions that need to be
// invalidated will be known.
(void)EE->getPointerToFunction(EntryFn);
// Clear instruction cache before code will be executed.
if (RTDyldMM)
static_cast<SectionMemoryManager*>(RTDyldMM)->invalidateInstructionCache();
// Run main.
Result = EE->runFunctionAsMain(EntryFn, InputArgv, envp);
// Run static destructors.
EE->runStaticConstructorsDestructors(true);
// If the program didn't call exit explicitly, we should call it now.
// This ensures that any atexit handlers get called correctly.
if (Function *ExitF = dyn_cast<Function>(Exit)) {
std::vector<GenericValue> Args;
GenericValue ResultGV;
ResultGV.IntVal = APInt(32, Result);
Args.push_back(ResultGV);
EE->runFunction(ExitF, Args);
errs() << "ERROR: exit(" << Result << ") returned!\n";
abort();
} else {
errs() << "ERROR: exit defined with wrong prototype!\n";
abort();
}
} else {
// else == "if (RemoteMCJIT)"
// Remote target MCJIT doesn't (yet) support static constructors. No reason
// it couldn't. This is a limitation of the LLI implementation, not the
// MCJIT itself. FIXME.
// Lanch the remote process and get a channel to it.
std::unique_ptr<FDRawChannel> C = launchRemote();
if (!C) {
errs() << "Failed to launch remote JIT.\n";
exit(1);
}
// Create a remote target client running over the channel.
typedef orc::remote::OrcRemoteTargetClient<orc::rpc::RawByteChannel>
MyRemote;
auto R = ExitOnErr(MyRemote::Create(*C));
// Create a remote memory manager.
std::unique_ptr<MyRemote::RCMemoryManager> RemoteMM;
ExitOnErr(R->createRemoteMemoryManager(RemoteMM));
// Forward MCJIT's memory manager calls to the remote memory manager.
static_cast<ForwardingMemoryManager*>(RTDyldMM)->setMemMgr(
std::move(RemoteMM));
// Forward MCJIT's symbol resolution calls to the remote.
static_cast<ForwardingMemoryManager *>(RTDyldMM)->setResolver(
orc::createLambdaResolver(
[](const std::string &Name) { return nullptr; },
[&](const std::string &Name) {
if (auto Addr = ExitOnErr(R->getSymbolAddress(Name)))
return JITSymbol(Addr, JITSymbolFlags::Exported);
return JITSymbol(nullptr);
}));
// Grab the target address of the JIT'd main function on the remote and call
// it.
// FIXME: argv and envp handling.
JITTargetAddress Entry = EE->getFunctionAddress(EntryFn->getName().str());
EE->finalizeObject();
DEBUG(dbgs() << "Executing '" << EntryFn->getName() << "' at 0x"
<< format("%llx", Entry) << "\n");
Result = ExitOnErr(R->callIntVoid(Entry));
// Like static constructors, the remote target MCJIT support doesn't handle
// this yet. It could. FIXME.
// Delete the EE - we need to tear it down *before* we terminate the session
// with the remote, otherwise it'll crash when it tries to release resources
// on a remote that has already been disconnected.
EE.reset();
// Signal the remote target that we're done JITing.
ExitOnErr(R->terminateSession());
}
return Result;
}
std::unique_ptr<FDRawChannel> launchRemote() {
#ifndef LLVM_ON_UNIX
llvm_unreachable("launchRemote not supported on non-Unix platforms");
#else
int PipeFD[2][2];
pid_t ChildPID;
// Create two pipes.
if (pipe(PipeFD[0]) != 0 || pipe(PipeFD[1]) != 0)
perror("Error creating pipe: ");
ChildPID = fork();
if (ChildPID == 0) {
// In the child...
// Close the parent ends of the pipes
close(PipeFD[0][1]);
close(PipeFD[1][0]);
// Execute the child process.
std::unique_ptr<char[]> ChildPath, ChildIn, ChildOut;
{
ChildPath.reset(new char[ChildExecPath.size() + 1]);
std::copy(ChildExecPath.begin(), ChildExecPath.end(), &ChildPath[0]);
ChildPath[ChildExecPath.size()] = '\0';
std::string ChildInStr = utostr(PipeFD[0][0]);
ChildIn.reset(new char[ChildInStr.size() + 1]);
std::copy(ChildInStr.begin(), ChildInStr.end(), &ChildIn[0]);
ChildIn[ChildInStr.size()] = '\0';
std::string ChildOutStr = utostr(PipeFD[1][1]);
ChildOut.reset(new char[ChildOutStr.size() + 1]);
std::copy(ChildOutStr.begin(), ChildOutStr.end(), &ChildOut[0]);
ChildOut[ChildOutStr.size()] = '\0';
}
char * const args[] = { &ChildPath[0], &ChildIn[0], &ChildOut[0], nullptr };
int rc = execv(ChildExecPath.c_str(), args);
if (rc != 0)
perror("Error executing child process: ");
llvm_unreachable("Error executing child process");
}
// else we're the parent...
// Close the child ends of the pipes
close(PipeFD[0][0]);
close(PipeFD[1][1]);
// Return an RPC channel connected to our end of the pipes.
return llvm::make_unique<FDRawChannel>(PipeFD[1][0], PipeFD[0][1]);
#endif
}