Add a minimal C interpreter example.

- Demonstrates how to build a standalone tool which loads source code using the
   Driver and Frontend libraries, and then uses CodeGen and the JIT to actually
   execute the code.

 - Still more complicated than it should be, but hey its only 153 lines. :)

--
ddunbar@ozzy:tmp$ cat hello.c
#include <stdio.h>
int main() { printf("hello world\n"); return 0; }
ddunbar@ozzy:tmp$ clang-interpreter hello.c
hello world
--

llvm-svn: 97133

clang/examples/Makefile

@@ -9,6 +9,6 @@
 
 LEVEL = ../../..
 
-PARALLEL_DIRS := PrintFunctionNames wpa
+PARALLEL_DIRS := clang-interpreter PrintFunctionNames wpa
 
 include $(LEVEL)/Makefile.common

clang/examples/clang-interpreter/Makefile

@@ -0,0 +1,28 @@
+##===- examples/clang-interpreter/Makefile -----------------*- Makefile -*-===##
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+#
+##===----------------------------------------------------------------------===##
+
+LEVEL = ../../../..
+
+TOOLNAME = clang-interpreter
+CPPFLAGS += -I$(PROJ_SRC_DIR)/../../include -I$(PROJ_OBJ_DIR)/../../include
+NO_INSTALL = 1
+TOOL_NO_EXPORTS = 1
+
+# Include this here so we can get the configuration of the targets that have
+# been configured for construction. We have to do this early so we can set up
+# LINK_COMPONENTS before including Makefile.rules
+include $(LEVEL)/Makefile.config
+
+LINK_COMPONENTS := jit interpreter nativecodegen bitreader bitwriter ipo \
+	selectiondag
+USEDLIBS = clangFrontend.a clangDriver.a clangCodeGen.a clangSema.a \
+           clangChecker.a clangAnalysis.a clangRewrite.a  clangAST.a \
+           clangParse.a clangLex.a clangBasic.a
+
+include $(LLVM_SRC_ROOT)/Makefile.rules

clang/examples/clang-interpreter/README.txt

@@ -0,0 +1,17 @@
+This is an example of Clang based interpreter, for executing standalone C
+programs.
+
+It demonstrates the following features:
+ 1. Parsing standard compiler command line arguments using the Driver library.
+
+ 2. Constructing a Clang compiler instance, using the appropriate arguments
+    derived in step #1.
+
+ 3. Invoking the Clang compiler to lex, parse, syntax check, and then generate
+    LLVM code.
+
+ 4. Use the LLVM JIT functionality to execute the final module.
+
+The implementation has many limitations and is not designed to be a full fledged
+C interpreter. It is designed to demonstrate a simple but functional use of the
+Clang compiler libraries.

clang/examples/clang-interpreter/main.cpp

@@ -0,0 +1,152 @@
+//===-- examples/clang-interpreter/main.cpp - Clang C Interpreter Example -===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Driver/Compilation.h"
+#include "clang/Driver/Driver.h"
+#include "clang/Driver/Tool.h"
+#include "clang/Frontend/CodeGenAction.h"
+#include "clang/Frontend/CompilerInvocation.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Frontend/DiagnosticOptions.h"
+#include "clang/Frontend/FrontendDiagnostic.h"
+#include "clang/Frontend/TextDiagnosticPrinter.h"
+
+#include "llvm/LLVMContext.h"
+#include "llvm/Module.h"
+#include "llvm/Config/config.h"
+#include "llvm/ADT/OwningPtr.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/Config/config.h"
+#include "llvm/ExecutionEngine/ExecutionEngine.h"
+#include "llvm/Support/ManagedStatic.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/System/Host.h"
+#include "llvm/System/Path.h"
+#include "llvm/Target/TargetSelect.h"
+using namespace clang;
+using namespace clang::driver;
+
+llvm::sys::Path GetExecutablePath(const char *Argv0) {
+  // This just needs to be some symbol in the binary; C++ doesn't
+  // allow taking the address of ::main however.
+  void *MainAddr = (void*) (intptr_t) GetExecutablePath;
+  return llvm::sys::Path::GetMainExecutable(Argv0, MainAddr);
+}
+
+int Execute(llvm::Module *Mod, char * const *envp) {
+  llvm::InitializeNativeTarget();
+
+  std::string Error;
+  llvm::OwningPtr<llvm::ExecutionEngine> EE(
+    llvm::ExecutionEngine::createJIT(Mod, &Error));
+  if (!EE) {
+    llvm::errs() << "unable to make execution engine: " << Error << "\n";
+    return 255;
+  }
+
+  llvm::Function *EntryFn = Mod->getFunction("main");
+  if (!EntryFn) {
+    llvm::errs() << "'main' function not found in module.\n";
+    return 255;
+  }
+
+  // FIXME: Support passing arguments.
+  std::vector<std::string> Args;
+  Args.push_back(Mod->getModuleIdentifier());
+
+  return EE->runFunctionAsMain(EntryFn, Args, envp);
+}
+
+int main(int argc, const char **argv, char * const *envp) {
+  void *MainAddr = (void*) (intptr_t) GetExecutablePath;
+  llvm::sys::Path Path = GetExecutablePath(argv[0]);
+  TextDiagnosticPrinter DiagClient(llvm::errs(), DiagnosticOptions());
+
+  Diagnostic Diags(&DiagClient);
+  Driver TheDriver(Path.getBasename(), Path.getDirname(),
+                   llvm::sys::getHostTriple(),
+                   "a.out", /*IsProduction=*/false, Diags);
+  TheDriver.setTitle("clang interpreter");
+
+  // FIXME: This is a hack to try to force the driver to do something we can
+  // recognize. We need to extend the driver library to support this use model
+  // (basically, exactly one input, and the operation mode is hard wired).
+  llvm::SmallVector<const char *, 16> Args(argv, argv + argc);
+  Args.push_back("-fsyntax-only");
+  llvm::OwningPtr<Compilation> C(TheDriver.BuildCompilation(Args.size(),
+                                                            Args.data()));
+  if (!C)
+    return 0;
+
+  // FIXME: This is copied from ASTUnit.cpp; simplify and eliminate.
+
+  // We expect to get back exactly one command job, if we didn't something
+  // failed. Extract that job from the compilation.
+  const driver::JobList &Jobs = C->getJobs();
+  if (Jobs.size() != 1 || !isa<driver::Command>(Jobs.begin())) {
+    llvm::SmallString<256> Msg;
+    llvm::raw_svector_ostream OS(Msg);
+    C->PrintJob(OS, C->getJobs(), "; ", true);
+    Diags.Report(diag::err_fe_expected_compiler_job) << OS.str();
+    return 1;
+  }
+
+  const driver::Command *Cmd = cast<driver::Command>(*Jobs.begin());
+  if (llvm::StringRef(Cmd->getCreator().getName()) != "clang") {
+    Diags.Report(diag::err_fe_expected_clang_command);
+    return 1;
+  }
+
+  // Initialize a compiler invocation object from the clang (-cc1) arguments.
+  const driver::ArgStringList &CCArgs = Cmd->getArguments();
+  llvm::OwningPtr<CompilerInvocation> CI(new CompilerInvocation);
+  CompilerInvocation::CreateFromArgs(*CI, (const char**) CCArgs.data(),
+                                     (const char**) CCArgs.data()+CCArgs.size(),
+                                     Diags);
+
+  // Show the invocation, with -v.
+  if (CI->getHeaderSearchOpts().Verbose) {
+    llvm::errs() << "clang invocation:\n";
+    C->PrintJob(llvm::errs(), C->getJobs(), "\n", true);
+    llvm::errs() << "\n";
+  }
+
+  // FIXME: This is copied from cc1_main.cpp; simplify and eliminate.
+
+  // Create a compiler instance to handle the actual work.
+  CompilerInstance Clang;
+  Clang.setLLVMContext(new llvm::LLVMContext);
+  Clang.setInvocation(CI.take());
+
+  // Create the compilers actual diagnostics engine.
+  Clang.createDiagnostics(int(CCArgs.size()), (char**) CCArgs.data());
+  if (!Clang.hasDiagnostics())
+    return 1;
+
+  // Infer the builtin include path if unspecified.
+  if (Clang.getHeaderSearchOpts().UseBuiltinIncludes &&
+      Clang.getHeaderSearchOpts().ResourceDir.empty())
+    Clang.getHeaderSearchOpts().ResourceDir =
+      CompilerInvocation::GetResourcesPath(argv[0], MainAddr);
+
+  // Create and execute the frontend to generate an LLVM bitcode module.
+  llvm::OwningPtr<CodeGenAction> Act(new EmitLLVMOnlyAction());
+  if (!Clang.ExecuteAction(*Act))
+    return 1;
+
+  int Res = 255;
+  if (llvm::Module *Module = Act->takeModule())
+    Res = Execute(Module, envp);
+
+  // Shutdown.
+
+  llvm::llvm_shutdown();
+
+  return Res;
+}