Use builtin clang::CompilerInvocation object

Recent llvm changed the calling convention of setInvocation, breaking
3.9/4.0 compatibility. This new approach works for both.
Signed-off-by: Brenden Blanco <bblanco@gmail.com>

src/cc/frontends/clang/loader.cc

@@ -211,24 +211,23 @@ int ClangLoader::parse(unique_ptr<llvm::Module> *mod, unique_ptr<vector<TableDes
   }
 
   // pre-compilation pass for generating tracepoint structures
-  auto invocation0 = make_unique<CompilerInvocation>();
-  if (!CompilerInvocation::CreateFromArgs(*invocation0, const_cast<const char **>(ccargs.data()),
+  CompilerInstance compiler0;
+  CompilerInvocation &invocation0 = compiler0.getInvocation();
+  if (!CompilerInvocation::CreateFromArgs(invocation0, const_cast<const char **>(ccargs.data()),
                                           const_cast<const char **>(ccargs.data()) + ccargs.size(), diags))
     return -1;
 
-  invocation0->getPreprocessorOpts().RetainRemappedFileBuffers = true;
+  invocation0.getPreprocessorOpts().RetainRemappedFileBuffers = true;
   for (const auto &f : remapped_files_)
-    invocation0->getPreprocessorOpts().addRemappedFile(f.first, &*f.second);
+    invocation0.getPreprocessorOpts().addRemappedFile(f.first, &*f.second);
 
   if (in_memory) {
-    invocation0->getPreprocessorOpts().addRemappedFile(main_path, &*main_buf);
-    invocation0->getFrontendOpts().Inputs.clear();
-    invocation0->getFrontendOpts().Inputs.push_back(FrontendInputFile(main_path, IK_C));
+    invocation0.getPreprocessorOpts().addRemappedFile(main_path, &*main_buf);
+    invocation0.getFrontendOpts().Inputs.clear();
+    invocation0.getFrontendOpts().Inputs.push_back(FrontendInputFile(main_path, IK_C));
   }
-  invocation0->getFrontendOpts().DisableFree = false;
+  invocation0.getFrontendOpts().DisableFree = false;
 
-  CompilerInstance compiler0;
-  compiler0.setInvocation(invocation0.release());
   compiler0.createDiagnostics(new IgnoringDiagConsumer());
 
   // capture the rewritten c file
@@ -239,24 +238,23 @@ int ClangLoader::parse(unique_ptr<llvm::Module> *mod, unique_ptr<vector<TableDes
   unique_ptr<llvm::MemoryBuffer> out_buf = llvm::MemoryBuffer::getMemBuffer(out_str);
 
   // first pass
-  auto invocation1 = make_unique<CompilerInvocation>();
-  if (!CompilerInvocation::CreateFromArgs(*invocation1, const_cast<const char **>(ccargs.data()),
+  CompilerInstance compiler1;
+  CompilerInvocation &invocation1 = compiler1.getInvocation();
+  if (!CompilerInvocation::CreateFromArgs(invocation1, const_cast<const char **>(ccargs.data()),
                                           const_cast<const char **>(ccargs.data()) + ccargs.size(), diags))
     return -1;
 
   // This option instructs clang whether or not to free the file buffers that we
   // give to it. Since the embedded header files should be copied fewer times
   // and reused if possible, set this flag to true.
-  invocation1->getPreprocessorOpts().RetainRemappedFileBuffers = true;
+  invocation1.getPreprocessorOpts().RetainRemappedFileBuffers = true;
   for (const auto &f : remapped_files_)
-    invocation1->getPreprocessorOpts().addRemappedFile(f.first, &*f.second);
-  invocation1->getPreprocessorOpts().addRemappedFile(main_path, &*out_buf);
-  invocation1->getFrontendOpts().Inputs.clear();
-  invocation1->getFrontendOpts().Inputs.push_back(FrontendInputFile(main_path, IK_C));
-  invocation1->getFrontendOpts().DisableFree = false;
+    invocation1.getPreprocessorOpts().addRemappedFile(f.first, &*f.second);
+  invocation1.getPreprocessorOpts().addRemappedFile(main_path, &*out_buf);
+  invocation1.getFrontendOpts().Inputs.clear();
+  invocation1.getFrontendOpts().Inputs.push_back(FrontendInputFile(main_path, IK_C));
+  invocation1.getFrontendOpts().DisableFree = false;
 
-  CompilerInstance compiler1;
-  compiler1.setInvocation(invocation1.release());
   compiler1.createDiagnostics();
 
   // capture the rewritten c file
@@ -270,21 +268,20 @@ int ClangLoader::parse(unique_ptr<llvm::Module> *mod, unique_ptr<vector<TableDes
   *tables = bact.take_tables();
 
   // second pass, clear input and take rewrite buffer
-  auto invocation2 = make_unique<CompilerInvocation>();
-  if (!CompilerInvocation::CreateFromArgs(*invocation2, const_cast<const char **>(ccargs.data()),
+  CompilerInstance compiler2;
+  CompilerInvocation &invocation2 = compiler2.getInvocation();
+  if (!CompilerInvocation::CreateFromArgs(invocation2, const_cast<const char **>(ccargs.data()),
                                           const_cast<const char **>(ccargs.data()) + ccargs.size(), diags))
     return -1;
-  CompilerInstance compiler2;
-  invocation2->getPreprocessorOpts().RetainRemappedFileBuffers = true;
+  invocation2.getPreprocessorOpts().RetainRemappedFileBuffers = true;
   for (const auto &f : remapped_files_)
-    invocation2->getPreprocessorOpts().addRemappedFile(f.first, &*f.second);
-  invocation2->getPreprocessorOpts().addRemappedFile(main_path, &*out_buf1);
-  invocation2->getFrontendOpts().Inputs.clear();
-  invocation2->getFrontendOpts().Inputs.push_back(FrontendInputFile(main_path, IK_C));
-  invocation2->getFrontendOpts().DisableFree = false;
+    invocation2.getPreprocessorOpts().addRemappedFile(f.first, &*f.second);
+  invocation2.getPreprocessorOpts().addRemappedFile(main_path, &*out_buf1);
+  invocation2.getFrontendOpts().Inputs.clear();
+  invocation2.getFrontendOpts().Inputs.push_back(FrontendInputFile(main_path, IK_C));
+  invocation2.getFrontendOpts().DisableFree = false;
   // suppress warnings in the 2nd pass, but bail out on errors (our fault)
-  invocation2->getDiagnosticOpts().IgnoreWarnings = true;
-  compiler2.setInvocation(invocation2.release());
+  invocation2.getDiagnosticOpts().IgnoreWarnings = true;
   compiler2.createDiagnostics();
 
   EmitLLVMOnlyAction ir_act(&*ctx_);