Introduce a new lexer function to compute the "preamble" of a file,

which is the part of the file that contains all of the initial
comments, includes, and preprocessor directives that occur before any
of the actual code. Added a new -print-preamble cc1 action that is
only used for testing.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@108913 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 33 insertions, 0 deletions

diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 00363d91fd..b007ac4bd3 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -331,6 +331,7 @@ static const char *getActionName(frontend::ActionKind Kind) {
   case frontend::ParsePrintCallbacks:    return "-parse-print-callbacks";
   case frontend::ParseSyntaxOnly:        return "-fsyntax-only";
   case frontend::PrintDeclContext:       return "-print-decl-contexts";
+  case frontend::PrintPreamble:          return "-print-preamble";
   case frontend::PrintPreprocessedInput: return "-E";
   case frontend::RewriteMacros:          return "-rewrite-macros";
   case frontend::RewriteObjC:            return "-rewrite-objc";
@@ -989,6 +990,8 @@ static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
       Opts.ProgramAction = frontend::ParseSyntaxOnly; break;
     case OPT_print_decl_contexts:
       Opts.ProgramAction = frontend::PrintDeclContext; break;
+    case OPT_print_preamble:
+      Opts.ProgramAction = frontend::PrintPreamble; break;
     case OPT_E:
       Opts.ProgramAction = frontend::PrintPreprocessedInput; break;
     case OPT_rewrite_macros:
diff --git a/lib/Frontend/FrontendActions.cpp b/lib/Frontend/FrontendActions.cpp
index 3a53dee806..4db9c11ee3 100644
--- a/lib/Frontend/FrontendActions.cpp
+++ b/lib/Frontend/FrontendActions.cpp
@@ -19,6 +19,7 @@
 #include "clang/Frontend/FrontendDiagnostic.h"
 #include "clang/Frontend/Utils.h"
 #include "llvm/ADT/OwningPtr.h"
+#include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace clang;
 
@@ -192,3 +193,32 @@ void PrintPreprocessedAction::ExecuteAction() {
   DoPrintPreprocessedInput(CI.getPreprocessor(), OS,
                            CI.getPreprocessorOutputOpts());
 }
+
+void PrintPreambleAction::ExecuteAction() {
+  switch (getCurrentFileKind()) {
+  case IK_C:
+  case IK_CXX:
+  case IK_ObjC:
+  case IK_ObjCXX:
+  case IK_OpenCL:
+    break;
+      
+  case IK_None:
+  case IK_Asm:
+  case IK_PreprocessedC:
+  case IK_PreprocessedCXX:
+  case IK_PreprocessedObjC:
+  case IK_PreprocessedObjCXX:
+  case IK_AST:
+  case IK_LLVM_IR:
+    // We can't do anything with these.
+    return;
+  }
+  
+  llvm::MemoryBuffer *Buffer = llvm::MemoryBuffer::getFile(getCurrentFile());
+  if (Buffer) {
+    unsigned Preamble = Lexer::ComputePreamble(Buffer);
+    llvm::outs().write(Buffer->getBufferStart(), Preamble);
+    delete Buffer;
+  }
+}