tblgen: add preprocessor as a separate mode

This patch adds a preprocessor that can expand nested for-loops for
saving some copy-n-paste in *.td files.

The preprocessor is not yet integrated with TGParser, and so it has
no direct effect on *.td inputs.  However, you may preprocess an td
input (and only preprocess it).

To test the proprecessor, type:
  tblgen -E -o $@ $<

llvm-svn: 141079

1 files changed, 23 insertions, 0 deletions

diff --git a/llvm/lib/TableGen/Main.cpp b/llvm/lib/TableGen/Main.cpp
index 01bc55e..e15c09f 100644
--- a/llvm/lib/TableGen/Main.cpp
+++ b/llvm/lib/TableGen/Main.cpp
@@ -16,6 +16,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "TGParser.h"
+#include "TGPreprocessor.h"
 #include "llvm/ADT/OwningPtr.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -43,6 +44,12 @@ namespace {
   cl::list<std::string>
   IncludeDirs("I", cl::desc("Directory of include files"),
               cl::value_desc("directory"), cl::Prefix);
+
+  cl::opt<bool>
+  PreprocessOnly("E",
+                 cl::desc("Stop after the preprocessing stage; "
+                          "This is work in progress and has no effect yet"),
+                 cl::init(false));
 }
 
 namespace llvm {
@@ -67,6 +74,22 @@ int TableGenMain(char *argv0, TableGenAction &Action) {
     // it later.
     SrcMgr.setIncludeDirs(IncludeDirs);
 
+    // TODO(clchiou): Integrate preprocessor into TGParser
+    if (PreprocessOnly) {
+      std::string Error;
+      tool_output_file Out(OutputFilename.c_str(), Error);
+      if (!Error.empty()) {
+        errs() << argv0 << ": error opening " << OutputFilename
+          << ":" << Error << "\n";
+        return 1;
+      }
+      TGPreprocessor Preprocessor(SrcMgr, Out);
+      if (Preprocessor.PreprocessFile())
+        return 1;
+      Out.keep();
+      return 0;
+    }
+
     TGParser Parser(SrcMgr, Records);
 
     if (Parser.ParseFile())