Refactor Subzero initialization and add a browser callback handler.

src/IceCompiler.h

+//===- subzero/src/IceCompiler.h - Compiler driver --------------*- C++ -*-===//
+//
+//                        The Subzero Code Generator
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the driver for translating bitcode to native code.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SUBZERO_SRC_ICECOMPILER_H
+#define SUBZERO_SRC_ICECOMPILER_H
+
+#include "IceDefs.h"
+
+namespace Ice {
+
+class CompileServer;
+
+// A compiler driver. It may be called to handle a single compile request.
+class Compiler {
+  Compiler(const Compiler &) = delete;
+  Compiler &operator=(const Compiler &) = delete;
+
+public:
+  Compiler() : ReturnValue(0) {}
+
+  void run(int argc, char **argv, CompileServer &Server);

[Mircea Trofin, 2015/03/13 22:01:34]

Could argument passing happen before run is called? That way, for repeated
compiles taking the same arguments, just different input source, arg parsing can
be up-fronted.

[jvoung (off chromium), 2015/03/18 15:39:09]

Hmm, good point.

There is an Ice::ClFlags class that holds *most* of the flags. We could parse
immediately before running, set up a ClFlags object, and then only pass the
ClFlags object to run.

However, there are a bunch of flags not captured by the ClFlags object. There
could be a couple reasons (a) they are not checked by the downstream code so
don't need to be so global and (b) they are also not needed by the "release"
build.  I could create a separate class, Ice::ClFlagsExtra or something... Then
do run(Flags, FlagsExtra, Server).

There is also this related issue
https://code.google.com/p/nativeclient/issues/detail?id=4084, but I think that's
a separate change. The run(Flags, FlagsExtra, ...) structure may help with
that...

Some other things -- besides changing the input/output files across compiles, we
may also want to change the OptLevel or the RNG seed flags between compiles.

Thoughts?

[Mircea Trofin, 2015/03/18 16:51:06]

I think the 2 issues are indeed related. I believe a programmatic  API for the
compiler would address them both. 

I think it would be reasonable to separate the 2 changes, though (meaning, do
the API design separately). Issue 4048 seems like the right place to peg that
effort off.

+
+  int getReturnValue() const { return ReturnValue; }
+
+private:
+  void setReturnValue(int V) { ReturnValue = V; }
+
+  int ReturnValue;
+};
+
+} // end of namespace Ice
+
+#endif // SUBZERO_SRC_ICECOMPILER_H