Resubmit r237954 (MIR Serialization: print and parse LLVM IR using MIR format).

This commit a 3rd attempt at comitting the initial MIR serialization patch.
The first commit (r237708) was reverted in 237730. Then the second commit
(r237954) was reverted in r238007, as the MIR library under CodeGen caused
a circular dependency where the CodeGen library depended on MIR and MIR
library depended on CodeGen.

This commit has fixed the dependencies between CodeGen and MIR by
reorganizing the MIR serialization code - the code that prints out
MIR has been moved to CodeGen, and the MIR library has been renamed
to MIRParser. Now the CodeGen library doesn't depend on the
MIRParser library, thus the circular dependency no longer exists.

--Original Commit Message--

MIR Serialization: print and parse LLVM IR using MIR format.

This commit is the initial commit for the MIR serialization project.
It creates a new library under CodeGen called 'MIR'. This new
library adds a new machine function pass that prints out the LLVM IR
using the MIR format. This pass is then added as a last pass when a
'stop-after' option is used in llc. The new library adds the initial
functionality for parsing of MIR files as well. This commit also
extends the llc tool so that it can recognize and parse MIR input files.

Reviewers: Duncan P. N. Exon Smith, Matthias Braun, Philip Reames

Differential Revision: http://reviews.llvm.org/D9616 

llvm-svn: 238341

1 files changed, 85 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/MIRPrintingPass.cpp b/llvm/lib/CodeGen/MIRPrintingPass.cpp
new file mode 100644
index 00000000000..c66658cc977
--- /dev/null
+++ b/llvm/lib/CodeGen/MIRPrintingPass.cpp
@@ -0,0 +1,85 @@
+//===- MIRPrintingPass.cpp - Pass that prints out using the MIR format ----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a pass that prints out the LLVM module using the MIR
+// serialization format.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/YAMLTraits.h"
+
+using namespace llvm;
+
+namespace llvm {
+namespace yaml {
+
+/// This struct serializes the LLVM IR module.
+template <> struct BlockScalarTraits<Module> {
+  static void output(const Module &Mod, void *Ctxt, raw_ostream &OS) {
+    Mod.print(OS, nullptr);
+  }
+  static StringRef input(StringRef Str, void *Ctxt, Module &Mod) {
+    llvm_unreachable("LLVM Module is supposed to be parsed separately");
+    return "";
+  }
+};
+
+} // end namespace yaml
+} // end namespace llvm
+
+namespace {
+
+/// This pass prints out the LLVM IR to an output stream using the MIR
+/// serialization format.
+struct MIRPrintingPass : public MachineFunctionPass {
+  static char ID;
+  raw_ostream &OS;
+
+  MIRPrintingPass() : MachineFunctionPass(ID), OS(dbgs()) {}
+  MIRPrintingPass(raw_ostream &OS) : MachineFunctionPass(ID), OS(OS) {}
+
+  const char *getPassName() const override { return "MIR Printing Pass"; }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesAll();
+    MachineFunctionPass::getAnalysisUsage(AU);
+  }
+
+  virtual bool runOnMachineFunction(MachineFunction &MF) override {
+    // TODO: Print out the machine function.
+    return false;
+  }
+
+  virtual bool doFinalization(Module &M) override {
+    yaml::Output Out(OS);
+    Out << M;
+    return false;
+  }
+};
+
+char MIRPrintingPass::ID = 0;
+
+} // end anonymous namespace
+
+char &llvm::MIRPrintingPassID = MIRPrintingPass::ID;
+INITIALIZE_PASS(MIRPrintingPass, "mir-printer", "MIR Printer", false, false)
+
+namespace llvm {
+
+MachineFunctionPass *createPrintMIRPass(raw_ostream &OS) {
+  return new MIRPrintingPass(OS);
+}
+
+} // end namespace llvm