-dot-machine-cfg for printing MachineFunction to a dot file

This pass allows a user to dump a MIR function to a dot file
and view it as a graph. It is targeted to provide a similar
functionality as -dot-cfg pass on LLVM-IR. As of now the pass
also support below flags:
-dot-mcfg-only [optional][won't print instructions in the
graph just block name]
-mcfg-dot-filename-prefix [optional][prefix to add to output dot file]
-mcfg-func-name [optional] [specify function name or it's
substring, handy if mir file contains multiple functions and
you need to see graph of just one]

More flags and details can be introduced as per the requirements
in future. This pass is inspired from -dot-cfg IR pass and APIs
are written in almost identical format.

Patch by Yashwant Singh <Yashwant.Singh@amd.com> (yassingh)

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D133709

1 files changed, 95 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/MachineCFGPrinter.cpp b/llvm/lib/CodeGen/MachineCFGPrinter.cpp
new file mode 100644
index 000000000000..7bfb81771380
--- /dev/null
+++ b/llvm/lib/CodeGen/MachineCFGPrinter.cpp
@@ -0,0 +1,95 @@
+//===- MachineCFGPrinter.cpp - DOT Printer for Machine Functions ----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the `-dot-machine-cfg` analysis pass, which emits
+// Machine Function in DOT format in file titled `<prefix>.<function-name>.dot.
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/MachineCFGPrinter.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/TargetSubtargetInfo.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/PassRegistry.h"
+#include "llvm/Support/GraphWriter.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "dot-machine-cfg"
+
+static cl::opt<std::string>
+    MCFGFuncName("mcfg-func-name", cl::Hidden,
+                 cl::desc("The name of a function (or its substring)"
+                          " whose CFG is viewed/printed."));
+
+static cl::opt<std::string> MCFGDotFilenamePrefix(
+    "mcfg-dot-filename-prefix", cl::Hidden,
+    cl::desc("The prefix used for the Machine CFG dot file names."));
+
+static cl::opt<bool>
+    CFGOnly("dot-mcfg-only", cl::init(false), cl::Hidden,
+            cl::desc("Print only the CFG without blocks body"));
+
+static void writeMCFGToDotFile(MachineFunction &MF) {
+  std::string Filename =
+      (MCFGDotFilenamePrefix + "." + MF.getName() + ".dot").str();
+  errs() << "Writing '" << Filename << "'...";
+
+  std::error_code EC;
+  raw_fd_ostream File(Filename, EC, sys::fs::OF_Text);
+
+  DOTMachineFuncInfo MCFGInfo(&MF);
+
+  if (!EC)
+    WriteGraph(File, &MCFGInfo, CFGOnly);
+  else
+    errs() << "  error opening file for writing!";
+  errs() << '\n';
+}
+
+namespace {
+
+class MachineCFGPrinter : public MachineFunctionPass {
+public:
+  static char ID;
+
+  MachineCFGPrinter();
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesCFG();
+    MachineFunctionPass::getAnalysisUsage(AU);
+  }
+};
+
+} // namespace
+
+char MachineCFGPrinter::ID = 0;
+
+char &llvm::MachineCFGPrinterID = MachineCFGPrinter::ID;
+
+INITIALIZE_PASS(MachineCFGPrinter, DEBUG_TYPE, "Machine CFG Printer Pass",
+                false, true)
+
+/// Default construct and initialize the pass.
+MachineCFGPrinter::MachineCFGPrinter() : MachineFunctionPass(ID) {
+  initializeMachineCFGPrinterPass(*PassRegistry::getPassRegistry());
+}
+
+bool MachineCFGPrinter::runOnMachineFunction(MachineFunction &MF) {
+  if (!MCFGFuncName.empty() && !MF.getName().contains(MCFGFuncName))
+    return false;
+  errs() << "Writing Machine CFG for function ";
+  errs().write_escaped(MF.getName()) << '\n';
+
+  writeMCFGToDotFile(MF);
+  return false;
+}