[ARC] Add option to ARCOptAddrMode to disable the pass and diagnose errors

[marksl]

Summary

This change adds an option that allows you to dump the machine instructions before and after the pass to easily see what change was made by the pass. The option is defined as a set of bits. One of those bits also allows you to disable the pass.

[jdpickens]

Looks good

llvm/lib/Target/ARC/ARCOptAddrMode.cpp

 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineInstr.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/IR/Function.h"
 #include "llvm/InitializePasses.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
 
 #define OPTADDRMODE_DESC "ARC load/store address mode"
 #define OPTADDRMODE_NAME "arc-addr-mode"
 #define DEBUG_TYPE "arc-addr-mode"
 
 namespace llvm {
+
+static cl::opt<unsigned> ArcKillAddrMode("arc-kill-addr-mode", cl::init(0),
+                                         cl::ReallyHidden, cl::ZeroOrMore);
+
+#define DUMP_BEFORE() ((ArcKillAddrMode & 0x0001) != 0)
+#define DUMP_AFTER() ((ArcKillAddrMode & 0x0002) != 0)
+#define VIEW_BEFORE() ((ArcKillAddrMode & 0x0004) != 0)
+#define VIEW_AFTER() ((ArcKillAddrMode & 0x0008) != 0)
+#define KILL_PASS() ((ArcKillAddrMode & 0x0010) != 0)
+
 FunctionPass *createARCOptAddrMode();
 void initializeARCOptAddrModePass(PassRegistry &);
 } // end namespace llvm
 
 namespace {
 class ARCOptAddrMode : public MachineFunctionPass {
 public:
   static char ID;
if (Res) {
       // Res points to the next instruction. Rewind to process it
       MI = std::prev(Res->getIterator());
     }
   }
   return Changed;
 }
 
 bool ARCOptAddrMode::runOnMachineFunction(MachineFunction &MF) {
-  if (skipFunction(MF.getFunction()))
+  if (skipFunction(MF.getFunction()) || KILL_PASS())
     return false;
 
+  if (DUMP_BEFORE())
+    MF.dump();
+  if (VIEW_BEFORE())
+    MF.viewCFG();
+
   AST = &MF.getSubtarget<ARCSubtarget>();
   AII = AST->getInstrInfo();
   MRI = &MF.getRegInfo();
   MDT = &getAnalysis<MachineDominatorTree>();
 
   bool Changed = false;
   for (auto &MBB : MF)
     Changed |= processBasicBlock(MBB);
+
+  if (DUMP_AFTER())
+    MF.dump();
+  if (VIEW_AFTER())
+    MF.viewCFG();
   return Changed;
 }
 
 //===----------------------------------------------------------------------===//
 //                         Public Constructor Functions
 //===----------------------------------------------------------------------===//
 
 FunctionPass *llvm::createARCOptAddrMode() { return new ARCOptAddrMode(); }