[ResetMachineFunctionPass] Add visited functions statistics info

[zhutianyang]

Summary

Adding a "NumFunctionsVisited" for collecting the visited function number.
It can be used to collect function pass rate in some tests,
the pass rate = (NumberVisited - NumberReset)/NumberVisited.
e.g. it can be used for caculating GlobalISel pass rate in Test-Suite.

[dsanders]

LGTM

llvm/trunk/lib/CodeGen/ResetMachineFunctionPass.cpp

 #include "llvm/CodeGen/Passes.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/Support/Debug.h"
 using namespace llvm;
 
 #define DEBUG_TYPE "reset-machine-function"
 
 STATISTIC(NumFunctionsReset, "Number of functions reset");
+STATISTIC(NumFunctionsVisited, "Number of functions visited");
 
 namespace {
   class ResetMachineFunction : public MachineFunctionPass {
     /// Tells whether or not this pass should emit a fallback
     /// diagnostic when it resets a function.
     bool EmitFallbackDiag;
     /// Whether we should abort immediately instead of resetting the function.
     bool AbortOnFailedISel;
 
   public:
     static char ID; // Pass identification, replacement for typeid
     ResetMachineFunction(bool EmitFallbackDiag = false,
                          bool AbortOnFailedISel = false)
         : MachineFunctionPass(ID), EmitFallbackDiag(EmitFallbackDiag),
           AbortOnFailedISel(AbortOnFailedISel) {}
 
     StringRef getPassName() const override { return "ResetMachineFunction"; }
 
     void getAnalysisUsage(AnalysisUsage &AU) const override {
       AU.addPreserved<StackProtector>();
       MachineFunctionPass::getAnalysisUsage(AU);
     }
 
     bool runOnMachineFunction(MachineFunction &MF) override {
+      ++NumFunctionsVisited;
       // No matter what happened, whether we successfully selected the function
       // or not, nothing is going to use the vreg types after us. Make sure they
       // disappear.
       auto ClearVRegTypesOnReturn =
           make_scope_exit([&MF]() { MF.getRegInfo().clearVirtRegTypes(); });
 
       if (MF.getProperties().hasProperty(
               MachineFunctionProperties::Property::FailedISel)) {