Add option to time passes

Summary:
As we begin to work on optimization passes for bolt, it is important to
keep track of the time spent in each of these to measure their
contribution to the time bolt takes to finish rewriting a program.

(cherry picked from FBD4301136)

bolt/BinaryPassManager.cpp

@@ -10,6 +10,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "BinaryPassManager.h"
+#include "llvm/Support/Timer.h"
 
 using namespace llvm;
 
@@ -19,6 +20,10 @@ extern llvm::cl::opt<bool> PrintAll;
 extern llvm::cl::opt<bool> DumpDotAll;
 extern llvm::cl::opt<bool> DynoStatsAll;
 
+llvm::cl::opt<bool> TimeOpts("time-opts",
+                             cl::desc("print time spent in each optimization"),
+                             cl::init(false), cl::ZeroOrMore);
+
 static cl::opt<bool>
 EliminateUnreachable("eliminate-unreachable",
                      cl::desc("eliminate unreachable code"),
@@ -135,6 +140,9 @@ namespace bolt {
 
 using namespace opts;
 
+const char BinaryFunctionPassManager::TimerGroupName[] =
+    "Binary Function Pass Manager";
+
 cl::opt<bool> BinaryFunctionPassManager::AlwaysOn(
   "always-run-pass",
   cl::desc("Used for passes that are always enabled"),
@@ -148,6 +156,8 @@ void BinaryFunctionPassManager::runPasses() {
 
     auto &Pass = OptPassPair.second;
 
+    NamedRegionTimer(Pass->getName(), TimerGroupName, TimeOpts);
+
     callWithDynoStats(
       [this,&Pass] {
         Pass->runOnFunctions(BC, BFs, LargeFunctions);

bolt/BinaryPassManager.h

@@ -34,6 +34,7 @@ class BinaryFunctionPassManager {
   std::set<uint64_t> &LargeFunctions;
   std::vector<std::pair<const cl::opt<bool> &,
                         std::unique_ptr<BinaryFunctionPass>>> Passes;
+  static const char TimerGroupName[];
 
  public:
   BinaryFunctionPassManager(BinaryContext &BC,