Subzero: Add a few performance measurement tools.

src/IceRegAlloc.cpp

Index: src/IceRegAlloc.cpp
diff --git a/src/IceRegAlloc.cpp b/src/IceRegAlloc.cpp
index 69353a1df9bb20ff8dd3ee86cd8ed9b6f5ccc1db..c375a09f2ddac86bc57b38767b49e3024de10d9f 100644
--- a/src/IceRegAlloc.cpp
+++ b/src/IceRegAlloc.cpp
@@ -65,7 +65,7 @@ void dumpDisableOverlap(const Cfg *Func, const Variable *Var,
 // Variable.
 void LinearScan::scan(const llvm::SmallBitVector &RegMaskFull) {
   static TimerIdT IDscan = GlobalContext::getTimerID("linearScan");
-  TimerMarker T(IDscan, Func->getContext());
+  TimerMarker T(IDscan, Func);
   assert(RegMaskFull.any()); // Sanity check
   Unhandled.clear();
   UnhandledPrecolored.clear();
@@ -88,7 +88,7 @@ void LinearScan::scan(const llvm::SmallBitVector &RegMaskFull) {
   {
     static TimerIdT IDinitUnhandled =
         GlobalContext::getTimerID("initUnhandled");
-    TimerMarker T(IDinitUnhandled, Func->getContext());
+    TimerMarker T(IDinitUnhandled, Func);
     for (Variable *Var : Vars) {
       // Explicitly don't consider zero-weight variables, which are
       // meant to be spill slots.