Created Ice::Instrumentation base class and accompanying hooks.

src/IceGlobalContext.cpp

Index: src/IceGlobalContext.cpp
diff --git a/src/IceGlobalContext.cpp b/src/IceGlobalContext.cpp
index 058825b79dc194647e46f2f937eb674b21d14ea7..0d53127dd114cf1e2f648a5c236881f5187cf601 100644
--- a/src/IceGlobalContext.cpp
+++ b/src/IceGlobalContext.cpp
@@ -486,6 +486,10 @@ void GlobalContext::lowerGlobals(const std::string &SectionSuffix) {
     RandomShuffle(Globals.begin(), Globals.end(),
                   [&RNG](int N) { return (uint32_t)RNG.next(N); });
   }
+
+  if (!BuildDefs::minimal() && Instrumentor)

[Karl, 2016/06/07 14:42:40]

Shouldn't this also be based on a command line flag?

I would expect that at some point, one may want to control instrumenting both
ASAN and MSAM. What is not clear by the way the code is written, how this code
has been designed for this possibility.

If you expect the Instrumentor to be conditional on command-line flags (and
hence only one instrumentor), this should be made clearer with comments on the
Instrument class. If you expect to use different instrument classes for each,
then why does the instrument class have virtual functions?

[tlively, 2016/06/07 18:14:42]

If no instrumentation has occurred then Instrumentor will be false. Added more
detail to top of IceInstrumentation.h explaining model.

+    Instrumentor->instrumentGlobals();
+
   DataLowering->lowerGlobals(Globals, SectionSuffix);
   if (ProfileBlockInfos.empty() && DisposeGlobalVariablesAfterLowering) {
     Globals.clearAndPurge();