[GMR] Add a flag to enable GlobalsModRef in the normal compilation

pipeline.

Even before I started improving its runtime, it was already crazy fast
once the call graph exists, and if we can get it to be conservatively
correct, will still likely catch a lot of interesting and useful cases.
So it may well be useful to enable by default.

But more importantly for me, this should make it easier for me to test
that changes aren't breaking it in fundamental ways by enabling it for
normal builds.

llvm-svn: 242895

llvm/lib/Transforms/IPO/PassManagerBuilder.cpp

@@ -89,6 +89,11 @@ static cl::opt<bool> EnableLoopDistribute(
     "enable-loop-distribute", cl::init(false), cl::Hidden,
     cl::desc("Enable the new, experimental LoopDistribution Pass"));
 
+static cl::opt<bool> EnableNonLTOGlobalsModRef(
+    "enable-non-lto-gmr", cl::init(false), cl::Hidden,
+    cl::desc(
+        "Enable the GlobalsModRef AliasAnalysis outside of the LTO pipeline."));
+
 PassManagerBuilder::PassManagerBuilder() {
     OptLevel = 2;
     SizeLevel = 0;
@@ -213,6 +218,12 @@ void PassManagerBuilder::populateModulePassManager(
     MPM.add(createCFGSimplificationPass());   // Clean up after IPCP & DAE
   }
 
+  if (EnableNonLTOGlobalsModRef)
+    // We add a module alias analysis pass here. In part due to bugs in the
+    // analysis infrastructure this "works" in that the analysis stays alive
+    // for the entire SCC pass run below.
+    MPM.add(createGlobalsModRefPass());
+
   // Start of CallGraph SCC passes.
   if (!DisableUnitAtATime)
     MPM.add(createPruneEHPass());             // Remove dead EH info