[NFC] Introduce option to switch off compatible invokes merge

Does not affect default behavior (transform is on).

Author: xortator

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

@@ -167,6 +167,10 @@ static cl::opt<unsigned> BranchFoldToCommonDestVectorMultiplier(
              "to fold branch to common destination when vector operations are "
              "present"));
 
+static cl::opt<bool> EnableMergeCompatibleInvokes(
+    "simplifycfg-merge-compatible-invokes", cl::Hidden, cl::init(true),
+    cl::desc("Allow SimplifyCFG to merge invokes together when appropriate"));
+
 STATISTIC(NumBitMaps, "Number of switch instructions turned into bitmaps");
 STATISTIC(NumLinearMaps,
           "Number of switch instructions turned into linear mapping");
@@ -2528,6 +2532,9 @@ static void MergeCompatibleInvokesImpl(ArrayRef<InvokeInst *> Invokes,
 /// edges invoke0->cont0 and invoke1->cont1 are "compatible",
 /// and the invoked functions are "compatible".
 static bool MergeCompatibleInvokes(BasicBlock *BB, DomTreeUpdater *DTU) {
+  if (!EnableMergeCompatibleInvokes)
+    return false;
+
   bool Changed = false;
 
   // FIXME: generalize to all exception handling blocks?