Tell PassManager that this pass does not invalidate the CFG so that dominator
information and Loop info will not have to be recomputed after this runs.

llvm-svn: 4269
diff --git a/llvm/lib/CodeGen/InstrSelection/InstrSelection.cpp b/llvm/lib/CodeGen/InstrSelection/InstrSelection.cpp
index 28bfb74..a9d1331 100644
--- a/llvm/lib/CodeGen/InstrSelection/InstrSelection.cpp
+++ b/llvm/lib/CodeGen/InstrSelection/InstrSelection.cpp
@@ -63,6 +63,10 @@
                                        int ruleForNode, short* nts);
   public:
     InstructionSelection(TargetMachine &T) : Target(T) {}
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.setPreservesCFG();
+    }
     
     bool runOnFunction(Function &F);
   };