use external template to suppres OptBisect::shouldRunPass() instantiation

[lijinpei]

Summary

There are explicit instantiations for OptBisect::shouldRunPass() in lib/IR/OptBiset.cpp, so we can add extern template declarations in include/llvm/IR/OptBiset.h to suppress template instantiations in every .c file.

include/llvm/IR/OptBisect.h

 namespace llvm {
 
 class Pass;
+class Module;
+class Function;
+class BasicBlock;
+class Loop;
+class CallGraphSCC;
+class Region;
 
 /// This class implements a mechanism to disable passes and individual
 /// optimizations at compile time based on a command line option

   unsigned LastBisectNum = 0;
 };
 
+extern template bool OptBisect::shouldRunPass(const Pass *, const Module &);
+extern template bool OptBisect::shouldRunPass(const Pass *, const Function &);
+extern template bool OptBisect::shouldRunPass(const Pass *, const BasicBlock &);
+extern template bool OptBisect::shouldRunPass(const Pass *, const Loop &);
+extern template bool OptBisect::shouldRunPass(const Pass *, const CallGraphSCC &);
+extern template bool OptBisect::shouldRunPass(const Pass *, const Region &);
+
 } // end namespace llvm
 
 #endif // LLVM_IR_OPTBISECT_H