Add opt-bisect support to polly

[efriedma]

Summary

This is useful for debugging miscompiles and extracting testcases for crashes. See http://llvm.org/docs/OptBisect.html .

Depends on D33751.

[grosser]

Thank you Eli!

polly/trunk/lib/Analysis/ScopPass.cpp

 #include "llvm/Analysis/AssumptionCache.h"
 
 using namespace llvm;
 using namespace polly;
 
 bool ScopPass::runOnRegion(Region *R, RGPassManager &RGM) {
   S = nullptr;
 
+  if (skipRegion(*R))
+    return false;
+
   if ((S = getAnalysis<ScopInfoRegionPass>().getScop()))
     return runOnScop(*S);
 
   return false;
 }
 
 void ScopPass::print(raw_ostream &OS, const Module *M) const {
   if (S)

polly/trunk/lib/Transform/CodePreparation.cpp

void CodePreparation::getAnalysisUsage(AnalysisUsage &AU) const {
 
   AU.addPreserved<LoopInfoWrapperPass>();
   AU.addPreserved<RegionInfoPass>();
   AU.addPreserved<DominatorTreeWrapperPass>();
   AU.addPreserved<DominanceFrontierWrapperPass>();
 }
 
 bool CodePreparation::runOnFunction(Function &F) {
+  if (skipFunction(F))
+    return false;
+
   LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
   SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
 
   splitEntryBlockForAlloca(&F.getEntryBlock(), this);
 
-  return false;
+  return true;
 }
 
 void CodePreparation::releaseMemory() { clear(); }
 
 void CodePreparation::print(raw_ostream &OS, const Module *) const {}
 
 char CodePreparation::ID = 0;
 char &polly::CodePreparationID = CodePreparation::ID;
 
 Pass *polly::createCodePreparationPass() { return new CodePreparation(); }
 
 INITIALIZE_PASS_BEGIN(CodePreparation, "polly-prepare",
                       "Polly - Prepare code for polly", false, false)
 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
 INITIALIZE_PASS_END(CodePreparation, "polly-prepare",
                     "Polly - Prepare code for polly", false, false)