Preserve assumption cache in loop-rotate

[efriedma]

Summary

No testcase included because I can't figure out how to reduce it. (It's easy to write a testcase where rotation clones an assume, but that doesn't actually seem to trigger the crash in opt on its own; maybe an issue with the laziness?)

[hfinkel]

LGTM

What assert are you hitting?

[efriedma]

Assertion:

clang++: [source]/lib/Analysis/AssumptionCache.cpp:127: virtual void llvm::AssumptionCacheTracker::verifyAnalysis() const: Assertion `AssumptionSet.count(cast<CallInst>(&II)) && "Assumption in scanned function not in cache"' failed.

Triggers in AssumptionCacheTracker::doFinalization().

llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp

if (V && LI->replacementPreservesLCSSAForm(C, V)) {
       }
     } else {
       ValueMap[Inst] = C;
     }
     if (C) {
       // Otherwise, stick the new instruction into the new block!
       C->setName(Inst->getName());
       C->insertBefore(LoopEntryBranch);
+
+      if (auto *II = dyn_cast<IntrinsicInst>(C))
+        if (II->getIntrinsicID() == Intrinsic::assume)
+          AC->registerAssumption(II);
     }
   }
 
   // Along with all the other instructions, we just cloned OrigHeader's
   // terminator into OrigPreHeader. Fix up the PHI nodes in each of OrigHeader's
   // successors by duplicating their incoming values for OrigHeader.
   TerminatorInst *TI = OrigHeader->getTerminator();
   for (BasicBlock *SuccBB : TI->successors())