Teach isAddressUse() in LoopStrengthReduce.cpp about memory intrinsics

[jonpa]

Summary

This was originally part of https://reviews.llvm.org/D35049, but broken out of it on request.

Return true for memset, memcpy and memmove for the address operands.

There is no test included here, but there is a test that depends on this in the original revision.

[qcolombet]

LGTM

[jonpa]

Since this makes a lot of changes in output on its own, I will wait to commit this until https://reviews.llvm.org/D35049 is also ready and commited.

[jonpa]

r308729

lib/Transforms/Scalar/LoopStrengthReduce.cpp

     // of intrinsics.
     switch (II->getIntrinsicID()) {
       default: break;
+      case Intrinsic::memset:
       case Intrinsic::prefetch:
         if (II->getArgOperand(0) == OperandVal)
           isAddress = true;
         break;
+      case Intrinsic::memmove:
+      case Intrinsic::memcpy:
+        if (II->getArgOperand(0) == OperandVal ||
+            II->getArgOperand(1) == OperandVal)
+          isAddress = true;
+        break;
     }
   } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
     if (RMW->getPointerOperand() == OperandVal)