Fix BorrowedFromInst operand ownership.

This instruction obviously borrows its base value. Liveness extends to the uses
of the result.

Code that switches on OperandOwnership assumes that an Instantaneous use does
not propagate any information that may extend liveness.

Author: atrick

lib/SIL/IR/OperandOwnership.cpp

@@ -429,7 +429,7 @@ OperandOwnershipClassifier::visitBeginBorrowInst(BeginBorrowInst *borrow) {
 OperandOwnership
 OperandOwnershipClassifier::visitBorrowedFromInst(BorrowedFromInst *bfi) {
   return getOperandIndex() == 0 ? OperandOwnership::GuaranteedForwarding
-                                : OperandOwnership::InstantaneousUse;
+                                : OperandOwnership::Borrow;
 }
 
 // MARK: Instructions whose use ownership depends on the operand in question.