Add a BeginBorrowInst::getEndBorrows helper.

Author: atrick

include/swift/SIL/SILInstruction.h

@@ -3252,11 +3252,20 @@ class BeginBorrowInst
                                   SingleValueInstruction> {
   friend class SILBuilder;
 
+  /// Predicate used to filter EndBorrowRange.
+  struct UseToEndBorrow;
+
   BeginBorrowInst(SILDebugLocation DebugLoc, SILValue LValue)
       : UnaryInstructionBase(DebugLoc, LValue,
                              LValue->getType().getObjectType()) {}
 
 public:
+  using EndBorrowRange =
+      OptionalTransformRange<use_range, UseToEndBorrow, use_iterator>;
+
+  /// Return a range over all EndBorrow instructions for this BeginBorrow.
+  EndBorrowRange getEndBorrows() const;
+
   /// Return the single use of this BeginBorrowInst, not including any
   /// EndBorrowInst uses, or return nullptr if the borrow is dead or has
   /// multiple uses.
@@ -3355,6 +3364,20 @@ class EndBorrowInst
   }
 };
 
+struct BeginBorrowInst::UseToEndBorrow {
+  Optional<EndBorrowInst *> operator()(Operand *use) const {
+    if (auto borrow = dyn_cast<EndBorrowInst>(use->getUser())) {
+      return borrow;
+    } else {
+      return None;
+    }
+  }
+};
+
+inline auto BeginBorrowInst::getEndBorrows() const -> EndBorrowRange {
+  return EndBorrowRange(getUses(), UseToEndBorrow());
+}
+
 /// Different kinds of access.
 enum class SILAccessKind : uint8_t {
   /// An access which takes uninitialized memory and initializes it.