[NFC] PrunedLiveness: Factor out areWithinBoundary

For historical reasons, there was an API to check whether operands were
within the boundary which just checked whether those operands' users
were within the buondary.  Make a copy of the method deal in
instructions and factor the original API through it.

Author: nate-chandler

include/swift/SIL/PrunedLiveness.h

@@ -729,6 +729,20 @@ class PrunedLiveRange : public PrunedLiveness {
   bool isWithinBoundary(SILInstruction *inst,
                         DeadEndBlocks *deadEndBlocks) const;
 
+  /// Whether all \p insts are between this def and the liveness boundary;
+  /// \p deadEndBlocks is optional.
+  template <typename Instructions>
+  bool areWithinBoundary(Instructions insts,
+                         DeadEndBlocks *deadEndBlocks) const {
+    assert(asImpl().isInitialized());
+
+    for (auto *inst : insts) {
+      if (!isWithinBoundary(inst, deadEndBlocks))
+        return false;
+    }
+    return true;
+  };
+
   /// Returns true when all \p uses are between this def and the liveness
   /// boundary \p deadEndBlocks is optional.
   bool areUsesWithinBoundary(ArrayRef<Operand *> uses,

lib/SIL/Utils/PrunedLiveness.cpp

@@ -796,14 +796,8 @@ static FunctionTest SSAPrunedLiveness__areUsesWithinBoundary(
 template <typename LivenessWithDefs>
 bool PrunedLiveRange<LivenessWithDefs>::areUsesWithinBoundary(
     ArrayRef<Operand *> uses, DeadEndBlocks *deadEndBlocks) const {
-  assert(asImpl().isInitialized());
-
-  for (auto *use : uses) {
-    auto *user = use->getUser();
-    if (!isWithinBoundary(user, deadEndBlocks))
-      return false;
-  }
-  return true;
+  SILInstruction::OperandUserRange users(uses, SILInstruction::OperandToUser());
+  return areWithinBoundary(users, deadEndBlocks);
 }
 
 template <typename LivenessWithDefs>