[CanonicalizeBorrowScope] Adopted BitfieldRef.

Author: nate-chandler

include/swift/SILOptimizer/Utils/CanonicalizeBorrowScope.h

@@ -60,10 +60,13 @@ class CanonicalizeBorrowScope {
   // The borrow that begins this scope.
   BorrowedValue borrowedValue;
 
+  /// The function containing this scope.
+  SILFunction *function;
+
   /// Pruned liveness for the extended live range including copies. For this
   /// purpose, only consuming instructions are considered "lifetime
   /// ending". end_borrows do not end a liverange that may include owned copies.
-  SSAPrunedLiveness liveness;
+  BitfieldRef<SSAPrunedLiveness> liveness;
 
   InstructionDeleter &deleter;
 
@@ -86,11 +89,11 @@ class CanonicalizeBorrowScope {
 
 public:
   CanonicalizeBorrowScope(SILFunction *function, InstructionDeleter &deleter)
-    : liveness(function), deleter(deleter) {}
+      : function(function), deleter(deleter) {}
 
   BorrowedValue getBorrowedValue() const { return borrowedValue; }
 
-  const SSAPrunedLiveness &getLiveness() const { return liveness; }
+  const SSAPrunedLiveness &getLiveness() const { return *liveness; }
 
   InstructionDeleter &getDeleter() { return deleter; }
 
@@ -136,11 +139,13 @@ class CanonicalizeBorrowScope {
 
 protected:
   void initBorrow(BorrowedValue borrow) {
-    assert(borrow && liveness.empty() && persistentCopies.empty());
+    assert(borrow && persistentCopies.empty() &&
+           (!liveness || liveness->empty()));
 
     updatedCopies.clear();
     borrowedValue = borrow;
-    liveness.initializeDef(borrowedValue.value);
+    if (liveness)
+      liveness->initializeDef(borrowedValue.value);
   }
 
   bool computeBorrowLiveness();

lib/SILOptimizer/Utils/CanonicalizeBorrowScope.cpp

@@ -180,7 +180,7 @@ bool CanonicalizeBorrowScope::computeBorrowLiveness() {
   // the reborrowed value will not be rewritten when canonicalizing the current
   // borrow scope because they are "hidden" behind the reborrow.
   borrowedValue.visitLocalScopeEndingUses([this](Operand *use) {
-    liveness.updateForUse(use->getUser(), /*lifetimeEnding*/ true);
+    liveness->updateForUse(use->getUser(), /*lifetimeEnding*/ true);
     return true;
   });
   return true;
@@ -837,12 +837,13 @@ bool CanonicalizeBorrowScope::canonicalizeFunctionArgument(
 /// forwarding operations.
 bool CanonicalizeBorrowScope::
 canonicalizeBorrowScope(BorrowedValue borrowedValue) {
+  BitfieldRef<SSAPrunedLiveness>::StackState livenessBitfieldContainer(
+      liveness, function);
+
   LLVM_DEBUG(llvm::dbgs() << "*** Canonicalize Borrow: " << borrowedValue);
 
   initBorrow(borrowedValue);
 
-  SWIFT_DEFER { liveness.invalidate(); };
-
   if (!computeBorrowLiveness())
     return false;