[OwnershipLiveness] End at extend_lifetime.

All ownership liveness types treat `extend_lifetime` instructions as
lifetime-ending (on the C++ side, there is no corresponding caching on
the Swift side).  As such, `LinearLiveness` adds these instructions to
its backing range tracking gadget.  On the C++ side, this can be
disabled for the purposes of verification.

Author: nate-chandler

SwiftCompilerSources/Sources/Optimizer/Utilities/OwnershipLiveness.swift

@@ -64,8 +64,11 @@ func computeLinearLiveness(for definingValue: Value, _ context: Context)
   var range = InstructionRange(for: definingValue, context)
 
   // Compute liveness.
-  definingValue.lookThroughBorrowedFromUser.uses.endingLifetime.forEach {
-    range.insert($0.instruction)
+ for use in definingValue.lookThroughBorrowedFromUser.uses {
+    let instruction = use.instruction
+    if use.endsLifetime || instruction is ExtendLifetimeInst {
+      range.insert(instruction)
+    }
   }
   return range
 }

include/swift/SIL/OwnershipLiveness.h

@@ -206,9 +206,19 @@ class LinearLiveness : public OSSALiveness {
   friend LinearLivenessVisitor;
 
 public:
-  LinearLiveness(SILValue def);
+  /// Whether extend_lifetime instructions should be added to the boundary.
+  /// Used to verify extend_lifetime instructions.
+  enum IncludeExtensions_t {
+    DoNotIncludeExtensions = false,
+    IncludeExtensions = true,
+  };
+  LinearLiveness(SILValue def,
+                 IncludeExtensions_t includeExtensions = IncludeExtensions);
 
   void compute();
+
+private:
+  const IncludeExtensions_t includeExtensions;
 };
 
 // Internal implementation

include/swift/SIL/OwnershipUseVisitor.h

@@ -213,6 +213,11 @@ bool OwnershipUseVisitor<Impl>::visitLifetimeEndingUses(SILValue ssaDef) {
 template <typename Impl>
 bool OwnershipUseVisitor<Impl>::visitConsumes(SILValue ssaDef) {
   for (Operand *use : ssaDef->getUses()) {
+    if (isa<ExtendLifetimeInst>(use->getUser())) {
+      if (!handleUsePoint(use, UseLifetimeConstraint::LifetimeEnding))
+        return false;
+      continue;
+    }
     if (use->isConsuming()) {
       if (PhiOperand(use) && !asImpl().handleOwnedPhi(use))
         return false;

lib/SIL/Utils/OwnershipLiveness.cpp

@@ -38,6 +38,13 @@ struct LinearLivenessVisitor :
     linearLiveness(linearLiveness){}
 
   bool handleUsePoint(Operand *use, UseLifetimeConstraint useConstraint) {
+    if (isa<ExtendLifetimeInst>(use->getUser())) {
+      if (linearLiveness.includeExtensions) {
+        linearLiveness.liveness.updateForUse(use->getUser(),
+                                             /*lifetimeEnding=*/true);
+      }
+      return true;
+    }
     linearLiveness.liveness.updateForUse(
       use->getUser(), useConstraint == UseLifetimeConstraint::LifetimeEnding);
     return true;
@@ -71,7 +78,9 @@ struct LinearLivenessVisitor :
   }
 };
 
-LinearLiveness::LinearLiveness(SILValue def): OSSALiveness(def) {
+LinearLiveness::LinearLiveness(SILValue def,
+                               IncludeExtensions_t includeExtensions)
+    : OSSALiveness(def), includeExtensions(includeExtensions) {
   if (def->getOwnershipKind() != OwnershipKind::Owned) {
     BorrowedValue borrowedValue(def);
     assert(borrowedValue && borrowedValue.isLocalScope());
@@ -118,7 +127,9 @@ struct InteriorLivenessVisitor :
 
   bool handleUsePoint(Operand *use, UseLifetimeConstraint useConstraint) {
     interiorLiveness.liveness.updateForUse(
-      use->getUser(), useConstraint == UseLifetimeConstraint::LifetimeEnding);
+        use->getUser(),
+        (useConstraint == UseLifetimeConstraint::LifetimeEnding) ||
+            isa<ExtendLifetimeInst>(use->getUser()));
     return true;
   }
 
@@ -302,7 +313,9 @@ struct ExtendedLinearLivenessVisitor
 
   bool handleUsePoint(Operand *use, UseLifetimeConstraint useConstraint) {
     extendedLiveness.liveness.updateForUse(
-      use->getUser(), useConstraint == UseLifetimeConstraint::LifetimeEnding);
+        use->getUser(),
+        (useConstraint == UseLifetimeConstraint::LifetimeEnding) ||
+            isa<ExtendLifetimeInst>(use->getUser()));
     return true;
   }
 

lib/SIL/Utils/OwnershipUtils.cpp

@@ -950,6 +950,10 @@ bool BorrowedValue::visitLocalScopeEndingUses(
   case BorrowedValueKind::Phi:
   case BorrowedValueKind::BeginApplyToken:
     for (auto *use : lookThroughBorrowedFromUser(value)->getUses()) {
+      if (isa<ExtendLifetimeInst>(use->getUser())) {
+        if (!visitor(use))
+          return false;
+      }
       if (use->isLifetimeEnding()) {
         if (!visitor(use))
           return false;