While verifiying mark_dependence [nonescaping], skip visiting phis

TODO: Handle verification of mark_dependence [nonescaping] with phi uses
separately in the ownership verifier

Author: meg-gupta

lib/SIL/IR/SILInstruction.cpp

@@ -1792,11 +1792,10 @@ bool SILInstruction::maySuspend() const {
   return false;
 }
 
-static bool visitRecursivelyLifetimeEndingUses(
-  SILValue i,
-  bool &noUsers,
-  llvm::function_ref<bool(Operand *)> func)
-{
+static bool
+visitRecursivelyLifetimeEndingUses(SILValue i, bool &noUsers,
+                                   llvm::function_ref<bool(Operand *)> func,
+                                   bool skipVisitingPhis) {
   for (Operand *use : i->getConsumingUses()) {
     noUsers = false;
     if (isa<DestroyValueInst>(use->getUser())) {
@@ -1813,6 +1812,11 @@ static bool visitRecursivelyLifetimeEndingUses(
       }
       continue;
     }
+    if (skipVisitingPhis) {
+      if (PhiOperand(use)) {
+        continue;
+      }
+    }
     // FIXME: Handle store to indirect result
 
     // There shouldn't be any dead-end consumptions of a nonescaping
@@ -1835,7 +1839,8 @@ static bool visitRecursivelyLifetimeEndingUses(
                                "forwarded to a destroy_value");
     }
     for (auto res : use->getUser()->getResults()) {
-      if (!visitRecursivelyLifetimeEndingUses(res, noUsers, func)) {
+      if (!visitRecursivelyLifetimeEndingUses(res, noUsers, func,
+                                              skipVisitingPhis)) {
         return false;
       }
     }
@@ -1851,7 +1856,8 @@ PartialApplyInst::visitOnStackLifetimeEnds(
          && "only meaningful for OSSA stack closures");
   bool noUsers = true;
 
-  if (!visitRecursivelyLifetimeEndingUses(this, noUsers, func)) {
+  if (!visitRecursivelyLifetimeEndingUses(this, noUsers, func,
+                                          /*skipVisitingPhis*/ false)) {
     return false;
   }
   return !noUsers;
@@ -1863,7 +1869,8 @@ visitNonEscapingLifetimeEnds(llvm::function_ref<bool (Operand *)> func) const {
          && "only meaningful for nonescaping dependencies");
   bool noUsers = true;
 
-  if (!visitRecursivelyLifetimeEndingUses(this, noUsers, func)) {
+  if (!visitRecursivelyLifetimeEndingUses(this, noUsers, func,
+                                          /*skipVisitingPhis*/ true)) {
     return false;
   }
   return !noUsers;

lib/SIL/Verifier/SILOwnershipVerifier.cpp

@@ -261,6 +261,7 @@ bool SILValueOwnershipChecker::gatherNonGuaranteedUsers(
       guaranteedPhiVerifier.verifyReborrows(
           cast<BeginBorrowInst>(op->getUser()));
     }
+    // TODO: Verify mark_dependence [nonescaping]'s transitive phi uses.
   }
 
   return foundError;

test/SIL/lifetime_dependence_buffer_view_test.swift

@@ -2,7 +2,6 @@
 // RUN:   -disable-experimental-parser-round-trip \
 // RUN:   -enable-experimental-feature NonescapableTypes \
 // RUN:   -enable-experimental-feature NoncopyableGenerics \
-// RUN:   -enable-experimental-lifetime-dependence-inference \
 // RUN:   -disable-lifetime-dependence-diagnostics
 
 // REQUIRES: asserts
@@ -64,7 +63,7 @@ public struct BufferView<Element> : ~Escapable {
   private var baseAddress: UnsafeRawPointer { start._rawValue }
 // TODO: Enable diagnostics once this initializer's store to temporary is handled  
 // CHECK: sil @$s31lifetime_dependence_scope_fixup10BufferViewV11baseAddress5count9dependsOnACyxGSVYls_Siqd__htclufC : $@convention(method) <Element><Owner> (UnsafeRawPointer, Int, @in_guaranteed Owner, @thin BufferView<Element>.Type) -> _scope(1) @owned BufferView<Element> {
-  public init<Owner>(
+  public init<Owner: ~Copyable & ~Escapable>(
       baseAddress: UnsafeRawPointer,
       count: Int,
       dependsOn owner: borrowing Owner
@@ -74,7 +73,7 @@ public struct BufferView<Element> : ~Escapable {
       )
   }
 // CHECK: sil hidden @$s31lifetime_dependence_scope_fixup10BufferViewV5start5count9dependsOnACyxGAA0eF5IndexVyxGYls_Siqd__htclufC : $@convention(method) <Element><Owner> (BufferViewIndex<Element>, Int, @in_guaranteed Owner, @thin BufferView<Element>.Type) -> _scope(1) @owned BufferView<Element> {
-  init<Owner>(
+  init<Owner: ~Copyable & ~Escapable>(
     start index: BufferViewIndex<Element>,
     count: Int,
     dependsOn owner: borrowing Owner
@@ -110,6 +109,11 @@ extension BufferView {
 
   public var startIndex: Index { start }
   public var endIndex: Index { start.advanced(by: count) }  
+
+  @inlinable @inline(__always) 
+  public func distance(from start: Index, to end: Index) -> Int {
+    start.distance(to: end)
+  }
 
   public subscript(position: Index) -> Element {
     get {
@@ -131,6 +135,23 @@ extension BufferView {
       )
     }
   }
+
+  borrowing public func prefix(upTo index: BufferViewIndex<Element>) -> _borrow(self) Self {
+    index == startIndex
+    ? Self(start: start, count: 0, dependsOn: copy self)
+    : prefix(through: index.advanced(by: -1))
+  }
+
+  borrowing public func prefix(through index: Index) -> _borrow(self) Self {
+    let nc = distance(from: startIndex, to: index) &+ 1
+    return Self(start: start, count: nc, dependsOn: copy self)
+  }
+
+  consuming public func prefix(_ maxLength: Int) -> _consume(self) Self {
+    precondition(maxLength >= 0, "Can't have a prefix of negative length.")
+    let nc = maxLength < count ? maxLength : count
+    return Self(start: start, count: nc, dependsOn: self)
+  }
 }
 
 extension Array {