AddressLowering: Allow lowering of begin_borrow [lexical] with no lexical address producers

Author: meg-gupta

lib/SILOptimizer/Mandatory/AddressLowering.cpp

@@ -2760,21 +2760,16 @@ void UseRewriter::visitBeginBorrowInst(BeginBorrowInst *borrow) {
   assert(use == getProjectedDefOperand(borrow));
 
   // Mark the value as rewritten and use the operand's storage.
-  auto address = pass.valueStorageMap.getStorage(use->get()).storageAddress;
-  markRewritten(borrow, address);
+  auto storageAddr = pass.valueStorageMap.getStorage(use->get()).storageAddress;
+  markRewritten(borrow, storageAddr);
 
   // Borrows are irrelevant unless they are marked lexical.
   if (borrow->isLexical()) {
-    if (auto *allocStack = dyn_cast<AllocStackInst>(address)) {
+    if (auto *allocStack = dyn_cast<AllocStackInst>(storageAddr)) {
       allocStack->setIsLexical();
       return;
     }
-    // Function arguments are inherently lexical.
-    if (isa<SILFunctionArgument>(address))
-      return;
-
-    SWIFT_ASSERT_ONLY(address->dump());
-    llvm_unreachable("^^^ unknown lexical address producer");
+    return;
   }
 }
 

test/SILGen/opaque_values_silgen.swift

@@ -156,8 +156,8 @@ func propOfLValue(_ x: Error) -> String {
 // HECK: [[LOAD:%.*]] = load [copy] %{{.*}} : $*T
 // HECK: return [[LOAD]] : $T
 // CHECK-LABEL: } // end sil function '$s20opaque_values_silgen7lastValyxxd_tlF'
-func lastVal<T>(_ rest: T...) -> T {
-  var minValue: T
+func lastVal<T>(_ initial: T, _ rest: T...) -> T {
+  var minValue = initial
   for value in rest {
     minValue = value
   }
@@ -399,7 +399,7 @@ func testEmptyReturnClosure() {
 // CHECK: bb1(%{{.*}} : @guaranteed $C):
 // CHECK: bb2(%{{.*}} : @guaranteed $AnyObject):
 // CHECK-LABEL: } // end sil function
-func testCastClassToAnyObject(_ c: C) -> AnyObject {
+func testCastClassToAnyObject(_ c: C) {
   switch (c) {
   case let x as AnyObject:
     _ = x
@@ -412,7 +412,7 @@ func testCastClassToAnyObject(_ c: C) -> AnyObject {
 // CHECK:   [[CP:%.*]] = copy_value %0 : $AnyObject
 // CHECK:   checked_cast_br [[CP]] : $AnyObject to C, bb1, bb2
 // CHECK-LABEL: } // end sil function '$s20opaque_values_silgen24testCastAnyObjectToClassyAA1CCyXlF'
-func testCastAnyObjectToClass(_ o: AnyObject) -> C {
+func testCastAnyObjectToClass(_ o: AnyObject) {
   switch (o) {
   case let x as C:
     _ = x
@@ -427,7 +427,7 @@ func testCastAnyObjectToClass(_ o: AnyObject) -> C {
 // CHECK:   [[CP:%.*]] = copy_value %0 : $T
 // CHECK:   checked_cast_br [[CP]] : $T to C, bb1, bb2
 // CHECK-LABEL: } // end sil function '$s20opaque_values_silgen024testCastClassArchetypeToF0yAA1CCxRlzClF'
-func testCastClassArchetypeToClass<T : AnyObject>(_ o: T) -> C {
+func testCastClassArchetypeToClass<T : AnyObject>(_ o: T) {
   switch (o) {
   case let x as C:
     _ = x
@@ -438,7 +438,10 @@ func testCastClassArchetypeToClass<T : AnyObject>(_ o: T) -> C {
 }
 
 class TestGeneric<T> {
-  init() {}
+  init(_ _generic:T, _ _borrowedGeneric:T) {
+    generic = _generic
+    borrowedGeneric = _borrowedGeneric
+  }
 
   var generic: T
   @_borrowed