AccessUtils: fix handling of store_borrow in AccessBase.isDistinct

The result of a store_borrow can "escape" to other access bases, like a "pointer" access base.
Then a store-borrow access base is _not_ distinct from such another base.

Author: eeckstein

SwiftCompilerSources/Sources/SIL/Utilities/AccessUtils.swift

@@ -286,11 +286,11 @@ public enum AccessBase : CustomStringConvertible, Hashable {
     case (.storeBorrow(let arg), .storeBorrow(let otherArg)):
       return arg.allocStack != otherArg.allocStack
 
-    // A StoreBorrow location can only be used by other StoreBorrows.
-    case (.storeBorrow, _):
-      return true
-    case (_, .storeBorrow):
-      return true
+    // Handle the special case of store_borrow - alloc_stack, because that would give a false result in the default case.
+    case (.storeBorrow(let sbi), .stack(let asi)):
+      return sbi.allocStack != asi
+    case (.stack(let asi), .storeBorrow(let sbi)):
+      return sbi.allocStack != asi
 
     default:
       // As we already handled pairs of the same kind, here we handle pairs with different kinds.

test/SILOptimizer/basic-aa.sil

@@ -684,3 +684,25 @@ bb0(%0 : @guaranteed $GenericClass<Int32>, %1 : @guaranteed $GenericClass<Int>):
   return %9999 : $()
 }
 
+// CHECK-LABEL: @test_store_borrow
+// CHECK:       PAIR #7.
+// CHECK-NEXT:      %1 = alloc_stack $X
+// CHECK-NEXT:      %2 = store_borrow %0 to %1 : $*X
+// CHECK-NEXT:    MayAlias
+// CHECK:       PAIR #13.
+// CHECK-NEXT:      %2 = store_borrow %0 to %1 : $*X
+// CHECK-NEXT:      %4 = pointer_to_address %3 : $Builtin.RawPointer to [strict] $*X
+// CHECK-NEXT:    MayAlias
+sil [ossa] @test_store_borrow : $@convention(thin) (@guaranteed X) -> () {
+bb0(%0 :  @guaranteed $X):
+  %1 = alloc_stack $X
+  %2 = store_borrow %0 to %1 : $*X
+  %3 = address_to_pointer %2 : $*X to $Builtin.RawPointer
+  %4 = pointer_to_address %3 : $Builtin.RawPointer to [strict] $*X
+  fix_lifetime %4 : $*X
+  end_borrow %2 : $*X
+  dealloc_stack %1 : $*X
+  %7 = tuple ()
+  return %7 : $()
+}
+