SILGen: Don't copy a borrowed noncopyable address-only base of a computed property access.

We can probably avoid this copy in more circumstances, but make the change only for
noncopyable types for now, since that's the case where it's most semantically apparent.
rdar://109161396

Author: jckarter

lib/SILGen/SILGenApply.cpp

@@ -6394,7 +6394,12 @@ ArgumentSource AccessorBaseArgPreparer::prepareAccessorAddressBaseArg() {
   // If the base is currently an address, we may have to copy it.
   if (shouldLoadBaseAddress()) {
     if (selfParam.isConsumed() ||
-        base.getType().isAddressOnly(SGF.F)) {
+        (base.getType().isAddressOnly(SGF.F)
+         // If a move-only base is borrowed, then we have to try our best to
+         // borrow it in-place without copying.
+         // TODO: Can we avoid copying a non-move-only value too in this
+         // circumstance?
+         && !base.getType().isMoveOnly())) {
       // The load can only be a take if the base is a +1 rvalue.
       auto shouldTake = IsTake_t(base.hasCleanup());
 
@@ -6403,6 +6408,11 @@ ArgumentSource AccessorBaseArgPreparer::prepareAccessorAddressBaseArg() {
                                       SGFContext(), shouldTake);
       return ArgumentSource(loc, RValue(SGF, loc, baseFormalType, base));
     }
+    
+    // If the type is address-only, we can borrow the memory location as is.
+    if (base.getType().isAddressOnly(SGF.F)) {
+      return ArgumentSource(loc, RValue(SGF, loc, baseFormalType, base));
+    }
 
     // If we do not have a consumed base and need to perform a load, perform a
     // formal access load borrow.

lib/SILGen/SILGenLValue.cpp

@@ -1165,6 +1165,11 @@ namespace {
       assert(base
              && base.getType().isAddress()
              && "should have an address base to borrow from");
+      // If the base value is address-only then we can borrow from the
+      // address in-place.
+      if (!base.getType().isLoadable(SGF.F)) {
+        return base;
+      }
       auto result = SGF.B.createLoadBorrow(loc, base.getValue());
       return SGF.emitFormalEvaluationManagedBorrowedRValueWithCleanup(loc,
          base.getValue(), result);

test/ModuleInterface/moveonly_user.swift

@@ -5,17 +5,13 @@
 // RUN: %target-swift-frontend -emit-sil -sil-verify-all -I %t %s > /dev/null
 
 // >> now again with library evolution; we expect the same result.
-// FIXME: move checker doesn't like it when you specify library evolution
 // RUN: %target-swift-frontend -DSYNTHESIZE_ACCESSORS -enable-library-evolution -emit-module -o %t/Hello.swiftmodule %S/Inputs/moveonly_api.swift
 // RUN: %target-swift-frontend -emit-sil -sil-verify-all -I %t %s > /dev/null
 
 // FIXME: ideally this would also try executing the program rather than just generating SIL
 
 // FIXME: make this test work when we're not synthesizing the accessors
 
-// rdar://106164128
-// XFAIL: *
-
 import Hello
 
 func simpleTest() {

test/SILGen/moveonly_addressonly_computed_property.swift

@@ -0,0 +1,80 @@
+// RUN: %target-swift-emit-silgen %s | %FileCheck %s
+// RUN: %target-swift-frontend -emit-sil -verify %s
+
+// rdar://109161396
+
+public protocol P {}
+
+@_moveOnly
+public struct M {
+   private var x: P
+   var other: CInt { 0 }
+
+   var otherMoveOnly: M {
+       _read {
+           yield self
+       }
+   }
+
+   @_silgen_name("no")
+   init()
+}
+
+// CHECK-LABEL: sil [ossa] @${{.*}}4test3mut
+// CHECK: [[CHECK:%.*]] = mark_must_check [consumable_and_assignable] %0
+// CHECK: [[ACCESS:%.*]] = begin_access [read] [unknown] [[CHECK]]
+// CHECK: [[RESULT:%.*]] = apply {{.*}}([[ACCESS]])
+// CHECK; end_access [[ACCESS]]
+// CHECK: return [[RESULT]]
+public func test(mut: inout M) -> CInt {
+  return mut.other
+}
+
+// CHECK-LABEL: sil [ossa] @${{.*}}4test6borrow
+// CHECK: [[CHECK:%.*]] = mark_must_check [no_consume_or_assign] %0
+// CHECK: [[RESULT:%.*]] = apply {{.*}}([[CHECK]])
+// CHECK: return [[RESULT]]
+public func test(borrow: borrowing M) -> CInt {
+  return borrow.other
+}
+
+// CHECK-LABEL: sil [ossa] @${{.*}}4test7consume
+// CHECK: [[BOX:%.*]] = project_box
+// CHECK: [[ACCESS:%.*]] = begin_access [read] [unknown] [[BOX]]
+// CHECK: [[CHECK:%.*]] = mark_must_check [no_consume_or_assign] [[ACCESS]]
+// CHECK: [[RESULT:%.*]] = apply {{.*}}([[CHECK]])
+// CHECK; end_access [[ACCESS]]
+// CHECK: return [[RESULT]]
+public func test(consume: consuming M) -> CInt {
+  return consume.other
+}
+
+// CHECK-LABEL: sil [ossa] @${{.*}}4test3own
+// CHECK: [[CHECK:%.*]] = mark_must_check [consumable_and_assignable] %0
+// CHECK: [[RESULT:%.*]] = apply {{.*}}([[CHECK]])
+// CHECK: return [[RESULT]]
+public func test(own: __owned M) -> CInt {
+  return own.other
+}
+
+func use(_: CInt, andMutate _: inout M) {}
+func use(_: CInt, andConsume _: consuming M) {}
+func borrow(_: borrowing M, andMutate _: inout M) {}
+func borrow(_: borrowing M, andConsume _: consuming M) {}
+
+public func testNoInterferenceGet(mut: inout M, extra: consuming M) {
+    // This should not cause exclusivity interference, since the result of
+    // the getter can have an independent lifetime from the borrow.
+    use(mut.other, andMutate: &mut)
+    use(mut.other, andConsume: mut)
+    mut = extra
+}
+
+public func testInterferenceRead(mut: inout M, extra: consuming M) {
+    // This should cause exclusivity interference, since in order to borrow
+    // the yielded result from the `_read`, we need to keep the borrow of
+    // the base going.
+    borrow(mut.otherMoveOnly, andMutate: &mut) // expected-error{{}} expected-note{{}}
+    borrow(mut.otherMoveOnly, andConsume: mut) // expected-error{{}} expected-note{{}}
+    mut = extra
+}