From b13c37726c4dc5cc60d1117c6de629810d2519f0 Mon Sep 17 00:00:00 2001
From: Daco Harkes <dacoharkes@google.com>
Date: Fri, 16 Oct 2020 11:16:02 +0000
Subject: [PATCH] [cfe/ffi] Transformation changes for structs-by-value

Changes the kernel representation of structs in two ways.
1. `_addressOf` field of `Struct` gets type `Object` because it will be
   either `TypedData` or `Pointer` in structs by value CL.
2. Subtypes of `Struct` get a pragma `vm:ffi:struct-fields` which
   contains a const list of the native types of the fields of the struct
   which will be read in the VM to do compute the locations of structs
   in the target ABI.

Split off from https://dart-review.googlesource.com/c/sdk/+/140290/23
to make that CL smaller. That CL will no longer have changes to the
kernel representation of FFI code after this CL lands separately.

These changes are not consumed in the VM in this CL, but they are tested
by the expect files.

Issue: https://github.com/dart-lang/sdk/issues/36730.

Change-Id: I5d3babd5be07f78c6d2bd80bbc1fd492c51bc01f
Cq-Include-Trybots: luci.dart.try:front-end-linux-release-x64-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/167280
Commit-Queue: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>
---
 .../general/ffi_sample.dart.outline.expect    |  2 +-
 .../general/ffi_sample.dart.strong.expect     |  2 +-
 .../ffi_sample.dart.strong.transformed.expect | 40 ++++++++++--------
 .../ffi_sample.dart.weak.expect               |  2 +-
 .../ffi_sample.dart.weak.transformed.expect   | 40 ++++++++++--------
 .../ffi_01.yaml.world.1.expect                | 40 ++++++++++--------
 .../ffi_01.yaml.world.2.expect                | 40 ++++++++++--------
 .../ffi_02.yaml.world.1.expect                | 40 ++++++++++--------
 .../no_outline_change_35.yaml.world.1.expect  | 40 ++++++++++--------
 .../no_outline_change_35.yaml.world.2.expect  | 40 ++++++++++--------
 .../no_outline_change_35.yaml.world.3.expect  | 40 ++++++++++--------
 pkg/vm/lib/transformations/ffi.dart           |  2 +
 .../lib/transformations/ffi_definitions.dart  | 41 ++++++++++++++++---
 pkg/vm/lib/transformations/ffi_use_sites.dart | 25 ++++++-----
 sdk/lib/ffi/struct.dart                       |  2 +-
 15 files changed, 239 insertions(+), 157 deletions(-)

diff --git a/pkg/front_end/testcases/general/ffi_sample.dart.outline.expect b/pkg/front_end/testcases/general/ffi_sample.dart.outline.expect
index 2a3bf2683899..c1e27d7ee1eb 100644
--- a/pkg/front_end/testcases/general/ffi_sample.dart.outline.expect
+++ b/pkg/front_end/testcases/general/ffi_sample.dart.outline.expect
@@ -14,7 +14,7 @@ class Coordinate extends ffi::Struct {
   field ffi::Pointer<self::Coordinate*>* next;
   static factory allocate(core::double* x, core::double* y, ffi::Pointer<self::Coordinate*>* next) → self::Coordinate*
     ;
-  abstract member-signature get _addressOf() → ffi::Pointer<ffi::Struct*>*; -> ffi::Struct::_addressOf
+  abstract member-signature get _addressOf() → core::Object*; -> ffi::Struct::_addressOf
   abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
   abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
   abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
diff --git a/pkg/front_end/testcases/general/ffi_sample.dart.strong.expect b/pkg/front_end/testcases/general/ffi_sample.dart.strong.expect
index 0e669c094a97..a8534216b1ec 100644
--- a/pkg/front_end/testcases/general/ffi_sample.dart.strong.expect
+++ b/pkg/front_end/testcases/general/ffi_sample.dart.strong.expect
@@ -20,7 +20,7 @@ class Coordinate extends ffi::Struct {
       #t1.{self::Coordinate::next} = next;
     } =>#t1;
   }
-  abstract member-signature get _addressOf() → ffi::Pointer<ffi::Struct*>*; -> ffi::Struct::_addressOf
+  abstract member-signature get _addressOf() → core::Object*; -> ffi::Struct::_addressOf
   abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
   abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
   abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
diff --git a/pkg/front_end/testcases/general/ffi_sample.dart.strong.transformed.expect b/pkg/front_end/testcases/general/ffi_sample.dart.strong.transformed.expect
index c402dcaca161..324ae5feccac 100644
--- a/pkg/front_end/testcases/general/ffi_sample.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/ffi_sample.dart.strong.transformed.expect
@@ -8,9 +8,10 @@ import "dart:ffi";
 import "package:ffi/ffi.dart";
 
 @#C3
+@#C8
 class Coordinate extends ffi::Struct {
   @#C3
-  static final field core::int* #sizeOf = (#C6).{core::List::[]}(ffi::_abi());
+  static final field core::int* #sizeOf = (#C11).{core::List::[]}(ffi::_abi());
   @#C3
   constructor #fromPointer(dynamic #pointer) → dynamic
     : super ffi::Struct::_fromPointer(#pointer)
@@ -22,7 +23,7 @@ class Coordinate extends ffi::Struct {
       #t1.{self::Coordinate::next} = next;
     } =>#t1;
   }
-  abstract member-signature get _addressOf() → ffi::Pointer<ffi::Struct*>*; -> ffi::Struct::_addressOf
+  abstract member-signature get _addressOf() → core::Object*; -> ffi::Struct::_addressOf
   abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
   abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
   abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
@@ -34,17 +35,17 @@ class Coordinate extends ffi::Struct {
   abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
   abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
   get x() → core::double*
-    return ffi::_loadDouble(this.{ffi::Struct::_addressOf}, (#C8).{core::List::[]}(ffi::_abi()));
+    return ffi::_loadDouble(this.{ffi::Struct::_addressOf}, (#C13).{core::List::[]}(ffi::_abi()));
   set x(core::double* #v) → void
-    return ffi::_storeDouble(this.{ffi::Struct::_addressOf}, (#C8).{core::List::[]}(ffi::_abi()), #v);
+    return ffi::_storeDouble(this.{ffi::Struct::_addressOf}, (#C13).{core::List::[]}(ffi::_abi()), #v);
   get y() → core::double*
-    return ffi::_loadDouble(this.{ffi::Struct::_addressOf}, (#C10).{core::List::[]}(ffi::_abi()));
+    return ffi::_loadDouble(this.{ffi::Struct::_addressOf}, (#C15).{core::List::[]}(ffi::_abi()));
   set y(core::double* #v) → void
-    return ffi::_storeDouble(this.{ffi::Struct::_addressOf}, (#C10).{core::List::[]}(ffi::_abi()), #v);
+    return ffi::_storeDouble(this.{ffi::Struct::_addressOf}, (#C15).{core::List::[]}(ffi::_abi()), #v);
   get next() → ffi::Pointer<self::Coordinate*>*
-    return ffi::_fromAddress<self::Coordinate*>(ffi::_loadIntPtr(this.{ffi::Struct::_addressOf}, (#C12).{core::List::[]}(ffi::_abi())));
+    return ffi::_fromAddress<self::Coordinate*>(ffi::_loadIntPtr(this.{ffi::Struct::_addressOf}, (#C17).{core::List::[]}(ffi::_abi())));
   set next(ffi::Pointer<self::Coordinate*>* #v) → void
-    return ffi::_storeIntPtr(this.{ffi::Struct::_addressOf}, (#C12).{core::List::[]}(ffi::_abi()), #v.{ffi::Pointer::address});
+    return ffi::_storeIntPtr(this.{ffi::Struct::_addressOf}, (#C17).{core::List::[]}(ffi::_abi()), #v.{ffi::Pointer::address});
 }
 static method main() → dynamic {}
 
@@ -52,13 +53,18 @@ constants  {
   #C1 = "vm:entry-point"
   #C2 = null
   #C3 = core::pragma {name:#C1, options:#C2}
-  #C4 = 24
-  #C5 = 20
-  #C6 = <core::int*>[#C4, #C5, #C4]
-  #C7 = 0
-  #C8 = <core::int*>[#C7, #C7, #C7]
-  #C9 = 8
-  #C10 = <core::int*>[#C9, #C9, #C9]
-  #C11 = 16
-  #C12 = <core::int*>[#C11, #C11, #C11]
+  #C4 = "vm:ffi:struct-fields"
+  #C5 = TypeLiteralConstant(ffi::Double)
+  #C6 = TypeLiteralConstant(ffi::Pointer<ffi::NativeType>)
+  #C7 = <core::Type>[#C5, #C5, #C6]
+  #C8 = core::pragma {name:#C4, options:#C7}
+  #C9 = 24
+  #C10 = 20
+  #C11 = <core::int*>[#C9, #C10, #C9]
+  #C12 = 0
+  #C13 = <core::int*>[#C12, #C12, #C12]
+  #C14 = 8
+  #C15 = <core::int*>[#C14, #C14, #C14]
+  #C16 = 16
+  #C17 = <core::int*>[#C16, #C16, #C16]
 }
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/ffi_sample.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/ffi_sample.dart.weak.expect
index 0e669c094a97..a8534216b1ec 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/ffi_sample.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/ffi_sample.dart.weak.expect
@@ -20,7 +20,7 @@ class Coordinate extends ffi::Struct {
       #t1.{self::Coordinate::next} = next;
     } =>#t1;
   }
-  abstract member-signature get _addressOf() → ffi::Pointer<ffi::Struct*>*; -> ffi::Struct::_addressOf
+  abstract member-signature get _addressOf() → core::Object*; -> ffi::Struct::_addressOf
   abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
   abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
   abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/ffi_sample.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/ffi_sample.dart.weak.transformed.expect
index c402dcaca161..324ae5feccac 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/ffi_sample.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/ffi_sample.dart.weak.transformed.expect
@@ -8,9 +8,10 @@ import "dart:ffi";
 import "package:ffi/ffi.dart";
 
 @#C3
+@#C8
 class Coordinate extends ffi::Struct {
   @#C3
-  static final field core::int* #sizeOf = (#C6).{core::List::[]}(ffi::_abi());
+  static final field core::int* #sizeOf = (#C11).{core::List::[]}(ffi::_abi());
   @#C3
   constructor #fromPointer(dynamic #pointer) → dynamic
     : super ffi::Struct::_fromPointer(#pointer)
@@ -22,7 +23,7 @@ class Coordinate extends ffi::Struct {
       #t1.{self::Coordinate::next} = next;
     } =>#t1;
   }
-  abstract member-signature get _addressOf() → ffi::Pointer<ffi::Struct*>*; -> ffi::Struct::_addressOf
+  abstract member-signature get _addressOf() → core::Object*; -> ffi::Struct::_addressOf
   abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
   abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
   abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
@@ -34,17 +35,17 @@ class Coordinate extends ffi::Struct {
   abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
   abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
   get x() → core::double*
-    return ffi::_loadDouble(this.{ffi::Struct::_addressOf}, (#C8).{core::List::[]}(ffi::_abi()));
+    return ffi::_loadDouble(this.{ffi::Struct::_addressOf}, (#C13).{core::List::[]}(ffi::_abi()));
   set x(core::double* #v) → void
-    return ffi::_storeDouble(this.{ffi::Struct::_addressOf}, (#C8).{core::List::[]}(ffi::_abi()), #v);
+    return ffi::_storeDouble(this.{ffi::Struct::_addressOf}, (#C13).{core::List::[]}(ffi::_abi()), #v);
   get y() → core::double*
-    return ffi::_loadDouble(this.{ffi::Struct::_addressOf}, (#C10).{core::List::[]}(ffi::_abi()));
+    return ffi::_loadDouble(this.{ffi::Struct::_addressOf}, (#C15).{core::List::[]}(ffi::_abi()));
   set y(core::double* #v) → void
-    return ffi::_storeDouble(this.{ffi::Struct::_addressOf}, (#C10).{core::List::[]}(ffi::_abi()), #v);
+    return ffi::_storeDouble(this.{ffi::Struct::_addressOf}, (#C15).{core::List::[]}(ffi::_abi()), #v);
   get next() → ffi::Pointer<self::Coordinate*>*
-    return ffi::_fromAddress<self::Coordinate*>(ffi::_loadIntPtr(this.{ffi::Struct::_addressOf}, (#C12).{core::List::[]}(ffi::_abi())));
+    return ffi::_fromAddress<self::Coordinate*>(ffi::_loadIntPtr(this.{ffi::Struct::_addressOf}, (#C17).{core::List::[]}(ffi::_abi())));
   set next(ffi::Pointer<self::Coordinate*>* #v) → void
-    return ffi::_storeIntPtr(this.{ffi::Struct::_addressOf}, (#C12).{core::List::[]}(ffi::_abi()), #v.{ffi::Pointer::address});
+    return ffi::_storeIntPtr(this.{ffi::Struct::_addressOf}, (#C17).{core::List::[]}(ffi::_abi()), #v.{ffi::Pointer::address});
 }
 static method main() → dynamic {}
 
@@ -52,13 +53,18 @@ constants  {
   #C1 = "vm:entry-point"
   #C2 = null
   #C3 = core::pragma {name:#C1, options:#C2}
-  #C4 = 24
-  #C5 = 20
-  #C6 = <core::int*>[#C4, #C5, #C4]
-  #C7 = 0
-  #C8 = <core::int*>[#C7, #C7, #C7]
-  #C9 = 8
-  #C10 = <core::int*>[#C9, #C9, #C9]
-  #C11 = 16
-  #C12 = <core::int*>[#C11, #C11, #C11]
+  #C4 = "vm:ffi:struct-fields"
+  #C5 = TypeLiteralConstant(ffi::Double)
+  #C6 = TypeLiteralConstant(ffi::Pointer<ffi::NativeType>)
+  #C7 = <core::Type>[#C5, #C5, #C6]
+  #C8 = core::pragma {name:#C4, options:#C7}
+  #C9 = 24
+  #C10 = 20
+  #C11 = <core::int*>[#C9, #C10, #C9]
+  #C12 = 0
+  #C13 = <core::int*>[#C12, #C12, #C12]
+  #C14 = 8
+  #C15 = <core::int*>[#C14, #C14, #C14]
+  #C16 = 16
+  #C17 = <core::int*>[#C16, #C16, #C16]
 }
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/ffi_01.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/ffi_01.yaml.world.1.expect
index 07b6c8065ac6..0fc8261aa63c 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/ffi_01.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/ffi_01.yaml.world.1.expect
@@ -4,9 +4,10 @@ library from "org-dartlang-test:///lib.dart" as lib {
   import "dart:ffi";
 
   @#C3
+  @#C8
   class Coordinate extends dart.ffi::Struct {
     @#C3
-    static final field dart.core::int* #sizeOf = (#C6).{dart.core::List::[]}(dart.ffi::_abi());
+    static final field dart.core::int* #sizeOf = (#C11).{dart.core::List::[]}(dart.ffi::_abi());
     @#C3
     constructor #fromPointer(dynamic #pointer) → dynamic
       : super dart.ffi::Struct::_fromPointer(#pointer)
@@ -14,7 +15,7 @@ library from "org-dartlang-test:///lib.dart" as lib {
     static factory allocate(dart.core::double* x, dart.core::double* y, dart.ffi::Pointer<lib::Coordinate*>* next) → lib::Coordinate* {
       return null;
     }
-    abstract member-signature get _addressOf() → dart.ffi::Pointer<dart.ffi::Struct*>*; -> dart.ffi::Struct::_addressOf
+    abstract member-signature get _addressOf() → dart.core::Object*; -> dart.ffi::Struct::_addressOf
     abstract member-signature get _identityHashCode() → dart.core::int*; -> dart.core::Object::_identityHashCode
     abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → dart.core::bool*; -> dart.core::Object::_instanceOf
     abstract member-signature method _simpleInstanceOf(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOf
@@ -26,17 +27,17 @@ library from "org-dartlang-test:///lib.dart" as lib {
     abstract member-signature method noSuchMethod(dart.core::Invocation* invocation) → dynamic; -> dart.core::Object::noSuchMethod
     abstract member-signature get runtimeType() → dart.core::Type*; -> dart.core::Object::runtimeType
     get x() → dart.core::double*
-      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C8).{dart.core::List::[]}(dart.ffi::_abi()));
+      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C13).{dart.core::List::[]}(dart.ffi::_abi()));
     set x(dart.core::double* #v) → void
-      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C8).{dart.core::List::[]}(dart.ffi::_abi()), #v);
+      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C13).{dart.core::List::[]}(dart.ffi::_abi()), #v);
     get y() → dart.core::double*
-      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C10).{dart.core::List::[]}(dart.ffi::_abi()));
+      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C15).{dart.core::List::[]}(dart.ffi::_abi()));
     set y(dart.core::double* #v) → void
-      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C10).{dart.core::List::[]}(dart.ffi::_abi()), #v);
+      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C15).{dart.core::List::[]}(dart.ffi::_abi()), #v);
     get next() → dart.ffi::Pointer<lib::Coordinate*>*
-      return dart.ffi::_fromAddress<lib::Coordinate*>(dart.ffi::_loadIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C12).{dart.core::List::[]}(dart.ffi::_abi())));
+      return dart.ffi::_fromAddress<lib::Coordinate*>(dart.ffi::_loadIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C17).{dart.core::List::[]}(dart.ffi::_abi())));
     set next(dart.ffi::Pointer<lib::Coordinate*>* #v) → void
-      return dart.ffi::_storeIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C12).{dart.core::List::[]}(dart.ffi::_abi()), #v.{dart.ffi::Pointer::address});
+      return dart.ffi::_storeIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C17).{dart.core::List::[]}(dart.ffi::_abi()), #v.{dart.ffi::Pointer::address});
   }
 }
 library from "org-dartlang-test:///main.dart" as main {
@@ -54,13 +55,18 @@ constants  {
   #C1 = "vm:entry-point"
   #C2 = null
   #C3 = dart.core::pragma {name:#C1, options:#C2}
-  #C4 = 24
-  #C5 = 20
-  #C6 = <dart.core::int*>[#C4, #C5, #C4]
-  #C7 = 0
-  #C8 = <dart.core::int*>[#C7, #C7, #C7]
-  #C9 = 8
-  #C10 = <dart.core::int*>[#C9, #C9, #C9]
-  #C11 = 16
-  #C12 = <dart.core::int*>[#C11, #C11, #C11]
+  #C4 = "vm:ffi:struct-fields"
+  #C5 = TypeLiteralConstant(dart.ffi::Double)
+  #C6 = TypeLiteralConstant(dart.ffi::Pointer<dart.ffi::NativeType>)
+  #C7 = <dart.core::Type>[#C5, #C5, #C6]
+  #C8 = dart.core::pragma {name:#C4, options:#C7}
+  #C9 = 24
+  #C10 = 20
+  #C11 = <dart.core::int*>[#C9, #C10, #C9]
+  #C12 = 0
+  #C13 = <dart.core::int*>[#C12, #C12, #C12]
+  #C14 = 8
+  #C15 = <dart.core::int*>[#C14, #C14, #C14]
+  #C16 = 16
+  #C17 = <dart.core::int*>[#C16, #C16, #C16]
 }
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/ffi_01.yaml.world.2.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/ffi_01.yaml.world.2.expect
index c592dbf78ce7..492675028bfd 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/ffi_01.yaml.world.2.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/ffi_01.yaml.world.2.expect
@@ -4,9 +4,10 @@ library from "org-dartlang-test:///lib.dart" as lib {
   import "dart:ffi";
 
   @#C3
+  @#C8
   class Coordinate extends dart.ffi::Struct {
     @#C3
-    static final field dart.core::int* #sizeOf = (#C6).{dart.core::List::[]}(dart.ffi::_abi());
+    static final field dart.core::int* #sizeOf = (#C11).{dart.core::List::[]}(dart.ffi::_abi());
     @#C3
     constructor #fromPointer(dynamic #pointer) → dynamic
       : super dart.ffi::Struct::_fromPointer(#pointer)
@@ -14,7 +15,7 @@ library from "org-dartlang-test:///lib.dart" as lib {
     static factory allocate(dart.core::double* x, dart.core::double* y, dart.ffi::Pointer<lib::Coordinate*>* next) → lib::Coordinate* {
       return null;
     }
-    abstract member-signature get _addressOf() → dart.ffi::Pointer<dart.ffi::Struct*>*; -> dart.ffi::Struct::_addressOf
+    abstract member-signature get _addressOf() → dart.core::Object*; -> dart.ffi::Struct::_addressOf
     abstract member-signature get _identityHashCode() → dart.core::int*; -> dart.core::Object::_identityHashCode
     abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → dart.core::bool*; -> dart.core::Object::_instanceOf
     abstract member-signature method _simpleInstanceOf(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOf
@@ -26,17 +27,17 @@ library from "org-dartlang-test:///lib.dart" as lib {
     abstract member-signature method noSuchMethod(dart.core::Invocation* invocation) → dynamic; -> dart.core::Object::noSuchMethod
     abstract member-signature get runtimeType() → dart.core::Type*; -> dart.core::Object::runtimeType
     get x() → dart.core::double*
-      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C8).{dart.core::List::[]}(dart.ffi::_abi()));
+      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C13).{dart.core::List::[]}(dart.ffi::_abi()));
     set x(dart.core::double* #v) → void
-      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C8).{dart.core::List::[]}(dart.ffi::_abi()), #v);
+      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C13).{dart.core::List::[]}(dart.ffi::_abi()), #v);
     get y() → dart.core::double*
-      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C10).{dart.core::List::[]}(dart.ffi::_abi()));
+      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C15).{dart.core::List::[]}(dart.ffi::_abi()));
     set y(dart.core::double* #v) → void
-      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C10).{dart.core::List::[]}(dart.ffi::_abi()), #v);
+      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C15).{dart.core::List::[]}(dart.ffi::_abi()), #v);
     get next() → dart.ffi::Pointer<lib::Coordinate*>*
-      return dart.ffi::_fromAddress<lib::Coordinate*>(dart.ffi::_loadIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C12).{dart.core::List::[]}(dart.ffi::_abi())));
+      return dart.ffi::_fromAddress<lib::Coordinate*>(dart.ffi::_loadIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C17).{dart.core::List::[]}(dart.ffi::_abi())));
     set next(dart.ffi::Pointer<lib::Coordinate*>* #v) → void
-      return dart.ffi::_storeIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C12).{dart.core::List::[]}(dart.ffi::_abi()), #v.{dart.ffi::Pointer::address});
+      return dart.ffi::_storeIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C17).{dart.core::List::[]}(dart.ffi::_abi()), #v.{dart.ffi::Pointer::address});
   }
 }
 library from "org-dartlang-test:///main.dart" as main {
@@ -58,13 +59,18 @@ constants  {
   #C1 = "vm:entry-point"
   #C2 = null
   #C3 = dart.core::pragma {name:#C1, options:#C2}
-  #C4 = 24
-  #C5 = 20
-  #C6 = <dart.core::int*>[#C4, #C5, #C4]
-  #C7 = 0
-  #C8 = <dart.core::int*>[#C7, #C7, #C7]
-  #C9 = 8
-  #C10 = <dart.core::int*>[#C9, #C9, #C9]
-  #C11 = 16
-  #C12 = <dart.core::int*>[#C11, #C11, #C11]
+  #C4 = "vm:ffi:struct-fields"
+  #C5 = TypeLiteralConstant(dart.ffi::Double)
+  #C6 = TypeLiteralConstant(dart.ffi::Pointer<dart.ffi::NativeType>)
+  #C7 = <dart.core::Type>[#C5, #C5, #C6]
+  #C8 = dart.core::pragma {name:#C4, options:#C7}
+  #C9 = 24
+  #C10 = 20
+  #C11 = <dart.core::int*>[#C9, #C10, #C9]
+  #C12 = 0
+  #C13 = <dart.core::int*>[#C12, #C12, #C12]
+  #C14 = 8
+  #C15 = <dart.core::int*>[#C14, #C14, #C14]
+  #C16 = 16
+  #C17 = <dart.core::int*>[#C16, #C16, #C16]
 }
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/ffi_02.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/ffi_02.yaml.world.1.expect
index fae41df26cf9..afc46dc896a0 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/ffi_02.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/ffi_02.yaml.world.1.expect
@@ -4,9 +4,10 @@ library from "org-dartlang-test:///lib.dart" as lib {
   import "dart:ffi";
 
   @#C3
+  @#C8
   class Coordinate extends dart.ffi::Struct {
     @#C3
-    static final field dart.core::int* #sizeOf = (#C6).{dart.core::List::[]}(dart.ffi::_abi());
+    static final field dart.core::int* #sizeOf = (#C11).{dart.core::List::[]}(dart.ffi::_abi());
     @#C3
     constructor #fromPointer(dynamic #pointer) → dynamic
       : super dart.ffi::Struct::_fromPointer(#pointer)
@@ -14,7 +15,7 @@ library from "org-dartlang-test:///lib.dart" as lib {
     static factory allocate(dart.core::double* x, dart.core::double* y, dart.ffi::Pointer<lib::Coordinate*>* next) → lib::Coordinate* {
       return null;
     }
-    abstract member-signature get _addressOf() → dart.ffi::Pointer<dart.ffi::Struct*>*; -> dart.ffi::Struct::_addressOf
+    abstract member-signature get _addressOf() → dart.core::Object*; -> dart.ffi::Struct::_addressOf
     abstract member-signature get _identityHashCode() → dart.core::int*; -> dart.core::Object::_identityHashCode
     abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → dart.core::bool*; -> dart.core::Object::_instanceOf
     abstract member-signature method _simpleInstanceOf(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOf
@@ -26,17 +27,17 @@ library from "org-dartlang-test:///lib.dart" as lib {
     abstract member-signature method noSuchMethod(dart.core::Invocation* invocation) → dynamic; -> dart.core::Object::noSuchMethod
     abstract member-signature get runtimeType() → dart.core::Type*; -> dart.core::Object::runtimeType
     get x() → dart.core::double*
-      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C8).{dart.core::List::[]}(dart.ffi::_abi()));
+      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C13).{dart.core::List::[]}(dart.ffi::_abi()));
     set x(dart.core::double* #v) → void
-      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C8).{dart.core::List::[]}(dart.ffi::_abi()), #v);
+      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C13).{dart.core::List::[]}(dart.ffi::_abi()), #v);
     get y() → dart.core::double*
-      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C10).{dart.core::List::[]}(dart.ffi::_abi()));
+      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C15).{dart.core::List::[]}(dart.ffi::_abi()));
     set y(dart.core::double* #v) → void
-      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C10).{dart.core::List::[]}(dart.ffi::_abi()), #v);
+      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C15).{dart.core::List::[]}(dart.ffi::_abi()), #v);
     get next() → dart.ffi::Pointer<lib::Coordinate*>*
-      return dart.ffi::_fromAddress<lib::Coordinate*>(dart.ffi::_loadIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C12).{dart.core::List::[]}(dart.ffi::_abi())));
+      return dart.ffi::_fromAddress<lib::Coordinate*>(dart.ffi::_loadIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C17).{dart.core::List::[]}(dart.ffi::_abi())));
     set next(dart.ffi::Pointer<lib::Coordinate*>* #v) → void
-      return dart.ffi::_storeIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C12).{dart.core::List::[]}(dart.ffi::_abi()), #v.{dart.ffi::Pointer::address});
+      return dart.ffi::_storeIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C17).{dart.core::List::[]}(dart.ffi::_abi()), #v.{dart.ffi::Pointer::address});
   }
 }
 library from "org-dartlang-test:///main.dart" as main {
@@ -55,13 +56,18 @@ constants  {
   #C1 = "vm:entry-point"
   #C2 = null
   #C3 = dart.core::pragma {name:#C1, options:#C2}
-  #C4 = 24
-  #C5 = 20
-  #C6 = <dart.core::int*>[#C4, #C5, #C4]
-  #C7 = 0
-  #C8 = <dart.core::int*>[#C7, #C7, #C7]
-  #C9 = 8
-  #C10 = <dart.core::int*>[#C9, #C9, #C9]
-  #C11 = 16
-  #C12 = <dart.core::int*>[#C11, #C11, #C11]
+  #C4 = "vm:ffi:struct-fields"
+  #C5 = TypeLiteralConstant(dart.ffi::Double)
+  #C6 = TypeLiteralConstant(dart.ffi::Pointer<dart.ffi::NativeType>)
+  #C7 = <dart.core::Type>[#C5, #C5, #C6]
+  #C8 = dart.core::pragma {name:#C4, options:#C7}
+  #C9 = 24
+  #C10 = 20
+  #C11 = <dart.core::int*>[#C9, #C10, #C9]
+  #C12 = 0
+  #C13 = <dart.core::int*>[#C12, #C12, #C12]
+  #C14 = 8
+  #C15 = <dart.core::int*>[#C14, #C14, #C14]
+  #C16 = 16
+  #C17 = <dart.core::int*>[#C16, #C16, #C16]
 }
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_35.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_35.yaml.world.1.expect
index 07b6c8065ac6..0fc8261aa63c 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_35.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_35.yaml.world.1.expect
@@ -4,9 +4,10 @@ library from "org-dartlang-test:///lib.dart" as lib {
   import "dart:ffi";
 
   @#C3
+  @#C8
   class Coordinate extends dart.ffi::Struct {
     @#C3
-    static final field dart.core::int* #sizeOf = (#C6).{dart.core::List::[]}(dart.ffi::_abi());
+    static final field dart.core::int* #sizeOf = (#C11).{dart.core::List::[]}(dart.ffi::_abi());
     @#C3
     constructor #fromPointer(dynamic #pointer) → dynamic
       : super dart.ffi::Struct::_fromPointer(#pointer)
@@ -14,7 +15,7 @@ library from "org-dartlang-test:///lib.dart" as lib {
     static factory allocate(dart.core::double* x, dart.core::double* y, dart.ffi::Pointer<lib::Coordinate*>* next) → lib::Coordinate* {
       return null;
     }
-    abstract member-signature get _addressOf() → dart.ffi::Pointer<dart.ffi::Struct*>*; -> dart.ffi::Struct::_addressOf
+    abstract member-signature get _addressOf() → dart.core::Object*; -> dart.ffi::Struct::_addressOf
     abstract member-signature get _identityHashCode() → dart.core::int*; -> dart.core::Object::_identityHashCode
     abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → dart.core::bool*; -> dart.core::Object::_instanceOf
     abstract member-signature method _simpleInstanceOf(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOf
@@ -26,17 +27,17 @@ library from "org-dartlang-test:///lib.dart" as lib {
     abstract member-signature method noSuchMethod(dart.core::Invocation* invocation) → dynamic; -> dart.core::Object::noSuchMethod
     abstract member-signature get runtimeType() → dart.core::Type*; -> dart.core::Object::runtimeType
     get x() → dart.core::double*
-      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C8).{dart.core::List::[]}(dart.ffi::_abi()));
+      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C13).{dart.core::List::[]}(dart.ffi::_abi()));
     set x(dart.core::double* #v) → void
-      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C8).{dart.core::List::[]}(dart.ffi::_abi()), #v);
+      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C13).{dart.core::List::[]}(dart.ffi::_abi()), #v);
     get y() → dart.core::double*
-      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C10).{dart.core::List::[]}(dart.ffi::_abi()));
+      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C15).{dart.core::List::[]}(dart.ffi::_abi()));
     set y(dart.core::double* #v) → void
-      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C10).{dart.core::List::[]}(dart.ffi::_abi()), #v);
+      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C15).{dart.core::List::[]}(dart.ffi::_abi()), #v);
     get next() → dart.ffi::Pointer<lib::Coordinate*>*
-      return dart.ffi::_fromAddress<lib::Coordinate*>(dart.ffi::_loadIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C12).{dart.core::List::[]}(dart.ffi::_abi())));
+      return dart.ffi::_fromAddress<lib::Coordinate*>(dart.ffi::_loadIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C17).{dart.core::List::[]}(dart.ffi::_abi())));
     set next(dart.ffi::Pointer<lib::Coordinate*>* #v) → void
-      return dart.ffi::_storeIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C12).{dart.core::List::[]}(dart.ffi::_abi()), #v.{dart.ffi::Pointer::address});
+      return dart.ffi::_storeIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C17).{dart.core::List::[]}(dart.ffi::_abi()), #v.{dart.ffi::Pointer::address});
   }
 }
 library from "org-dartlang-test:///main.dart" as main {
@@ -54,13 +55,18 @@ constants  {
   #C1 = "vm:entry-point"
   #C2 = null
   #C3 = dart.core::pragma {name:#C1, options:#C2}
-  #C4 = 24
-  #C5 = 20
-  #C6 = <dart.core::int*>[#C4, #C5, #C4]
-  #C7 = 0
-  #C8 = <dart.core::int*>[#C7, #C7, #C7]
-  #C9 = 8
-  #C10 = <dart.core::int*>[#C9, #C9, #C9]
-  #C11 = 16
-  #C12 = <dart.core::int*>[#C11, #C11, #C11]
+  #C4 = "vm:ffi:struct-fields"
+  #C5 = TypeLiteralConstant(dart.ffi::Double)
+  #C6 = TypeLiteralConstant(dart.ffi::Pointer<dart.ffi::NativeType>)
+  #C7 = <dart.core::Type>[#C5, #C5, #C6]
+  #C8 = dart.core::pragma {name:#C4, options:#C7}
+  #C9 = 24
+  #C10 = 20
+  #C11 = <dart.core::int*>[#C9, #C10, #C9]
+  #C12 = 0
+  #C13 = <dart.core::int*>[#C12, #C12, #C12]
+  #C14 = 8
+  #C15 = <dart.core::int*>[#C14, #C14, #C14]
+  #C16 = 16
+  #C17 = <dart.core::int*>[#C16, #C16, #C16]
 }
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_35.yaml.world.2.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_35.yaml.world.2.expect
index 879c49737d34..b4e95441bc7f 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_35.yaml.world.2.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_35.yaml.world.2.expect
@@ -4,9 +4,10 @@ library from "org-dartlang-test:///lib.dart" as lib {
   import "dart:ffi";
 
   @#C3
+  @#C8
   class Coordinate extends dart.ffi::Struct {
     @#C3
-    static final field dart.core::int* #sizeOf = (#C6).{dart.core::List::[]}(dart.ffi::_abi());
+    static final field dart.core::int* #sizeOf = (#C11).{dart.core::List::[]}(dart.ffi::_abi());
     @#C3
     constructor #fromPointer(dynamic #pointer) → dynamic
       : super dart.ffi::Struct::_fromPointer(#pointer)
@@ -14,7 +15,7 @@ library from "org-dartlang-test:///lib.dart" as lib {
     static factory allocate(dart.core::double* x, dart.core::double* y, dart.ffi::Pointer<lib::Coordinate*>* next) → lib::Coordinate* {
       return null;
     }
-    abstract member-signature get _addressOf() → dart.ffi::Pointer<dart.ffi::Struct*>*; -> dart.ffi::Struct::_addressOf
+    abstract member-signature get _addressOf() → dart.core::Object*; -> dart.ffi::Struct::_addressOf
     abstract member-signature get _identityHashCode() → dart.core::int*; -> dart.core::Object::_identityHashCode
     abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → dart.core::bool*; -> dart.core::Object::_instanceOf
     abstract member-signature method _simpleInstanceOf(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOf
@@ -26,17 +27,17 @@ library from "org-dartlang-test:///lib.dart" as lib {
     abstract member-signature method noSuchMethod(dart.core::Invocation* invocation) → dynamic; -> dart.core::Object::noSuchMethod
     abstract member-signature get runtimeType() → dart.core::Type*; -> dart.core::Object::runtimeType
     get x() → dart.core::double*
-      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C8).{dart.core::List::[]}(dart.ffi::_abi()));
+      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C13).{dart.core::List::[]}(dart.ffi::_abi()));
     set x(dart.core::double* #v) → void
-      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C8).{dart.core::List::[]}(dart.ffi::_abi()), #v);
+      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C13).{dart.core::List::[]}(dart.ffi::_abi()), #v);
     get y() → dart.core::double*
-      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C10).{dart.core::List::[]}(dart.ffi::_abi()));
+      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C15).{dart.core::List::[]}(dart.ffi::_abi()));
     set y(dart.core::double* #v) → void
-      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C10).{dart.core::List::[]}(dart.ffi::_abi()), #v);
+      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C15).{dart.core::List::[]}(dart.ffi::_abi()), #v);
     get next() → dart.ffi::Pointer<lib::Coordinate*>*
-      return dart.ffi::_fromAddress<lib::Coordinate*>(dart.ffi::_loadIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C12).{dart.core::List::[]}(dart.ffi::_abi())));
+      return dart.ffi::_fromAddress<lib::Coordinate*>(dart.ffi::_loadIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C17).{dart.core::List::[]}(dart.ffi::_abi())));
     set next(dart.ffi::Pointer<lib::Coordinate*>* #v) → void
-      return dart.ffi::_storeIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C12).{dart.core::List::[]}(dart.ffi::_abi()), #v.{dart.ffi::Pointer::address});
+      return dart.ffi::_storeIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C17).{dart.core::List::[]}(dart.ffi::_abi()), #v.{dart.ffi::Pointer::address});
   }
 }
 library from "org-dartlang-test:///main.dart" as main {
@@ -55,13 +56,18 @@ constants  {
   #C1 = "vm:entry-point"
   #C2 = null
   #C3 = dart.core::pragma {name:#C1, options:#C2}
-  #C4 = 24
-  #C5 = 20
-  #C6 = <dart.core::int*>[#C4, #C5, #C4]
-  #C7 = 0
-  #C8 = <dart.core::int*>[#C7, #C7, #C7]
-  #C9 = 8
-  #C10 = <dart.core::int*>[#C9, #C9, #C9]
-  #C11 = 16
-  #C12 = <dart.core::int*>[#C11, #C11, #C11]
+  #C4 = "vm:ffi:struct-fields"
+  #C5 = TypeLiteralConstant(dart.ffi::Double)
+  #C6 = TypeLiteralConstant(dart.ffi::Pointer<dart.ffi::NativeType>)
+  #C7 = <dart.core::Type>[#C5, #C5, #C6]
+  #C8 = dart.core::pragma {name:#C4, options:#C7}
+  #C9 = 24
+  #C10 = 20
+  #C11 = <dart.core::int*>[#C9, #C10, #C9]
+  #C12 = 0
+  #C13 = <dart.core::int*>[#C12, #C12, #C12]
+  #C14 = 8
+  #C15 = <dart.core::int*>[#C14, #C14, #C14]
+  #C16 = 16
+  #C17 = <dart.core::int*>[#C16, #C16, #C16]
 }
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_35.yaml.world.3.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_35.yaml.world.3.expect
index c31f2701e9f4..3c5ae831ad73 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_35.yaml.world.3.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_35.yaml.world.3.expect
@@ -4,9 +4,10 @@ library from "org-dartlang-test:///lib.dart" as lib {
   import "dart:ffi";
 
   @#C3
+  @#C8
   class Coordinate extends dart.ffi::Struct {
     @#C3
-    static final field dart.core::int* #sizeOf = (#C6).{dart.core::List::[]}(dart.ffi::_abi());
+    static final field dart.core::int* #sizeOf = (#C11).{dart.core::List::[]}(dart.ffi::_abi());
     @#C3
     constructor #fromPointer(dynamic #pointer) → dynamic
       : super dart.ffi::Struct::_fromPointer(#pointer)
@@ -15,7 +16,7 @@ library from "org-dartlang-test:///lib.dart" as lib {
       dart.core::print("hello");
       return null;
     }
-    abstract member-signature get _addressOf() → dart.ffi::Pointer<dart.ffi::Struct*>*; -> dart.ffi::Struct::_addressOf
+    abstract member-signature get _addressOf() → dart.core::Object*; -> dart.ffi::Struct::_addressOf
     abstract member-signature get _identityHashCode() → dart.core::int*; -> dart.core::Object::_identityHashCode
     abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → dart.core::bool*; -> dart.core::Object::_instanceOf
     abstract member-signature method _simpleInstanceOf(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOf
@@ -27,17 +28,17 @@ library from "org-dartlang-test:///lib.dart" as lib {
     abstract member-signature method noSuchMethod(dart.core::Invocation* invocation) → dynamic; -> dart.core::Object::noSuchMethod
     abstract member-signature get runtimeType() → dart.core::Type*; -> dart.core::Object::runtimeType
     get x() → dart.core::double*
-      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C8).{dart.core::List::[]}(dart.ffi::_abi()));
+      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C13).{dart.core::List::[]}(dart.ffi::_abi()));
     set x(dart.core::double* #v) → void
-      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C8).{dart.core::List::[]}(dart.ffi::_abi()), #v);
+      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C13).{dart.core::List::[]}(dart.ffi::_abi()), #v);
     get y() → dart.core::double*
-      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C10).{dart.core::List::[]}(dart.ffi::_abi()));
+      return dart.ffi::_loadDouble(this.{dart.ffi::Struct::_addressOf}, (#C15).{dart.core::List::[]}(dart.ffi::_abi()));
     set y(dart.core::double* #v) → void
-      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C10).{dart.core::List::[]}(dart.ffi::_abi()), #v);
+      return dart.ffi::_storeDouble(this.{dart.ffi::Struct::_addressOf}, (#C15).{dart.core::List::[]}(dart.ffi::_abi()), #v);
     get next() → dart.ffi::Pointer<lib::Coordinate*>*
-      return dart.ffi::_fromAddress<lib::Coordinate*>(dart.ffi::_loadIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C12).{dart.core::List::[]}(dart.ffi::_abi())));
+      return dart.ffi::_fromAddress<lib::Coordinate*>(dart.ffi::_loadIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C17).{dart.core::List::[]}(dart.ffi::_abi())));
     set next(dart.ffi::Pointer<lib::Coordinate*>* #v) → void
-      return dart.ffi::_storeIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C12).{dart.core::List::[]}(dart.ffi::_abi()), #v.{dart.ffi::Pointer::address});
+      return dart.ffi::_storeIntPtr(this.{dart.ffi::Struct::_addressOf}, (#C17).{dart.core::List::[]}(dart.ffi::_abi()), #v.{dart.ffi::Pointer::address});
   }
 }
 library from "org-dartlang-test:///main.dart" as main {
@@ -56,13 +57,18 @@ constants  {
   #C1 = "vm:entry-point"
   #C2 = null
   #C3 = dart.core::pragma {name:#C1, options:#C2}
-  #C4 = 24
-  #C5 = 20
-  #C6 = <dart.core::int*>[#C4, #C5, #C4]
-  #C7 = 0
-  #C8 = <dart.core::int*>[#C7, #C7, #C7]
-  #C9 = 8
-  #C10 = <dart.core::int*>[#C9, #C9, #C9]
-  #C11 = 16
-  #C12 = <dart.core::int*>[#C11, #C11, #C11]
+  #C4 = "vm:ffi:struct-fields"
+  #C5 = TypeLiteralConstant(dart.ffi::Double)
+  #C6 = TypeLiteralConstant(dart.ffi::Pointer<dart.ffi::NativeType>)
+  #C7 = <dart.core::Type>[#C5, #C5, #C6]
+  #C8 = dart.core::pragma {name:#C4, options:#C7}
+  #C9 = 24
+  #C10 = 20
+  #C11 = <dart.core::int*>[#C9, #C10, #C9]
+  #C12 = 0
+  #C13 = <dart.core::int*>[#C12, #C12, #C12]
+  #C14 = 8
+  #C15 = <dart.core::int*>[#C14, #C14, #C14]
+  #C16 = 16
+  #C17 = <dart.core::int*>[#C16, #C16, #C16]
 }
diff --git a/pkg/vm/lib/transformations/ffi.dart b/pkg/vm/lib/transformations/ffi.dart
index 716ba06b22a5..2752c237e64b 100644
--- a/pkg/vm/lib/transformations/ffi.dart
+++ b/pkg/vm/lib/transformations/ffi.dart
@@ -192,6 +192,7 @@ class FfiTransformer extends Transformer {
   final Class intClass;
   final Class doubleClass;
   final Class listClass;
+  final Class typeClass;
   final Class pragmaClass;
   final Field pragmaName;
   final Field pragmaOptions;
@@ -233,6 +234,7 @@ class FfiTransformer extends Transformer {
         intClass = coreTypes.intClass,
         doubleClass = coreTypes.doubleClass,
         listClass = coreTypes.listClass,
+        typeClass = coreTypes.typeClass,
         pragmaClass = coreTypes.pragmaClass,
         pragmaName = coreTypes.pragmaName,
         pragmaOptions = coreTypes.pragmaOptions,
diff --git a/pkg/vm/lib/transformations/ffi_definitions.dart b/pkg/vm/lib/transformations/ffi_definitions.dart
index 13498bcc2487..b8a3e62b2510 100644
--- a/pkg/vm/lib/transformations/ffi_definitions.dart
+++ b/pkg/vm/lib/transformations/ffi_definitions.dart
@@ -227,9 +227,9 @@ class _FfiDefinitionTransformer extends FfiTransformer {
             f.fileUri);
       } else {
         final DartType nativeType = InterfaceType(
-            nativeTypesClasses[nativeTypeAnnos.first.index],
+            nativeTypesClasses[_getFieldType(nativeTypeAnnos.first).index],
             Nullability.legacy);
-        // TODO(36730): Support structs inside structs.
+        // TODO(dartbug.com/37271): Support structs inside structs.
         final DartType shouldBeDartType = convertNativeTypeToDartType(
             nativeType, /*allowStructs=*/ false, /*allowHandle=*/ false);
         if (shouldBeDartType == null ||
@@ -294,6 +294,7 @@ class _FfiDefinitionTransformer extends FfiTransformer {
   ///
   /// Returns the total size of the struct (for all ABIs).
   Map<Abi, int> _replaceFields(Class node, IndexedClass indexedClass) {
+    final classes = <Class>[];
     final types = <NativeType>[];
     final fields = <int, Field>{};
     final getters = <int, Procedure>{};
@@ -304,18 +305,22 @@ class _FfiDefinitionTransformer extends FfiTransformer {
       final dartType = _structFieldMemberType(m);
 
       NativeType nativeType;
+      Class clazz;
       if (_isPointerType(dartType)) {
         nativeType = NativeType.kPointer;
+        clazz = pointerClass;
       } else {
         final nativeTypeAnnos = _getNativeTypeAnnotations(m).toList();
         if (nativeTypeAnnos.length == 1) {
-          nativeType = nativeTypeAnnos.first;
+          clazz = nativeTypeAnnos.first;
+          nativeType = _getFieldType(clazz);
         }
       }
 
       if ((m is Field || (m is Procedure && m.isGetter)) &&
           nativeType != null) {
         types.add(nativeType);
+        classes.add(clazz);
         if (m is Field) {
           fields[i] = m;
         }
@@ -332,6 +337,8 @@ class _FfiDefinitionTransformer extends FfiTransformer {
       }
     }
 
+    _annoteStructWithFields(node, classes);
+
     final sizeAndOffsets = <Abi, SizeAndOffsets>{};
     for (final Abi abi in Abi.values) {
       sizeAndOffsets[abi] = _calculateSizeAndOffsets(types, abi);
@@ -377,6 +384,29 @@ class _FfiDefinitionTransformer extends FfiTransformer {
     return sizeAndOffsets.map((k, v) => MapEntry(k, v.size));
   }
 
+  void _annoteStructWithFields(Class node, List<Class> fieldTypes) {
+    final types = fieldTypes.map((Class c) {
+      List<DartType> typeArg = const [];
+      if (c == pointerClass) {
+        typeArg = [
+          InterfaceType(pointerClass.superclass, Nullability.nonNullable)
+        ];
+      }
+      return TypeLiteralConstant(
+          InterfaceType(c, Nullability.nonNullable, typeArg));
+    }).toList();
+
+    node.addAnnotation(ConstantExpression(
+        InstanceConstant(pragmaClass.reference, [], {
+          pragmaName.reference: StringConstant("vm:ffi:struct-fields"),
+          // TODO(dartbug.com/38158): Wrap list in class to be able to encode
+          // more information when needed.
+          pragmaOptions.reference: ListConstant(
+              InterfaceType(typeClass, Nullability.nonNullable), types)
+        }),
+        InterfaceType(pragmaClass, Nullability.nonNullable, [])));
+  }
+
   /// Expression that queries VM internals at runtime to figure out on which ABI
   /// we are.
   Expression _runtimeBranchOnLayout(Map<Abi, int> values) {
@@ -571,14 +601,13 @@ class _FfiDefinitionTransformer extends FfiTransformer {
     return fieldType;
   }
 
-  Iterable<NativeType> _getNativeTypeAnnotations(Member node) {
+  Iterable<Class> _getNativeTypeAnnotations(Member node) {
     return node.annotations
         .whereType<ConstantExpression>()
         .map((expr) => expr.constant)
         .whereType<InstanceConstant>()
         .map((constant) => constant.classNode)
-        .map((klass) => _getFieldType(klass))
-        .where((type) => type != null);
+        .where((klass) => _getFieldType(klass) != null);
   }
 }
 
diff --git a/pkg/vm/lib/transformations/ffi_use_sites.dart b/pkg/vm/lib/transformations/ffi_use_sites.dart
index e198b1012295..b0926a106e1b 100644
--- a/pkg/vm/lib/transformations/ffi_use_sites.dart
+++ b/pkg/vm/lib/transformations/ffi_use_sites.dart
@@ -171,17 +171,18 @@ class _FfiUseSiteTransformer extends FfiTransformer {
             nativeFunctionClass, Nullability.legacy, [node.arguments.types[0]]);
         final DartType dartType = node.arguments.types[1];
 
-        _ensureNativeTypeValid(nativeType, node);
-        _ensureNativeTypeToDartType(nativeType, dartType, node);
-
+        _ensureNativeTypeValid(nativeType, node, allowStructs: false);
+        _ensureNativeTypeToDartType(nativeType, dartType, node,
+            allowStructs: false);
         return _replaceLookupFunction(node);
       } else if (target == asFunctionMethod) {
         final DartType dartType = node.arguments.types[1];
         final DartType nativeType = InterfaceType(
             nativeFunctionClass, Nullability.legacy, [node.arguments.types[0]]);
 
-        _ensureNativeTypeValid(nativeType, node);
-        _ensureNativeTypeToDartType(nativeType, dartType, node);
+        _ensureNativeTypeValid(nativeType, node, allowStructs: false);
+        _ensureNativeTypeToDartType(nativeType, dartType, node,
+            allowStructs: false);
 
         final DartType nativeSignature =
             (nativeType as InterfaceType).typeArguments[0];
@@ -198,20 +199,22 @@ class _FfiUseSiteTransformer extends FfiTransformer {
 
         _ensureIsStaticFunction(func);
 
-        // TODO(36730): Allow passing/returning structs by value.
-        _ensureNativeTypeValid(nativeType, node);
-        _ensureNativeTypeToDartType(nativeType, dartType, node);
+        _ensureNativeTypeValid(nativeType, node, allowStructs: false);
+        _ensureNativeTypeToDartType(nativeType, dartType, node,
+            allowStructs: false);
 
         // Check `exceptionalReturn`'s type.
         final FunctionType funcType = dartType;
-        final NativeType expectedReturn = getType(
+        final Class expectedReturnClass =
             ((node.arguments.types[0] as FunctionType).returnType
                     as InterfaceType)
-                .classNode);
+                .classNode;
+        final NativeType expectedReturn = getType(expectedReturnClass);
 
         if (expectedReturn == NativeType.kVoid ||
             expectedReturn == NativeType.kPointer ||
-            expectedReturn == NativeType.kHandle) {
+            expectedReturn == NativeType.kHandle ||
+            expectedReturnClass.superclass == structClass) {
           if (node.arguments.positional.length > 1) {
             diagnosticReporter.report(
                 templateFfiExpectedNoExceptionalReturn.withArguments(
diff --git a/sdk/lib/ffi/struct.dart b/sdk/lib/ffi/struct.dart
index f4cb315a7a6b..0faf7ca5207c 100644
--- a/sdk/lib/ffi/struct.dart
+++ b/sdk/lib/ffi/struct.dart
@@ -18,7 +18,7 @@ part of dart.ffi;
 /// by native memory. The may allocated via allocation or loaded from a
 /// [Pointer], but not by a generative constructor.
 abstract class Struct extends NativeType {
-  final Pointer<Struct> _addressOf;
+  final Object _addressOf;
 
   /// Construct a reference to the [nullptr].
   ///