diff --git a/runtime/bin/ffi_test/ffi_test_functions_generated.cc b/runtime/bin/ffi_test/ffi_test_functions_generated.cc
index cbb631f24e0..74f27e4229b 100644
--- a/runtime/bin/ffi_test/ffi_test_functions_generated.cc
+++ b/runtime/bin/ffi_test/ffi_test_functions_generated.cc
@@ -2386,6 +2386,131 @@ DART_EXPORT double PassStruct40BytesHomogeneousDoubleStruct4BytesHomo(
   return result;
 }
 
+// Used for testing structs by value.
+// Test alignment and padding of 16 byte int within struct.
+DART_EXPORT double PassInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int(
+    int32_t a0,
+    int32_t a1,
+    int32_t a2,
+    int32_t a3,
+    int32_t a4,
+    int32_t a5,
+    int32_t a6,
+    int32_t a7,
+    double a8,
+    double a9,
+    double a10,
+    double a11,
+    double a12,
+    double a13,
+    double a14,
+    double a15,
+    int64_t a16,
+    int8_t a17,
+    Struct1ByteInt a18,
+    int64_t a19,
+    int8_t a20,
+    Struct4BytesHomogeneousInt16 a21,
+    int64_t a22,
+    int8_t a23,
+    Struct8BytesInt a24,
+    int64_t a25,
+    int8_t a26,
+    Struct8BytesHomogeneousFloat a27,
+    int64_t a28,
+    int8_t a29,
+    Struct8BytesMixed a30,
+    int64_t a31,
+    int8_t a32,
+    StructAlignmentInt16 a33,
+    int64_t a34,
+    int8_t a35,
+    StructAlignmentInt32 a36,
+    int64_t a37,
+    int8_t a38,
+    StructAlignmentInt64 a39) {
+  std::cout << "PassInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int"
+            << "(" << a0 << ", " << a1 << ", " << a2 << ", " << a3 << ", " << a4
+            << ", " << a5 << ", " << a6 << ", " << a7 << ", " << a8 << ", "
+            << a9 << ", " << a10 << ", " << a11 << ", " << a12 << ", " << a13
+            << ", " << a14 << ", " << a15 << ", " << a16 << ", "
+            << static_cast<int>(a17) << ", (" << static_cast<int>(a18.a0)
+            << "), " << a19 << ", " << static_cast<int>(a20) << ", (" << a21.a0
+            << ", " << a21.a1 << "), " << a22 << ", " << static_cast<int>(a23)
+            << ", (" << a24.a0 << ", " << a24.a1 << ", " << a24.a2 << "), "
+            << a25 << ", " << static_cast<int>(a26) << ", (" << a27.a0 << ", "
+            << a27.a1 << "), " << a28 << ", " << static_cast<int>(a29) << ", ("
+            << a30.a0 << ", " << a30.a1 << ", " << a30.a2 << "), " << a31
+            << ", " << static_cast<int>(a32) << ", ("
+            << static_cast<int>(a33.a0) << ", " << a33.a1 << ", "
+            << static_cast<int>(a33.a2) << "), " << a34 << ", "
+            << static_cast<int>(a35) << ", (" << static_cast<int>(a36.a0)
+            << ", " << a36.a1 << ", " << static_cast<int>(a36.a2) << "), "
+            << a37 << ", " << static_cast<int>(a38) << ", ("
+            << static_cast<int>(a39.a0) << ", " << a39.a1 << ", "
+            << static_cast<int>(a39.a2) << "))"
+            << "\n";
+
+  double result = 0;
+
+  result += a0;
+  result += a1;
+  result += a2;
+  result += a3;
+  result += a4;
+  result += a5;
+  result += a6;
+  result += a7;
+  result += a8;
+  result += a9;
+  result += a10;
+  result += a11;
+  result += a12;
+  result += a13;
+  result += a14;
+  result += a15;
+  result += a16;
+  result += a17;
+  result += a18.a0;
+  result += a19;
+  result += a20;
+  result += a21.a0;
+  result += a21.a1;
+  result += a22;
+  result += a23;
+  result += a24.a0;
+  result += a24.a1;
+  result += a24.a2;
+  result += a25;
+  result += a26;
+  result += a27.a0;
+  result += a27.a1;
+  result += a28;
+  result += a29;
+  result += a30.a0;
+  result += a30.a1;
+  result += a30.a2;
+  result += a31;
+  result += a32;
+  result += a33.a0;
+  result += a33.a1;
+  result += a33.a2;
+  result += a34;
+  result += a35;
+  result += a36.a0;
+  result += a36.a1;
+  result += a36.a2;
+  result += a37;
+  result += a38;
+  result += a39.a0;
+  result += a39.a1;
+  result += a39.a2;
+
+  std::cout << "result = " << result << "\n";
+
+  return result;
+}
+
 // Used for testing structs by value.
 // Test alignment and padding of 16 byte int within struct.
 DART_EXPORT int64_t PassStructAlignmentInt16(StructAlignmentInt16 a0) {
@@ -6357,6 +6482,196 @@ DART_EXPORT intptr_t TestPassStruct40BytesHomogeneousDoubleStruct4BytesHomo(
   return 0;
 }
 
+// Used for testing structs by value.
+// Test alignment and padding of 16 byte int within struct.
+DART_EXPORT intptr_t TestPassInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int(
+    // NOLINTNEXTLINE(whitespace/parens)
+    double (*f)(int32_t a0,
+                int32_t a1,
+                int32_t a2,
+                int32_t a3,
+                int32_t a4,
+                int32_t a5,
+                int32_t a6,
+                int32_t a7,
+                double a8,
+                double a9,
+                double a10,
+                double a11,
+                double a12,
+                double a13,
+                double a14,
+                double a15,
+                int64_t a16,
+                int8_t a17,
+                Struct1ByteInt a18,
+                int64_t a19,
+                int8_t a20,
+                Struct4BytesHomogeneousInt16 a21,
+                int64_t a22,
+                int8_t a23,
+                Struct8BytesInt a24,
+                int64_t a25,
+                int8_t a26,
+                Struct8BytesHomogeneousFloat a27,
+                int64_t a28,
+                int8_t a29,
+                Struct8BytesMixed a30,
+                int64_t a31,
+                int8_t a32,
+                StructAlignmentInt16 a33,
+                int64_t a34,
+                int8_t a35,
+                StructAlignmentInt32 a36,
+                int64_t a37,
+                int8_t a38,
+                StructAlignmentInt64 a39)) {
+  int32_t a0;
+  int32_t a1;
+  int32_t a2;
+  int32_t a3;
+  int32_t a4;
+  int32_t a5;
+  int32_t a6;
+  int32_t a7;
+  double a8;
+  double a9;
+  double a10;
+  double a11;
+  double a12;
+  double a13;
+  double a14;
+  double a15;
+  int64_t a16;
+  int8_t a17;
+  Struct1ByteInt a18;
+  int64_t a19;
+  int8_t a20;
+  Struct4BytesHomogeneousInt16 a21;
+  int64_t a22;
+  int8_t a23;
+  Struct8BytesInt a24;
+  int64_t a25;
+  int8_t a26;
+  Struct8BytesHomogeneousFloat a27;
+  int64_t a28;
+  int8_t a29;
+  Struct8BytesMixed a30;
+  int64_t a31;
+  int8_t a32;
+  StructAlignmentInt16 a33;
+  int64_t a34;
+  int8_t a35;
+  StructAlignmentInt32 a36;
+  int64_t a37;
+  int8_t a38;
+  StructAlignmentInt64 a39;
+
+  a0 = -1;
+  a1 = 2;
+  a2 = -3;
+  a3 = 4;
+  a4 = -5;
+  a5 = 6;
+  a6 = -7;
+  a7 = 8;
+  a8 = -9.0;
+  a9 = 10.0;
+  a10 = -11.0;
+  a11 = 12.0;
+  a12 = -13.0;
+  a13 = 14.0;
+  a14 = -15.0;
+  a15 = 16.0;
+  a16 = -17;
+  a17 = 18;
+  a18.a0 = -19;
+  a19 = 20;
+  a20 = -21;
+  a21.a0 = 22;
+  a21.a1 = -23;
+  a22 = 24;
+  a23 = -25;
+  a24.a0 = 26;
+  a24.a1 = -27;
+  a24.a2 = 28;
+  a25 = -29;
+  a26 = 30;
+  a27.a0 = -31.0;
+  a27.a1 = 32.0;
+  a28 = -33;
+  a29 = 34;
+  a30.a0 = -35.0;
+  a30.a1 = 36;
+  a30.a2 = -37;
+  a31 = 38;
+  a32 = -39;
+  a33.a0 = 40;
+  a33.a1 = -41;
+  a33.a2 = 42;
+  a34 = -43;
+  a35 = 44;
+  a36.a0 = -45;
+  a36.a1 = 46;
+  a36.a2 = -47;
+  a37 = 48;
+  a38 = -49;
+  a39.a0 = 50;
+  a39.a1 = -51;
+  a39.a2 = 52;
+
+  std::cout << "Calling TestPassInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int("
+            << "(" << a0 << ", " << a1 << ", " << a2 << ", " << a3 << ", " << a4
+            << ", " << a5 << ", " << a6 << ", " << a7 << ", " << a8 << ", "
+            << a9 << ", " << a10 << ", " << a11 << ", " << a12 << ", " << a13
+            << ", " << a14 << ", " << a15 << ", " << a16 << ", "
+            << static_cast<int>(a17) << ", (" << static_cast<int>(a18.a0)
+            << "), " << a19 << ", " << static_cast<int>(a20) << ", (" << a21.a0
+            << ", " << a21.a1 << "), " << a22 << ", " << static_cast<int>(a23)
+            << ", (" << a24.a0 << ", " << a24.a1 << ", " << a24.a2 << "), "
+            << a25 << ", " << static_cast<int>(a26) << ", (" << a27.a0 << ", "
+            << a27.a1 << "), " << a28 << ", " << static_cast<int>(a29) << ", ("
+            << a30.a0 << ", " << a30.a1 << ", " << a30.a2 << "), " << a31
+            << ", " << static_cast<int>(a32) << ", ("
+            << static_cast<int>(a33.a0) << ", " << a33.a1 << ", "
+            << static_cast<int>(a33.a2) << "), " << a34 << ", "
+            << static_cast<int>(a35) << ", (" << static_cast<int>(a36.a0)
+            << ", " << a36.a1 << ", " << static_cast<int>(a36.a2) << "), "
+            << a37 << ", " << static_cast<int>(a38) << ", ("
+            << static_cast<int>(a39.a0) << ", " << a39.a1 << ", "
+            << static_cast<int>(a39.a2) << "))"
+            << ")\n";
+
+  double result =
+      f(a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15,
+        a16, a17, a18, a19, a20, a21, a22, a23, a24, a25, a26, a27, a28, a29,
+        a30, a31, a32, a33, a34, a35, a36, a37, a38, a39);
+
+  std::cout << "result = " << result << "\n";
+
+  CHECK_APPROX(26.0, result);
+
+  // Pass argument that will make the Dart callback throw.
+  a0 = 42;
+
+  result = f(a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14,
+             a15, a16, a17, a18, a19, a20, a21, a22, a23, a24, a25, a26, a27,
+             a28, a29, a30, a31, a32, a33, a34, a35, a36, a37, a38, a39);
+
+  CHECK_APPROX(0.0, result);
+
+  // Pass argument that will make the Dart callback return null.
+  a0 = 84;
+
+  result = f(a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14,
+             a15, a16, a17, a18, a19, a20, a21, a22, a23, a24, a25, a26, a27,
+             a28, a29, a30, a31, a32, a33, a34, a35, a36, a37, a38, a39);
+
+  CHECK_APPROX(0.0, result);
+
+  return 0;
+}
+
 // Used for testing structs by value.
 // Test alignment and padding of 16 byte int within struct.
 DART_EXPORT intptr_t TestPassStructAlignmentInt16(
diff --git a/tests/ffi/function_callbacks_structs_by_value_generated_test.dart b/tests/ffi/function_callbacks_structs_by_value_generated_test.dart
index 7985c51fab9..845ebb98578 100644
--- a/tests/ffi/function_callbacks_structs_by_value_generated_test.dart
+++ b/tests/ffi/function_callbacks_structs_by_value_generated_test.dart
@@ -171,6 +171,12 @@ final testCases = [
               PassStruct40BytesHomogeneousDoubleStruct4BytesHomoType>(
           passStruct40BytesHomogeneousDoubleStruct4BytesHomo, 0.0),
       passStruct40BytesHomogeneousDoubleStruct4BytesHomoAfterCallback),
+  CallbackTest.withCheck(
+      "PassInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int",
+      Pointer.fromFunction<
+              PassInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntType>(
+          passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int, 0.0),
+      passInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntAfterCallback),
   CallbackTest.withCheck(
       "PassStructAlignmentInt16",
       Pointer.fromFunction<PassStructAlignmentInt16Type>(
@@ -3704,6 +3710,277 @@ void passStruct40BytesHomogeneousDoubleStruct4BytesHomoAfterCallback() {
   Expect.approxEquals(-5.0, result);
 }
 
+typedef PassInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntType
+    = Double Function(
+        Int32,
+        Int32,
+        Int32,
+        Int32,
+        Int32,
+        Int32,
+        Int32,
+        Int32,
+        Double,
+        Double,
+        Double,
+        Double,
+        Double,
+        Double,
+        Double,
+        Double,
+        Int64,
+        Int8,
+        Struct1ByteInt,
+        Int64,
+        Int8,
+        Struct4BytesHomogeneousInt16,
+        Int64,
+        Int8,
+        Struct8BytesInt,
+        Int64,
+        Int8,
+        Struct8BytesHomogeneousFloat,
+        Int64,
+        Int8,
+        Struct8BytesMixed,
+        Int64,
+        Int8,
+        StructAlignmentInt16,
+        Int64,
+        Int8,
+        StructAlignmentInt32,
+        Int64,
+        Int8,
+        StructAlignmentInt64);
+
+// Global variables to be able to test inputs after callback returned.
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a0 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a1 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a2 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a3 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a4 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a5 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a6 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a7 = 0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a8 = 0.0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a9 = 0.0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a10 = 0.0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a11 = 0.0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a12 = 0.0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a13 = 0.0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a14 = 0.0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a15 = 0.0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a16 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a17 = 0;
+Struct1ByteInt passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a18 =
+    Struct1ByteInt();
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a19 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a20 = 0;
+Struct4BytesHomogeneousInt16
+    passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a21 =
+    Struct4BytesHomogeneousInt16();
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a22 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a23 = 0;
+Struct8BytesInt passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a24 =
+    Struct8BytesInt();
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a25 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a26 = 0;
+Struct8BytesHomogeneousFloat
+    passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a27 =
+    Struct8BytesHomogeneousFloat();
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a28 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a29 = 0;
+Struct8BytesMixed passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a30 =
+    Struct8BytesMixed();
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a31 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a32 = 0;
+StructAlignmentInt16 passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a33 =
+    StructAlignmentInt16();
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a34 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a35 = 0;
+StructAlignmentInt32 passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a36 =
+    StructAlignmentInt32();
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a37 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a38 = 0;
+StructAlignmentInt64 passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a39 =
+    StructAlignmentInt64();
+
+// Result variable also global, so we can delete it after the callback.
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntResult = 0.0;
+
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntCalculateResult() {
+  double result = 0;
+
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a2;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a3;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a4;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a5;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a6;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a7;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a8;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a9;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a10;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a11;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a12;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a13;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a14;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a15;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a16;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a17;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a18.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a19;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a20;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a21.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a21.a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a22;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a23;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a24.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a24.a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a24.a2;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a25;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a26;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a27.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a27.a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a28;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a29;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a30.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a30.a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a30.a2;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a31;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a32;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a33.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a33.a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a33.a2;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a34;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a35;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a36.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a36.a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a36.a2;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a37;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a38;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a39.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a39.a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a39.a2;
+
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntResult = result;
+
+  return result;
+}
+
+/// Test alignment and padding of 16 byte int within struct.
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int(
+    int a0,
+    int a1,
+    int a2,
+    int a3,
+    int a4,
+    int a5,
+    int a6,
+    int a7,
+    double a8,
+    double a9,
+    double a10,
+    double a11,
+    double a12,
+    double a13,
+    double a14,
+    double a15,
+    int a16,
+    int a17,
+    Struct1ByteInt a18,
+    int a19,
+    int a20,
+    Struct4BytesHomogeneousInt16 a21,
+    int a22,
+    int a23,
+    Struct8BytesInt a24,
+    int a25,
+    int a26,
+    Struct8BytesHomogeneousFloat a27,
+    int a28,
+    int a29,
+    Struct8BytesMixed a30,
+    int a31,
+    int a32,
+    StructAlignmentInt16 a33,
+    int a34,
+    int a35,
+    StructAlignmentInt32 a36,
+    int a37,
+    int a38,
+    StructAlignmentInt64 a39) {
+  print(
+      "passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int(${a0}, ${a1}, ${a2}, ${a3}, ${a4}, ${a5}, ${a6}, ${a7}, ${a8}, ${a9}, ${a10}, ${a11}, ${a12}, ${a13}, ${a14}, ${a15}, ${a16}, ${a17}, ${a18}, ${a19}, ${a20}, ${a21}, ${a22}, ${a23}, ${a24}, ${a25}, ${a26}, ${a27}, ${a28}, ${a29}, ${a30}, ${a31}, ${a32}, ${a33}, ${a34}, ${a35}, ${a36}, ${a37}, ${a38}, ${a39})");
+
+  // In legacy mode, possibly return null.
+
+  // In both nnbd and legacy mode, possibly throw.
+  if (a0 == 42 || a0 == 84) {
+    print("throwing!");
+    throw Exception(
+        "PassInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int throwing on purpuse!");
+  }
+
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a0 = a0;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a1 = a1;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a2 = a2;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a3 = a3;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a4 = a4;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a5 = a5;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a6 = a6;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a7 = a7;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a8 = a8;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a9 = a9;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a10 = a10;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a11 = a11;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a12 = a12;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a13 = a13;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a14 = a14;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a15 = a15;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a16 = a16;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a17 = a17;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a18 = a18;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a19 = a19;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a20 = a20;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a21 = a21;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a22 = a22;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a23 = a23;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a24 = a24;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a25 = a25;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a26 = a26;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a27 = a27;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a28 = a28;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a29 = a29;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a30 = a30;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a31 = a31;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a32 = a32;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a33 = a33;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a34 = a34;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a35 = a35;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a36 = a36;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a37 = a37;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a38 = a38;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a39 = a39;
+
+  final result =
+      passInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntCalculateResult();
+
+  print("result = $result");
+
+  return result;
+}
+
+void passInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntAfterCallback() {
+  final result =
+      passInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntCalculateResult();
+
+  print("after callback result = $result");
+
+  Expect.approxEquals(26.0, result);
+}
+
 typedef PassStructAlignmentInt16Type = Int64 Function(StructAlignmentInt16);
 
 // Global variables to be able to test inputs after callback returned.
diff --git a/tests/ffi/function_structs_by_value_generated_test.dart b/tests/ffi/function_structs_by_value_generated_test.dart
index 26f48eafe8d..35936e969cc 100644
--- a/tests/ffi/function_structs_by_value_generated_test.dart
+++ b/tests/ffi/function_structs_by_value_generated_test.dart
@@ -48,6 +48,7 @@ void main() {
     testPassDoublex6Struct16BytesMixedx4Int32();
     testPassInt32x4Struct16BytesMixedx4Double();
     testPassStruct40BytesHomogeneousDoubleStruct4BytesHomo();
+    testPassInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int();
     testPassStructAlignmentInt16();
     testPassStructAlignmentInt32();
     testPassStructAlignmentInt64();
@@ -3357,6 +3358,245 @@ void testPassStruct40BytesHomogeneousDoubleStruct4BytesHomo() {
   free(a2.addressOf);
 }
 
+final passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int =
+    ffiTestFunctions.lookupFunction<
+        Double Function(
+            Int32,
+            Int32,
+            Int32,
+            Int32,
+            Int32,
+            Int32,
+            Int32,
+            Int32,
+            Double,
+            Double,
+            Double,
+            Double,
+            Double,
+            Double,
+            Double,
+            Double,
+            Int64,
+            Int8,
+            Struct1ByteInt,
+            Int64,
+            Int8,
+            Struct4BytesHomogeneousInt16,
+            Int64,
+            Int8,
+            Struct8BytesInt,
+            Int64,
+            Int8,
+            Struct8BytesHomogeneousFloat,
+            Int64,
+            Int8,
+            Struct8BytesMixed,
+            Int64,
+            Int8,
+            StructAlignmentInt16,
+            Int64,
+            Int8,
+            StructAlignmentInt32,
+            Int64,
+            Int8,
+            StructAlignmentInt64),
+        double Function(
+            int,
+            int,
+            int,
+            int,
+            int,
+            int,
+            int,
+            int,
+            double,
+            double,
+            double,
+            double,
+            double,
+            double,
+            double,
+            double,
+            int,
+            int,
+            Struct1ByteInt,
+            int,
+            int,
+            Struct4BytesHomogeneousInt16,
+            int,
+            int,
+            Struct8BytesInt,
+            int,
+            int,
+            Struct8BytesHomogeneousFloat,
+            int,
+            int,
+            Struct8BytesMixed,
+            int,
+            int,
+            StructAlignmentInt16,
+            int,
+            int,
+            StructAlignmentInt32,
+            int,
+            int,
+            StructAlignmentInt64)>("PassInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int");
+
+/// Test alignment and padding of 16 byte int within struct.
+void testPassInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int() {
+  int a0;
+  int a1;
+  int a2;
+  int a3;
+  int a4;
+  int a5;
+  int a6;
+  int a7;
+  double a8;
+  double a9;
+  double a10;
+  double a11;
+  double a12;
+  double a13;
+  double a14;
+  double a15;
+  int a16;
+  int a17;
+  Struct1ByteInt a18 = allocate<Struct1ByteInt>().ref;
+  int a19;
+  int a20;
+  Struct4BytesHomogeneousInt16 a21 =
+      allocate<Struct4BytesHomogeneousInt16>().ref;
+  int a22;
+  int a23;
+  Struct8BytesInt a24 = allocate<Struct8BytesInt>().ref;
+  int a25;
+  int a26;
+  Struct8BytesHomogeneousFloat a27 =
+      allocate<Struct8BytesHomogeneousFloat>().ref;
+  int a28;
+  int a29;
+  Struct8BytesMixed a30 = allocate<Struct8BytesMixed>().ref;
+  int a31;
+  int a32;
+  StructAlignmentInt16 a33 = allocate<StructAlignmentInt16>().ref;
+  int a34;
+  int a35;
+  StructAlignmentInt32 a36 = allocate<StructAlignmentInt32>().ref;
+  int a37;
+  int a38;
+  StructAlignmentInt64 a39 = allocate<StructAlignmentInt64>().ref;
+
+  a0 = -1;
+  a1 = 2;
+  a2 = -3;
+  a3 = 4;
+  a4 = -5;
+  a5 = 6;
+  a6 = -7;
+  a7 = 8;
+  a8 = -9.0;
+  a9 = 10.0;
+  a10 = -11.0;
+  a11 = 12.0;
+  a12 = -13.0;
+  a13 = 14.0;
+  a14 = -15.0;
+  a15 = 16.0;
+  a16 = -17;
+  a17 = 18;
+  a18.a0 = -19;
+  a19 = 20;
+  a20 = -21;
+  a21.a0 = 22;
+  a21.a1 = -23;
+  a22 = 24;
+  a23 = -25;
+  a24.a0 = 26;
+  a24.a1 = -27;
+  a24.a2 = 28;
+  a25 = -29;
+  a26 = 30;
+  a27.a0 = -31.0;
+  a27.a1 = 32.0;
+  a28 = -33;
+  a29 = 34;
+  a30.a0 = -35.0;
+  a30.a1 = 36;
+  a30.a2 = -37;
+  a31 = 38;
+  a32 = -39;
+  a33.a0 = 40;
+  a33.a1 = -41;
+  a33.a2 = 42;
+  a34 = -43;
+  a35 = 44;
+  a36.a0 = -45;
+  a36.a1 = 46;
+  a36.a2 = -47;
+  a37 = 48;
+  a38 = -49;
+  a39.a0 = 50;
+  a39.a1 = -51;
+  a39.a2 = 52;
+
+  final result = passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int(
+      a0,
+      a1,
+      a2,
+      a3,
+      a4,
+      a5,
+      a6,
+      a7,
+      a8,
+      a9,
+      a10,
+      a11,
+      a12,
+      a13,
+      a14,
+      a15,
+      a16,
+      a17,
+      a18,
+      a19,
+      a20,
+      a21,
+      a22,
+      a23,
+      a24,
+      a25,
+      a26,
+      a27,
+      a28,
+      a29,
+      a30,
+      a31,
+      a32,
+      a33,
+      a34,
+      a35,
+      a36,
+      a37,
+      a38,
+      a39);
+
+  print("result = $result");
+
+  Expect.approxEquals(26.0, result);
+
+  free(a18.addressOf);
+  free(a21.addressOf);
+  free(a24.addressOf);
+  free(a27.addressOf);
+  free(a30.addressOf);
+  free(a33.addressOf);
+  free(a36.addressOf);
+  free(a39.addressOf);
+}
+
 final passStructAlignmentInt16 = ffiTestFunctions.lookupFunction<
     Int64 Function(StructAlignmentInt16),
     int Function(StructAlignmentInt16)>("PassStructAlignmentInt16");
diff --git a/tests/ffi/generator/structs_by_value_tests_configuration.dart b/tests/ffi/generator/structs_by_value_tests_configuration.dart
index 5ea4cffd633..46f5108b735 100644
--- a/tests/ffi/generator/structs_by_value_tests_configuration.dart
+++ b/tests/ffi/generator/structs_by_value_tests_configuration.dart
@@ -188,6 +188,58 @@ The double will be backfilled into the xmm register."""),
       """
 On various architectures, first struct is allocated on stack.
 Check that the other two arguments are allocated on registers."""),
+  FunctionType(
+      [
+        // Exhaust integer registers on all architectures
+        int32,
+        int32,
+        int32,
+        int32,
+        int32,
+        int32,
+        int32,
+        int32,
+        // Exhaust floating point registers on all architectures.
+        double_,
+        double_,
+        double_,
+        double_,
+        double_,
+        double_,
+        double_,
+        double_,
+        // Pass all kinds of structs to exercise stack placement behavior.
+        //
+        // For all structs, align stack with int64, then align to 1-byte with
+        // int8, then pass struct.
+        int64,
+        int8,
+        struct1byteInt,
+        int64,
+        int8,
+        struct4bytesInt,
+        int64,
+        int8,
+        struct8bytesInt,
+        int64,
+        int8,
+        struct8bytesFloat,
+        int64,
+        int8,
+        struct8BytesMixed,
+        int64,
+        int8,
+        structAlignmentInt16,
+        int64,
+        int8,
+        structAlignmentInt32,
+        int64,
+        int8,
+        structAlignmentInt64,
+      ],
+      double_,
+      """
+Test alignment and padding of 16 byte int within struct."""),
   FunctionType(
       [structAlignmentInt16],
       int64,
diff --git a/tests/ffi_2/function_callbacks_structs_by_value_generated_test.dart b/tests/ffi_2/function_callbacks_structs_by_value_generated_test.dart
index 76620d78cc2..38714fd91bf 100644
--- a/tests/ffi_2/function_callbacks_structs_by_value_generated_test.dart
+++ b/tests/ffi_2/function_callbacks_structs_by_value_generated_test.dart
@@ -171,6 +171,12 @@ final testCases = [
               PassStruct40BytesHomogeneousDoubleStruct4BytesHomoType>(
           passStruct40BytesHomogeneousDoubleStruct4BytesHomo, 0.0),
       passStruct40BytesHomogeneousDoubleStruct4BytesHomoAfterCallback),
+  CallbackTest.withCheck(
+      "PassInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int",
+      Pointer.fromFunction<
+              PassInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntType>(
+          passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int, 0.0),
+      passInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntAfterCallback),
   CallbackTest.withCheck(
       "PassStructAlignmentInt16",
       Pointer.fromFunction<PassStructAlignmentInt16Type>(
@@ -3816,6 +3822,281 @@ void passStruct40BytesHomogeneousDoubleStruct4BytesHomoAfterCallback() {
   Expect.approxEquals(-5.0, result);
 }
 
+typedef PassInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntType
+    = Double Function(
+        Int32,
+        Int32,
+        Int32,
+        Int32,
+        Int32,
+        Int32,
+        Int32,
+        Int32,
+        Double,
+        Double,
+        Double,
+        Double,
+        Double,
+        Double,
+        Double,
+        Double,
+        Int64,
+        Int8,
+        Struct1ByteInt,
+        Int64,
+        Int8,
+        Struct4BytesHomogeneousInt16,
+        Int64,
+        Int8,
+        Struct8BytesInt,
+        Int64,
+        Int8,
+        Struct8BytesHomogeneousFloat,
+        Int64,
+        Int8,
+        Struct8BytesMixed,
+        Int64,
+        Int8,
+        StructAlignmentInt16,
+        Int64,
+        Int8,
+        StructAlignmentInt32,
+        Int64,
+        Int8,
+        StructAlignmentInt64);
+
+// Global variables to be able to test inputs after callback returned.
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a0 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a1 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a2 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a3 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a4 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a5 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a6 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a7 = 0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a8 = 0.0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a9 = 0.0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a10 = 0.0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a11 = 0.0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a12 = 0.0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a13 = 0.0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a14 = 0.0;
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a15 = 0.0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a16 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a17 = 0;
+Struct1ByteInt passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a18 =
+    Struct1ByteInt();
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a19 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a20 = 0;
+Struct4BytesHomogeneousInt16
+    passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a21 =
+    Struct4BytesHomogeneousInt16();
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a22 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a23 = 0;
+Struct8BytesInt passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a24 =
+    Struct8BytesInt();
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a25 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a26 = 0;
+Struct8BytesHomogeneousFloat
+    passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a27 =
+    Struct8BytesHomogeneousFloat();
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a28 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a29 = 0;
+Struct8BytesMixed passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a30 =
+    Struct8BytesMixed();
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a31 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a32 = 0;
+StructAlignmentInt16 passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a33 =
+    StructAlignmentInt16();
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a34 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a35 = 0;
+StructAlignmentInt32 passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a36 =
+    StructAlignmentInt32();
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a37 = 0;
+int passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a38 = 0;
+StructAlignmentInt64 passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a39 =
+    StructAlignmentInt64();
+
+// Result variable also global, so we can delete it after the callback.
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntResult = 0.0;
+
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntCalculateResult() {
+  double result = 0;
+
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a2;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a3;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a4;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a5;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a6;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a7;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a8;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a9;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a10;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a11;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a12;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a13;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a14;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a15;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a16;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a17;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a18.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a19;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a20;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a21.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a21.a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a22;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a23;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a24.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a24.a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a24.a2;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a25;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a26;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a27.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a27.a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a28;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a29;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a30.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a30.a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a30.a2;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a31;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a32;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a33.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a33.a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a33.a2;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a34;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a35;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a36.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a36.a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a36.a2;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a37;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a38;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a39.a0;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a39.a1;
+  result += passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a39.a2;
+
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntResult = result;
+
+  return result;
+}
+
+/// Test alignment and padding of 16 byte int within struct.
+double passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int(
+    int a0,
+    int a1,
+    int a2,
+    int a3,
+    int a4,
+    int a5,
+    int a6,
+    int a7,
+    double a8,
+    double a9,
+    double a10,
+    double a11,
+    double a12,
+    double a13,
+    double a14,
+    double a15,
+    int a16,
+    int a17,
+    Struct1ByteInt a18,
+    int a19,
+    int a20,
+    Struct4BytesHomogeneousInt16 a21,
+    int a22,
+    int a23,
+    Struct8BytesInt a24,
+    int a25,
+    int a26,
+    Struct8BytesHomogeneousFloat a27,
+    int a28,
+    int a29,
+    Struct8BytesMixed a30,
+    int a31,
+    int a32,
+    StructAlignmentInt16 a33,
+    int a34,
+    int a35,
+    StructAlignmentInt32 a36,
+    int a37,
+    int a38,
+    StructAlignmentInt64 a39) {
+  print(
+      "passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int(${a0}, ${a1}, ${a2}, ${a3}, ${a4}, ${a5}, ${a6}, ${a7}, ${a8}, ${a9}, ${a10}, ${a11}, ${a12}, ${a13}, ${a14}, ${a15}, ${a16}, ${a17}, ${a18}, ${a19}, ${a20}, ${a21}, ${a22}, ${a23}, ${a24}, ${a25}, ${a26}, ${a27}, ${a28}, ${a29}, ${a30}, ${a31}, ${a32}, ${a33}, ${a34}, ${a35}, ${a36}, ${a37}, ${a38}, ${a39})");
+
+  // In legacy mode, possibly return null.
+  if (a0 == 84) {
+    print("returning null!");
+    return null;
+  }
+
+  // In both nnbd and legacy mode, possibly throw.
+  if (a0 == 42 || a0 == 84) {
+    print("throwing!");
+    throw Exception(
+        "PassInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int throwing on purpuse!");
+  }
+
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a0 = a0;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a1 = a1;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a2 = a2;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a3 = a3;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a4 = a4;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a5 = a5;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a6 = a6;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a7 = a7;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a8 = a8;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a9 = a9;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a10 = a10;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a11 = a11;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a12 = a12;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a13 = a13;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a14 = a14;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a15 = a15;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a16 = a16;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a17 = a17;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a18 = a18;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a19 = a19;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a20 = a20;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a21 = a21;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a22 = a22;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a23 = a23;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a24 = a24;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a25 = a25;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a26 = a26;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a27 = a27;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a28 = a28;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a29 = a29;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a30 = a30;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a31 = a31;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a32 = a32;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a33 = a33;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a34 = a34;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a35 = a35;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a36 = a36;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a37 = a37;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a38 = a38;
+  passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int_a39 = a39;
+
+  final result =
+      passInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntCalculateResult();
+
+  print("result = $result");
+
+  return result;
+}
+
+void passInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntAfterCallback() {
+  final result =
+      passInt32x8Doublex8Int64Int8Struct1ByteIntInt64IntCalculateResult();
+
+  print("after callback result = $result");
+
+  Expect.approxEquals(26.0, result);
+}
+
 typedef PassStructAlignmentInt16Type = Int64 Function(StructAlignmentInt16);
 
 // Global variables to be able to test inputs after callback returned.
diff --git a/tests/ffi_2/function_structs_by_value_generated_test.dart b/tests/ffi_2/function_structs_by_value_generated_test.dart
index a548274b7e7..dfb17cd0fd5 100644
--- a/tests/ffi_2/function_structs_by_value_generated_test.dart
+++ b/tests/ffi_2/function_structs_by_value_generated_test.dart
@@ -48,6 +48,7 @@ void main() {
     testPassDoublex6Struct16BytesMixedx4Int32();
     testPassInt32x4Struct16BytesMixedx4Double();
     testPassStruct40BytesHomogeneousDoubleStruct4BytesHomo();
+    testPassInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int();
     testPassStructAlignmentInt16();
     testPassStructAlignmentInt32();
     testPassStructAlignmentInt64();
@@ -3357,6 +3358,245 @@ void testPassStruct40BytesHomogeneousDoubleStruct4BytesHomo() {
   free(a2.addressOf);
 }
 
+final passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int =
+    ffiTestFunctions.lookupFunction<
+        Double Function(
+            Int32,
+            Int32,
+            Int32,
+            Int32,
+            Int32,
+            Int32,
+            Int32,
+            Int32,
+            Double,
+            Double,
+            Double,
+            Double,
+            Double,
+            Double,
+            Double,
+            Double,
+            Int64,
+            Int8,
+            Struct1ByteInt,
+            Int64,
+            Int8,
+            Struct4BytesHomogeneousInt16,
+            Int64,
+            Int8,
+            Struct8BytesInt,
+            Int64,
+            Int8,
+            Struct8BytesHomogeneousFloat,
+            Int64,
+            Int8,
+            Struct8BytesMixed,
+            Int64,
+            Int8,
+            StructAlignmentInt16,
+            Int64,
+            Int8,
+            StructAlignmentInt32,
+            Int64,
+            Int8,
+            StructAlignmentInt64),
+        double Function(
+            int,
+            int,
+            int,
+            int,
+            int,
+            int,
+            int,
+            int,
+            double,
+            double,
+            double,
+            double,
+            double,
+            double,
+            double,
+            double,
+            int,
+            int,
+            Struct1ByteInt,
+            int,
+            int,
+            Struct4BytesHomogeneousInt16,
+            int,
+            int,
+            Struct8BytesInt,
+            int,
+            int,
+            Struct8BytesHomogeneousFloat,
+            int,
+            int,
+            Struct8BytesMixed,
+            int,
+            int,
+            StructAlignmentInt16,
+            int,
+            int,
+            StructAlignmentInt32,
+            int,
+            int,
+            StructAlignmentInt64)>("PassInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int");
+
+/// Test alignment and padding of 16 byte int within struct.
+void testPassInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int() {
+  int a0;
+  int a1;
+  int a2;
+  int a3;
+  int a4;
+  int a5;
+  int a6;
+  int a7;
+  double a8;
+  double a9;
+  double a10;
+  double a11;
+  double a12;
+  double a13;
+  double a14;
+  double a15;
+  int a16;
+  int a17;
+  Struct1ByteInt a18 = allocate<Struct1ByteInt>().ref;
+  int a19;
+  int a20;
+  Struct4BytesHomogeneousInt16 a21 =
+      allocate<Struct4BytesHomogeneousInt16>().ref;
+  int a22;
+  int a23;
+  Struct8BytesInt a24 = allocate<Struct8BytesInt>().ref;
+  int a25;
+  int a26;
+  Struct8BytesHomogeneousFloat a27 =
+      allocate<Struct8BytesHomogeneousFloat>().ref;
+  int a28;
+  int a29;
+  Struct8BytesMixed a30 = allocate<Struct8BytesMixed>().ref;
+  int a31;
+  int a32;
+  StructAlignmentInt16 a33 = allocate<StructAlignmentInt16>().ref;
+  int a34;
+  int a35;
+  StructAlignmentInt32 a36 = allocate<StructAlignmentInt32>().ref;
+  int a37;
+  int a38;
+  StructAlignmentInt64 a39 = allocate<StructAlignmentInt64>().ref;
+
+  a0 = -1;
+  a1 = 2;
+  a2 = -3;
+  a3 = 4;
+  a4 = -5;
+  a5 = 6;
+  a6 = -7;
+  a7 = 8;
+  a8 = -9.0;
+  a9 = 10.0;
+  a10 = -11.0;
+  a11 = 12.0;
+  a12 = -13.0;
+  a13 = 14.0;
+  a14 = -15.0;
+  a15 = 16.0;
+  a16 = -17;
+  a17 = 18;
+  a18.a0 = -19;
+  a19 = 20;
+  a20 = -21;
+  a21.a0 = 22;
+  a21.a1 = -23;
+  a22 = 24;
+  a23 = -25;
+  a24.a0 = 26;
+  a24.a1 = -27;
+  a24.a2 = 28;
+  a25 = -29;
+  a26 = 30;
+  a27.a0 = -31.0;
+  a27.a1 = 32.0;
+  a28 = -33;
+  a29 = 34;
+  a30.a0 = -35.0;
+  a30.a1 = 36;
+  a30.a2 = -37;
+  a31 = 38;
+  a32 = -39;
+  a33.a0 = 40;
+  a33.a1 = -41;
+  a33.a2 = 42;
+  a34 = -43;
+  a35 = 44;
+  a36.a0 = -45;
+  a36.a1 = 46;
+  a36.a2 = -47;
+  a37 = 48;
+  a38 = -49;
+  a39.a0 = 50;
+  a39.a1 = -51;
+  a39.a2 = 52;
+
+  final result = passInt32x8Doublex8Int64Int8Struct1ByteIntInt64Int(
+      a0,
+      a1,
+      a2,
+      a3,
+      a4,
+      a5,
+      a6,
+      a7,
+      a8,
+      a9,
+      a10,
+      a11,
+      a12,
+      a13,
+      a14,
+      a15,
+      a16,
+      a17,
+      a18,
+      a19,
+      a20,
+      a21,
+      a22,
+      a23,
+      a24,
+      a25,
+      a26,
+      a27,
+      a28,
+      a29,
+      a30,
+      a31,
+      a32,
+      a33,
+      a34,
+      a35,
+      a36,
+      a37,
+      a38,
+      a39);
+
+  print("result = $result");
+
+  Expect.approxEquals(26.0, result);
+
+  free(a18.addressOf);
+  free(a21.addressOf);
+  free(a24.addressOf);
+  free(a27.addressOf);
+  free(a30.addressOf);
+  free(a33.addressOf);
+  free(a36.addressOf);
+  free(a39.addressOf);
+}
+
 final passStructAlignmentInt16 = ffiTestFunctions.lookupFunction<
     Int64 Function(StructAlignmentInt16),
     int Function(StructAlignmentInt16)>("PassStructAlignmentInt16");
diff --git a/tests/ffi_2/generator/structs_by_value_tests_configuration.dart b/tests/ffi_2/generator/structs_by_value_tests_configuration.dart
index 5ea4cffd633..46f5108b735 100644
--- a/tests/ffi_2/generator/structs_by_value_tests_configuration.dart
+++ b/tests/ffi_2/generator/structs_by_value_tests_configuration.dart
@@ -188,6 +188,58 @@ The double will be backfilled into the xmm register."""),
       """
 On various architectures, first struct is allocated on stack.
 Check that the other two arguments are allocated on registers."""),
+  FunctionType(
+      [
+        // Exhaust integer registers on all architectures
+        int32,
+        int32,
+        int32,
+        int32,
+        int32,
+        int32,
+        int32,
+        int32,
+        // Exhaust floating point registers on all architectures.
+        double_,
+        double_,
+        double_,
+        double_,
+        double_,
+        double_,
+        double_,
+        double_,
+        // Pass all kinds of structs to exercise stack placement behavior.
+        //
+        // For all structs, align stack with int64, then align to 1-byte with
+        // int8, then pass struct.
+        int64,
+        int8,
+        struct1byteInt,
+        int64,
+        int8,
+        struct4bytesInt,
+        int64,
+        int8,
+        struct8bytesInt,
+        int64,
+        int8,
+        struct8bytesFloat,
+        int64,
+        int8,
+        struct8BytesMixed,
+        int64,
+        int8,
+        structAlignmentInt16,
+        int64,
+        int8,
+        structAlignmentInt32,
+        int64,
+        int8,
+        structAlignmentInt64,
+      ],
+      double_,
+      """
+Test alignment and padding of 16 byte int within struct."""),
   FunctionType(
       [structAlignmentInt16],
       int64,