[Serialization] Serialize Differentiability WT index sorted

When there are sil_property and sil_differentiability_witness at once,
serialized file couldn't be deserialized because it's index table is
serialized un-sortedly but deserializer assumes that contents of table
index are sorted.

This patch fixes the un-sorted serialization and adds test case to
ensure that table index contents can be deserialized

Author: kateinoigakukun

lib/Serialization/Serialization.cpp

@@ -856,6 +856,8 @@ void Serializer::writeBlockInfoBlock() {
   BLOCK_RECORD(sil_index_block, SIL_DEFAULT_WITNESS_TABLE_NAMES);
   BLOCK_RECORD(sil_index_block, SIL_DEFAULT_WITNESS_TABLE_OFFSETS);
   BLOCK_RECORD(sil_index_block, SIL_PROPERTY_OFFSETS);
+  BLOCK_RECORD(sil_index_block, SIL_DIFFERENTIABILITY_WITNESS_NAMES);
+  BLOCK_RECORD(sil_index_block, SIL_DIFFERENTIABILITY_WITNESS_OFFSETS);
 
 #undef BLOCK
 #undef BLOCK_RECORD

lib/Serialization/SerializeSIL.cpp

@@ -2346,6 +2346,11 @@ void SILSerializer::writeIndexTables() {
                 DefaultWitnessTableOffset);
   }
 
+  if (!PropertyOffset.empty()) {
+    Offset.emit(ScratchRecord, sil_index_block::SIL_PROPERTY_OFFSETS,
+                PropertyOffset);
+  }
+
   if (!DifferentiabilityWitnessList.empty()) {
     writeIndexTable(S, List,
                     sil_index_block::SIL_DIFFERENTIABILITY_WITNESS_NAMES,
@@ -2355,11 +2360,6 @@ void SILSerializer::writeIndexTables() {
                 DifferentiabilityWitnessOffset);
   }
 
-  if (!PropertyOffset.empty()) {
-    Offset.emit(ScratchRecord, sil_index_block::SIL_PROPERTY_OFFSETS,
-                PropertyOffset);
-  }
-  
 }
 
 void SILSerializer::writeSILGlobalVar(const SILGlobalVariable &g) {

test/Serialization/index-table-order.sil

@@ -0,0 +1,51 @@
+// RUN: %empty-directory(%t)
+
+// Ensure that serialized sib can be deserialized correctly assuming 
+// contents of SIL_INDEX_BLOCK are sorted by their ids
+// RUN: %target-swift-frontend -emit-sib %s -module-name test -o %t/test.sib
+// RUN: %target-swift-frontend -emit-sil %t/test.sib -module-name test
+// CHECK-DAG: sil_vtable
+// CHECK-DAG: sil_global
+// CHECK-DAG: sil_witness_table
+// CHECK-DAG: sil_default_witness_table
+// CHECK-DAG: sil_property
+
+sil_stage canonical
+
+import Builtin
+import Swift
+
+// For SIL_FUNC_NAMES
+sil @id : $@convention(thin) (Float) -> Float {
+bb0(%0 : $Float):
+  return %0 : $Float
+}
+
+
+// For SIL_VTABLE_NAMES
+class C {}
+sil_vtable C {}
+
+// For SIL_GLOBALVAR_NAMES
+sil_global @x : $Int
+
+// For SIL_WITNESS_TABLE_NAMES
+protocol P1 {}
+struct S : P1 {}
+
+sil_witness_table S: P1 module test {}
+
+// For SIL_DEFAULT_WITNESS_TABLE_NAMES
+protocol P2 {}
+sil_default_witness_table P2 {}
+
+// For SIL_PROPERTY_OFFSETS
+struct A {
+  var a: Int
+}
+
+sil_property #A.a ()
+
+// For SIL_DIFFERENTIABILITY_WITNESS_NAMES
+sil_differentiability_witness [parameters 0] [results 0] @id : $@convention(thin) (Float) -> Float {}
+