diff --git a/include/swift/AST/SILOptions.h b/include/swift/AST/SILOptions.h
index 6942602c60e..8e92b4795cf 100644
--- a/include/swift/AST/SILOptions.h
+++ b/include/swift/AST/SILOptions.h
@@ -149,6 +149,9 @@ public:
   /// Enable the mandatory semantic arc optimizer.
   bool EnableMandatorySemanticARCOpts = false;
 
+  /// \brief Enable large loadable types IRGen pass.
+  bool EnableLargeLoadableTypes = false;
+
   SILOptions() : Sanitize(SanitizerKind::None) {}
 
   /// Return a hash code of any components from these options that should
diff --git a/include/swift/Option/FrontendOptions.td b/include/swift/Option/FrontendOptions.td
index baf691b4d20..ea8dc54bc36 100644
--- a/include/swift/Option/FrontendOptions.td
+++ b/include/swift/Option/FrontendOptions.td
@@ -264,6 +264,9 @@ def suppress_static_exclusivity_swap : Flag<["-"], "suppress-static-exclusivity-
 
 def enable_sil_opaque_values : Flag<["-"], "enable-sil-opaque-values">,
   HelpText<"Enable SIL Opaque Values">;
+  
+def enable_large_loadable_types : Flag<["-"], "enable-large-loadable-types">,
+  HelpText<"Enable Large Loadable types IRGen pass">;
 
 def enable_experimental_property_behaviors :
   Flag<["-"], "enable-experimental-property-behaviors">,
diff --git a/include/swift/SILOptimizer/PassManager/PassPipeline.def b/include/swift/SILOptimizer/PassManager/PassPipeline.def
index c0cfcf677e0..afd47de5022 100644
--- a/include/swift/SILOptimizer/PassManager/PassPipeline.def
+++ b/include/swift/SILOptimizer/PassManager/PassPipeline.def
@@ -37,7 +37,7 @@ PASSPIPELINE_WITH_OPTIONS(Performance, "Passes run at -O")
 PASSPIPELINE(Onone, "Passes run at -Onone")
 PASSPIPELINE(InstCount, "Utility pipeline to just run the inst count pass")
 PASSPIPELINE(Lowering, "SIL Address Lowering")
-PASSPIPELINE(IRGenPrepare, "Pipeline to run during IRGen")
+PASSPIPELINE_WITH_OPTIONS(IRGenPrepare, "Pipeline to run during IRGen")
 
 #undef PASSPIPELINE_WITH_OPTIONS
 #undef PASSPIPELINE
diff --git a/include/swift/SILOptimizer/PassManager/Passes.def b/include/swift/SILOptimizer/PassManager/Passes.def
index 17e23aec9a9..647f9e48a89 100644
--- a/include/swift/SILOptimizer/PassManager/Passes.def
+++ b/include/swift/SILOptimizer/PassManager/Passes.def
@@ -222,6 +222,8 @@ PASS(ReleaseHoisting, "release-hoisting",
      "SIL release Hoisting")
 PASS(LateReleaseHoisting, "late-release-hoisting",
      "Late SIL release Hoisting Preserving Epilogues")
+IRGEN_PASS(LoadableByAddress, "loadable-address",
+     "SIL Large Loadable type by-address lowering.")
 PASS(RemovePins, "remove-pins",
      "Remove SIL pin/unpin pairs")
 PASS(SideEffectsDumper, "side-effects-dump",
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 9ab8890c1fc..6ece5eba4a2 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -1374,6 +1374,7 @@ static bool ParseSILArgs(SILOptions &Opts, ArgList &Args,
     |= Args.hasArg(OPT_assume_parsing_unqualified_ownership_sil);
   Opts.EnableMandatorySemanticARCOpts |=
       !Args.hasArg(OPT_disable_mandatory_semantic_arc_opts);
+  Opts.EnableLargeLoadableTypes |= Args.hasArg(OPT_enable_large_loadable_types);
 
   if (Args.hasArg(OPT_debug_on_sil)) {
     // Derive the name of the SIL file for debugging from
diff --git a/lib/IRGen/IRGen.cpp b/lib/IRGen/IRGen.cpp
index 410cb12a527..d58fed30b5c 100644
--- a/lib/IRGen/IRGen.cpp
+++ b/lib/IRGen/IRGen.cpp
@@ -646,12 +646,19 @@ void swift::irgen::deleteIRGenModule(
 static void runIRGenPreparePasses(SILModule &Module,
                                   irgen::IRGenModule &IRModule) {
   SILPassManager PM(&Module, &IRModule);
+  bool largeLoadable = Module.getOptions().EnableLargeLoadableTypes;
 #define PASS(ID, Tag, Name)
 #define IRGEN_PASS(ID, Tag, Name)                                              \
-  PM.registerIRGenPass(swift::PassKind::ID, irgen::create##ID());
+  if (swift::PassKind::ID == swift::PassKind::LoadableByAddress) {             \
+    if (largeLoadable) {                                                       \
+      PM.registerIRGenPass(swift::PassKind::ID, irgen::create##ID());          \
+    }                                                                          \
+  } else {                                                                     \
+    PM.registerIRGenPass(swift::PassKind::ID, irgen::create##ID());            \
+  }
 #include "swift/SILOptimizer/PassManager/Passes.def"
   PM.executePassPipelinePlan(
-      SILPassPipelinePlan::getIRGenPreparePassPipeline());
+      SILPassPipelinePlan::getIRGenPreparePassPipeline(Module.getOptions()));
 }
 
 /// Generates LLVM IR, runs the LLVM passes and produces the output file.
diff --git a/lib/SILOptimizer/PassManager/PassPipeline.cpp b/lib/SILOptimizer/PassManager/PassPipeline.cpp
index 7b577d40d48..ade95e35eca 100644
--- a/lib/SILOptimizer/PassManager/PassPipeline.cpp
+++ b/lib/SILOptimizer/PassManager/PassPipeline.cpp
@@ -430,19 +430,17 @@ SILPassPipelinePlan::getLoweringPassPipeline() {
   return P;
 }
 
-/// Non-mandatory passes that should run as preparation for IRGen.
-static void addIRGenPreparePipeline(SILPassPipelinePlan &P) {
+SILPassPipelinePlan
+SILPassPipelinePlan::getIRGenPreparePassPipeline(const SILOptions &Options) {
+  SILPassPipelinePlan P;
   P.startPipeline("IRGen Preparation");
   // Insert SIL passes to run during IRGen.
   // Hoist generic alloc_stack instructions to the entry block to enable better
   // llvm-ir generation for dynamic alloca instructions.
   P.addAllocStackHoisting();
-  //P.addLoadableByAddress();
-}
-
-SILPassPipelinePlan SILPassPipelinePlan::getIRGenPreparePassPipeline() {
-  SILPassPipelinePlan P;
-  addIRGenPreparePipeline(P);
+  if (Options.EnableLargeLoadableTypes) {
+    P.addLoadableByAddress();
+  }
   return P;
 }
 
diff --git a/test/IRGen/big_types_corner_cases.swift b/test/IRGen/big_types_corner_cases.swift
new file mode 100644
index 00000000000..9ae7eb33f6f
--- /dev/null
+++ b/test/IRGen/big_types_corner_cases.swift
@@ -0,0 +1,113 @@
+// RUN: %target-swift-frontend -assume-parsing-unqualified-ownership-sil -enable-large-loadable-types %s -emit-ir | %FileCheck %s
+
+public struct BigStruct {
+  var i0 : Int32 = 0
+  var i1 : Int32 = 1
+  var i2 : Int32 = 2
+  var i3 : Int32 = 3
+  var i4 : Int32 = 4
+  var i5 : Int32 = 5
+  var i6 : Int32 = 6
+  var i7 : Int32 = 7
+  var i8 : Int32 = 8
+}
+
+func takeClosure(execute block: () -> Void) {
+}
+
+class OptionalInoutFuncType {
+  private var lp :  BigStruct?
+  private var _handler : ((BigStruct?, Error?) -> ())?
+
+  func execute(_ error: Error?) {
+    var p : BigStruct?
+    var handler: ((BigStruct?, Error?) -> ())?
+    
+    takeClosure {
+      p = self.lp
+      handler = self._handler
+      self._handler = nil
+    }
+
+    handler?(p, error)
+  }
+}
+
+// CHECK-LABEL: define{{( protected)?}} internal swiftcc void @_T022big_types_corner_cases21OptionalInoutFuncTypeC7executeys5Error_pSgFyycfU_(%T22big_types_corner_cases9BigStructVSg* nocapture dereferenceable({{.*}}), %T22big_types_corner_cases21OptionalInoutFuncTypeC*, %T22big_types_corner_cases9BigStructVSgs5Error_pSgIxcx_Sg* nocapture dereferenceable({{.*}})
+// CHECK: call void @_T0SqWy
+// CHECK: call void @_T0SqWe
+// CHECK: ret void
+
+public func f1_returns_BigType(_ x: BigStruct) -> BigStruct {
+  return x
+}
+
+public func f2_returns_f1() -> (_ x: BigStruct) -> BigStruct {
+  return f1_returns_BigType
+}
+
+public func f3_uses_f2() {
+  let x = BigStruct()
+  let useOfF2 = f2_returns_f1()
+  let _ = useOfF2(x)
+}
+
+// CHECK-LABEL: define{{( protected)?}} swiftcc void @_T022big_types_corner_cases10f3_uses_f2yyF()
+// CHECK: call swiftcc void @_T022big_types_corner_cases9BigStructVACycfC(%T22big_types_corner_cases9BigStructV* noalias nocapture sret
+// CHECK: call swiftcc { i8*, %swift.refcounted* } @_T022big_types_corner_cases13f2_returns_f1AA9BigStructVADcyF()
+// CHECK: call swiftcc void %16(%T22big_types_corner_cases9BigStructV* noalias nocapture sret %call.aggresult1, %T22big_types_corner_cases9BigStructV* noalias nocapture dereferenceable
+// CHECK: ret void
+
+public func f4_tuple_use_of_f2() {
+  let x = BigStruct()
+  let tupleWithFunc = (f2_returns_f1(), x)
+  let useOfF2 = tupleWithFunc.0
+  let _ = useOfF2(x)
+}
+
+// CHECK-LABEL: define{{( protected)?}} swiftcc void @_T022big_types_corner_cases18f4_tuple_use_of_f2yyF()
+// CHECK: [[TUPLE:%.*]] = call swiftcc { i8*, %swift.refcounted* } @_T022big_types_corner_cases13f2_returns_f1AA9BigStructVADcyF()
+// CHECK: [[TUPLE_EXTRACT:%.*]] = extractvalue { i8*, %swift.refcounted* } [[TUPLE]], 0
+// CHECK: [[CAST_EXTRACT:%.*]] = bitcast i8* [[TUPLE_EXTRACT]] to void (%T22big_types_corner_cases9BigStructV*, %T22big_types_corner_cases9BigStructV*, %swift.refcounted*)*
+// CHECK:  call swiftcc void [[CAST_EXTRACT]](%T22big_types_corner_cases9BigStructV* noalias nocapture sret %call.aggresult1, %T22big_types_corner_cases9BigStructV* noalias nocapture dereferenceable
+// CHECK: ret void
+
+public class BigClass {
+  public init() {
+  }
+
+  public var optVar: ((BigStruct)-> Void)? = nil
+    
+  func useBigStruct(bigStruct: BigStruct) {
+    optVar!(bigStruct)
+  }
+}
+
+// CHECK-LABEL define{{( protected)?}} hidden swiftcc void @_T022big_types_corner_cases8BigClassC03useE6StructyAA0eH0V0aH0_tF(%T22big_types_corner_cases9BigStructV* noalias nocapture dereferenceable({{.*}}), %T22big_types_corner_cases8BigClassC* swiftself) #0 {
+// CHECK: getelementptr inbounds %T22big_types_corner_cases8BigClassC, %T22big_types_corner_cases8BigClassC*
+// CHECK: call void @_T0SqWy
+// CHECK: [[BITCAST:%.*]] = bitcast i8* {{.*}} to void (%T22big_types_corner_cases9BigStructV*, %swift.refcounted*)*
+// CHECK: call swiftcc void [[BITCAST]](%T22big_types_corner_cases9BigStructV* noalias nocapture dereferenceable({{.*}}) %0, %swift.refcounted* swiftself 
+// CHECK: ret void
+
+public struct MyStruct {
+  public let a: Int
+  public let b: String?
+ }
+
+typealias UploadFunction = ((MyStruct, Int?) -> Void) -> Void
+func takesUploader(_ u: UploadFunction) { }
+
+class Foo {
+  func blam() {
+    takesUploader(self.myMethod) // crash compiling this
+  }
+
+  func myMethod(_ callback: (MyStruct, Int) -> Void) -> Void { }
+}
+
+// CHECK-LABEL: define{{( protected)?}} linkonce_odr hidden swiftcc { i8*, %swift.refcounted* } @_T022big_types_corner_cases3FooC8myMethodyyAA8MyStructV_SitcFTc(%T22big_types_corner_cases3FooC*)
+// CHECK: getelementptr inbounds %T22big_types_corner_cases3FooC, %T22big_types_corner_cases3FooC*
+// CHECK: getelementptr inbounds void (i8*, %swift.refcounted*, %T22big_types_corner_cases3FooC*)*, void (i8*, %swift.refcounted*, %T22big_types_corner_cases3FooC*)**
+// CHECK: call noalias %swift.refcounted* @swift_rt_swift_allocObject(%swift.type* getelementptr inbounds (%swift.full_boxmetadata, %swift.full_boxmetadata*
+// CHECK: ret { i8*, %swift.refcounted* }