SIL: Avoid serializing the bodies of the original copies of @_backDeploy functions to prevent the optimizer from inlining those bodies into their back deployment thunks. This ensures that the copy of the function in the library dylib is reliably called when it is available, both with and without optimizations enabled. Also update the attr_backDeploy_evolution test case to use precondition() instead of assert() since asserts are compiled out with optimizations enabled.

Resolves rdar://90525337

Author: tshortli

include/swift/SIL/SILDeclRef.h

@@ -372,6 +372,8 @@ struct SILDeclRef {
   bool isNoinline() const;
   /// True if the function has __always inline attribute.
   bool isAlwaysInline() const;
+  /// True if the function has the @_backDeploy attribute.
+  bool isBackDeployed() const;
 
   /// Return the expected linkage of this declaration.
   SILLinkage getLinkage(ForDefinition_t forDefinition) const;

include/swift/SIL/SILLinkage.h

@@ -135,7 +135,7 @@ enum IsSerialized_t : unsigned char {
   ///
   /// This flag is only valid for Public, PublicNonABI, PublicExternal,
   /// HiddenExternal and Shared functions.
-  /// Functions with external linkage (PublicExternl, HiddenExternal) will not
+  /// Functions with external linkage (PublicExternal, HiddenExternal) will not
   /// be serialized, because they are available in a different module (from which
   /// they were de-serialized).
   ///

lib/SIL/IR/SILDeclRef.cpp

@@ -689,6 +689,19 @@ IsSerialized_t SILDeclRef::isSerialized() const {
   if (isClangImported())
     return IsSerialized;
 
+  // Handle back deployed functions. The original back deployed function
+  // should not be serialized, but the thunk and fallback should be since they
+  // need to be emitted into the client.
+  if (isBackDeployed()) {
+    switch (backDeploymentKind) {
+      case BackDeploymentKind::None:
+        return IsNotSerialized;
+      case BackDeploymentKind::Fallback:
+      case BackDeploymentKind::Thunk:
+        return IsSerialized;
+    }
+  }
+
   // Otherwise, ask the AST if we're inside an @inlinable context.
   if (dc->getResilienceExpansion() == ResilienceExpansion::Minimal)
     return IsSerialized;
@@ -736,6 +749,17 @@ bool SILDeclRef::isAlwaysInline() const {
   return false;
 }
 
+bool SILDeclRef::isBackDeployed() const {
+  if (!hasDecl())
+    return false;
+
+  auto *decl = getDecl();
+  if (auto afd = dyn_cast<AbstractFunctionDecl>(decl))
+    return afd->isBackDeployed();
+
+  return false;
+}
+
 bool SILDeclRef::isAnyThunk() const {
   return isForeignToNativeThunk() || isNativeToForeignThunk() ||
          isDistributedThunk() || isBackDeploymentThunk();

test/SILGen/back_deploy_attribute_accessor.swift

@@ -36,7 +36,7 @@ public struct TopLevelStruct {
   // CHECK:   return [[RETURN_BB_ARG]] : $TopLevelStruct
 
   // -- Original definition of TopLevelStruct.property.getter
-  // CHECK-LABEL: sil [serialized] [available 10.51] [ossa] @$s11back_deploy14TopLevelStructV8propertyACvg : $@convention(method) (TopLevelStruct) -> TopLevelStruct
+  // CHECK-LABEL: sil [available 10.51] [ossa] @$s11back_deploy14TopLevelStructV8propertyACvg : $@convention(method) (TopLevelStruct) -> TopLevelStruct
   @available(macOS 10.51, *)
   @_backDeploy(before: macOS 10.52)
   public var property: TopLevelStruct { self }

test/SILGen/back_deploy_attribute_func.swift

@@ -36,7 +36,7 @@
 // CHECK:   return [[RESULT]] : $()
 
 // -- Original definition of trivialFunc()
-// CHECK-LABEL: sil [serialized] [available 10.51] [ossa] @$s11back_deploy11trivialFuncyyF : $@convention(thin) () -> ()
+// CHECK-LABEL: sil [available 10.51] [ossa] @$s11back_deploy11trivialFuncyyF : $@convention(thin) () -> ()
 @available(macOS 10.51, *)
 @_backDeploy(before: macOS 10.52)
 public func trivialFunc() {}
@@ -71,7 +71,7 @@ public func trivialFunc() {}
 // CHECK:   return [[RETURN_BB_ARG]] : $Bool
 
 // -- Original definition of isNumber(_:)
-// CHECK-LABEL: sil [serialized] [available 10.51] [ossa] @$s11back_deploy8isNumberySbSiF : $@convention(thin) (Int) -> Bool
+// CHECK-LABEL: sil [available 10.51] [ossa] @$s11back_deploy8isNumberySbSiF : $@convention(thin) (Int) -> Bool
 @available(macOS 10.51, *)
 @_backDeploy(before: macOS 10.52)
 public func isNumber(_ x: Int) -> Bool {

test/SILGen/back_deploy_attribute_generic_func.swift

@@ -37,7 +37,7 @@
 // CHECK:   return [[RESULT]] : $()
 
 // -- Original definition of genericFunc()
-// CHECK-LABEL: sil [serialized] [available 10.51] [ossa] @$s11back_deploy11genericFuncyxxlF : $@convention(thin) <T> (@in_guaranteed T) -> @out T
+// CHECK-LABEL: sil [available 10.51] [ossa] @$s11back_deploy11genericFuncyxxlF : $@convention(thin) <T> (@in_guaranteed T) -> @out T
 @available(macOS 10.51, *)
 @_backDeploy(before: macOS 10.52)
 public func genericFunc<T>(_ t: T) -> T {

test/SILGen/back_deploy_attribute_struct_method.swift

@@ -38,7 +38,7 @@ public struct TopLevelStruct {
   // CHECK:   return [[RESULT]] : $()
 
   // -- Original definition of TopLevelStruct.trivialMethod()
-  // CHECK-LABEL: sil [serialized] [available 10.51] [ossa] @$s11back_deploy14TopLevelStructV13trivialMethodyyF : $@convention(method) (TopLevelStruct) -> ()
+  // CHECK-LABEL: sil [available 10.51] [ossa] @$s11back_deploy14TopLevelStructV13trivialMethodyyF : $@convention(method) (TopLevelStruct) -> ()
   @available(macOS 10.51, *)
   @_backDeploy(before: macOS 10.52)
   public func trivialMethod() {}

test/SILGen/back_deploy_attribute_throwing_func.swift

@@ -49,7 +49,7 @@
 // CHECK:   throw [[RETHROW_BB_ARG]] : $Error
 
 // -- Original definition of throwingFunc()
-// CHECK-LABEL: sil [serialized] [available 10.51] [ossa] @$s11back_deploy12throwingFuncyyKF : $@convention(thin) () -> @error Error
+// CHECK-LABEL: sil [available 10.51] [ossa] @$s11back_deploy12throwingFuncyyKF : $@convention(thin) () -> @error Error
 @available(macOS 10.51, *)
 @_backDeploy(before: macOS 10.52)
 public func throwingFunc() throws {}

test/attr/attr_backDeploy_evolution.swift

@@ -32,9 +32,6 @@
 // REQUIRES: executable_test
 // REQUIRES: VENDOR=apple
 
-// rdar://90525337
-// UNSUPPORTED: swift_test_mode_optimize
-
 // ---- (0) Prepare SDK
 // RUN: %empty-directory(%t)
 // RUN: %empty-directory(%t/SDK_ABI)
@@ -119,34 +116,34 @@ testPrint(handle: #dsohandle, "check")
 testPrint(handle: libraryHandle(), "check")
 
 if isV2OrLater() {
-  assert(!v2APIsAreStripped())
+  precondition(!v2APIsAreStripped())
 }
 
 // CHECK-ABI: library: trivial
 // CHECK-BD: client: trivial
 trivial()
 
-assert(try! pleaseThrow(false))
+precondition(try! pleaseThrow(false))
 do {
   _ = try pleaseThrow(true)
   fatalError("Should have thrown")
 } catch {
-  assert(error as? BadError == BadError.bad)
+  precondition(error as? BadError == BadError.bad)
 }
 
 do {
   let zero = MutableInt.zero
-  assert(zero.value == 0)
+  precondition(zero.value == 0)
 
   var int = MutableInt(5)
 
   // CHECK-ABI: library: 5
   // CHECK-BD: client: 5
   int.print()
 
-  assert(int.increment(by: 2) == 7)
-  assert(genericIncrement(&int, by: 3) == 10)
-  assert(int.decrement(by: 1) == 9)
+  precondition(int.increment(by: 2) == 7)
+  precondition(genericIncrement(&int, by: 3) == 10)
+  precondition(int.decrement(by: 1) == 9)
 
   var incrementable: any Incrementable = int.toIncrementable()
 
@@ -156,13 +153,13 @@ do {
 
   let int2 = MutableInt(0x7BB7914B)
   for (i, expectedByte) in [0x4B, 0x91, 0xB7, 0x7B].enumerated() {
-    assert(int2[byteAt: i] == expectedByte)
+    precondition(int2[byteAt: i] == expectedByte)
   }
 }
 
 do {
   let zero = ReferenceInt.zero
-  assert(zero.value == 0)
+  precondition(zero.value == 0)
 
   var int = ReferenceInt(42)
 
@@ -172,13 +169,13 @@ do {
 
   do {
     let copy = int.copy()
-    assert(int !== copy)
-    assert(copy.value == 42)
+    precondition(int !== copy)
+    precondition(copy.value == 42)
   }
 
-  assert(int.increment(by: 2) == 44)
-  assert(genericIncrement(&int, by: 3) == 47)
-  assert(int.decrement(by: 46) == 1)
+  precondition(int.increment(by: 2) == 44)
+  precondition(genericIncrement(&int, by: 3) == 47)
+  precondition(int.decrement(by: 46) == 1)
 
   var incrementable: any Incrementable = int.toIncrementable()
 
@@ -188,6 +185,6 @@ do {
 
   let int2 = MutableInt(0x08AFAB76)
   for (i, expectedByte) in [0x76, 0xAB, 0xAF, 0x08].enumerated() {
-    assert(int2[byteAt: i] == expectedByte)
+    precondition(int2[byteAt: i] == expectedByte)
   }
 }