From c77ecbf49941d6c50c4bd039d59a9af9c1fcdb44 Mon Sep 17 00:00:00 2001
From: Slava Pestov <spestov@apple.com>
Date: Thu, 10 May 2018 00:46:55 -0400
Subject: [PATCH] IRGen: Fix enum lowering with -enable-resilience-bypass

The layout of an enum type will only use spare bits if the
payload types have a fixed size in all resilience domains
where they are visible. In practice, this means that:

- If the enum is internal or resilient, we can use spare bits
  if the payload types are fixed size from inside the current
  module.

- If the enum is public and not resilient, we can use spare bits
  if the payload types are fixed size from all resilience
  domains.

The bug was that the 'fixed size in all resilience domains'
check was returning true for resilient types when the
-enable-resilience-bypass flag was on. This is wrong, because
this meant that building a module with and without
-enable-resilience-bypass could produce different lowerings
for enum types.

Fixes <rdar://problem/40034143>.
---
 lib/IRGen/GenDecl.cpp                            |  4 +++-
 test/IRGen/Inputs/resilience_bypass/first.swift  |  9 +++++++++
 test/IRGen/Inputs/resilience_bypass/second.swift |  6 ++++++
 test/IRGen/resilience_bypass.swift               | 16 ++++++++++++++++
 4 files changed, 34 insertions(+), 1 deletion(-)
 create mode 100644 test/IRGen/Inputs/resilience_bypass/first.swift
 create mode 100644 test/IRGen/Inputs/resilience_bypass/second.swift
 create mode 100644 test/IRGen/resilience_bypass.swift

diff --git a/lib/IRGen/GenDecl.cpp b/lib/IRGen/GenDecl.cpp
index 13da1237d3867..81c674f79f44b 100644
--- a/lib/IRGen/GenDecl.cpp
+++ b/lib/IRGen/GenDecl.cpp
@@ -4067,8 +4067,10 @@ IRGenModule::getAddrOfGlobalUTF16ConstantString(StringRef utf8) {
 /// - For classes, the superclass might change the size or number
 ///   of stored properties
 bool IRGenModule::isResilient(NominalTypeDecl *D, ResilienceExpansion expansion) {
-  if (Types.isCompletelyFragile())
+  if (expansion == ResilienceExpansion::Maximal &&
+      Types.isCompletelyFragile()) {
     return false;
+  }
   return D->isResilient(getSwiftModule(), expansion);
 }
 
diff --git a/test/IRGen/Inputs/resilience_bypass/first.swift b/test/IRGen/Inputs/resilience_bypass/first.swift
new file mode 100644
index 0000000000000..8f9771e50def1
--- /dev/null
+++ b/test/IRGen/Inputs/resilience_bypass/first.swift
@@ -0,0 +1,9 @@
+public class C {}
+
+public struct S {
+  public let c: C
+
+  public init() {
+    self.c = C()
+  }
+}
diff --git a/test/IRGen/Inputs/resilience_bypass/second.swift b/test/IRGen/Inputs/resilience_bypass/second.swift
new file mode 100644
index 0000000000000..019596bfafe5d
--- /dev/null
+++ b/test/IRGen/Inputs/resilience_bypass/second.swift
@@ -0,0 +1,6 @@
+import first
+
+public enum E {
+  case a(S)
+  case b(S)
+}
diff --git a/test/IRGen/resilience_bypass.swift b/test/IRGen/resilience_bypass.swift
new file mode 100644
index 0000000000000..95b59e292e800
--- /dev/null
+++ b/test/IRGen/resilience_bypass.swift
@@ -0,0 +1,16 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swift-frontend -emit-module -enable-resilience -emit-module-path=%t/first.swiftmodule -module-name=first %S/Inputs/resilience_bypass/first.swift
+// RUN: %target-swift-frontend -emit-module -emit-module-path=%t/second.swiftmodule -module-name=second %S/Inputs/resilience_bypass/second.swift -I %t
+// RUN: %target-swift-frontend -emit-ir -enable-resilience-bypass %s -I %t | %FileCheck %s -DINT=i%target-ptrsize
+
+import second
+
+// CHECK:       define{{( protected)?}} swiftcc [[INT]] @"$S17resilience_bypass7getSizeSiyF"() {{.*}} {
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    ret [[INT]] {{5|9}}
+// CHECK-NEXT:  }
+
+public func getSize() -> Int {
+  return MemoryLayout<E>.size
+}