IRGen: Don't hoist metadata for weakly linked types

rdar://46438608

Author: aschwaighofer

lib/IRGen/AllocStackHoisting.cpp

@@ -57,6 +57,11 @@ static bool isHoistable(AllocStackInst *Inst, irgen::IRGenModule &Mod) {
   if (TI.isFixedSize())
     return false;
 
+  // Don't hoist weakly imported (weakly linked) types.
+  auto *nominalDecl = SILTy.getASTType()->getNominalOrBoundGenericNominal();
+  if (nominalDecl->isWeakImported(Mod.getSILModule().getSwiftModule()))
+    return false;
+
   // Don't hoist generics with opened archetypes. We would have to hoist the
   // open archetype instruction which might not be possible.
   return Inst->getTypeDependentOperands().empty();

test/IRGen/Inputs/weakly_linked.swift

@@ -0,0 +1,10 @@
+public func getVersion() -> Int {
+  // Used to return 0.
+  return 1
+}
+
+@_weakLinked public struct ResilientStruct {
+  public init() {}
+
+  public func fn(_ x: Int) {}
+}

test/IRGen/resilience_weakly_linked.swift

@@ -0,0 +1,20 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swift-frontend -emit-module -enable-resilience -emit-module-path=%t/weak.swiftmodule -module-name=weak %S/Inputs/weakly_linked.swift
+// RUN: %target-swift-frontend -emit-ir %s -I %t | %FileCheck %s -DINT=i%target-ptrsize
+import weak
+
+// We should not hoist the metadata accessor accross the version check.
+
+// CHECK-LABEL: define{{.*}} void @"$s24resilience_weakly_linked015test_not_hoist_b1_C0yyF"()
+// CHECK-NOT: 15ResilientStructVMa
+// CHECK: getVersion
+// CHECK: 15ResilientStructVMa
+// CHECK: ret
+
+public func test_not_hoist_weakly_linked() {
+  if getVersion() == 1 {
+     var s = ResilientStruct()
+     s.fn(5)
+  }
+}

validation-test/Evolution/test_backward_deploy_struct.swift

@@ -9,25 +9,19 @@ var BackwardDeployStructTest = TestSuite("BackwardDeployStruct")
 
 BackwardDeployStructTest.test("ResilientStruct") {
   if getVersion() == 1 {
-    // FIXME: IRGen inserts the metadata load outside the version check
-    // apparently. Work around that here. <rdar://problem/46438608>
-    @inline(never) func helper() {
-      var s = ResilientStruct()
+    var s = ResilientStruct()
 
-      s.fn(s.storedProp)
-      s.storedProp = 1
-      s.storedProp += 1
-
-      s.fn(s.computedProp)
-      s.computedProp = 1
-      s.computedProp += 1
+    s.fn(s.storedProp)
+    s.storedProp = 1
+    s.storedProp += 1
 
-      s.fn(s[0])
-      s[0] = 1
-      s[0] += 1
-    }
+    s.fn(s.computedProp)
+    s.computedProp = 1
+    s.computedProp += 1
 
-    helper()
+    s.fn(s[0])
+    s[0] = 1
+    s[0] += 1
   }
 }