[embedded] Don't retain subclass vtable entries if the base method was DCE'd

Author: kubamracek

lib/SILOptimizer/IPO/DeadFunctionElimination.cpp

@@ -556,6 +556,12 @@ class DeadFunctionAndGlobalElimination {
         auto *fd = getBaseMethod(
             cast<AbstractFunctionDecl>(entry.getMethod().getDecl()));
 
+        // In Embedded Swift, we don't expect SILFunction without definitions on
+        // vtable entries. Having one means the base method was DCE'd already,
+        // so let's avoid marking it alive in the subclass vtable either.
+        bool embedded = Module->getOptions().EmbeddedSwift;
+        if (embedded && !F->isDefinition()) { continue; }
+        
         if (// We also have to check the method declaration's access level.
             // Needed if it's a public base method declared in another
             // compilation unit (for this we have no SILFunction).

test/embedded/modules-subclasses.swift

@@ -7,6 +7,18 @@
 // RUN: %target-clang %t/a.o %t/print.o -o %t/a.out
 // RUN: %target-run %t/a.out | %FileCheck %s
 
+// RUN: %target-swift-frontend -O -emit-module -o %t/MyModule.swiftmodule %t/MyModule.swift -enable-experimental-feature Embedded -parse-as-library
+// RUN: %target-swift-frontend -O -c -I %t %t/Main.swift -enable-experimental-feature Embedded -o %t/a.o
+// RUN: %target-clang -x c -c %S/Inputs/print.c -o %t/print.o
+// RUN: %target-clang %t/a.o %t/print.o -o %t/a.out
+// RUN: %target-run %t/a.out | %FileCheck %s
+
+// RUN: %target-swift-frontend -Osize -emit-module -o %t/MyModule.swiftmodule %t/MyModule.swift -enable-experimental-feature Embedded -parse-as-library
+// RUN: %target-swift-frontend -Osize -c -I %t %t/Main.swift -enable-experimental-feature Embedded -o %t/a.o
+// RUN: %target-clang -x c -c %S/Inputs/print.c -o %t/print.o
+// RUN: %target-clang %t/a.o %t/print.o -o %t/a.out
+// RUN: %target-run %t/a.out | %FileCheck %s
+
 // REQUIRES: swift_in_compiler
 // REQUIRES: executable_test
 // REQUIRES: OS=macosx || OS=linux-gnu