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[embedded] Don't retain subclass vtable entries if the base method was DCE'd #72898

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Merged
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Apr 9, 2024
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[embedded] Don't retain subclass vtable entries if the base method was DCE'd #72898

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6 changes: 6 additions & 0 deletions lib/SILOptimizer/IPO/DeadFunctionElimination.cpp
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Expand Up @@ -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;
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@eeckstein I wonder if you think this is the right approach? Alternatively, is there a way to have the subclass vtable not contain the (removed in the base class) entry in the first place?

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).
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12 changes: 12 additions & 0 deletions test/embedded/modules-subclasses.swift
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Expand Up @@ -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
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