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Use llvm.used for __objc_protorefs and __objc_protolist #27346

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Merged
merged 1 commit into from
Oct 3, 2019
Merged

Use llvm.used for __objc_protorefs and __objc_protolist #27346

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10 changes: 10 additions & 0 deletions lib/IRGen/GenObjC.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -363,6 +363,11 @@ IRGenModule::getObjCProtocolGlobalVars(ProtocolDecl *proto) {
protocolLabel->setSection(GetObjCSectionName("__objc_protolist",
"coalesced,no_dead_strip"));

// Mark used to prevent DCE of public unreferenced protocols to ensure
// that they are available for external use when a used module is used
// as a library.
addUsedGlobal(protocolLabel);

// Introduce a variable to reference the protocol.
auto *protocolRef =
new llvm::GlobalVariable(Module, Int8PtrTy, /*constant*/ false,
Expand All @@ -374,6 +379,11 @@ IRGenModule::getObjCProtocolGlobalVars(ProtocolDecl *proto) {
protocolRef->setSection(GetObjCSectionName("__objc_protorefs",
"coalesced,no_dead_strip"));

// Mark used to prevent DCE of public unreferenced protocols to ensure
// that they are available for external use when a used module is used
// as a library.
addUsedGlobal(protocolRef);

ObjCProtocolPair pair{protocolRecord, protocolRef};
ObjCProtocols.insert({proto, pair});

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29 changes: 29 additions & 0 deletions test/IRGen/objc_protocol_vars.sil
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Original file line number Diff line number Diff line change
@@ -0,0 +1,29 @@
// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -enable-objc-interop -parse-as-library -emit-ir %s | %FileCheck %s

// It tests whether the vars @"\01l_OBJC_LABEL_PROTOCOL_$__TtP18objc_protocol_vars1T_"
// and @"\01l_OBJC_PROTOCOL_REFERENCE_$__TtP18objc_protocol_vars1T_" are in llvm.used.
//
// import Foundation
// @objc
// public protocol T: AnyObject {
//
// var current: Int32 { get }
//
// func clone() -> T
//
//}
sil_stage canonical

import Builtin
import Swift
import SwiftShims

import Foundation

@objc public protocol T : AnyObject {
@objc var current: Int32 { get }
@objc func clone() -> T
}

// CHECK: @llvm.used = appending global [{{.*}}] [{{.*}}, i8* bitcast (i8** @"\01l_OBJC_LABEL_PROTOCOL_$__TtP18objc_protocol_vars1T_" to i8*), i8* bitcast (i8** @"\01l_OBJC_PROTOCOL_REFERENCE_$__TtP18objc_protocol_vars1T_" to i8*), {{.*}}], {{.*}}