CodeGen: mark protocols as common data

This allows for the coalescing of the protocol declarations.  When the protocols
are declared in headers, multiple definitions of the protocol would be emitted.
Marking them as common data indicates that any one can be selected.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@285073 91177308-0d34-0410-b5e6-96231b3b80d8

Author: compnerd

lib/CodeGen/CGObjCMac.cpp

@@ -6562,15 +6562,20 @@ llvm::Constant *CGObjCNonFragileABIMac::GetOrEmitProtocolRef(
   const ObjCProtocolDecl *PD) {
   llvm::GlobalVariable *&Entry = Protocols[PD->getIdentifier()];
 
-  if (!Entry)
+  if (!Entry) {
     // We use the initializer as a marker of whether this is a forward
     // reference or not. At module finalization we add the empty
     // contents for protocols which were referenced but never defined.
-    Entry =
-        new llvm::GlobalVariable(CGM.getModule(), ObjCTypes.ProtocolnfABITy,
-                                 false, llvm::GlobalValue::ExternalLinkage,
-                                 nullptr,
-                                 "\01l_OBJC_PROTOCOL_$_" + PD->getObjCRuntimeNameAsString());
+    llvm::SmallString<64> Protocol;
+    llvm::raw_svector_ostream(Protocol) << "\01l_OBJC_PROTOCOL_$_"
+                                        << PD->getObjCRuntimeNameAsString();
+
+    Entry = new llvm::GlobalVariable(CGM.getModule(), ObjCTypes.ProtocolnfABITy,
+                                     false, llvm::GlobalValue::ExternalLinkage,
+                                     nullptr, Protocol);
+    if (!CGM.getTriple().isOSBinFormatMachO())
+      Entry->setComdat(CGM.getModule().getOrInsertComdat(Protocol));
+  }
 
   return Entry;
 }
@@ -6688,10 +6693,16 @@ llvm::Constant *CGObjCNonFragileABIMac::GetOrEmitProtocol(
     Entry->setLinkage(llvm::GlobalValue::WeakAnyLinkage);
     Entry->setInitializer(Init);
   } else {
-    Entry =
-      new llvm::GlobalVariable(CGM.getModule(), ObjCTypes.ProtocolnfABITy,
-                               false, llvm::GlobalValue::WeakAnyLinkage, Init,
-                               "\01l_OBJC_PROTOCOL_$_" + PD->getObjCRuntimeNameAsString());
+    llvm::SmallString<64> Protocol;
+    llvm::raw_svector_ostream(Protocol) << "\01l_OBJC_PROTOCOL_$_"
+                                        << PD->getObjCRuntimeNameAsString();
+
+    Entry = new llvm::GlobalVariable(CGM.getModule(), ObjCTypes.ProtocolnfABITy,
+                                     false, llvm::GlobalValue::WeakAnyLinkage,
+                                     Init, Protocol);
+    if (!CGM.getTriple().isOSBinFormatMachO())
+      Entry->setComdat(CGM.getModule().getOrInsertComdat(Protocol));
+
     Entry->setAlignment(
       CGM.getDataLayout().getABITypeAlignment(ObjCTypes.ProtocolnfABITy));
 
@@ -6702,13 +6713,20 @@ llvm::Constant *CGObjCNonFragileABIMac::GetOrEmitProtocol(
 
   // Use this protocol meta-data to build protocol list table in section
   // __DATA, __objc_protolist
+  llvm::SmallString<64> ProtocolRef;
+  llvm::raw_svector_ostream(ProtocolRef) << "\01l_OBJC_LABEL_PROTOCOL_$_"
+                                         << PD->getObjCRuntimeNameAsString();
+
   llvm::GlobalVariable *PTGV =
     new llvm::GlobalVariable(CGM.getModule(), ObjCTypes.ProtocolnfABIPtrTy,
                              false, llvm::GlobalValue::WeakAnyLinkage, Entry,
-                             "\01l_OBJC_LABEL_PROTOCOL_$_" + PD->getObjCRuntimeNameAsString());
+                             ProtocolRef);
+  if (!CGM.getTriple().isOSBinFormatMachO())
+    PTGV->setComdat(CGM.getModule().getOrInsertComdat(ProtocolRef));
   PTGV->setAlignment(
     CGM.getDataLayout().getABITypeAlignment(ObjCTypes.ProtocolnfABIPtrTy));
-  PTGV->setSection("__DATA, __objc_protolist, coalesced, no_dead_strip");
+  if (CGM.getTriple().isOSBinFormatMachO())
+    PTGV->setSection("__DATA, __objc_protolist, coalesced, no_dead_strip");
   PTGV->setVisibility(llvm::GlobalValue::HiddenVisibility);
   CGM.addCompilerUsedGlobal(PTGV);
   return Entry;

test/CodeGenObjC/protocol-comdat.m

@@ -0,0 +1,20 @@
+// RUN: %clang -cc1 -triple thumbv7--windows-itanium -fobjc-runtime=ios -emit-llvm -o - %s -Wno-objc-root-class | FileCheck %s
+
+@protocol P
+- (void) method;
+@end
+
+@interface I<P>
+@end
+
+@implementation I
+- (void) method { }
+@end
+
+
+// CHECK: $"\01l_OBJC_PROTOCOL_$_P" = comdat any
+// CHECK: $"\01l_OBJC_LABEL_PROTOCOL_$_P" = comdat any
+
+// CHECK: @"\01l_OBJC_PROTOCOL_$_P" = {{.*}}, comdat
+// CHECK: @"\01l_OBJC_LABEL_PROTOCOL_$_P" = {{.*}}, comdat
+