From 0e776a3b8e697ec27cc3a665df4e5eded0cbbfba Mon Sep 17 00:00:00 2001
From: Saleem Abdulrasool <compnerd@compnerd.org>
Date: Tue, 25 Oct 2016 14:50:44 +0000
Subject: [PATCH] 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
---
 lib/CodeGen/CGObjCMac.cpp          | 42 +++++++++++++++++++++---------
 test/CodeGenObjC/protocol-comdat.m | 20 ++++++++++++++
 2 files changed, 50 insertions(+), 12 deletions(-)
 create mode 100644 test/CodeGenObjC/protocol-comdat.m

diff --git a/lib/CodeGen/CGObjCMac.cpp b/lib/CodeGen/CGObjCMac.cpp
index 201bc518f5..e20761ba48 100644
--- a/lib/CodeGen/CGObjCMac.cpp
+++ b/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;
diff --git a/test/CodeGenObjC/protocol-comdat.m b/test/CodeGenObjC/protocol-comdat.m
new file mode 100644
index 0000000000..65e1b9fa2c
--- /dev/null
+++ b/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
+
-- 
2.50.1