[CodeGen][ObjC] Remove the leading 'l' from symbols for protocol metadata and protocol list

[ahatanak]

Summary

The leading 'l' tells ld64 to remove the symbol name, which can make debugging difficult.

rdar://problem/47256637

[ahatanak]

There are other symbols that starts with 'l' and have private linkage. I haven't made any changes to those symbols in this patch, but I think it's possible to remove the leading 'l' from those symbols and change the linkage to internal if we want to keep the symbol names.

[rjmccall]

Using internal linkage instead of private makes sense to me. Even if we wanted to use private linkage, it never made sense to be doing this with \01l instead of just setting the linkage properly. Maybe this was implemented before LLVM directly supported private linkage, but that hasn't been a constraint in 10+ years.

[ahatanak]

Okay, I'll remove the leading 'l' from other symbols and make them internal in a separate patch.

cfe/trunk/lib/CodeGen/CGObjCMac.cpp

llvm::Constant *CGObjCNonFragileABIMac::GetOrEmitProtocolRef(
   const ObjCProtocolDecl *PD) {
   llvm::GlobalVariable *&Entry = Protocols[PD->getIdentifier()];
 
   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.
     llvm::SmallString<64> Protocol;
-    llvm::raw_svector_ostream(Protocol) << "\01l_OBJC_PROTOCOL_$_"
+    llvm::raw_svector_ostream(Protocol) << "_OBJC_PROTOCOL_$_"
                                         << 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));
   }
llvm::Constant *CGObjCNonFragileABIMac::GetOrEmitProtocol(
 
   if (Entry) {
     // Already created, fix the linkage and update the initializer.
     Entry->setLinkage(llvm::GlobalValue::WeakAnyLinkage);
     values.finishAndSetAsInitializer(Entry);
   } else {
     llvm::SmallString<64> symbolName;
     llvm::raw_svector_ostream(symbolName)
-      << "\01l_OBJC_PROTOCOL_$_" << PD->getObjCRuntimeNameAsString();
+      << "_OBJC_PROTOCOL_$_" << PD->getObjCRuntimeNameAsString();
 
     Entry = values.finishAndCreateGlobal(symbolName, CGM.getPointerAlign(),
                                          /*constant*/ false,
                                          llvm::GlobalValue::WeakAnyLinkage);
     if (!CGM.getTriple().isOSBinFormatMachO())
       Entry->setComdat(CGM.getModule().getOrInsertComdat(symbolName));
 
     Protocols[PD->getIdentifier()] = Entry;
   }
   Entry->setVisibility(llvm::GlobalValue::HiddenVisibility);
   CGM.addUsedGlobal(Entry);
 
   // 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_$_"
+  llvm::raw_svector_ostream(ProtocolRef) << "_OBJC_LABEL_PROTOCOL_$_"
                                          << PD->getObjCRuntimeNameAsString();
 
   llvm::GlobalVariable *PTGV =
     new llvm::GlobalVariable(CGM.getModule(), ObjCTypes.ProtocolnfABIPtrTy,
                              false, llvm::GlobalValue::WeakAnyLinkage, Entry,
                              ProtocolRef);
   if (!CGM.getTriple().isOSBinFormatMachO())
     PTGV->setComdat(CGM.getModule().getOrInsertComdat(ProtocolRef));

cfe/trunk/test/CodeGenObjC/forward-protocol-metadata-symbols.m

 +(Class) getClass { return self; }
 @end
 
 int main() {
   Protocol *P0 = @protocol(P0);
   return 0;
 }
 
-// CHECK: @"\01l_OBJC_PROTOCOL_$_P0" = weak hidden global
-// CHECK: @"\01l_OBJC_LABEL_PROTOCOL_$_P0" = weak hidden global
+// CHECK: @"_OBJC_PROTOCOL_$_P0" = weak hidden global
+// CHECK: @"_OBJC_LABEL_PROTOCOL_$_P0" = weak hidden global
 // CHECK: @"\01l_OBJC_CLASS_PROTOCOLS_$_A" = private global
 // CHECK: @"\01l_OBJC_PROTOCOL_REFERENCE_$_P0" = weak hidden global
 
 // CHECK: llvm.used = appending global [3 x i8*]
-// CHECK-SAME: "\01l_OBJC_PROTOCOL_$_P0"
-// CHECK-SAME: "\01l_OBJC_LABEL_PROTOCOL_$_P0"
+// CHECK-SAME: "_OBJC_PROTOCOL_$_P0"
+// CHECK-SAME: "_OBJC_LABEL_PROTOCOL_$_P0"
 // CHECK-SAME: "\01l_OBJC_PROTOCOL_REFERENCE_$_P0"
 
 // CHECK: llvm.compiler.used = appending global [7 x i8*]
 // CHECK-SAME: OBJC_CLASS_NAME_
 // CHECK-SAME: OBJC_METH_VAR_NAME_
 // CHECK-SAME: OBJC_METH_VAR_TYPE_
 // CHECK-SAME: "\01l_OBJC_$_CLASS_METHODS_A"
 // CHECK-SAME: OBJC_CLASS_NAME_.1
 // CHECK-SAME: "\01l_OBJC_CLASS_PROTOCOLS_$_A"
 // CHECK-SAME: "OBJC_LABEL_CLASS_$"
 // CHECK-SAME: section "llvm.metadata"

cfe/trunk/test/CodeGenObjC/hidden-visibility.m

 // RUN: %clang_cc1 -triple i386-apple-macosx -fvisibility hidden -emit-llvm -o - %s | FileCheck %s
 // CHECK: @"OBJC_IVAR_$_I.P" = hidden
 // CHECK: @"OBJC_CLASS_$_I" = hidden
 // CHECK: @"OBJC_METACLASS_$_I" = hidden
-// CHECK: @"\01l_OBJC_PROTOCOL_$_Prot0" = weak hidden
+// CHECK: @"_OBJC_PROTOCOL_$_Prot0" = weak hidden
 
 @interface I {
   int P;
 }
 
 @property int P;
 @end
 

cfe/trunk/test/CodeGenObjC/metadata-class-properties.m

 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.11  -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.10  -emit-llvm -o - %s | FileCheck -check-prefix=CHECK-NULL %s
 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.11  -emit-llvm -o - -fobjc-runtime=macosx-fragile-10.5 %s | FileCheck -check-prefix=CHECK-FRAGILE %s
 
 // CHECK: @"\01l_OBJC_$_CLASS_PROP_LIST_Proto" = private global {{.*}} section "__DATA, __objc_const", align 8
-// CHECK: @"\01l_OBJC_PROTOCOL_$_Proto" = {{.*}} global %struct._protocol_t { {{.*}} i32 96, i32 {{.*}} @"\01l_OBJC_$_CLASS_PROP_LIST_Proto" {{.*}} }
+// CHECK: @"_OBJC_PROTOCOL_$_Proto" = {{.*}} global %struct._protocol_t { {{.*}} i32 96, i32 {{.*}} @"\01l_OBJC_$_CLASS_PROP_LIST_Proto" {{.*}} }
 // CHECK: @"\01l_OBJC_$_CLASS_PROP_LIST_Foo_$_Category" = private global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK: @"\01l_OBJC_$_CATEGORY_Foo_$_Category" = private global %struct._category_t { {{.*}} @"\01l_OBJC_$_CLASS_PROP_LIST_Foo_$_Category" {{.*}}, i32 64 }, section "__DATA, __objc_const", align 8
 
 // CHECK: @"\01l_OBJC_$_CLASS_PROP_LIST_C" = private global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK: @"\01l_OBJC_METACLASS_RO_$_C" = private global %struct._class_ro_t { {{.*}} @"\01l_OBJC_$_CLASS_PROP_LIST_C" {{.*}} }, section "__DATA, __objc_const", align 8
 
 // CHECK: !{i32 1, !"Objective-C Class Properties", i32 64}
 
 // CHECK-NULL-NOT: @"\01l_OBJC_$_CLASS_PROP_LIST_Proto"
-// CHECK-NULL: @"\01l_OBJC_PROTOCOL_$_Proto" = {{.*}} global %struct._protocol_t { {{.*}} %struct._prop_list_t* null, i32 96, i32 {{.*}} %struct._prop_list_t* null }
+// CHECK-NULL: @"_OBJC_PROTOCOL_$_Proto" = {{.*}} global %struct._protocol_t { {{.*}} %struct._prop_list_t* null, i32 96, i32 {{.*}} %struct._prop_list_t* null }
 // CHECK-NULL-NOT: @"\01l_OBJC_$_CLASS_PROP_LIST_Foo_$_Category" = private global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK-NULL: @"\01l_OBJC_$_CATEGORY_Foo_$_Category" = private global %struct._category_t { {{.*}} %struct._prop_list_t* null, %struct._prop_list_t* null, {{.*}} }, section "__DATA, __objc_const", align 8
 
 // CHECK-NULL-NOT: @"\01l_OBJC_$_CLASS_PROP_LIST_C" = private global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK-NULL: @"\01l_OBJC_METACLASS_RO_$_C" = private global %struct._class_ro_t { {{.*}} %struct._prop_list_t* null }, section "__DATA, __objc_const", align 8
 
 // CHECK-NULL: !{i32 1, !"Objective-C Class Properties", i32 64}
 

cfe/trunk/test/CodeGenObjC/metadata-symbols-64.m

 // RUN: %clang_cc1 -triple x86_64-apple-darwin10 -fobjc-dispatch-method=mixed -emit-llvm -o - %s | FileCheck %s
 
 // CHECK: @"OBJC_IVAR_$_A._ivar" = global {{.*}} section "__DATA, __objc_ivar", align 8
 // CHECK: @_objc_empty_cache = external global
 // CHECK: @_objc_empty_vtable = external global
 // CHECK: @"OBJC_CLASS_$_A" = global
 // CHECK: @"OBJC_METACLASS_$_A" = global {{.*}} section "__DATA, __objc_data", align 8
 // CHECK: @OBJC_CLASS_NAME_{{[0-9]*}} = private unnamed_addr constant {{.*}} section "__TEXT,__objc_classname,cstring_literals", align 1
 // CHECK: @OBJC_METH_VAR_NAME_{{[0-9]*}} = private unnamed_addr constant {{.*}} section "__TEXT,__objc_methname,cstring_literals", align 1
 // CHECK: @OBJC_METH_VAR_TYPE_{{[0-9]*}} = private unnamed_addr constant {{.*}} section "__TEXT,__objc_methtype,cstring_literals", align 1
 // CHECK: @"\01l_OBJC_$_CLASS_METHODS_A" = private global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK: @"\01l_OBJC_$_PROTOCOL_INSTANCE_METHODS_P" = private global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK: @"\01l_OBJC_$_PROTOCOL_CLASS_METHODS_P" = private global {{.*}} section "__DATA, __objc_const", align 8
-// CHECK: @"\01l_OBJC_PROTOCOL_$_P" = weak hidden global {{.*}}, align 8
-// CHECK: @"\01l_OBJC_LABEL_PROTOCOL_$_P" = weak hidden global {{.*}} section "__DATA,__objc_protolist,coalesced,no_dead_strip", align 8
+// CHECK: @"_OBJC_PROTOCOL_$_P" = weak hidden global {{.*}}, align 8
+// CHECK: @"_OBJC_LABEL_PROTOCOL_$_P" = weak hidden global {{.*}} section "__DATA,__objc_protolist,coalesced,no_dead_strip", align 8
 // CHECK: @"\01l_OBJC_CLASS_PROTOCOLS_$_A" = private global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK: @"\01l_OBJC_METACLASS_RO_$_A" = private global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK: @"\01l_OBJC_$_INSTANCE_METHODS_A" = private global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK: @"\01l_OBJC_$_INSTANCE_VARIABLES_A" = private global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK: @OBJC_PROP_NAME_ATTR_{{[0-9]*}} = private unnamed_addr constant {{.*}} section "__TEXT,__cstring,cstring_literals", align 1
 // CHECK: @"\01l_OBJC_$_PROP_LIST_A" = private global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK: @"\01l_OBJC_CLASS_RO_$_A" = private global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK: @"\01l_OBJC_$_CATEGORY_INSTANCE_METHODS_A_$_Cat" = private global {{.*}} section "__DATA, __objc_const", align 8

cfe/trunk/test/CodeGenObjC/protocol-comdat.m

 @implementation I
 - (void) method { }
 @end
 
 _Bool f(void) {
   return @protocol(Q) == @protocol(R);
 }
 
-// CHECK: $"\01l_OBJC_PROTOCOL_$_P" = comdat any
-// CHECK: $"\01l_OBJC_LABEL_PROTOCOL_$_P" = comdat any
+// CHECK: $"_OBJC_PROTOCOL_$_P" = comdat any
+// CHECK: $"_OBJC_LABEL_PROTOCOL_$_P" = comdat any
 // CHECK: $"\01l_OBJC_PROTOCOL_REFERENCE_$_Q" = comdat any
 // CHECK: $"\01l_OBJC_PROTOCOL_REFERENCE_$_R" = comdat any
 
-// CHECK: @"\01l_OBJC_PROTOCOL_$_P" = {{.*}}, comdat
-// CHECK: @"\01l_OBJC_LABEL_PROTOCOL_$_P" = {{.*}}, comdat
+// CHECK: @"_OBJC_PROTOCOL_$_P" = {{.*}}, comdat
+// CHECK: @"_OBJC_LABEL_PROTOCOL_$_P" = {{.*}}, comdat
 

cfe/trunk/test/CodeGenObjC/protocol-in-extended-class.m

 @end
 
 @implementation ItDoesntWork
 -(void) Meth {
     ItDoesntWork <MyProtocol, ExtendedProtocol> *p = 0;
  }
 @end
 
-// CHECK-LP64: l_OBJC_PROTOCOL_$_ExtendedProtocol:
+// CHECK-LP64: __OBJC_PROTOCOL_$_ExtendedProtocol:
 
 // CHECK-LP32: L_OBJC_PROTOCOL_ExtendedProtocol:

cfe/trunk/test/CodeGenObjC/protocols.m

-// RUN: %clang_cc1 -emit-llvm-only %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -emit-llvm -o - %s | FileCheck %s
+
+// HECK: @[[PROTO_P1:"_OBJC_PROTOCOL_$_P1"]] = weak hidden
+// CHECK: @[[PROTO_P1:"_OBJC_PROTOCOL_\$_P1"]] = weak hidden
+// CHECK: @[[LABEL_PROTO_P1:"_OBJC_LABEL_PROTOCOL_\$_P1"]] = weak hidden global %{{.*}}* @[[PROTO_P1]]
+// CHECK: @[[PROTO_P2:"_OBJC_PROTOCOL_\$_P2"]] = weak hidden
+// CHECK: @[[LABEL_PROTO_P2:"_OBJC_LABEL_PROTOCOL_\$_P2"]] = weak hidden global %{{.*}}* @[[PROTO_P2]]
+// CHECK: @"\01l_OBJC_$_PROTOCOL_REFS_P3" = private global { i64, [3 x %{{.*}}] } { i64 2, [3 x %{{.*}}*] [%{{.*}}* @[[PROTO_P1]], %{{.*}}* @[[PROTO_P2]], %{{.*}}* null] }
+// CHECK: @[[PROTO_P3:"_OBJC_PROTOCOL_\$_P3"]] = weak hidden
+// CHECK: @[[LABEL_PROTO_P3:"_OBJC_LABEL_PROTOCOL_\$_P3"]] = weak hidden global %{{.*}}* @[[PROTO_P3]]
+// CHECK: "\01l_OBJC_PROTOCOL_REFERENCE_$_P3" = weak hidden global %{{.*}}* bitcast (%{{.*}}* @[[PROTO_P3]] to %{{.*}}*)
+// CHECK: @[[PROTO_P0:"_OBJC_PROTOCOL_\$_P0"]] = weak hidden
+// CHECK: @[[LABEL_PROTO_P0:"_OBJC_LABEL_PROTOCOL_\$_P0"]] = weak hidden global %{{.*}}* @[[PROTO_P0]]
+// CHECK: "\01l_OBJC_PROTOCOL_REFERENCE_$_P0" = weak hidden global %0* bitcast (%{{.*}}* @[[PROTO_P0]] to %{{.*}}*)
+// CHECK: "\01l_OBJC_PROTOCOL_REFERENCE_$_P1" = weak hidden global %0* bitcast (%{{.*}}* @[[PROTO_P1]] to %{{.*}}*)
+// CHECK: "\01l_OBJC_PROTOCOL_REFERENCE_$_P2" = weak hidden global %0* bitcast (%{{.*}}* @[[PROTO_P2]] to %{{.*}}*)
 
 void p(const char*, ...);
 
 @interface Root
 +(int) maxValue;
 -(int) conformsTo: (id) x;
 @end
 

cfe/trunk/test/CodeGenObjC/sections.m

_Bool f(J *j) {
   [j m];
   return [I class] == @protocol(P);
 }
 
 // CHECK-COFF: @"OBJC_CLASSLIST_SUP_REFS_$_" = {{.*}}, section ".objc_superrefs$B"
 // CHECK-COFF: @OBJC_SELECTOR_REFERENCES_ = {{.*}}, section ".objc_selrefs$B"
 // CHECK-COFF: @"OBJC_CLASSLIST_REFERENCES_$_" = {{.*}}, section ".objc_classrefs$B"
 // CHECK-COFF: @"\01l_objc_msgSend_fixup_class" = {{.*}}, section ".objc_msgrefs$B"
-// CHECK-COFF: @"\01l_OBJC_LABEL_PROTOCOL_$_P" = {{.*}}, section ".objc_protolist$B"
+// CHECK-COFF: @"_OBJC_LABEL_PROTOCOL_$_P" = {{.*}}, section ".objc_protolist$B"
 // CHECK-COFF: @"\01l_OBJC_PROTOCOL_REFERENCE_$_P" = {{.*}}, section ".objc_protorefs$B"
 // CHECK-COFF: @"OBJC_LABEL_CLASS_$" = {{.*}}, section ".objc_classlist$B"
 // CHECK-COFF: @"OBJC_LABEL_NONLAZY_CLASS_$" = {{.*}}, section ".objc_nlclslist$B"
 // CHECK-COFF: @"OBJC_LABEL_CATEGORY_$" = {{.*}}, section ".objc_catlist$B"
 // CHECK-COFF: @"OBJC_LABEL_NONLAZY_CATEGORY_$" = {{.*}}, section ".objc_nlcatlist$B"
 // CHECK-COFF: !{{[0-9]+}} = !{i32 1, !"Objective-C Image Info Section", !".objc_imageinfo$B"}
 
 // CHECK-ELF: @"OBJC_CLASSLIST_SUP_REFS_$_" = {{.*}}, section "objc_superrefs"
 // CHECK-ELF: @OBJC_SELECTOR_REFERENCES_ = {{.*}}, section "objc_selrefs"
 // CHECK-ELF: @"OBJC_CLASSLIST_REFERENCES_$_" = {{.*}}, section "objc_classrefs"
 // CHECK-ELF: @"\01l_objc_msgSend_fixup_class" = {{.*}}, section "objc_msgrefs"
-// CHECK-ELF: @"\01l_OBJC_LABEL_PROTOCOL_$_P" = {{.*}}, section "objc_protolist"
+// CHECK-ELF: @"_OBJC_LABEL_PROTOCOL_$_P" = {{.*}}, section "objc_protolist"
 // CHECK-ELF: @"\01l_OBJC_PROTOCOL_REFERENCE_$_P" = {{.*}}, section "objc_protorefs"
 // CHECK-ELF: @"OBJC_LABEL_CLASS_$" = {{.*}}, section "objc_classlist"
 // CHECK-ELF: @"OBJC_LABEL_NONLAZY_CLASS_$" = {{.*}}, section "objc_nlclslist"
 // CHECK-ELF: @"OBJC_LABEL_CATEGORY_$" = {{.*}}, section "objc_catlist"
 // CHECK-ELF: @"OBJC_LABEL_NONLAZY_CATEGORY_$" = {{.*}}, section "objc_nlcatlist"
 // CHECK-ELF: !{{[0-9]+}} = !{i32 1, !"Objective-C Image Info Section", !"objc_imageinfo"}
 
 // CHECK-MACHO: @"OBJC_CLASSLIST_SUP_REFS_$_" = {{.*}}, section "__DATA,__objc_superrefs,regular,no_dead_strip"
 // CHECK-MACHO: @OBJC_SELECTOR_REFERENCES_ = {{.*}}, section "__DATA,__objc_selrefs,literal_pointers,no_dead_strip"
 // CHECK-MACHO: @"OBJC_CLASSLIST_REFERENCES_$_" = {{.*}}, section "__DATA,__objc_classrefs,regular,no_dead_strip"
 // CHECK-MACHO: @"\01l_objc_msgSend_fixup_class" = {{.*}}, section "__DATA,__objc_msgrefs,coalesced"
-// CHECK-MACHO: @"\01l_OBJC_LABEL_PROTOCOL_$_P" = {{.*}}, section "__DATA,__objc_protolist,coalesced,no_dead_strip"
+// CHECK-MACHO: @"_OBJC_LABEL_PROTOCOL_$_P" = {{.*}}, section "__DATA,__objc_protolist,coalesced,no_dead_strip"
 // CHECK-MACHO: @"\01l_OBJC_PROTOCOL_REFERENCE_$_P" = {{.*}}, section "__DATA,__objc_protorefs,coalesced,no_dead_strip"
 // CHECK-MACHO: @"OBJC_LABEL_CLASS_$" = {{.*}}, section "__DATA,__objc_classlist,regular,no_dead_strip"
 // CHECK-MACHO: @"OBJC_LABEL_NONLAZY_CLASS_$" = {{.*}}, section "__DATA,__objc_nlclslist,regular,no_dead_strip"
 // CHECK-MACHO: @"OBJC_LABEL_CATEGORY_$" = {{.*}}, section "__DATA,__objc_catlist,regular,no_dead_strip"
 // CHECK-MACHO: @"OBJC_LABEL_NONLAZY_CATEGORY_$" = {{.*}}, section "__DATA,__objc_nlcatlist,regular,no_dead_strip"
 // CHECK-MACHO: !{{[0-9]+}} = !{i32 1, !"Objective-C Image Info Section", !"__DATA,__objc_imageinfo,regular,no_dead_strip"}
 

cfe/trunk/test/CodeGenObjC/undefined-protocol2.m

 // RUN: %clang_cc1 -triple x86_64-apple-macosx -emit-llvm %s -o - | FileCheck %s
 
 // Test that we produce a declaration for the protocol. It must be matched
 // by a definition in another TU, so external is the correct linkage
 // (not extern_weak).
-// CHECK: @"\01l_OBJC_PROTOCOL_$_p1" = external global
+// CHECK: @"_OBJC_PROTOCOL_$_p1" = external global
 
 @interface NSObject
 @end
 
 @protocol p1;
 
 @interface I1 : NSObject <p1>
 @end
 
 @implementation I1
 @end