Remove Linkage::Appending

It can only be used for certain LLVM internal variables like
llvm.global_ctors which users are not allowed to define.

compiler/rustc_codegen_gcc/src/base.rs

@@ -49,7 +49,6 @@ pub fn global_linkage_to_gcc(linkage: Linkage) -> GlobalKind {
         Linkage::LinkOnceODR => unimplemented!(),
         Linkage::WeakAny => unimplemented!(),
         Linkage::WeakODR => unimplemented!(),
-        Linkage::Appending => unimplemented!(),
         Linkage::Internal => GlobalKind::Internal,
         Linkage::ExternalWeak => GlobalKind::Imported, // TODO(antoyo): should be weak linkage.
         Linkage::Common => unimplemented!(),
@@ -65,7 +64,6 @@ pub fn linkage_to_gcc(linkage: Linkage) -> FunctionType {
         Linkage::LinkOnceODR => unimplemented!(),
         Linkage::WeakAny => FunctionType::Exported, // FIXME(antoyo): should be similar to linkonce.
         Linkage::WeakODR => unimplemented!(),
-        Linkage::Appending => unimplemented!(),
         Linkage::Internal => FunctionType::Internal,
         Linkage::ExternalWeak => unimplemented!(),
         Linkage::Common => unimplemented!(),

compiler/rustc_codegen_llvm/src/base.rs

@@ -157,7 +157,6 @@ pub(crate) fn linkage_to_llvm(linkage: Linkage) -> llvm::Linkage {
         Linkage::LinkOnceODR => llvm::Linkage::LinkOnceODRLinkage,
         Linkage::WeakAny => llvm::Linkage::WeakAnyLinkage,
         Linkage::WeakODR => llvm::Linkage::WeakODRLinkage,
-        Linkage::Appending => llvm::Linkage::AppendingLinkage,
         Linkage::Internal => llvm::Linkage::InternalLinkage,
         Linkage::ExternalWeak => llvm::Linkage::ExternalWeakLinkage,
         Linkage::Common => llvm::Linkage::CommonLinkage,

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -41,7 +41,6 @@ fn linkage_by_name(tcx: TyCtxt<'_>, def_id: LocalDefId, name: &str) -> Linkage {
     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
     // and don't have to be, LLVM treats them as no-ops.
     match name {
-        "appending" => Appending,
         "available_externally" => AvailableExternally,
         "common" => Common,
         "extern_weak" => ExternalWeak,

compiler/rustc_codegen_ssa/src/mir/naked_asm.rs

@@ -190,7 +190,6 @@ fn prefix_and_suffix<'tcx>(
             Linkage::Internal => {
                 // write nothing
             }
-            Linkage::Appending => emit_fatal("Only global variables can have appending linkage!"),
             Linkage::Common => emit_fatal("Functions may not have common linkage"),
             Linkage::AvailableExternally => {
                 // this would make the function equal an extern definition

compiler/rustc_middle/src/mir/mono.rs

@@ -327,7 +327,6 @@ pub enum Linkage {
     LinkOnceODR,
     WeakAny,
     WeakODR,
-    Appending,
     Internal,
     ExternalWeak,
     Common,

compiler/rustc_monomorphize/src/partitioning.rs

@@ -1238,7 +1238,6 @@ fn collect_and_partition_mono_items(tcx: TyCtxt<'_>, (): ()) -> MonoItemPartitio
                         Linkage::LinkOnceODR => "OnceODR",
                         Linkage::WeakAny => "WeakAny",
                         Linkage::WeakODR => "WeakODR",
-                        Linkage::Appending => "Appending",
                         Linkage::Internal => "Internal",
                         Linkage::ExternalWeak => "ExternalWeak",
                         Linkage::Common => "Common",