__patchable_function_entries: don't use linkage field 'unique' with -no-integrated-as

.section name, "flags"G, @type, GroupName[, linkage]

As of binutils 2.33, linkage cannot be 'unique'.  For integrated
assembler, we use both 'o' flag and 'unique' linkage to support
--gc-sections and COMDAT with lld.

https://sourceware.org/ml/binutils/2019-11/msg00266.html

Author: MaskRay

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -3204,26 +3204,29 @@ void AsmPrinter::emitPatchableFunctionEntries() {
   const unsigned PointerSize = getPointerSize();
   if (TM.getTargetTriple().isOSBinFormatELF()) {
     auto Flags = ELF::SHF_WRITE | ELF::SHF_ALLOC;
-    std::string GroupName;
-    if (F.hasComdat()) {
-      Flags |= ELF::SHF_GROUP;
-      GroupName = F.getComdat()->getName();
-    }
 
-    // As of binutils 2.33, GNU as does not support section flag "o". Use
-    // SHF_LINK_ORDER if we are using the integrated assembler.
-    MCSymbolELF *Link = MAI->useIntegratedAssembler()
-                            ? cast<MCSymbolELF>(CurrentFnSym)
-                            : nullptr;
-    if (Link)
+    // As of binutils 2.33, GNU as does not support section flag "o" or linkage
+    // field "unique". Use SHF_LINK_ORDER if we are using the integrated
+    // assembler.
+    if (MAI->useIntegratedAssembler()) {
       Flags |= ELF::SHF_LINK_ORDER;
-
-    MCSection *Section = getObjFileLowering().SectionForGlobal(&F, TM);
-    auto R = PatchableFunctionEntryID.try_emplace(
-        Section, PatchableFunctionEntryID.size());
-    OutStreamer->SwitchSection(OutContext.getELFSection(
-        "__patchable_function_entries", ELF::SHT_PROGBITS, Flags, 0, GroupName,
-        R.first->second, Link));
+      std::string GroupName;
+      if (F.hasComdat()) {
+        Flags |= ELF::SHF_GROUP;
+        GroupName = F.getComdat()->getName();
+      }
+      MCSection *Section = getObjFileLowering().SectionForGlobal(&F, TM);
+      unsigned UniqueID =
+          PatchableFunctionEntryID
+              .try_emplace(Section, PatchableFunctionEntryID.size())
+              .first->second;
+      OutStreamer->SwitchSection(OutContext.getELFSection(
+          "__patchable_function_entries", ELF::SHT_PROGBITS, Flags, 0,
+          GroupName, UniqueID, cast<MCSymbolELF>(CurrentFnSym)));
+    } else {
+      OutStreamer->SwitchSection(OutContext.getELFSection(
+          "__patchable_function_entries", ELF::SHT_PROGBITS, Flags));
+    }
     EmitAlignment(Align(PointerSize));
     OutStreamer->EmitSymbolValue(CurrentFnBegin, PointerSize);
   }

llvm/test/CodeGen/AArch64/patchable-function-entry.ll

@@ -3,6 +3,7 @@
 ; RUN: llc -mtriple=aarch64 -no-integrated-as %s -o - | FileCheck --check-prefix=NOLINK %s
 
 ; NOLINK-NOT: "awo"
+; NOLINK-NOT: ,unique,0
 
 define i32 @f0() "patchable-function-entry"="0" {
 ; CHECK-LABEL: f0: