[ELF] Insert linkerscript symbols directly into symbol table

[phosek]

Summary

This change exposes the symbol table insert method and uses it to insert the linkerscript defined symbols directly into the symbol table to avoid unnecessarily pulling the object out of an archive.

This change addresses PR32026.

[ruiu]

LGTM

test/ELF/linkerscript/Inputs/lazy-symbols.s

3–7

You don't need to make symbol` foo` have real contents, so you can remove this.

test/ELF/linkerscript/lazy-symbols.s

2

Please add a comment to say that this test is to make sure that a linker script can define a symbol which have the same name as a lazy symbol.

ELF/LinkerScript.cpp

 using namespace llvm::support::endian;
 using namespace lld;
 using namespace lld::elf;
 
 LinkerScriptBase *elf::ScriptBase;
 ScriptConfiguration *elf::ScriptConfig;
 
 template <class ELFT> static SymbolBody *addRegular(SymbolAssignment *Cmd) {
+  Symbol *Sym;
   uint8_t Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
-  Symbol *Sym = Symtab<ELFT>::X->addUndefined(
-      Cmd->Name, /*IsLocal=*/false, STB_GLOBAL, Visibility,
-      /*Type*/ 0,
-      /*CanOmitFromDynSym*/ false, /*File*/ nullptr);
-
+  std::tie(Sym, std::ignore) = Symtab<ELFT>::X->insert(
+      Cmd->Name, /*Type*/ 0, Visibility, /*CanOmitFromDynSym*/ false,
+      /*File*/ nullptr);
+  Sym->Binding = STB_GLOBAL;
   replaceBody<DefinedRegular<ELFT>>(Sym, Cmd->Name, /*IsLocal=*/false,
                                     Visibility, STT_NOTYPE, 0, 0, nullptr,
                                     nullptr);
   return Sym->body();
 }
 
 template <class ELFT> static SymbolBody *addSynthetic(SymbolAssignment *Cmd) {
+  Symbol *Sym;
   uint8_t Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
   const OutputSectionBase *Sec =
       ScriptConfig->HasSections ? nullptr : Cmd->Expression.Section();
-  Symbol *Sym = Symtab<ELFT>::X->addUndefined(
-      Cmd->Name, /*IsLocal=*/false, STB_GLOBAL, Visibility,
-      /*Type*/ 0,
-      /*CanOmitFromDynSym*/ false, /*File*/ nullptr);
-
+  std::tie(Sym, std::ignore) = Symtab<ELFT>::X->insert(
+      Cmd->Name, /*Type*/ 0, Visibility, /*CanOmitFromDynSym*/ false,
+      /*File*/ nullptr);
+  Sym->Binding = STB_GLOBAL;
   replaceBody<DefinedSynthetic>(Sym, Cmd->Name, 0, Sec);
   return Sym->body();
 }
 
 static bool isUnderSysroot(StringRef Path) {
   if (Config->Sysroot == "")
     return false;
   for (; !Path.empty(); Path = sys::path::parent_path(Path))

ELF/SymbolTable.h

public:
   void addLazyObject(StringRef Name, LazyObjectFile &Obj);
   Symbol *addBitcode(StringRef Name, uint8_t Binding, uint8_t StOther,
                      uint8_t Type, bool CanOmitFromDynSym, BitcodeFile *File);
 
   Symbol *addCommon(StringRef N, uint64_t Size, uint64_t Alignment,
                     uint8_t Binding, uint8_t StOther, uint8_t Type,
                     InputFile *File);
 
+  std::pair<Symbol *, bool> insert(StringRef Name);
+  std::pair<Symbol *, bool> insert(StringRef Name, uint8_t Type,
+                                   uint8_t Visibility, bool CanOmitFromDynSym,
+                                   InputFile *File);
+
   void scanUndefinedFlags();
   void scanShlibUndefined();
   void scanVersionScript();
 
   SymbolBody *find(StringRef Name);
   SymbolBody *findInCurrentDSO(StringRef Name);
 
   void trace(StringRef Name);
   void wrap(StringRef Name);
 
   std::vector<InputSectionBase<ELFT> *> Sections;
 
 private:
-  std::pair<Symbol *, bool> insert(StringRef Name);
-  std::pair<Symbol *, bool> insert(StringRef Name, uint8_t Type,
-                                   uint8_t Visibility, bool CanOmitFromDynSym,
-                                   InputFile *File);
-
   std::vector<SymbolBody *> findByVersion(SymbolVersion Ver);
   std::vector<SymbolBody *> findAllByVersion(SymbolVersion Ver);
 
   llvm::StringMap<std::vector<SymbolBody *>> &getDemangledSyms();
   void handleAnonymousVersion();
   void assignExactVersion(SymbolVersion Ver, uint16_t VersionId,
                           StringRef VersionName);
   void assignWildcardVersion(SymbolVersion Ver, uint16_t VersionId);

test/ELF/linkerscript/Inputs/lazy-symbols.s

+.globl foo
+foo:
+ .long .Linfo_string
+
+.section .debug_str,"MS",@progbits,1
+.Linfo_string:
+  .asciz "foo"

test/ELF/linkerscript/lazy-symbols.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %S/Inputs/lazy-symbols.s -o %t1
+# RUN: llvm-ar rcs %tar %t1
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t2
+# RUN: echo "foo = 1;" > %t.script
+# RUN: ld.lld %t2 %tar --script %t.script -o %tout
+# RUN: llvm-readobj -symbols %tout | FileCheck %s
+
+# CHECK: Name: foo
+# CHECK-NEXT: Value: 0x1