[ORC] Fix materialization of weak local symbols

[benlangmuir]

Summary

We were adding all defined weak symbols to the materialization
responsibility, but local symbols will not be in the symbol table, so it
failed to materialize due to the "missing" symbol.

Local weak symbols come up in practice when using ld -r with a hidden
weak symbol.

rdar://85574696

[lhames]

Nice catch! LGTM.

[benlangmuir]

4c94760f360bd4e24519a61bea3bde0413aaf78a

llvm/lib/ExecutionEngine/Orc/ObjectLinkingLayer.cpp

private:
 
   Error claimOrExternalizeWeakAndCommonSymbols(LinkGraph &G) {
     auto &ES = Layer.getExecutionSession();
 
     SymbolFlagsMap NewSymbolsToClaim;
     std::vector<std::pair<SymbolStringPtr, Symbol *>> NameToSym;
 
     auto ProcessSymbol = [&](Symbol *Sym) {
-      if (Sym->hasName() && Sym->getLinkage() == Linkage::Weak) {
+      if (Sym->hasName() && Sym->getLinkage() == Linkage::Weak &&
+          Sym->getScope() != Scope::Local) {
         auto Name = ES.intern(Sym->getName());
         if (!MR->getSymbols().count(ES.intern(Sym->getName()))) {
           JITSymbolFlags SF = JITSymbolFlags::Weak;
           if (Sym->getScope() == Scope::Default)
             SF |= JITSymbolFlags::Exported;
           NewSymbolsToClaim[Name] = SF;
           NameToSym.push_back(std::make_pair(std::move(Name), Sym));
         }

llvm/test/ExecutionEngine/JITLink/X86/MachO_weak_local.s

+# RUN: llvm-mc -triple=x86_64-apple-macosx10.9 -filetype=obj -o %t %s
+# RUN: llvm-jitlink -noexec %t -show-graph | FileCheck %s
+
+# CHECK: linkage: weak, scope: local, live  -   _foo_weak
+
+# _foo_weak is weak and local. Make sure we can link it.
+  .section  __TEXT,__text,regular,pure_instructions
+  .weak_definition  _foo_weak
+  .p2align  4, 0x90
+_foo_weak:
+  retq
+
+  .globl  _main
+  .p2align  4, 0x90
+_main:
+  jmp _foo_weak