ELF: Preserve MustBeInDynSym for bitcode symbols.

[pcc]

Summary

Make sure to copy the MustBeInDynSym field when replacing shared symbols with
bitcode symbols, and when replacing bitcode symbols with regular symbols
in addCombinedLtoObject. Fixes interposition of DSO symbols with bitcode
symbols in the main executable.

[davide]

I think this one is correct.

lld/trunk/ELF/SymbolTable.cpp

template <class ELFT> void SymbolTable<ELFT>::addCombinedLtoObject() {
   // Replace bitcode symbols.
   llvm::DenseSet<StringRef> DummyGroups;
   Obj->parse(DummyGroups);
   for (SymbolBody *Body : Obj->getNonLocalSymbols()) {
     Symbol *Sym = insert(Body);
     Sym->Body->setUsedInRegularObj();
     if (!Sym->Body->isUndefined() && Body->isUndefined())
       continue;
+    if (Sym->Body->MustBeInDynSym)
+      Body->MustBeInDynSym = true;
     Sym->Body = Body;
   }
   ObjectFiles.emplace_back(Obj);
 }
 
 // Add an undefined symbol.
 template <class ELFT>
 SymbolBody *SymbolTable<ELFT>::addUndefined(StringRef Name) {

lld/trunk/ELF/Symbols.cpp

template <class ELFT> int SymbolBody::compare(SymbolBody *Other) {
 
   if (IsUsedInRegularObj || Other->IsUsedInRegularObj)
     IsUsedInRegularObj = Other->IsUsedInRegularObj = true;
 
   // We want to export all symbols that exist both in the executable
   // and in DSOs, so that the symbols in the executable can interrupt
   // symbols in the DSO at runtime.
   if (isShared() != Other->isShared())
-    if (isa<DefinedRegular<ELFT>>(isShared() ? Other : this))
+    if (isa<Defined>(isShared() ? Other : this)) {
+      IsUsedInRegularObj = Other->IsUsedInRegularObj = true;
       MustBeInDynSym = Other->MustBeInDynSym = true;
+    }
 
   if (L != R)
     return -1;
   if (!isDefined() || isShared() || isWeak())
     return 1;
   if (!isCommon() && !Other->isCommon())
     return 0;
   if (isCommon() && Other->isCommon())

lld/trunk/test/ELF/lto/Inputs/dynsym.s

+.globl foo
+foo:
+ret

lld/trunk/test/ELF/lto/dynsym.ll

+; REQUIRES: x86
+; RUN: llvm-mc -filetype=obj -o %t.o %p/Inputs/dynsym.s
+; RUN: ld.lld -m elf_x86_64 %t.o -o %t.so -shared
+; RUN: llvm-as %s -o %t2.o
+; RUN: ld.lld -m elf_x86_64 %t2.o %t.so -o %t
+; RUN: llvm-readobj -dyn-symbols %t | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @_start() {
+  call void @foo()
+  ret void
+}
+
+; CHECK:      Name: foo
+; CHECK-NEXT: Value:
+; CHECK-NEXT: Size:
+; CHECK-NEXT: Binding:
+; CHECK-NEXT: Type:
+; CHECK-NEXT: Other:
+; CHECK-NEXT: Section: .text
+define void @foo() {
+  ret void
+}