[ELF] Simplify handling of exportDynamic and canBeOmittedFromSymbolTable

When computing whether a defined symbol is exported, we set
`exportDynamic` in Defined and CommonSymbol's ctor and merge the bit in
symbol resolution. The complexity is for the LTO special case
canBeOmittedFromSymbolTable, which can be simplified by introducing a
new bit.

We might simplify the state by caching includeInDynsym in exportDynamic
in the future.

1 files changed, 5 insertions, 2 deletions

diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index 97b3e164bdc3..9ff6ed58688c 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/lld/ELF/InputFiles.cpp
@@ -1742,8 +1742,11 @@ static void createBitcodeSymbol(Ctx &ctx, Symbol *&sym,
   } else {
     Defined newSym(ctx, &f, StringRef(), binding, visibility, type, 0, 0,
                    nullptr);
-    if (objSym.canBeOmittedFromSymbolTable())
-      newSym.exportDynamic = false;
+    // The definition can be omitted if all bitcode definitions satisfy
+    // `canBeOmittedFromSymbolTable()` and isUsedInRegularObj is false.
+    // The latter condition is tested in Symbol::includeInDynsym.
+    sym->ltoCanOmit = objSym.canBeOmittedFromSymbolTable() &&
+                      (!sym->isDefined() || sym->ltoCanOmit);
     sym->resolve(ctx, newSym);
   }
 }