[lld] [lld] Merge GOT entries for symbols that have been ICFed (PR #131630)

[Pranav Kant via llvm-commits]

================
@@ -667,6 +667,19 @@ GotSection::GotSection(Ctx &ctx)
 void GotSection::addConstant(const Relocation &r) { relocations.push_back(r); }
 void GotSection::addEntry(const Symbol &sym) {
   assert(sym.auxIdx == ctx.symAux.size() - 1);
+  if (auto *d = dyn_cast<Defined>(&sym)) {
----------------
pranavk wrote:

Note that there's no canonical unfolded symbol definition (I updated the commit message to briefly mention this). ICF links symbols to their canonical section (through d->section).

Also, ICF doesn't rewrite relocations which means there may be relocations that are still referencing old ICFed symbols. If we don't call addEntry for ICFed symbols, such relocations would try to get the GotIdx for such symbols and eventually fail.

https://github.com/llvm/llvm-project/pull/131630