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

[Peter Collingbourne via llvm-commits]

================
@@ -667,6 +667,20 @@ 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);
+  auto *d = dyn_cast<Defined>(&sym);
+  if (d && ctx.arg.icf != ICFLevel::None) {
+    // There may be symbols that have been ICFed in which case d->section
+    // points to their canonical section and d->value is offset in to that section.
+    // We add only a single GOT entry for all such symbols.
+    auto [it, inserted] = gotEntries.insert(
+      std::make_pair(std::make_pair(d->section, d->value),
+      numEntries));
+    if (!inserted && d->folded) {
----------------
pcc wrote:

Yes, I'm not sure why we even need the `folded` check here. I think we can just let the first symbol we see set the `gotIdx`.

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