[LLD][COFF] Move resolving alternate names to SymbolTable (NFC) (llvm#149495)

(cherry picked from commit 38cd66a)

Author: cjacek

lld/COFF/Driver.cpp

@@ -2554,28 +2554,7 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
             e.symbolName = symtab.mangleMaybe(e.sym);
         }
 
-        // Add weak aliases. Weak aliases is a mechanism to give remaining
-        // undefined symbols final chance to be resolved successfully.
-        for (auto pair : symtab.alternateNames) {
-          StringRef from = pair.first;
-          StringRef to = pair.second;
-          Symbol *sym = symtab.find(from);
-          if (!sym)
-            continue;
-          if (auto *u = dyn_cast<Undefined>(sym)) {
-            if (u->weakAlias) {
-              // On ARM64EC, anti-dependency aliases are treated as undefined
-              // symbols unless a demangled symbol aliases a defined one, which
-              // is part of the implementation.
-              if (!symtab.isEC() || !u->isAntiDep)
-                continue;
-              if (!isa<Undefined>(u->weakAlias) &&
-                  !isArm64ECMangledFunctionName(u->getName()))
-                continue;
-            }
-            u->setWeakAlias(symtab.addUndefined(to));
-          }
-        }
+        symtab.resolveAlternateNames();
       });
 
       ctx.forEachActiveSymtab([&](SymbolTable &symtab) {

lld/COFF/SymbolTable.cpp

@@ -1344,6 +1344,31 @@ void SymbolTable::parseAlternateName(StringRef s) {
   alternateNames.insert(it, std::make_pair(from, to));
 }
 
+void SymbolTable::resolveAlternateNames() {
+  // Add weak aliases. Weak aliases is a mechanism to give remaining
+  // undefined symbols final chance to be resolved successfully.
+  for (auto pair : alternateNames) {
+    StringRef from = pair.first;
+    StringRef to = pair.second;
+    Symbol *sym = find(from);
+    if (!sym)
+      continue;
+    if (auto *u = dyn_cast<Undefined>(sym)) {
+      if (u->weakAlias) {
+        // On ARM64EC, anti-dependency aliases are treated as undefined
+        // symbols unless a demangled symbol aliases a defined one, which
+        // is part of the implementation.
+        if (!isEC() || !u->isAntiDep)
+          continue;
+        if (!isa<Undefined>(u->weakAlias) &&
+            !isArm64ECMangledFunctionName(u->getName()))
+          continue;
+      }
+      u->setWeakAlias(addUndefined(to));
+    }
+  }
+}
+
 // Parses /aligncomm option argument.
 void SymbolTable::parseAligncomm(StringRef s) {
   auto [name, align] = s.split(',');

lld/COFF/SymbolTable.h

@@ -69,6 +69,9 @@ class SymbolTable {
   // symbols and warn about imported local symbols.
   void resolveRemainingUndefines();
 
+  // Try to resolve undefined symbols with alternate names.
+  void resolveAlternateNames();
+
   // Load lazy objects that are needed for MinGW automatic import and for
   // doing stdcall fixups.
   void loadMinGWSymbols();