[llvm] [llvm-lib][Object] Add support for EC importlib symbols. (PR #81059)

[Daniel Paoliello via llvm-commits]

================
@@ -641,27 +653,54 @@ Error writeImportLibrary(StringRef ImportName, StringRef Path,
       ImportType = IMPORT_CONST;
 
     StringRef SymbolName = E.SymbolName.empty() ? E.Name : E.SymbolName;
-    ImportNameType NameType = E.Noname
-                                  ? IMPORT_ORDINAL
-                                  : getNameType(SymbolName, E.Name,
-                                                Machine, MinGW);
-    Expected<std::string> Name = E.ExtName.empty()
-                                     ? std::string(SymbolName)
-                                     : replace(SymbolName, E.Name, E.ExtName);
-
-    if (!Name)
-      return Name.takeError();
-
-    if (!E.AliasTarget.empty() && *Name != E.AliasTarget) {
+    std::string Name;
+
+    if (E.ExtName.empty()) {
+      Name = std::string(SymbolName);
+    } else {
+      Expected<std::string> ReplacedName =
+          replace(SymbolName, E.Name, E.ExtName);
+      if (!ReplacedName)
+        return ReplacedName.takeError();
+      Name.swap(*ReplacedName);
+    }
+
+    if (!E.AliasTarget.empty() && Name != E.AliasTarget) {
       Members.push_back(
-          OF.createWeakExternal(E.AliasTarget, *Name, false, Machine));
+          OF.createWeakExternal(E.AliasTarget, Name, false, Machine));
       Members.push_back(
-          OF.createWeakExternal(E.AliasTarget, *Name, true, Machine));
+          OF.createWeakExternal(E.AliasTarget, Name, true, Machine));
       continue;
     }
 
-    Members.push_back(
-        OF.createShortImport(*Name, E.Ordinal, ImportType, NameType, Machine));
+    ImportNameType NameType;
+    std::string ExportName;
+    if (E.Noname) {
+      NameType = IMPORT_ORDINAL;
+    } else if (!E.ExportAs.empty()) {
+      NameType = IMPORT_NAME_EXPORTAS;
+      ExportName = E.ExportAs;
+    } else {
+      NameType = getNameType(SymbolName, E.Name, Machine, MinGW);
+    }
+
+    // On ARM64EC, use EXPORTAS to import demangled name for mangled symbols.
+    if (ImportType == IMPORT_CODE && isArm64EC(Machine)) {
+      if (ExportName.empty()) {
+        NameType = IMPORT_NAME_EXPORTAS;
+        if (std::optional<std::string> DemangledName =
+                getArm64ECDemangledFunctionName(Name))
+          ExportName = std::move(*DemangledName);
+        else
+          ExportName = Name;
+      }
+      if (std::optional<std::string> MangledName =
+              getArm64ECMangledFunctionName(Name))
----------------
dpaoliello wrote:

Can we avoid remangling if we successfully demangled above?

https://github.com/llvm/llvm-project/pull/81059