Backport fixes for ARM64EC import libraries

lld/test/COFF/def-export-cpp.s

@@ -10,6 +10,7 @@
 
 # IMPLIB: File: foo.dll
 # IMPLIB: Name type: undecorate
+# IMPLIB-NEXT: Export name: GetPathOnDisk
 # IMPLIB-NEXT: Symbol: __imp_?GetPathOnDisk@@YA_NPEA_W@Z
 # IMPLIB-NEXT: Symbol: ?GetPathOnDisk@@YA_NPEA_W@Z
 

lld/test/COFF/def-export-stdcall.s

@@ -6,15 +6,19 @@
 # RUN: llvm-readobj --coff-exports %t.dll | FileCheck -check-prefix UNDECORATED-EXPORTS %s
 
 # UNDECORATED-IMPLIB: Name type: noprefix
+# UNDECORATED-IMPLIB-NEXT: Export name: _underscored
 # UNDECORATED-IMPLIB-NEXT: __imp___underscored
 # UNDECORATED-IMPLIB-NEXT: __underscored
 # UNDECORATED-IMPLIB: Name type: undecorate
+# UNDECORATED-IMPLIB-NEXT: Export name: fastcall
 # UNDECORATED-IMPLIB-NEXT: __imp_@fastcall@8
 # UNDECORATED-IMPLIB-NEXT: fastcall@8
 # UNDECORATED-IMPLIB: Name type: undecorate
+# UNDECORATED-IMPLIB-NEXT: Export name: stdcall
 # UNDECORATED-IMPLIB-NEXT: __imp__stdcall@8
 # UNDECORATED-IMPLIB-NEXT: _stdcall@8
 # UNDECORATED-IMPLIB: Name type: undecorate
+# UNDECORATED-IMPLIB-NEXT: Export name: vectorcall
 # UNDECORATED-IMPLIB-NEXT: __imp_vectorcall@@8
 # UNDECORATED-IMPLIB-NEXT: vectorcall@@8
 
@@ -30,12 +34,15 @@
 # RUN: llvm-readobj --coff-exports %t.dll | FileCheck -check-prefix DECORATED-EXPORTS %s
 
 # DECORATED-IMPLIB: Name type: name
+# DECORATED-IMPLIB-NEXT: Export name: @fastcall@8
 # DECORATED-IMPLIB-NEXT: __imp_@fastcall@8
 # DECORATED-IMPLIB-NEXT: @fastcall@8
 # DECORATED-IMPLIB: Name type: name
+# DECORATED-IMPLIB-NEXT: Export name: _stdcall@8
 # DECORATED-IMPLIB-NEXT: __imp__stdcall@8
 # DECORATED-IMPLIB-NEXT: _stdcall@8
 # DECORATED-IMPLIB: Name type: name
+# DECORATED-IMPLIB-NEXT: Export name: vectorcall@@8
 # DECORATED-IMPLIB-NEXT: __imp_vectorcall@@8
 # DECORATED-IMPLIB-NEXT: vectorcall@@8
 
@@ -51,14 +58,17 @@
 # RUN: llvm-readobj --coff-exports %t.dll | FileCheck -check-prefix DECORATED-MINGW-EXPORTS %s
 
 # DECORATED-MINGW-IMPLIB: Name type: name
+# DECORATED-MINGW-IMPLIB-NEXT: Export name: @fastcall@8
 # DECORATED-MINGW-IMPLIB-NEXT: __imp_@fastcall@8
 # DECORATED-MINGW-IMPLIB-NEXT: fastcall@8
 # DECORATED-MINGW-IMPLIB: Name type: noprefix
+# DECORATED-MINGW-IMPLIB-NEXT: Export name: stdcall@8
 # DECORATED-MINGW-IMPLIB-NEXT: __imp__stdcall@8
 # DECORATED-MINGW-IMPLIB-NEXT: _stdcall@8
 # GNU tools don't support vectorcall, but this test is just to track that
 # lld's behaviour remains consistent over time.
 # DECORATED-MINGW-IMPLIB: Name type: name
+# DECORATED-MINGW-IMPLIB-NEXT: Export name: vectorcall@@8
 # DECORATED-MINGW-IMPLIB-NEXT: __imp_vectorcall@@8
 # DECORATED-MINGW-IMPLIB-NEXT: vectorcall@@8
 
@@ -75,14 +85,17 @@
 # RUN: llvm-readobj --coff-exports %t.dll | FileCheck -check-prefix MINGW-KILL-AT-EXPORTS %s
 
 # MINGW-KILL-AT-IMPLIB: Name type: noprefix
+# MINGW-KILL-AT-IMPLIB: Export name: fastcall
 # MINGW-KILL-AT-IMPLIB: __imp__fastcall
 # MINGW-KILL-AT-IMPLIB-NEXT: _fastcall
 # MINGW-KILL-AT-IMPLIB: Name type: noprefix
+# MINGW-KILL-AT-IMPLIB-NEXT: Export name: stdcall
 # MINGW-KILL-AT-IMPLIB-NEXT: __imp__stdcall
 # MINGW-KILL-AT-IMPLIB-NEXT: _stdcall
 # GNU tools don't support vectorcall, but this test is just to track that
 # lld's behaviour remains consistent over time.
 # MINGW-KILL-AT-IMPLIB: Name type: noprefix
+# MINGW-KILL-AT-IMPLIB-NEXT: Export name: vectorcall
 # MINGW-KILL-AT-IMPLIB-NEXT: __imp__vectorcall
 # MINGW-KILL-AT-IMPLIB-NEXT: _vectorcall
 

lld/test/COFF/dllexport.s

@@ -6,15 +6,19 @@
 # RUN: llvm-readobj --coff-exports %t.dll | FileCheck -check-prefix DECORATED-EXPORTS %s
 
 # DECORATED-IMPLIB: Name type: name
+# DECORATED-IMPLIB-NEXT: Export name: @fastcall@8
 # DECORATED-IMPLIB-NEXT: __imp_@fastcall@8
 # DECORATED-IMPLIB-NEXT: @fastcall@8
 # DECORATED-IMPLIB: Name type: name
+# DECORATED-IMPLIB-NEXT: Export name: _stdcall@8
 # DECORATED-IMPLIB-NEXT: __imp__stdcall@8
 # DECORATED-IMPLIB-NEXT: _stdcall@8
 # DECORATED-IMPLIB: Name type: noprefix
+# DECORATED-IMPLIB-NEXT: Export name: _underscored
 # DECORATED-IMPLIB-NEXT: __imp___underscored
 # DECORATED-IMPLIB-NEXT: __underscored
 # DECORATED-IMPLIB: Name type: name
+# DECORATED-IMPLIB-NEXT: Export name: vectorcall@@8
 # DECORATED-IMPLIB-NEXT: __imp_vectorcall@@8
 # DECORATED-IMPLIB-NEXT: vectorcall@@8
 

llvm/include/llvm/BinaryFormat/COFF.h

@@ -716,7 +716,10 @@ enum ImportNameType : unsigned {
   IMPORT_NAME_NOPREFIX = 2,
   /// The import name is the public symbol name, but skipping the leading ?,
   /// @, or optionally _, and truncating at the first @.
-  IMPORT_NAME_UNDECORATE = 3
+  IMPORT_NAME_UNDECORATE = 3,
+  /// The import name is specified as a separate string in the import library
+  /// object file.
+  IMPORT_NAME_EXPORTAS = 4
 };
 
 enum class GuardFlags : uint32_t {

llvm/include/llvm/Object/COFF.h

@@ -1362,6 +1362,47 @@ class SectionStrippedError
   SectionStrippedError() { setErrorCode(object_error::section_stripped); }
 };
 
+inline std::optional<std::string>
+getArm64ECMangledFunctionName(StringRef Name) {
+  bool IsCppFn = Name[0] == '?';
+  if (IsCppFn && Name.find("$$h") != std::string::npos)
+    return std::nullopt;
+  if (!IsCppFn && Name[0] == '#')
+    return std::nullopt;
+
+  StringRef Prefix = "$$h";
+  size_t InsertIdx = 0;
+  if (IsCppFn) {
+    InsertIdx = Name.find("@@");
+    size_t ThreeAtSignsIdx = Name.find("@@@");
+    if (InsertIdx != std::string::npos && InsertIdx != ThreeAtSignsIdx) {
+      InsertIdx += 2;
+    } else {
+      InsertIdx = Name.find("@");
+      if (InsertIdx != std::string::npos)
+        InsertIdx++;
+    }
+  } else {
+    Prefix = "#";
+  }
+
+  return std::optional<std::string>(
+      (Name.substr(0, InsertIdx) + Prefix + Name.substr(InsertIdx)).str());
+}
+
+inline std::optional<std::string>
+getArm64ECDemangledFunctionName(StringRef Name) {
+  if (Name[0] == '#')
+    return std::string(Name.substr(1));
+  if (Name[0] != '?')
+    return std::nullopt;
+
+  std::pair<StringRef, StringRef> Pair = Name.split("$$h");
+  if (Pair.second.empty())
+    return std::nullopt;
+  return (Pair.first + Pair.second).str();
+}
+
 } // end namespace object
 
 } // end namespace llvm

llvm/include/llvm/Object/COFFImportFile.h

@@ -26,7 +26,16 @@
 namespace llvm {
 namespace object {
 
+constexpr std::string_view ImportDescriptorPrefix = "__IMPORT_DESCRIPTOR_";
+constexpr std::string_view NullImportDescriptorSymbolName =
+    "__NULL_IMPORT_DESCRIPTOR";
+constexpr std::string_view NullThunkDataPrefix = "\x7f";
+constexpr std::string_view NullThunkDataSuffix = "_NULL_THUNK_DATA";
+
 class COFFImportFile : public SymbolicFile {
+private:
+  enum SymbolIndex { ImpSymbol, ThunkSymbol, ECAuxSymbol, ECThunkSymbol };
+
 public:
   COFFImportFile(MemoryBufferRef Source)
       : SymbolicFile(ID_COFFImportFile, Source) {}
@@ -36,9 +45,23 @@ class COFFImportFile : public SymbolicFile {
   void moveSymbolNext(DataRefImpl &Symb) const override { ++Symb.p; }
 
   Error printSymbolName(raw_ostream &OS, DataRefImpl Symb) const override {
-    if (Symb.p == 0)
+    switch (Symb.p) {
+    case ImpSymbol:
       OS << "__imp_";
-    OS << StringRef(Data.getBufferStart() + sizeof(coff_import_header));
+      break;
+    case ECAuxSymbol:
+      OS << "__imp_aux_";
+      break;
+    }
+    const char *Name = Data.getBufferStart() + sizeof(coff_import_header);
+    if (Symb.p != ECThunkSymbol && COFF::isArm64EC(getMachine())) {
+      if (std::optional<std::string> DemangledName =
+              getArm64ECDemangledFunctionName(Name)) {
+        OS << StringRef(*DemangledName);
+        return Error::success();
+      }
+    }
+    OS << StringRef(Name);
     return Error::success();
   }
 
@@ -52,7 +75,12 @@ class COFFImportFile : public SymbolicFile {
 
   basic_symbol_iterator symbol_end() const override {
     DataRefImpl Symb;
-    Symb.p = isData() ? 1 : 2;
+    if (isData())
+      Symb.p = ImpSymbol + 1;
+    else if (COFF::isArm64EC(getMachine()))
+      Symb.p = ECThunkSymbol + 1;
+    else
+      Symb.p = ThunkSymbol + 1;
     return BasicSymbolRef(Symb, this);
   }
 
@@ -66,6 +94,7 @@ class COFFImportFile : public SymbolicFile {
   uint16_t getMachine() const { return getCOFFImportHeader()->Machine; }
 
   StringRef getFileFormatName() const;
+  StringRef getExportName() const;
 
 private:
   bool isData() const {

llvm/lib/Object/ArchiveWriter.cpp

@@ -677,6 +677,13 @@ static bool isECObject(object::SymbolicFile &Obj) {
   return false;
 }
 
+bool isImportDescriptor(StringRef Name) {
+  return Name.starts_with(ImportDescriptorPrefix) ||
+         Name == StringRef{NullImportDescriptorSymbolName} ||
+         (Name.starts_with(NullThunkDataPrefix) &&
+          Name.ends_with(NullThunkDataSuffix));
+}
+
 static Expected<std::vector<unsigned>> getSymbols(SymbolicFile *Obj,
                                                   uint16_t Index,
                                                   raw_ostream &SymNames,
@@ -704,6 +711,10 @@ static Expected<std::vector<unsigned>> getSymbols(SymbolicFile *Obj,
       if (Map == &SymMap->Map) {
         Ret.push_back(SymNames.tell());
         SymNames << Name << '\0';
+        // If EC is enabled, then the import descriptors are NOT put into EC
+        // objects so we need to copy them to the EC map manually.
+        if (SymMap->UseECMap && isImportDescriptor(Name))
+          SymMap->ECMap[Name] = Index;
       }
     } else {
       Ret.push_back(SymNames.tell());