Index: lld/COFF/Chunks.cpp
===================================================================
--- lld/COFF/Chunks.cpp
+++ lld/COFF/Chunks.cpp
@@ -447,6 +447,8 @@
     applyRelARM(off, rel.Type, os, s, p, imageBase);
     break;
   case ARM64:
+  case ARM64EC:
+  case ARM64X:
     applyRelARM64(off, rel.Type, os, s, p, imageBase);
     break;
   default:
@@ -532,6 +534,8 @@
       return IMAGE_REL_BASED_ARM_MOV32T;
     return IMAGE_REL_BASED_ABSOLUTE;
   case ARM64:
+  case ARM64EC:
+  case ARM64X:
     if (rel.Type == IMAGE_REL_ARM64_ADDR64)
       return IMAGE_REL_BASED_DIR64;
     return IMAGE_REL_BASED_ABSOLUTE;
Index: lld/COFF/Config.h
===================================================================
--- lld/COFF/Config.h
+++ lld/COFF/Config.h
@@ -37,6 +37,8 @@
 // Short aliases.
 static const auto AMD64 = llvm::COFF::IMAGE_FILE_MACHINE_AMD64;
 static const auto ARM64 = llvm::COFF::IMAGE_FILE_MACHINE_ARM64;
+static const auto ARM64EC = llvm::COFF::IMAGE_FILE_MACHINE_ARM64EC;
+static const auto ARM64X = llvm::COFF::IMAGE_FILE_MACHINE_ARM64X;
 static const auto ARMNT = llvm::COFF::IMAGE_FILE_MACHINE_ARMNT;
 static const auto I386 = llvm::COFF::IMAGE_FILE_MACHINE_I386;
 
@@ -96,7 +98,9 @@
 // Global configuration.
 struct Configuration {
   enum ManifestKind { Default, SideBySide, Embed, No };
-  bool is64() const { return machine == AMD64 || machine == ARM64; }
+  bool is64() const {
+    return machine == AMD64 || llvm::COFF::isAnyArm64(machine);
+  }
 
   llvm::COFF::MachineTypes machine = IMAGE_FILE_MACHINE_UNKNOWN;
   size_t wordsize;
Index: lld/COFF/Writer.cpp
===================================================================
--- lld/COFF/Writer.cpp
+++ lld/COFF/Writer.cpp
@@ -1436,7 +1436,16 @@
   // Write COFF header
   auto *coff = reinterpret_cast<coff_file_header *>(buf);
   buf += sizeof(*coff);
-  coff->Machine = config->machine;
+  switch (config->machine) {
+  case ARM64EC:
+    coff->Machine = AMD64;
+    break;
+  case ARM64X:
+    coff->Machine = ARM64;
+    break;
+  default:
+    coff->Machine = config->machine;
+  }
   coff->NumberOfSections = ctx.outputSections.size();
   coff->Characteristics = IMAGE_FILE_EXECUTABLE_IMAGE;
   if (config->largeAddressAware)
Index: lld/test/COFF/arm64ec.test
===================================================================
--- /dev/null
+++ lld/test/COFF/arm64ec.test
@@ -0,0 +1,23 @@
+REQUIRES: aarch64
+RUN: split-file %s %t.dir && cd %t.dir
+
+RUN: llvm-mc -filetype=obj -triple=arm64ec-windows arm64ec-data-sym.s -o arm64ec-data-sym.obj
+RUN: llvm-cvtres -machine:arm64x -out:arm64x-resource.obj %S/Inputs/resource.res
+
+RUN: lld-link -out:test.dll -machine:arm64ec arm64ec-data-sym.obj -dll -noentry
+RUN: llvm-readobj --file-headers test.dll | FileCheck -check-prefix=ARM64EC-HEADER %s
+ARM64EC-HEADER:      Format: COFF-x86-64
+ARM64EC-HEADER-NEXT: Arch: x86_64
+ARM64EC-HEADER-NEXT: AddressSize: 64bit
+ARM64EC-HEADER:      Machine: IMAGE_FILE_MACHINE_AMD64 (0x8664)
+
+RUN: lld-link -out:test.dll -machine:arm64x arm64x-resource.obj -dll -noentry
+RUN: llvm-readobj --file-headers test.dll | FileCheck -check-prefix=ARM64X-HEADER %s
+ARM64X-HEADER:      Machine: IMAGE_FILE_MACHINE_ARM64 (0xAA64)
+
+#--- arm64ec-data-sym.s
+    .data
+    .globl arm64ec_data_sym
+    .p2align 2, 0x0
+arm64ec_data_sym:
+    .word 0x02020202