Index: llvm/lib/Support/Triple.cpp
===================================================================
--- llvm/lib/Support/Triple.cpp
+++ llvm/lib/Support/Triple.cpp
@@ -1149,6 +1149,10 @@
     if (SubArch == MipsSubArch_r6)
       return "mipsisa64r6el";
     break;
+  case Triple::aarch64:
+    if (SubArch == AArch64SubArch_arm64ec)
+      return "arm64ec";
+    break;
   default:
     break;
   }
Index: llvm/unittests/ADT/TripleTest.cpp
===================================================================
--- llvm/unittests/ADT/TripleTest.cpp
+++ llvm/unittests/ADT/TripleTest.cpp
@@ -693,6 +693,13 @@
   EXPECT_EQ(Triple::UnknownEnvironment, T.getEnvironment());
   EXPECT_TRUE(T.isArch64Bit());
 
+  T = Triple("arm64ec-pc-windows-msvc");
+  EXPECT_EQ(Triple::aarch64, T.getArch());
+  EXPECT_EQ(Triple::AArch64SubArch_arm64ec, T.getSubArch());
+  EXPECT_EQ(Triple::Win32, T.getOS());
+  EXPECT_EQ(Triple::MSVC, T.getEnvironment());
+  EXPECT_TRUE(T.isArch64Bit());
+
   T = Triple("arm64_32-apple-ios");
   EXPECT_EQ(Triple::aarch64_32, T.getArch());
   EXPECT_EQ(Triple::IOS, T.getOS());
@@ -1990,6 +1997,11 @@
     EXPECT_EQ(Triple::aarch64, T.getArch());
     EXPECT_EQ(Triple::AArch64SubArch_arm64e, T.getSubArch());
   }
+  {
+    Triple T = Triple("arm64ec");
+    EXPECT_EQ(Triple::aarch64, T.getArch());
+    EXPECT_EQ(Triple::AArch64SubArch_arm64ec, T.getSubArch());
+  }
 }
 
 TEST(TripleTest, isArmT32) {