diff --git a/clang/include/clang/Basic/BuiltinsWebAssembly.def b/clang/include/clang/Basic/BuiltinsWebAssembly.def
--- a/clang/include/clang/Basic/BuiltinsWebAssembly.def
+++ b/clang/include/clang/Basic/BuiltinsWebAssembly.def
@@ -154,6 +154,7 @@
 TARGET_BUILTIN(__builtin_wasm_bitmask_i8x16, "iV16Sc", "nc", "simd128")
 TARGET_BUILTIN(__builtin_wasm_bitmask_i16x8, "iV8s", "nc", "simd128")
 TARGET_BUILTIN(__builtin_wasm_bitmask_i32x4, "iV4i", "nc", "simd128")
+TARGET_BUILTIN(__builtin_wasm_bitmask_i64x2, "iV2LLi", "nc", "simd128")
 
 TARGET_BUILTIN(__builtin_wasm_abs_f32x4, "V4fV4f", "nc", "simd128")
 TARGET_BUILTIN(__builtin_wasm_abs_f64x2, "V2dV2d", "nc", "simd128")
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -16734,7 +16734,8 @@
   }
   case WebAssembly::BI__builtin_wasm_bitmask_i8x16:
   case WebAssembly::BI__builtin_wasm_bitmask_i16x8:
-  case WebAssembly::BI__builtin_wasm_bitmask_i32x4: {
+  case WebAssembly::BI__builtin_wasm_bitmask_i32x4:
+  case WebAssembly::BI__builtin_wasm_bitmask_i64x2: {
     Value *Vec = EmitScalarExpr(E->getArg(0));
     Function *Callee =
         CGM.getIntrinsic(Intrinsic::wasm_bitmask, Vec->getType());
diff --git a/clang/test/CodeGen/builtins-wasm.c b/clang/test/CodeGen/builtins-wasm.c
--- a/clang/test/CodeGen/builtins-wasm.c
+++ b/clang/test/CodeGen/builtins-wasm.c
@@ -728,6 +728,12 @@
   // WEBASSEMBLY: ret
 }
 
+int bitmask_i64x2(i64x2 x) {
+  return __builtin_wasm_bitmask_i64x2(x);
+  // WEBASSEMBLY: call i32 @llvm.wasm.bitmask.v2i64(<2 x i64> %x)
+  // WEBASSEMBLY: ret
+}
+
 f32x4 abs_f32x4(f32x4 x) {
   return __builtin_wasm_abs_f32x4(x);
   // WEBASSEMBLY: call <4 x float> @llvm.fabs.v4f32(<4 x float> %x)
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td b/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
@@ -848,6 +848,7 @@
 defm BITMASK : SIMDBitmask<v16i8, "i8x16", 100>;
 defm BITMASK : SIMDBitmask<v8i16, "i16x8", 132>;
 defm BITMASK : SIMDBitmask<v4i32, "i32x4", 164>;
+defm BITMASK : SIMDBitmask<v2i64, "i64x2", 196>;
 
 //===----------------------------------------------------------------------===//
 // Bit shifts
diff --git a/llvm/test/CodeGen/WebAssembly/simd-intrinsics.ll b/llvm/test/CodeGen/WebAssembly/simd-intrinsics.ll
--- a/llvm/test/CodeGen/WebAssembly/simd-intrinsics.ll
+++ b/llvm/test/CodeGen/WebAssembly/simd-intrinsics.ll
@@ -646,6 +646,16 @@
   ret i32 %a
 }
 
+; CHECK-LABEL: bitmask_v2i64:
+; SIMD128-NEXT: .functype bitmask_v2i64 (v128) -> (i32){{$}}
+; SIMD128-NEXT: i64x2.bitmask $push[[R:[0-9]+]]=, $0{{$}}
+; SIMD128-NEXT: return $pop[[R]]{{$}}
+declare i32 @llvm.wasm.bitmask.v2i64(<2 x i64>)
+define i32 @bitmask_v2i64(<2 x i64> %x) {
+  %a = call i32 @llvm.wasm.bitmask.v2i64(<2 x i64> %x)
+  ret i32 %a
+}
+
 ; CHECK-LABEL: bitselect_v2i64:
 ; SIMD128-NEXT: .functype bitselect_v2i64 (v128, v128, v128) -> (v128){{$}}
 ; SIMD128-NEXT: v128.bitselect $push[[R:[0-9]+]]=, $0, $1, $2{{$}}
diff --git a/llvm/test/MC/WebAssembly/simd-encodings.s b/llvm/test/MC/WebAssembly/simd-encodings.s
--- a/llvm/test/MC/WebAssembly/simd-encodings.s
+++ b/llvm/test/MC/WebAssembly/simd-encodings.s
@@ -523,6 +523,9 @@
     # CHECK: i64x2.all_true # encoding: [0xfd,0xc3,0x01]
     i64x2.all_true
 
+    # CHECK: i64x2.bitmask # encoding: [0xfd,0xc4,0x01]
+    i64x2.bitmask
+
     # CHECK: i64x2.widen_low_i32x4_s # encoding: [0xfd,0xc7,0x01]
     i64x2.widen_low_i32x4_s