Index: lib/Target/X86/AsmParser/X86AsmParser.cpp
===================================================================
--- lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ lib/Target/X86/AsmParser/X86AsmParser.cpp
@@ -1049,6 +1049,7 @@
     .Cases("WORD", "word", 16)
     .Cases("DWORD", "dword", 32)
     .Cases("QWORD", "qword", 64)
+    .Cases("MMWORD", "mmword", 64)
     .Cases("XWORD", "xword", 80)
     .Cases("TBYTE", "tbyte", 80)
     .Cases("XMMWORD", "xmmword", 128)
Index: test/MC/X86/intel-syntax.s
===================================================================
--- test/MC/X86/intel-syntax.s
+++ test/MC/X86/intel-syntax.s
@@ -704,3 +704,6 @@
 
 sal eax, 123
 // CHECK: shll	$123, %eax
+
+psignw    mm0, MMWORD PTR t2
+// CHECK: psignw  mm0, qword ptr [t2]
\ No newline at end of file