--- old/src/hotspot/cpu/x86/macroAssembler_x86.cpp	2017-11-29 17:39:33.427673100 -0800
+++ new/src/hotspot/cpu/x86/macroAssembler_x86.cpp	2017-11-29 17:39:32.820395000 -0800
@@ -6609,6 +6609,13 @@
   }
   // Clear upper bits of YMM registers to avoid SSE <-> AVX transition penalty.
   vzeroupper();
+  // Reset k1 to 0xffff.
+  if (VM_Version::supports_evex()) {
+    push(rcx);
+    movl(rcx, 0xffff);
+    kmovwl(k1, rcx);
+    pop(rcx);
+  }
 
 #ifndef _LP64
   // Either restore the x87 floating pointer control word after returning