--- old/src/hotspot/cpu/x86/x86_64.ad	2018-11-12 22:57:28.809456592 +0100
+++ new/src/hotspot/cpu/x86/x86_64.ad	2018-11-12 22:57:28.576457824 +0100
@@ -12046,9 +12046,9 @@
   ins_pipe(ialu_cr_reg_mem);
 %}
 
-instruct testB_mem_imm(rFlagsReg cr, memory mem, immI8 imm, immI0 zero)
+instruct testUB_mem_imm(rFlagsReg cr, memory mem, immU8 imm, immI0 zero)
 %{
-  match(Set cr (CmpI (AndI (LoadB mem) imm) zero));
+  match(Set cr (CmpI (AndI (LoadUB mem) imm) zero));
 
   ins_cost(125);
   format %{ "testb   $mem, $imm" %}