6890984: Comparison of 2 arrays could cause VM crash

Summary: Restore original null checks.
Reviewed-by: never, cfang

src/cpu/sparc/vm/sparc.ad

@@ -3016,7 +3016,7 @@ enc_class enc_Array_Equals(o0RegP ary1, o1RegP ary2, g3RegP tmp1, notemp_iRegI r
 
     // return true if the same array
     __ cmp(ary1_reg, ary2_reg);
-    __ br(Assembler::equal, true, Assembler::pn, Ldone);
+    __ brx(Assembler::equal, true, Assembler::pn, Ldone);
     __ delayed()->add(G0, 1, result_reg); // equal
 
     __ br_null(ary1_reg, true, Assembler::pn, Ldone);

src/cpu/x86/vm/assembler_x86.cpp

@@ -8634,8 +8634,10 @@ void MacroAssembler::char_arrays_equals(bool is_array_equ, Register ary1, Regist
 
   if (is_array_equ) {
     // Need additional checks for arrays_equals.
-    andptr(ary1, ary2);
-    jcc(Assembler::zero, FALSE_LABEL); // One pointer is NULL
+    testptr(ary1, ary1);
+    jcc(Assembler::zero, FALSE_LABEL);
+    testptr(ary2, ary2);
+    jcc(Assembler::zero, FALSE_LABEL);
 
     // Check the lengths
     movl(limit, Address(ary1, length_offset));