X86: Implement the XLAT instruction.

--HG--
extra : convert_revision : 22d7d9e79e722293b4dc1e66d8610301dc04c5fa

src/arch/x86/isa/decoder/one_byte_opcodes.isa

@@ -463,7 +463,7 @@
                 0x0: UD2();
                 default: WarnUnimpl::salc();
             }
-            0x7: WarnUnimpl::xlat();
+            0x7: XLAT();
         }
         ##include "x87.isa"
         0x1C: decode OPCODE_OP_BOTTOM3 {

src/arch/x86/isa/insts/general_purpose/data_conversion/translate.py

@@ -53,8 +53,12 @@
 #
 # Authors: Gabe Black
 
-microcode = ""
-#let {{
-#    class XLAT(Inst):
-#	"GenFault ${new UnimpInstFault}"
-#}};
+microcode = '''
+def macroop XLAT {
+    zext t1, rax, 8
+    # Here, t1 can be used directly. The value of al is supposed to be treated
+    # as unsigned. Since we zero extended it from 8 bits above and the address
+    # size has to be at least 16 bits, t1 will not be sign extended.
+    ld rax, seg, [1, rbx, t1], dataSize=1
+};
+'''