intel/tools: Handle illegal instruction

Allow assembler to handle illegal instruction even though mesa doesn't
use it but might be required at some point in future.

Signed-off-by: Sagar Ghuge <sagar.ghuge@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3952>

src/intel/tools/i965_gram.y

@@ -616,6 +616,7 @@ instruction:
 	| syncinstruction
 	| ternaryinstruction
 	| sendinstruction
+	| illegalinstruction
 	;
 
 relocatableinstruction:
@@ -625,6 +626,15 @@ relocatableinstruction:
 	| loopinstruction
 	;
 
+illegalinstruction:
+	ILLEGAL execsize instoptions
+	{
+		brw_next_insn(p, $1);
+		brw_inst_set_exec_size(p->devinfo, brw_last_inst, $2);
+		i965_asm_set_instruction_options(p, $3);
+	}
+	;
+
 /* Unary instruction */
 unaryinstruction:
 	predicate unaryopcodes saturate cond_mod execsize dst srcaccimm	instoptions