linux-kernel - Re: [PATCH 3/3] tracing: Rewrite filter logic to be simpler and faster

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Message-ID: <20180312124246.GC23111@krava>
Date:   Mon, 12 Mar 2018 13:42:46 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...IV.linux.org.uk>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>
Subject: Re: [PATCH 3/3] tracing: Rewrite filter logic to be simpler and
 faster

On Fri, Mar 09, 2018 at 09:34:45PM -0500, Steven Rostedt wrote:

SNIP

>  
> -/* If not of not match is equal to not of not, then it is a match */
> +/*
> + * Without going into a formal proof, this explains the method that is used in
> + * parsing the logical expressions.
> + *
> + * For example, if we have: "a && !(!b || (c && g)) || d || e && !f"
> + * The first pass will convert it into the following program:
> + *
> + * n1: r=a;       l1: if (!r) goto l4;
> + * n2: r=b;       l2: if (!r) goto l4;

got stuck in here.. should that be 'goto l5' ?

jirka

> + * n3: r=c; r=!r; l3: if (r) goto l4;
> + * n4: r=g; r=!r; l4: if (r) goto l5;
> + * n5: r=d;       l5: if (r) goto T
> + * n6: r=e;       l6: if (!r) goto l7;
> + * n7: r=f; r=!r; l7: if (!r) goto F
> + * T: return TRUE
> + * F: return FALSE

jirka