From: Aurelien Jarno <aurelien@aurel32.net>
To: Richard Henderson <rth@twiddle.net>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 03/10] tcg: Swap commutative double-word comparisons
Date: Tue, 9 Oct 2012 17:48:35 +0200 [thread overview]
Message-ID: <20121009154835.GF14078@ohm.aurel32.net> (raw)
In-Reply-To: <50744363.7080108@twiddle.net>
On Tue, Oct 09, 2012 at 08:31:47AM -0700, Richard Henderson wrote:
> On 10/09/2012 08:16 AM, Aurelien Jarno wrote:
> >> > +static bool swap_commutative2(TCGArg *p1, TCGArg *p2)
> >> > +{
> >> > + int sum = 0;
> >> > + sum += temps[p1[0]].state == TCG_TEMP_CONST;
> >> > + sum += temps[p1[1]].state == TCG_TEMP_CONST;
> >> > + sum -= temps[p2[0]].state == TCG_TEMP_CONST;
> >> > + sum -= temps[p2[1]].state == TCG_TEMP_CONST;
> >> > + if (sum > 0) {
> ...
> > Same comment are for the swap_commutative() patch, otherwise:
>
> While I don't have an explicit test case for swap_commutative2 like
> I do for swap_commutative, think about how many conditionals you'd
> have to use to write this without using SUM:
>
> if (((temps[p1[0]].state == TCG_TEMP_CONST // if both p1 are const
> && temps[p1[1]].state == TCG_TEMP_CONST
> && !(temps[p2[0]].state == TCG_TEMP_CONST // ... and not both p2 are const
> && temps[p2[1]].state == TCG_TEMP_CONST))
> || ((temps[p1[0]].state == TCG_TEMP_CONST // if either p1 are const
> || temps[p1[1]].state == TCG_TEMP_CONST)
> && !temps[p2[0]].state == TCG_TEMP_CONST // ... and neither p2 are const
> && !temps[p2[1]].state == TCG_TEMP_CONST))
>
> I don't see how that can possibly be easier to understand.
>
>
For that one I agree.
--
Aurelien Jarno GPG: 1024D/F1BCDB73
aurelien@aurel32.net http://www.aurel32.net
next prev parent reply other threads:[~2012-10-09 15:49 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-02 18:32 [Qemu-devel] [PATCH v2 00/10] Double-word tcg/optimize improvements Richard Henderson
2012-10-02 18:32 ` [Qemu-devel] [PATCH 01/10] tcg: Split out swap_commutative as a subroutine Richard Henderson
2012-10-09 15:13 ` Aurelien Jarno
2012-10-09 15:23 ` Richard Henderson
2012-10-09 15:31 ` Aurelien Jarno
2012-10-09 16:40 ` Richard Henderson
2012-10-02 18:32 ` [Qemu-devel] [PATCH 02/10] tcg: Canonicalize add2 operand ordering Richard Henderson
2012-10-09 15:14 ` Aurelien Jarno
2012-10-02 18:32 ` [Qemu-devel] [PATCH 03/10] tcg: Swap commutative double-word comparisons Richard Henderson
2012-10-09 15:16 ` Aurelien Jarno
2012-10-09 15:31 ` Richard Henderson
2012-10-09 15:48 ` Aurelien Jarno [this message]
2012-10-02 18:32 ` [Qemu-devel] [PATCH 04/10] tcg: Use common code when failing to optimize Richard Henderson
2012-10-09 15:25 ` Aurelien Jarno
2012-10-09 15:33 ` Richard Henderson
2012-10-02 18:32 ` [Qemu-devel] [PATCH 05/10] tcg: Optimize double-word comparisons against zero Richard Henderson
2012-10-09 16:32 ` Aurelien Jarno
2012-10-02 18:32 ` [Qemu-devel] [PATCH 06/10] tcg: Split out subroutines from do_constant_folding_cond Richard Henderson
2012-10-09 16:33 ` Aurelien Jarno
2012-10-02 18:32 ` [Qemu-devel] [PATCH 07/10] tcg: Do constant folding on double-word comparisons Richard Henderson
2012-10-10 9:45 ` Aurelien Jarno
2012-10-02 18:32 ` [Qemu-devel] [PATCH 08/10] tcg: Constant fold add2 and sub2 Richard Henderson
2012-10-10 9:52 ` Aurelien Jarno
2012-10-02 18:32 ` [Qemu-devel] [PATCH 09/10] tcg: Optimize half-dead add2/sub2 Richard Henderson
2012-10-16 23:25 ` Aurelien Jarno
2012-10-02 18:32 ` [Qemu-devel] [PATCH 10/10] tcg: Optimize mulu2 Richard Henderson
2012-10-16 23:25 ` Aurelien Jarno
2012-10-17 1:09 ` Richard Henderson
2012-10-17 10:58 ` Avi Kivity
2012-10-17 16:41 ` [Qemu-devel] [PATCH v2 00/10] Double-word tcg/optimize improvements Aurelien Jarno
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