From: Laurent Vivier <laurent@vivier.eu>
To: Richard Henderson <rth@twiddle.net>, qemu-devel@nongnu.org
Cc: Aurelien Jarno <aurelien@aurel32.net>
Subject: Re: [Qemu-devel] [PATCH 4/4] target-m68k: add fscale, fgetman and fgetexp
Date: Tue, 4 Jul 2017 02:07:26 +0200 [thread overview]
Message-ID: <6b52c76c-a5a6-0f35-3a1d-d5038ef42356@vivier.eu> (raw)
In-Reply-To: <fd4d0cfa-b746-7ea8-f1a0-2409b519f5bf@twiddle.net>
Le 03/07/2017 à 22:31, Richard Henderson a écrit :
> On 07/03/2017 12:50 PM, Laurent Vivier wrote:
>> fmove.x #0x000000000ABCDEF12345,%fp0
>> fgetman.x %fp0,%fp6
>> fp0 2.1518178707571747286191852003521627e-4938 (raw
>> 0x0000000000000abcdef12345)
>> fp6 1.342222103012886691431049257516861 (raw
>> 0x3fff0000abcdef1234500000)
>
> This one shows exactly what I was thinking about.
>
>> So I guess the mantissa must be shifted to left until we have a 1 in the
>> explicit integer part bit?
>
> Yes.
>
> Please try fgetexp on this same input.
fmove.x #0x000000000ABCDEF12345,%fp0
fgetexp.x %fp0,%fp6
fp0 (raw 0x0000000000000abcdef12345)
fp6 -16403
> I suspect the answer is -16384 - clz64(val->l.lower).
It looks like -16383 - clz64(val->l.lower)
fmove.x #0x000056789ABCDEF12345,%fp0
fgetexp.x %fp0,%fp6
fp0 (raw 0x0000000056789abcdef12345)
fp6 -16384
fmove.x #0x000086789ABCDEF12345,%fp0
fgetexp.x %fp0,%fp6
fp0 (raw 0x0000000086789abcdef12345)
fp6 -16383
Thanks,
Laurent
prev parent reply other threads:[~2017-07-04 0:07 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-03 16:23 [Qemu-devel] [PATCH 0/4] target/m68k: implement 680x0 FPU (part 3) Laurent Vivier
2017-07-03 16:23 ` [Qemu-devel] [PATCH 1/4] softfloat: use floatx80_infinity in softfloat Laurent Vivier
2017-07-03 18:06 ` Richard Henderson
2017-07-03 16:23 ` [Qemu-devel] [PATCH 2/4] target/m68k: add FPU trigonometric instructions Laurent Vivier
2017-07-03 19:11 ` Richard Henderson
2017-07-03 19:17 ` Richard Henderson
2017-07-03 16:23 ` [Qemu-devel] [PATCH 3/4] target/m68k: add fmod/frem Laurent Vivier
2017-07-03 19:14 ` Richard Henderson
2017-07-03 16:23 ` [Qemu-devel] [PATCH 4/4] target-m68k: add fscale, fgetman and fgetexp Laurent Vivier
2017-07-03 19:26 ` Richard Henderson
2017-07-03 19:50 ` Laurent Vivier
2017-07-03 20:31 ` Richard Henderson
2017-07-04 0:07 ` Laurent Vivier [this message]
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