From: Rich Felker <dalias@libc.org>
To: musl@lists.openwall.com
Subject: Re: [PATCH] math: move x86_64 fabs, fabsf to C with inline asm
Date: Sun, 5 Jan 2020 15:05:41 -0500 [thread overview]
Message-ID: <20200105200541.GM30412@brightrain.aerifal.cx> (raw)
In-Reply-To: <20200105163639.25963-1-amonakov@ispras.ru>
On Sun, Jan 05, 2020 at 07:36:39PM +0300, Alexander Monakov wrote:
> ---
>
> Questions:
>
> Why are there amd64-specific fabs implementations in the first place?
> (Only) because GCC generated poor code for the generic C version?
I think so. It generates:
0000000000000000 <fabs>:
0: 66 48 0f 7e c0 movq %xmm0,%rax
5: 48 ba ff ff ff ff ff movabs $0x7fffffffffffffff,%rdx
c: ff ff 7f
f: 48 21 d0 and %rdx,%rax
12: 48 89 44 24 f8 mov %rax,-0x8(%rsp)
17: f2 0f 10 44 24 f8 movsd -0x8(%rsp),%xmm0
1d: c3 retq
> Do annotations for mask manipulation in the patch help? Any way to make
> them less ambiguous?
I think so. I like how you did individual asm statements with
dependency relationship between them so compiler could even schedule
them if it likes. I wonder if you could just write 0x7fffffffffffffff
as an operand and have the compiler load it, though.
Rich
next prev parent reply other threads:[~2020-01-05 20:05 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-05 16:35 math patches for moving bare asm to C " Alexander Monakov
2020-01-05 16:36 ` [PATCH] math: move x86_64 fabs, fabsf to C with " Alexander Monakov
2020-01-05 20:05 ` Rich Felker [this message]
2020-01-05 21:32 ` Alexander Monakov
2020-01-05 22:43 ` Rich Felker
2020-01-06 8:17 ` Alexander Monakov
2020-01-06 8:40 ` [PATCH] math: move more x86-family fabs functions to C Alexander Monakov
2020-03-21 17:06 ` [musl] " Rich Felker
2020-01-06 16:50 ` [PATCH] math: move trivial x86-family sqrt " Alexander Monakov
2020-01-06 17:43 ` [PATCH] math: move i386 sqrtf " Alexander Monakov
2020-01-06 18:32 ` Pascal Cuoq
2020-01-09 15:55 ` Alexander Monakov
2020-01-09 17:00 ` Rich Felker
2020-01-09 21:00 ` Szabolcs Nagy
2020-01-09 22:00 ` Rich Felker
2020-01-09 23:18 ` Szabolcs Nagy
2020-01-10 2:07 ` Rich Felker
2020-01-10 9:17 ` Szabolcs Nagy
2020-01-14 17:59 ` [musl] " Alexander Monakov
2020-01-14 18:47 ` Szabolcs Nagy
2020-01-07 13:06 ` [PATCH] math: move i386 sqrt " Alexander Monakov
2020-01-08 7:26 ` Rich Felker
2020-03-21 17:53 ` [musl] " Rich Felker
2020-03-21 17:57 ` Rich Felker
2020-03-21 20:30 ` Alexander Monakov
2020-01-11 15:06 ` [PATCH] math: move x86_64 (l)lrint(f) functions " Alexander Monakov
2020-01-11 15:23 ` [PATCH] math: move more x86-family lrint " Alexander Monakov
2020-01-11 16:07 ` Rich Felker
2020-01-11 16:22 ` Rich Felker
2020-01-14 11:54 ` [musl] [PATCH] math: move x86-family rint " Alexander Monakov
2020-01-14 18:17 ` [musl] Q: dealing with missing removal of excess precision Alexander Monakov
2020-01-14 18:50 ` Szabolcs Nagy
2020-01-14 18:58 ` Rich Felker
2020-01-14 19:53 ` Alexander Monakov
2020-02-06 14:51 ` Rich Felker
2020-02-06 17:15 ` Alexander Monakov
2020-02-06 17:46 ` Rich Felker
2020-02-06 19:03 ` Rich Felker
2020-02-06 20:02 ` Rich Felker
2020-02-06 22:08 ` Szabolcs Nagy
2020-02-22 19:59 ` Rich Felker
2020-02-22 20:21 ` Alexander Monakov
2020-02-23 0:19 ` Rich Felker
2020-02-23 16:14 ` Alexander Monakov
2020-03-20 18:12 ` Rich Felker
2020-03-22 1:19 ` Rich Felker
2020-03-22 17:40 ` Alexander Monakov
2020-03-22 17:53 ` Rich Felker
2020-03-22 18:51 ` Alexander Monakov
2020-03-22 19:10 ` Rich Felker
2020-03-22 19:46 ` Alexander Monakov
2020-01-14 20:41 ` [musl] [PATCH] math: move x86-family remainder functions to C Alexander Monakov
2020-01-15 6:54 ` Szabolcs Nagy
2020-01-15 15:44 ` [musl] [PATCH] math: move x86-family fmod " Alexander Monakov
2020-01-16 21:00 ` [musl] [PATCH] math: add x86_64 remquol Alexander Monakov
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