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From: "unlvsur at live dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/99582] No intrinsics to access rcl or rcr instruction on x86_64
Date: Mon, 15 Mar 2021 10:21:38 +0000 [thread overview]
Message-ID: <bug-99582-4-NE7SRFdOID@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-99582-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99582
--- Comment #2 from cqwrteur <unlvsur at live dot com> ---
(In reply to Richard Biener from comment #1)
> ROR can be open-coded, GCC tries hard to detect common patterns.
>
> RCR is difficult because it involves the carry flag and thus the carry
> producer
> would have to be explicit. Or it would need to be an awkward intrinsic
> like
>
> __builtin_rcr ({unsigned, unsigned short, unsigned char} word, bool carry,
> unsigned amnt);
>
> and you'd need to hope the compiler can arrange 'carry' to be produced in
> the carry flag ...
so is that possible to __builtin_rcl and __builtin_rcr? I think a lot of
cryptography and multi-precision libraries need that for pow stuffs
next prev parent reply other threads:[~2021-03-15 10:21 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-14 7:14 [Bug c++/99582] New: " unlvsur at live dot com
2021-03-15 8:43 ` [Bug target/99582] " rguenth at gcc dot gnu.org
2021-03-15 10:21 ` unlvsur at live dot com [this message]
2021-03-23 14:11 ` amonakov at gcc dot gnu.org
2021-03-23 14:14 ` unlvsur at live dot com
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