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Re: PATCH: Use__builtin_bswap[32|64] in i386/x86_64 bits/byteswap.h
- From: Richard Henderson <rth at twiddle dot net>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: GNU C Library <libc-alpha at sourceware dot org>
- Date: Mon, 19 Mar 2012 10:37:50 -0700
- Subject: Re: PATCH: Use__builtin_bswap[32|64] in i386/x86_64 bits/byteswap.h
- References: <CAMe9rOpRv9gDkjN5Kg1580gu7BxmNYtKYd5y6k5DxKm=WK8pFw@mail.gmail.com>
On 03/19/12 10:33, H.J. Lu wrote:
> Here is a patch to use __builtin_bswap[32|64] in i386/x86_64 bits/byteswap.h
> for GCC >= 4.2. I didn't use __builtin_bswap32 for __bswap_16 since it is
> less efficient:
For size, yes. For speed, is the partial register stall on rorw larger than
a single extra shift insn?
r~