From: David Woodhouse <dwmw2@infradead.org>
To: dwmw2@infradead.org
Cc: linux-arch@vger.kernel.org, x86@kernel.org,
linuxppc-dev@lists.ozlabs.org
Subject: [PATCH 1/4] byteorder: allow arch to opt to use GCC intrinsics for byteswapping
Date: Tue, 4 Dec 2012 10:15:27 +0000 [thread overview]
Message-ID: <1354616130-21587-2-git-send-email-dwmw2@infradead.org> (raw)
In-Reply-To: <1354616130-21587-1-git-send-email-dwmw2@infradead.org>
From: David Woodhouse <David.Woodhouse@intel.com>
Since GCC 4.4, there have been __builtin_bswap32() and __builtin_bswap16()
intrinsics. A __builtin_bswap16() came a little later (4.6 for PowerPC,
48 for other platforms).
By using these instead of the inline assembler that most architectures
have in their __arch_swabXX() macros, we let the compiler see what's
actually happening. The resulting code should be at least as good, and
much *better* in the cases where it can be combined with a nearby load
or store, using a load-and-byteswap or store-and-byteswap instruction
(e.g. lwbrx/stwbrx on PowerPC, movbe on Atom).
When GCC is sufficiently recent *and* the architecture opts in to using
the intrinsics by setting CONFIG_ARCH_USE_BUILTIN_BSWAP, they will be
used in preference to the __arch_swabXX() macros. An architecture which
does not set ARCH_USE_BUILTIN_BSWAP will continue to use its own
hand-crafted macros.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
---
include/linux/compiler-gcc4.h | 10 ++++++++++
include/linux/compiler-intel.h | 7 +++++++
include/uapi/linux/swab.h | 12 +++++++++---
3 files changed, 26 insertions(+), 3 deletions(-)
diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h
index 412bc6c..dc16a85 100644
--- a/include/linux/compiler-gcc4.h
+++ b/include/linux/compiler-gcc4.h
@@ -63,3 +63,13 @@
#define __compiletime_warning(message) __attribute__((warning(message)))
#define __compiletime_error(message) __attribute__((error(message)))
#endif
+
+#ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP
+#if __GNUC_MINOR__ >= 4
+#define __HAVE_BUILTIN_BSWAP32__
+#define __HAVE_BUILTIN_BSWAP64__
+#endif
+#if __GNUC_MINOR__ >= 8 || (defined(__powerpc__) && __GNUC_MINOR__ >= 6)
+#define __HAVE_BUILTIN_BSWAP16__
+#endif
+#endif
diff --git a/include/linux/compiler-intel.h b/include/linux/compiler-intel.h
index d8e636e..973ce10 100644
--- a/include/linux/compiler-intel.h
+++ b/include/linux/compiler-intel.h
@@ -29,3 +29,10 @@
#endif
#define uninitialized_var(x) x
+
+#ifndef __HAVE_BUILTIN_BSWAP16__
+/* icc has this, but it's called _bswap16 */
+#define __HAVE_BUILTIN_BSWAP16__
+#define __builtin_bswap16 _bswap16
+#endif
+
diff --git a/include/uapi/linux/swab.h b/include/uapi/linux/swab.h
index e811474..0e011eb 100644
--- a/include/uapi/linux/swab.h
+++ b/include/uapi/linux/swab.h
@@ -45,7 +45,9 @@
static inline __attribute_const__ __u16 __fswab16(__u16 val)
{
-#ifdef __arch_swab16
+#ifdef __HAVE_BUILTIN_BSWAP16__
+ return __builtin_bswap16(val);
+#elif defined (__arch_swab16)
return __arch_swab16(val);
#else
return ___constant_swab16(val);
@@ -54,7 +56,9 @@ static inline __attribute_const__ __u16 __fswab16(__u16 val)
static inline __attribute_const__ __u32 __fswab32(__u32 val)
{
-#ifdef __arch_swab32
+#ifdef __HAVE_BUILTIN_BSWAP32__
+ return __builtin_bswap32(val);
+#elif defined(__arch_swab32)
return __arch_swab32(val);
#else
return ___constant_swab32(val);
@@ -63,7 +67,9 @@ static inline __attribute_const__ __u32 __fswab32(__u32 val)
static inline __attribute_const__ __u64 __fswab64(__u64 val)
{
-#ifdef __arch_swab64
+#ifdef __HAVE_BUILTIN_BSWAP64__
+ return __builtin_bswap64(val);
+#elif defined (__arch_swab64)
return __arch_swab64(val);
#elif defined(__SWAB_64_THRU_32__)
__u32 h = val >> 32;
--
1.8.0
next prev parent reply other threads:[~2012-12-04 10:15 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-04 10:15 [PATCH 0/4] Use compiler intrinsics for byteswapping David Woodhouse
2012-12-04 10:15 ` David Woodhouse [this message]
2012-12-04 10:15 ` [PATCH 2/4] powerpc: enable ARCH_USE_BUILTIN_BSWAP David Woodhouse
2012-12-04 11:02 ` Stephen Rothwell
2012-12-04 14:32 ` David Woodhouse
2012-12-04 10:15 ` [PATCH 3/4] x86: " David Woodhouse
2012-12-04 10:15 ` [PATCH 4/4] x86: add CONFIG_X86_MOVBE option David Woodhouse
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1354616130-21587-2-git-send-email-dwmw2@infradead.org \
--to=dwmw2@infradead.org \
--cc=linux-arch@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).