From: Jiri Slaby <jslaby@suse.cz>
To: gregkh@linuxfoundation.org
Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
Jiri Slaby <jslaby@suse.cz>
Subject: [PATCH 09/16] vc_screen: eliminate ifdefs from vcs_write_buf
Date: Tue, 18 Aug 2020 10:56:59 +0200 [thread overview]
Message-ID: <20200818085706.12163-9-jslaby@suse.cz> (raw)
In-Reply-To: <20200818085706.12163-1-jslaby@suse.cz>
Introduce a new inline function called vc_compile_le16 and do the shifts
and ORs there. Depending on LE x BE.
I tried cpu_to_le16, but it ends up with worse assembly on BE for
whatever reason -- the compiler seems to be unable to optimize the swap.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
drivers/tty/vt/vc_screen.c | 29 +++++++++++++++++------------
1 file changed, 17 insertions(+), 12 deletions(-)
diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c
index 10a26fd5f1b7..36b967825f68 100644
--- a/drivers/tty/vt/vc_screen.c
+++ b/drivers/tty/vt/vc_screen.c
@@ -481,6 +481,19 @@ static u16 *vcs_write_buf_noattr(struct vc_data *vc, const char *con_buf,
return org;
}
+/*
+ * Compilers (gcc 10) are unable to optimize the swap in cpu_to_le16. So do it
+ * the poor man way.
+ */
+static inline u16 vc_compile_le16(u8 hi, u8 lo)
+{
+#ifdef __BIG_ENDIAN
+ return (lo << 8u) | hi;
+#else
+ return (hi << 8u) | lo;
+#endif
+}
+
static u16 *vcs_write_buf(struct vc_data *vc, const char *con_buf,
unsigned int pos, unsigned int count, bool viewed, u16 **org0)
{
@@ -513,13 +526,8 @@ static u16 *vcs_write_buf(struct vc_data *vc, const char *con_buf,
if (pos & 1) {
count--;
c = *con_buf++;
-#ifdef __BIG_ENDIAN
- vcs_scr_writew(vc, c |
- (vcs_scr_readw(vc, org) & 0xff00), org);
-#else
- vcs_scr_writew(vc, (c << 8) |
- (vcs_scr_readw(vc, org) & 0xff), org);
-#endif
+ vcs_scr_writew(vc, vc_compile_le16(c, vcs_scr_readw(vc, org)),
+ org);
org++;
pos++;
if (++col == maxcol) {
@@ -551,11 +559,8 @@ static u16 *vcs_write_buf(struct vc_data *vc, const char *con_buf,
/* odd pos -- the remaining character */
c = *con_buf++;
-#ifdef __BIG_ENDIAN
- vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff) | (c << 8), org);
-#else
- vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff00) | c, org);
-#endif
+ vcs_scr_writew(vc, vc_compile_le16(vcs_scr_readw(vc, org) >> 8, c),
+ org);
return org;
}
--
2.28.0
next prev parent reply other threads:[~2020-08-18 8:57 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-18 8:56 [PATCH 01/16] vt: make vc_data pointers const in selection.h Jiri Slaby
2020-08-18 8:56 ` [PATCH 02/16] vt: declare xy for get/putconsxy properly Jiri Slaby
2020-08-18 11:43 ` Greg KH
2020-08-19 7:09 ` Jiri Slaby
2020-08-18 8:56 ` [PATCH 03/16] vc: propagate "viewed as bool" from screenpos up Jiri Slaby
2020-08-18 8:56 ` [PATCH 04/16] vc_screen: document and cleanup vcs_vc Jiri Slaby
2020-08-18 8:56 ` [PATCH 05/16] vc_screen: rewrite vcs_size to accept vc, not inode Jiri Slaby
2020-08-18 8:56 ` [PATCH 06/16] vc_screen: sanitize types in vcs_write Jiri Slaby
2020-08-18 8:56 ` [PATCH 07/16] vc_screen: extract vcs_write_buf_noattr Jiri Slaby
2020-08-18 8:56 ` [PATCH 08/16] vc_screen: extract vcs_write_buf Jiri Slaby
2020-08-18 8:56 ` Jiri Slaby [this message]
2020-08-18 8:57 ` [PATCH 10/16] vc_screen: sanitize types in vcs_read Jiri Slaby
2020-08-18 8:57 ` [PATCH 11/16] vs_screen: kill tmp_count from vcs_read Jiri Slaby
2020-08-18 8:57 ` [PATCH 12/16] vc_screen: extract vcs_read_buf_uni Jiri Slaby
2020-08-18 8:57 ` [PATCH 13/16] vc_screen: extract vcs_read_buf_noattr Jiri Slaby
2020-08-18 8:57 ` [PATCH 14/16] vc_screen: extract vcs_read_buf Jiri Slaby
2020-08-18 8:57 ` [PATCH 15/16] vc_screen: extract vcs_read_buf_header Jiri Slaby
2020-08-25 16:48 ` Peilin Ye
2020-08-25 16:48 ` [Linux-kernel-mentees] " Peilin Ye
2020-08-25 16:59 ` Greg KH
2020-08-25 16:59 ` [Linux-kernel-mentees] " Greg KH
2020-08-25 17:12 ` Peilin Ye
2020-08-25 17:12 ` [Linux-kernel-mentees] " Peilin Ye
2020-08-18 8:57 ` [PATCH 16/16] vc_screen: prune macros Jiri Slaby
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=20200818085706.12163-9-jslaby@suse.cz \
--to=jslaby@suse.cz \
--cc=gregkh@linuxfoundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-serial@vger.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.