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vc_screen: eliminate ifdefs from vcs_write_buf

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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>
Link: https://lore.kernel.org/r/20200818085706.12163-9-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jiri Slaby 2020-08-18 10:56:59 +02:00 committed by Greg Kroah-Hartman
parent 95e0d57fd4
commit d7c91c5081
1 changed files with 17 additions and 12 deletions
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29
drivers/tty/vt/vc_screen.c
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@ -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;
}