Commit d7c91c50 authored by Jiri Slaby's avatar Jiri Slaby Committed by Greg Kroah-Hartman
Browse files

vc_screen: eliminate ifdefs from vcs_write_buf 



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: default avatarJiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200818085706.12163-9-jslaby@suse.cz


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 95e0d57f

drivers/tty/vt/vc_screen.c

+17 −12
Original line number Diff line number Diff line
@@ -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;

}

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