mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-07-22 17:27:37 -04:00
255dc0ec0b
The hot path in vc_process_ucs() asks two independent questions about the
same code point -- "is it double-width?" and "is it zero-width?" -- and
was answering each with its own bsearch over its own table. For anything
past the leading bounds check that meant two scans of the BMP width
tables back to back for what is logically a single lookup.
Replace both with one ucs_get_width(cp) returning 0, 1, or 2 in a single
bsearch, while keeping the total table footprint at the same 2384 B as
before.
To do so, merge the zero-width and double-width ranges per region into
one sorted-by-`first` table. BMP entries stay 4 bytes; per-entry width
is hosted in spare bits of the non-BMP table's `last` field. Non-BMP
code points use only 20 of 32 bits, so each u32 has 12 unused high bits.
Store first/last shifted left by 12 and use the low 12 bits of `last`
for metadata: bit 11 is this entry's own width flag, bits 0..7 host an
8-bit chunk of the BMP double-width bitmap. Because the metadata bits
sit strictly below the lowest cp-scale bit, the bsearch comparator
remains a plain u32 compare on shifted keys with no masking.
In vc_process_ucs() the overwhelmingly common single-width path now
collapses to a single predicted branch:
if (likely(w == 1))
return 1;
Note: scripts/checkpatch.pl complains about "Macros with complex values
should be enclosed in parentheses" for the BMP_*WIDTH and
RANGE_*WIDTH macros. They are deliberately defined to expand to a
comma-separated (first, last) pair so they can populate the two
adjacent fields of a struct initializer; wrapping them in
parentheses would turn that into a comma-expression and defeat
the whole construction. Please ignore.
Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Link: https://patch.msgid.link/20260515034857.2514225-1-nico@fluxnic.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
81 lines
1.6 KiB
C
81 lines
1.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
/*
|
|
* consolemap.h
|
|
*
|
|
* Interface between console.c, selection.c and consolemap.c
|
|
*/
|
|
#ifndef __LINUX_CONSOLEMAP_H__
|
|
#define __LINUX_CONSOLEMAP_H__
|
|
|
|
enum translation_map {
|
|
LAT1_MAP,
|
|
GRAF_MAP,
|
|
IBMPC_MAP,
|
|
USER_MAP,
|
|
|
|
FIRST_MAP = LAT1_MAP,
|
|
LAST_MAP = USER_MAP,
|
|
};
|
|
|
|
#include <linux/types.h>
|
|
|
|
struct vc_data;
|
|
|
|
#ifdef CONFIG_CONSOLE_TRANSLATIONS
|
|
u16 inverse_translate(const struct vc_data *conp, u16 glyph, bool use_unicode);
|
|
unsigned short *set_translate(enum translation_map m, struct vc_data *vc);
|
|
int conv_uni_to_pc(struct vc_data *conp, long ucs);
|
|
u32 conv_8bit_to_uni(unsigned char c);
|
|
int conv_uni_to_8bit(u32 uni);
|
|
void console_map_init(void);
|
|
unsigned int ucs_get_width(uint32_t cp);
|
|
u32 ucs_recompose(u32 base, u32 mark);
|
|
u32 ucs_get_fallback(u32 cp);
|
|
#else
|
|
static inline u16 inverse_translate(const struct vc_data *conp, u16 glyph,
|
|
bool use_unicode)
|
|
{
|
|
return glyph;
|
|
}
|
|
|
|
static inline unsigned short *set_translate(enum translation_map m,
|
|
struct vc_data *vc)
|
|
{
|
|
return NULL;
|
|
}
|
|
|
|
static inline int conv_uni_to_pc(struct vc_data *conp, long ucs)
|
|
{
|
|
return ucs > 0xff ? -1 : ucs;
|
|
}
|
|
|
|
static inline u32 conv_8bit_to_uni(unsigned char c)
|
|
{
|
|
return c;
|
|
}
|
|
|
|
static inline int conv_uni_to_8bit(u32 uni)
|
|
{
|
|
return uni & 0xff;
|
|
}
|
|
|
|
static inline void console_map_init(void) { }
|
|
|
|
static inline unsigned int ucs_get_width(uint32_t cp)
|
|
{
|
|
return 1;
|
|
}
|
|
|
|
static inline u32 ucs_recompose(u32 base, u32 mark)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static inline u32 ucs_get_fallback(u32 cp)
|
|
{
|
|
return 0;
|
|
}
|
|
#endif /* CONFIG_CONSOLE_TRANSLATIONS */
|
|
|
|
#endif /* __LINUX_CONSOLEMAP_H__ */
|