[hackers] [libgrapheme] Mark likely branches || Laslo Hunhold

From: <git_AT_suckless.org>
Date: Tue, 4 Jan 2022 19:05:37 +0100 (CET)

commit e917e53a05de7cab2591d6b2fa3f2ce5ece89bcf
Author: Laslo Hunhold <dev_AT_frign.de>
AuthorDate: Tue Jan 4 18:56:38 2022 +0100
Commit: Laslo Hunhold <dev_AT_frign.de>
CommitDate: Tue Jan 4 18:56:38 2022 +0100

    Mark likely branches
    
    The likely() and unlikely() macros (known from the Linux kernel) in
    src/util.h are defined in a portable way.
    
    This addition brings a performance improvment of around 6%, which also
    shows how well-optimized grapheme_is_character_break() already is. One
    break check for two codepoints now takes only around 10µs on average on
    my machine, which is insanely fast when you consider the complexity of
    the algorithm behind it.
    
    Signed-off-by: Laslo Hunhold <dev_AT_frign.de>

diff --git a/src/character.c b/src/character.c
index 80a9a79..27e1cf0 100644
--- a/src/character.c
+++ b/src/character.c
_AT_@ -105,10 +105,10 @@ static const uint_least16_t dont_break_gb12_13[2 * NUM_BREAK_PROPS] = {
 static enum break_property
 get_break_prop(uint_least32_t cp)
 {
- if (cp > 0x10FFFF) {
- return BREAK_PROP_OTHER;
- } else {
+ if (likely(cp <= 0x10FFFF)) {
                 return prop[minor[major[cp >> 8] + (cp & 0xff)]].break_property;
+ } else {
+ return BREAK_PROP_OTHER;
         }
 }
 
_AT_@ -118,11 +118,11 @@ grapheme_is_character_break(uint_least32_t cp0, uint_least32_t cp1, GRAPHEME_STA
         enum break_property cp0_prop, cp1_prop;
         bool notbreak = false;
 
- if (state) {
- if (!state->prop_set) {
- cp0_prop = get_break_prop(cp0);
- } else {
+ if (likely(state)) {
+ if (likely(state->prop_set)) {
                         cp0_prop = state->prop;
+ } else {
+ cp0_prop = get_break_prop(cp0);
                 }
                 cp1_prop = get_break_prop(cp1);
 
_AT_@ -153,7 +153,7 @@ grapheme_is_character_break(uint_least32_t cp0, uint_least32_t cp1, GRAPHEME_STA
                             UINT16_C(1 << cp1_prop));
 
                 /* update or reset flags (when we have a break) */
- if (!notbreak) {
+ if (likely(!notbreak)) {
                         state->gb11_flag = state->gb12_13_flag = false;
                 }
         } else {
diff --git a/src/util.h b/src/util.h
index 049af2f..b61a026 100644
--- a/src/util.h
+++ b/src/util.h
_AT_@ -10,4 +10,19 @@
 
 #define LEN(x) (sizeof(x) / sizeof(*(x)))
 
+#undef likely
+#undef unlikely
+#ifdef __has_builtin
+ #if __has_builtin(__builtin_expect)
+ #define likely(expr) __builtin_expect(!!(expr), 1)
+ #define unlikely(expr) __builtin_expect(!!(expr), 0)
+ #else
+ #define likely(expr) (expr)
+ #define unlikely(expr) (expr)
+ #endif
+#else
+ #define likely(expr) (expr)
+ #define unlikely(expr) (expr)
+#endif
+
 #endif /* UTIL_H */
Received on Tue Jan 04 2022 - 19:05:37 CET