Skip to content

Add ASCII fast path to gototab to avoid bsearch #264

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
yhirose wants to merge 1 commit into
base: staging
Choose a base branch
from
Open

Add ASCII fast path to gototab to avoid bsearch #264

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
3 changes: 3 additions & 0 deletions awk.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -250,10 +250,13 @@ typedef struct gtte { /* gototab entry */
unsigned int state;
} gtte;

#define GOTO_DIRECT 128 /* size of ASCII direct-index fast path */

typedef struct gtt { /* gototab */
size_t allocated;
size_t inuse;
gtte *entries;
int direct[GOTO_DIRECT]; /* fast path for ASCII; 0 == miss */
} gtt;

typedef struct fa {
Expand Down
16 changes: 16 additions & 0 deletions b.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -106,6 +106,12 @@ extern int u8_nextlen(const char *s);
This should be dynamic, but for now things work ok for a single
code page of Unicode, which is the most likely case.

ASCII code points (0..GOTO_DIRECT-1) take a direct-indexed fast
path in each state's gototab, bypassing the bsearch entirely;
non-ASCII still goes through the sorted (codepoint, state) table.
This keeps the common case to a single load per input byte while
leaving Unicode handling unchanged.

The code changes are localized in run.c and b.c. I have added a
handful of functions to somewhat better hide the implementation,
but a lot more could be done.
Expand Down Expand Up @@ -169,6 +175,7 @@ resize_state(fa *f, int state)
f->posns = p3;

for (i = f->state_count; i < new_count; ++i) {
memset(f->gototab[i].direct, 0, sizeof(f->gototab[i].direct));
f->gototab[i].entries = (gtte *) calloc(NCHARS, sizeof(gtte));
if (f->gototab[i].entries == NULL)
goto out;
Expand Down Expand Up @@ -629,6 +636,9 @@ static int get_gototab(fa *f, int state, int ch) /* hide gototab implementation
gtte key;
gtte *item;

if ((unsigned)ch < GOTO_DIRECT)
return f->gototab[state].direct[ch];

key.ch = ch;
key.state = 0; /* irrelevant */
item = (gtte *) bsearch(& key, f->gototab[state].entries,
Expand All @@ -653,6 +663,11 @@ static int entry_cmp(const void *l, const void *r)

static int set_gototab(fa *f, int state, int ch, int val) /* hide gototab implementation */
{
if ((unsigned)ch < GOTO_DIRECT) {
f->gototab[state].direct[ch] = val;
return val;
}

if (f->gototab[state].inuse == 0) {
f->gototab[state].entries[0].ch = ch;
f->gototab[state].entries[0].state = val;
Expand Down Expand Up @@ -702,6 +717,7 @@ static int set_gototab(fa *f, int state, int ch, int val) /* hide gototab implem

static void clear_gototab(fa *f, int state)
{
memset(f->gototab[state].direct, 0, sizeof(f->gototab[state].direct));
memset(f->gototab[state].entries, 0,
f->gototab[state].allocated * sizeof(gtte));
f->gototab[state].inuse = 0;
Expand Down