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xdiff: remove "line_hash" field from xrecord_t 

Prior to commit 6a26019c81 (xdiff: split xrecord_t.ha into line_hash
and minimal_perfect_hash, 2025-11-18) the "ha" field of xrecord_t
initially held the "line_hash" value and once the line had been
interned that field was updated to hold the "minimal_perfect_hash". The
"line_hash" is only used to intern the line so there is no point in
storing it after all the input lines have been interned.

Removing the "line_hash" field from xrecord_t and storing it in
xdlclass_t where it is actually used makes it clearer that it is a
temporary value and it should not be used once we're calculated the
"minimal_perfect_hash". This also reduces the size of xrecord_t by 25%
on 64-bit platforms and 40% on 32-bit platforms. While the struct is
small we create one instance per input line so any saving is welcome.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
maint
Phillip Wood 2026-01-26 10:48:51 +00:00 committed by Junio C Hamano
parent 22ce0cb639
commit c27afcbfd0
2 changed files with 7 additions and 6 deletions
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12
xdiff/xprepare.c
View File

@ -34,6 +34,7 @@
#define INVESTIGATE 2

typedef struct s_xdlclass {
uint64_t line_hash;
struct s_xdlclass *next;
xrecord_t rec;
long idx;
@ -92,13 +93,14 @@ static void xdl_free_classifier(xdlclassifier_t *cf) {
}


static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t *rec) {
static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t *rec,
uint64_t line_hash) {
size_t hi;
xdlclass_t *rcrec;

hi = XDL_HASHLONG(rec->line_hash, cf->hbits);
hi = XDL_HASHLONG(line_hash, cf->hbits);
for (rcrec = cf->rchash[hi]; rcrec; rcrec = rcrec->next)
if (rcrec->rec.line_hash == rec->line_hash &&
if (rcrec->line_hash == line_hash &&
xdl_recmatch((const char *)rcrec->rec.ptr, (long)rcrec->rec.size,
(const char *)rec->ptr, (long)rec->size, cf->flags))
break;
@ -112,6 +114,7 @@ static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t
if (XDL_ALLOC_GROW(cf->rcrecs, cf->count, cf->alloc))
return -1;
cf->rcrecs[rcrec->idx] = rcrec;
rcrec->line_hash = line_hash;
rcrec->rec = *rec;
rcrec->len1 = rcrec->len2 = 0;
rcrec->next = cf->rchash[hi];
@ -158,8 +161,7 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
crec = &xdf->recs[xdf->nrec++];
crec->ptr = prev;
crec->size = cur - prev;
crec->line_hash = hav;
if (xdl_classify_record(pass, cf, crec) < 0)
if (xdl_classify_record(pass, cf, crec, hav) < 0)
goto abort;
}
}

1
xdiff/xtypes.h
View File

@ -41,7 +41,6 @@ typedef struct s_chastore {
typedef struct s_xrecord {
uint8_t const *ptr;
size_t size;
uint64_t line_hash;
size_t minimal_perfect_hash;
} xrecord_t;