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Reworked grm handling to prefer xoring, added lfsr_grm_xorgrm

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The original motiviation was to make the gstate-related logic a bit more
coherent, but it turns out lfsr_grm_xorgrm is quite useful for
simplifying gstate handling in lfsr_mdir_commit.

As a plus it looks like we save a surprisingly amount of stack cost, but
I think this may just be a symptom of our tooling not being able to
understand shrinkwrapped function calls:

            code          stack
  before:  33716           2832
  after    33692 (-0.1%)   2808 (-0.9%)
This commit is contained in:
Christopher Haster
2024-02-08 23:55:49 -06:00
parent 0fa33b7776
commit bd55822abc
1 changed files with 27 additions and 31 deletions
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lfs.c
+27 -31
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@@ -1881,6 +1881,19 @@ static inline int lfsr_grm_xor(lfs_t *lfs,
return lfsr_gdelta_xor(lfs, gdelta, LFSR_GRM_DSIZE, xor);
}
// needed by lfsr_grm_xorgrm
static lfsr_data_t lfsr_data_fromgrm(const lfsr_grm_t *grm,
uint8_t buffer[static LFSR_GRM_DSIZE]);
static inline void lfsr_grm_xorgrm(lfs_t *lfs,
uint8_t gdelta[static LFSR_GRM_DSIZE],
const lfsr_grm_t *grm) {
uint8_t buf[LFSR_GRM_DSIZE];
int err = lfsr_grm_xor(lfs, gdelta,
lfsr_data_fromgrm(grm, buf));
LFS_ASSERT(!err);
}
#define LFSR_DATA_FROMGRM(_grm, _buffer) \
lfsr_data_fromgrm(_grm, _buffer)
@@ -3569,37 +3582,29 @@ static int lfsr_rbyd_compact(lfs_t *lfs, lfsr_rbyd_t *rbyd_,
static int lfsr_rbyd_appendgdelta(lfs_t *lfs, lfsr_rbyd_t *rbyd) {
// need grm delta?
if (!lfsr_grm_iszero(lfs->grm_d)) {
// calculate our delta
uint8_t grm_buf[LFSR_GRM_DSIZE];
memset(grm_buf, 0, LFSR_GRM_DSIZE);
uint8_t grm_[LFSR_GRM_DSIZE];
memcpy(grm_, lfs->grm_d, LFSR_GRM_DSIZE);
// make sure to xor any existing delta
lfsr_data_t data;
int err = lfsr_rbyd_lookup(lfs, rbyd, -1, LFSR_TAG_GRMDELTA,
&data);
if (err && err != LFS_ERR_NOENT) {
return err;
}
if (err != LFS_ERR_NOENT) {
lfs_ssize_t grm_dsize = lfsr_data_read(lfs, &data,
grm_buf, LFSR_GRM_DSIZE);
if (grm_dsize < 0) {
return grm_dsize;
err = lfsr_grm_xor(lfs, grm_, data);
if (err) {
return err;
}
}
err = lfsr_grm_xor(lfs, grm_buf, LFSR_DATA_BUF(
&lfs->grm_d, LFSR_GRM_DSIZE));
if (err) {
return err;
}
// append to our rbyd, note this replaces the original delta
lfs_size_t size = lfsr_grm_size(grm_buf);
// append to our rbyd, replacing any existing delta
lfs_size_t size = lfsr_grm_size(grm_);
err = lfsr_rbyd_appendattr(lfs, rbyd, -1,
// opportunistically remove this tag if delta is all zero
(size == 0) ? LFSR_TAG_RM(GRMDELTA) : LFSR_TAG_GRMDELTA, 0,
LFSR_DATA_BUF(grm_buf, size));
LFSR_DATA_BUF(grm_, size));
if (err) {
return err;
}
@@ -6198,7 +6203,7 @@ static int lfsr_mdir_commit(lfs_t *lfs, lfsr_mdir_t *mdir,
if (attrs[i].tag == LFSR_TAG_GRM) {
// encode to disk
lfsr_grm_t *grm = lfsr_attr_grm(&attrs[i]);
lfsr_data_fromgrm(grm, lfs->grm_d);
lfsr_grm_xorgrm(lfs, lfs->grm_d, grm);
// xor with our current gstate to find our initial gdelta
int err = lfsr_grm_xor(lfs, lfs->grm_d,
@@ -6486,14 +6491,9 @@ static int lfsr_mdir_commit(lfs_t *lfs, lfsr_mdir_t *mdir,
// gd' = gd xor (grm' xor grm)
//
lfsr_grm_t *grm = lfsr_attr_grm(&attrs[i]);
uint8_t grm_buf[LFSR_GRM_DSIZE];
err = lfsr_grm_xor(lfs, lfs->grm_d,
lfsr_data_fromgrm(grm, grm_buf));
if (err) {
return err;
}
lfsr_grm_xorgrm(lfs, lfs->grm_d, grm);
// fix our grm
// patch our grm
for (int j = 0; j < 2; j++) {
if (lfsr_mid_bid(lfs, grm->rms[j])
== lfsr_mid_bid(lfs, lfs_smax32(mdir->mid, 0))) {
@@ -6507,12 +6507,8 @@ static int lfsr_mdir_commit(lfs_t *lfs, lfsr_mdir_t *mdir,
}
}
// xor our fix into our gdelta
err = lfsr_grm_xor(lfs, lfs->grm_d,
lfsr_data_fromgrm(grm, grm_buf));
if (err) {
return err;
}
// xor our patch into our gdelta
lfsr_grm_xorgrm(lfs, lfs->grm_d, grm);
}
}