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Changed cat count discriminator to positive/negative counts

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- cat_count <  0 => single in-RAM buffer
- cat_count >= 0 => multiple concatenated datas

Note that cat_count=0 has the same effect whether or not you interpret
the cat as single or multiple datas.

Unlike, say, lfsr_data_t's size, the cat count does not mean the same
thing in both modes, so it doesn't really make sense to operate on the
count with bits masked off. This makes cat_count more like the signed
size/err union we use often.

The hope was better code generation for single/multiple cat checks. I
noticed some questionable code generation around checking the uint16_t's
sign bit and realized this might be a bit messy on 32-bit thumb. Sign
extension is in theory more common/cheaper on 32-bit ISAs, but I don't
know if the results are really conclusive:

  before: 33538          2632
  after:  33514 (-0.1%)  2632 (+0.0%)
This commit is contained in:
Christopher Haster
2024-05-18 13:02:46 -05:00
parent 52bd47f0e5
commit db2e4e9856
1 changed files with 10 additions and 33 deletions
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lfs.c
+10 -33
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@@ -1457,7 +1457,7 @@ static inline lfsr_data_t lfsr_data_fromlleb128(uint32_t word,
typedef struct lfsr_attr {
lfsr_tag_t tag;
uint16_t cat_count;
int16_t cat_count;
lfsr_srid_t weight;
// sign(size)=0 => single in-RAM buffer
// sign(size)=1 => multiple concatenated datas
@@ -1465,13 +1465,10 @@ typedef struct lfsr_attr {
const void *cat;
} lfsr_attr_t;
// cat can either be a simple in-RAM buffer or concatenated datas
#define LFSR_CAT_ISCAT 0x8000
#define LFSR_ATTR_(_tag, _weight, _cat, _cat_count) \
((lfsr_attr_t){ \
.tag=_tag, \
.cat_count=_cat_count, \
.cat_count=(uint16_t){_cat_count}, \
.weight=_weight, \
.cat=_cat})
@@ -1493,7 +1490,7 @@ static inline lfsr_attr_t lfsr_attr(
#define LFSR_ATTR_CAT_(_tag, _weight, _datas, _data_count) \
((lfsr_attr_t){ \
.tag=_tag, \
.cat_count=LFSR_CAT_ISCAT | (_data_count), \
.cat_count=-(uint16_t){_data_count}, \
.weight=_weight, \
.cat=_datas})
@@ -1513,34 +1510,14 @@ static inline lfsr_attr_t lfsr_attr(
sizeof((const lfsr_attr_t[]){__VA_ARGS__}) / sizeof(lfsr_attr_t)
// cat helpers
static inline bool lfsr_cat_isbuf(const void *cat, uint16_t cat_count) {
(void)cat;
return !(cat_count & LFSR_CAT_ISCAT);
}
static inline bool lfsr_cat_iscat(const void *cat, uint16_t cat_count) {
(void)cat;
return cat_count & LFSR_CAT_ISCAT;
}
static inline lfs_size_t lfsr_cat_size_(const void *cat, uint16_t cat_count) {
LFS_ASSERT(lfsr_cat_isbuf(cat, cat_count));
return cat_count;
}
static inline lfs_size_t lfsr_cat_count(const void *cat, uint16_t cat_count) {
LFS_ASSERT(lfsr_cat_iscat(cat, cat_count));
return cat_count & ~LFSR_CAT_ISCAT;
}
static inline lfs_size_t lfsr_cat_size(const void *cat, uint16_t cat_count) {
static inline lfs_size_t lfsr_cat_size(const void *cat, int16_t cat_count) {
// this gets a bit complicated for concatenated data
if (lfsr_cat_isbuf(cat, cat_count)) {
if (cat_count >= 0) {
return cat_count;
} else {
const lfsr_data_t *datas = cat;
lfs_size_t data_count = lfsr_cat_count(cat, cat_count);
lfs_size_t data_count = -cat_count;
lfs_size_t size = 0;
for (lfs_size_t i = 0; i < data_count; i++) {
size += lfsr_data_size(datas[i]);
@@ -1552,17 +1529,17 @@ static inline lfs_size_t lfsr_cat_size(const void *cat, uint16_t cat_count) {
// cat <-> bd interactions
static int lfsr_bd_progcat(lfs_t *lfs,
lfs_block_t block, lfs_size_t off,
const void *cat, uint16_t cat_count,
const void *cat, int16_t cat_count,
uint32_t *cksum_) {
// direct buffer?
if (lfsr_cat_isbuf(cat, cat_count)) {
if (cat_count >= 0) {
return lfsr_bd_prog(lfs, block, off, cat, cat_count,
cksum_);
// indirect concatenated data?
} else {
const lfsr_data_t *datas = cat;
lfs_size_t data_count = lfsr_cat_count(cat, cat_count);
lfs_size_t data_count = -cat_count;
for (lfs_size_t i = 0; i < data_count; i++) {
int err = lfsr_bd_progdata(lfs, block, off, datas[i],
cksum_);
@@ -2694,7 +2671,7 @@ static int lfsr_rbyd_appendtag(lfs_t *lfs, lfsr_rbyd_t *rbyd,
}
static int lfsr_rbyd_appendcat(lfs_t *lfs, lfsr_rbyd_t *rbyd,
const void *cat, uint16_t cat_count) {
const void *cat, int16_t cat_count) {
uint32_t cksum_ = rbyd->cksum;
int err = lfsr_bd_progcat(lfs, rbyd->blocks[0], lfsr_rbyd_eoff(rbyd),
cat, cat_count,