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Merge branch 'twiddle_optim' into 'master'

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Optimise twiddle index calculation

See merge request simulant/GLdc!159
This commit is contained in:
Luke Benstead 2025-04-12 05:59:35 +00:00
commit 0057076958
1 changed files with 28 additions and 19 deletions
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47
GL/texture.c
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@ -44,19 +44,27 @@ static struct TwiddleTable {
int32_t* table;
} TWIDDLE_TABLE = {0, 0, NULL};
int32_t twiddle_recurse(int32_t* table, int32_t stride, int32_t x, int32_t y, int32_t block_size, int32_t idx) {
int32_t prev_idx = idx;
if(block_size == 1) {
table[y * stride + x] = idx++;
} else {
block_size = block_size >> 1;
idx += twiddle_recurse(table, stride, x, y, block_size, idx);
idx += twiddle_recurse(table, stride, x, y + block_size, block_size, idx);
idx += twiddle_recurse(table, stride, x + block_size, y, block_size, idx);
idx += twiddle_recurse(table, stride, x + block_size, y + block_size, block_size, idx);
}
static void calc_twiddle_factors(uint32_t w, uint32_t h, uint32_t* maskX, uint32_t* maskY) {
*maskX = 0;
*maskY = 0;
int shift = 0;
return (idx - prev_idx);
for (; w > 1 || h > 1; w >>= 1, h >>= 1) {
if (w > 1 && h > 1) {
// Add interleaved X and Y bits
*maskX += 0x02 << shift;
*maskY += 0x01 << shift;
shift += 2;
} else if (w > 1) {
// Add a linear X bit
*maskX += 0x01 << shift;
shift += 1;
} else if (h > 1) {
// Add a linear Y bit
*maskY += 0x01 << shift;
shift += 1;
}
}
}
void build_twiddle_table(int32_t w, int32_t h) {
@ -66,15 +74,16 @@ void build_twiddle_table(int32_t w, int32_t h) {
TWIDDLE_TABLE.height = h;
int32_t idx = 0;
uint32_t idxX = 0, idxY = 0, maskX, maskY;
calc_twiddle_factors(w, h, &maskX, &maskY);
if(w < h) {
for(int32_t i = 0; i < h; i += w) {
idx += twiddle_recurse(TWIDDLE_TABLE.table, w, 0, i, w, idx);
}
} else {
for(int32_t i = 0; i < w; i += h) {
idx += twiddle_recurse(TWIDDLE_TABLE.table, w, i, 0, h, idx);
for (int32_t y = 0; y < h; y++) {
idxX = 0;
for (int32_t x = 0; x < w; x++) {
TWIDDLE_TABLE.table[idx++] = idxX | idxY;
idxX = (idxX - maskX) & maskX;
}
idxY = (idxY - maskY) & maskY;
}
}