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alloc: Simplified lookahead-relative block calculation

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Based on what we implemented for the preerase gbmap known window check,
adding one block_count before mod is way simpler than a negative-friendly
mod in C.

Saves a bit of code:

                    code          stack          ctx
  before:          35260           2136          660
  after:           35256 (-0.0%)   2136 (+0.0%)  660 (+0.0%)

                    code          stack          ctx
  gbmap before:    38616           2144          776
  gbmap after:     38612 (-0.0%)   2144 (+0.0%)  776 (+0.0%)

                    code          stack          ctx
  preerase before: 39280           2168          796
  preerase after:  39276 (-0.0%)   2168 (+0.0%)  796 (+0.0%)
This commit is contained in:
Christopher Haster
2026-01-04 00:59:17 -06:00
parent 29550900f2
commit 340b786e6b
1 changed files with 4 additions and 11 deletions
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lfs3.c
+4 -11
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@@ -10899,16 +10899,10 @@ static inline void lfs3_alloc_discard(lfs3_t *lfs3) {
// mark a block as in-use
#ifndef LFS3_RDONLY
static void lfs3_alloc_setinuse(lfs3_t *lfs3, lfs3_block_t block) {
// TODO can this be simplified?
// translate to lookahead-relative
lfs3_block_t block_ = ((
(lfs3_sblock_t)(block - lfs3->lookahead.window)
// we only need this mess because C's mod is actually rem, and
// we want real mod in case block_ goes negative
% (lfs3_sblock_t)lfs3->block_count)
+ (lfs3_sblock_t)lfs3->block_count)
% (lfs3_sblock_t)lfs3->block_count;
lfs3_block_t block_
= (block + lfs3->block_count - lfs3->lookahead.window)
% lfs3->block_count;
if (block_ < 8*lfs3->cfg->lookahead_size) {
// mark as in-use
@@ -11444,8 +11438,7 @@ static int lfs3_alloc_preerase(lfs3_t *lfs3) {
//
// we're only actually successful if the gbmap didn't allocate
// the block we were trying to erase
// TODO can this be simplified?
if (((block+lfs3->block_count - lfs3->gbmap.window)
if (((block + lfs3->block_count - lfs3->gbmap.window)
% lfs3->block_count)
< lfs3->gbmap.known) {
// increment preeraser