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Adopted mask bits for tag lookup/append

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This lets us cram in one more mask for potential redund bits:

  name                 tag    mask
  LFSR_TAG_MASK0    0x0000  0x0fff  ---- 1111 1111 1111
  LFSR_TAG_MASK2    0x1000  0x0ffc  ---- 1111 1111 11--
  LFSR_TAG_MASK8    0x2000  0x0f00  ---- 1111 ---- ----
  LFSR_TAG_MASK12   0x3000  0x0000  ---- ---- ---- ----
                                    '.-' '.-' '---.---'
                          mode bits -'    |       |   ^
                            suptype ------'       |   |
                            subtype --------------'   |
                        redund bits ------------------'

I toyed around with a bitwise alternative to the lookup table, but
couldn't come up with anything simpler than these:

- 0xfff & ~((((1<<((i>>1)*8))-1) << ((i&1)*4)) | ((1<<(i*2))-1))
- 0xfff & ~((1 << (((i>>1)*8)+((i&1)<<(1+(i>>1)))))-1)
- 0xfff & ~((1<<(2*i*i))-1) (requires multiply and 32-bit shift)

---

This also replaces the mdir/rbyd/btree/mtree lookup/sublookup/suplookup
functions with a single flexible lookup function that accepts tag masks.

This ended up adding a bit of code/stack (the extra NULL args are
surprisingly pricey), but will hopefully make the redund bits
easier/cheaper to use:

           code          stack          ctx
  before: 35548           2472          636
  after:  35584 (+0.1%)   2480 (+0.3%)  636 (+0.0%)
This commit is contained in:
Christopher Haster
2025-04-18 02:51:03 -05:00
parent 8f1ccf089e
commit 200830aafe
6 changed files with 1451 additions and 1502 deletions
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tests/test_files.toml
+3 -3
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@@ -979,7 +979,7 @@ code = '''
// delete any bshrub/btree
lfsr_mdir_commit(&lfs, &file.b.o.mdir, LFSR_RATTRS(
LFSR_RATTR(
LFSR_TAG_RM | LFSR_TAG_SUB | LFSR_TAG_STRUCT, 0))) => 0;
LFSR_TAG_RM | LFSR_TAG_MASK8 | LFSR_TAG_STRUCT, 0))) => 0;
lfsr_file_close(&lfs, &file) => 0;
@@ -1111,7 +1111,7 @@ code = '''
.rattr_count=1})))) => 0;
lfsr_mdir_commit(&lfs, &file.b.o.mdir, LFSR_RATTRS(
LFSR_RATTR_SHRUB(
LFSR_TAG_SUB | LFSR_TAG_BSHRUB, 0,
LFSR_TAG_MASK8 | LFSR_TAG_BSHRUB, 0,
&file.b.shrub_))) => 0;
lfsr_file_close(&lfs, &file) => 0;
@@ -1234,7 +1234,7 @@ code = '''
LFSR_RATTR(LFSR_TAG_RM, -1))) => 0;
lfsr_mdir_commit(&lfs, &file.b.o.mdir, LFSR_RATTRS(
LFSR_RATTR_BTREE(
LFSR_TAG_SUB | LFSR_TAG_BTREE, 0,
LFSR_TAG_MASK8 | LFSR_TAG_BTREE, 0,
&file.b.shrub))) => 0;
lfsr_file_close(&lfs, &file) => 0;