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Tweaked struct tag encoding so b*/m* tags are earlier

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These b*/m* struct tags have a common pattern that would be good to
emphasize in the encoding. The later struct tags get a bit more messy as
they leave space for future possible extensions.

New encoding:

  LFSR_TAG_STRUCT         0x03tt  v--- --11 -ttt ttrr

  LFSR_TAG_DATA           0x0300  v--- --11 ---- ----
  LFSR_TAG_BLOCK          0x0304  v--- --11 ---- -1rr
  LFSR_TAG_BSHRUB         0x0308  v--- --11 ---- 1---
  LFSR_TAG_BTREE          0x030c  v--- --11 ---- 11rr
  LFSR_TAG_MROOT          0x0310  v--- --11 ---1 --rr
  LFSR_TAG_MDIR           0x0314  v--- --11 ---1 -1rr
  LFSR_TAG_MSHRUB*        0x0318  v--- --11 ---1 1---
  LFSR_TAG_MTREE          0x031c  v--- --11 ---1 11rr
  LFSR_TAG_DID            0x0320  v--- --11 --1- ----
  LFSR_TAG_BRANCH         0x032c  v--- --11 --1- 11rr

  * Hypothetical

Note that all shrubs currently end with 1---, and all btrees, including
the awkward branch tag, end with 11rr.

This had no impact on code size:

           code          stack
  before: 33564           2816
  after:  33564 (+0.0%)   2816 (+0.0%)
This commit is contained in:
Christopher Haster
2024-04-24 02:14:20 -05:00
parent 5fa85583cd
commit 6e5d314c20
7 changed files with 45 additions and 45 deletions
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lfs.c
+5 -5
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@@ -742,11 +742,11 @@ enum lfsr_tag {
LFSR_TAG_BLOCK = 0x0304,
LFSR_TAG_BSHRUB = 0x0308,
LFSR_TAG_BTREE = 0x030c,
LFSR_TAG_DID = 0x0310,
LFSR_TAG_BRANCH = 0x031c,
LFSR_TAG_MROOT = 0x0321,
LFSR_TAG_MDIR = 0x0325,
LFSR_TAG_MTREE = 0x032c,
LFSR_TAG_MROOT = 0x0311,
LFSR_TAG_MDIR = 0x0315,
LFSR_TAG_MTREE = 0x031c,
LFSR_TAG_DID = 0x0320,
LFSR_TAG_BRANCH = 0x032c,
// user/sys attributes
LFSR_TAG_UATTR = 0x0400,