Mercurial > hg-old > index.cgi

annotate doc/internals.txt @ 448:5cccf90bf838 3.0 tip

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Fixed bug with complex external references generating invalid relocations in the object file
author lost@l-w.ca
date Fri, 05 Nov 2010 22:27:00 -0600
parents 656630007668
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
331
ed3553296580 Port manual forward with corrections from Jason Law
lost
parents:
diff changeset
1 LWASM Internals
ed3553296580 Port manual forward with corrections from Jason Law
lost
parents:
diff changeset
2 ===============
ed3553296580 Port manual forward with corrections from Jason Law
lost
parents:
diff changeset
3
ed3553296580 Port manual forward with corrections from Jason Law
lost
parents:
diff changeset
4 LWASM is a table-driven assembler that notionally uses two passes. However,
ed3553296580 Port manual forward with corrections from Jason Law
lost
parents:
diff changeset
5 it implements its assembly in several passes as follows.
ed3553296580 Port manual forward with corrections from Jason Law
lost
parents:
diff changeset
6
333
ebff3a3e8fa6 Updated internals to describe the multi-pass architecture
lost
parents: 331
diff changeset
7 Pass 1
ebff3a3e8fa6 Updated internals to describe the multi-pass architecture
lost
parents: 331
diff changeset
8 ------
331
ed3553296580 Port manual forward with corrections from Jason Law
lost
parents:
diff changeset
9
333
ebff3a3e8fa6 Updated internals to describe the multi-pass architecture
lost
parents: 331
diff changeset
10 This pass reads the entire source code and parses each line into an internal
ebff3a3e8fa6 Updated internals to describe the multi-pass architecture
lost
parents: 331
diff changeset
11 representation. Macros, file inclusions, and conditional assembly
363
d96c30e60ddf Added pass2 and various supporting logic including symbol lookups
lost@starbug
parents: 338
diff changeset
12 instructions are resolved at this point as well. Instructions with known
d96c30e60ddf Added pass2 and various supporting logic including symbol lookups
lost@starbug
parents: 338
diff changeset
13 sizes will have their sizes resolved at this point.
333
ebff3a3e8fa6 Updated internals to describe the multi-pass architecture
lost
parents: 331
diff changeset
14
ebff3a3e8fa6 Updated internals to describe the multi-pass architecture
lost
parents: 331
diff changeset
15 Pass 2
ebff3a3e8fa6 Updated internals to describe the multi-pass architecture
lost
parents: 331
diff changeset
16 ------
331
ed3553296580 Port manual forward with corrections from Jason Law
lost
parents:
diff changeset
17
363
d96c30e60ddf Added pass2 and various supporting logic including symbol lookups
lost@starbug
parents: 338
diff changeset
18 Check all exported symbols for validity and set them as imports if the
d96c30e60ddf Added pass2 and various supporting logic including symbol lookups
lost@starbug
parents: 338
diff changeset
19 assembler state says so. Also resolve all symbol references in all
d96c30e60ddf Added pass2 and various supporting logic including symbol lookups
lost@starbug
parents: 338
diff changeset
20 expressions to be direct references either to the symbol table or
d96c30e60ddf Added pass2 and various supporting logic including symbol lookups
lost@starbug
parents: 338
diff changeset
21 to the import list.
331
ed3553296580 Port manual forward with corrections from Jason Law
lost
parents:
diff changeset
22
333
ebff3a3e8fa6 Updated internals to describe the multi-pass architecture
lost
parents: 331
diff changeset
23 Pass 3
ebff3a3e8fa6 Updated internals to describe the multi-pass architecture
lost
parents: 331
diff changeset
24 ------
ebff3a3e8fa6 Updated internals to describe the multi-pass architecture
lost
parents: 331
diff changeset
25
ebff3a3e8fa6 Updated internals to describe the multi-pass architecture
lost
parents: 331
diff changeset
26 This pass resolves all instruction sizes that can be resolved without
365
6a98cc90c14f Added resolve passes
lost@starbug
parents: 363
diff changeset
27 forcing any instruction sizes. This pass will run repeatedly until no
6a98cc90c14f Added resolve passes
lost@starbug
parents: 363
diff changeset
28 no new resolution occurs.
331
ed3553296580 Port manual forward with corrections from Jason Law
lost
parents:
diff changeset
29
333
ebff3a3e8fa6 Updated internals to describe the multi-pass architecture
lost
parents: 331
diff changeset
30 Pass 4
ebff3a3e8fa6 Updated internals to describe the multi-pass architecture
lost
parents: 331
diff changeset
31 ------
331
ed3553296580 Port manual forward with corrections from Jason Law
lost
parents:
diff changeset
32
365
6a98cc90c14f Added resolve passes
lost@starbug
parents: 363
diff changeset
33 Work through all un-resolved instructions and force sizes. After each size
6a98cc90c14f Added resolve passes
lost@starbug
parents: 363
diff changeset
34 is forced, try re-resolving all other instructions. This is done starting
6a98cc90c14f Added resolve passes
lost@starbug
parents: 363
diff changeset
35 at the beginning of the source and working forward. If any instruction does
6a98cc90c14f Added resolve passes
lost@starbug
parents: 363
diff changeset
36 not resolve when forced, an error will be thrown.
367
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
37
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
38 Pass 5
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
39 ------
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
40
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
41 Constantize all line addresses and throw errors if any cannot be. This
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
42 pass will repeat until no further lines addresses are reduced to constants
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
43 at which time all lines will be checked for constant-ness.
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
44
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
45 Pass 6
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
46 ------
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
47
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
48 Finalize all expressions related to instructions. Carp about any that
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
49 cannot be reduced to a usable form. That means, for the non-object target
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
50 all expressions must resolve to a constant. For the object form, all
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
51 expressions must resolve to symbol references and constants. Those symbol
34dfc9747f23 Reduction passes complete
lost@starbug
parents: 365
diff changeset
52 references may be internal or external.
368
656630007668 Emit pass
lost@starbug
parents: 367
diff changeset
53
656630007668 Emit pass
lost@starbug
parents: 367
diff changeset
54 Pass 7
656630007668 Emit pass
lost@starbug
parents: 367
diff changeset
55 ------
656630007668 Emit pass
lost@starbug
parents: 367
diff changeset
56
656630007668 Emit pass
lost@starbug
parents: 367
diff changeset
57 Emit object code for each line for later output.