1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
|
# Compilation Pipeline
For a simple single-file program, the compilation process has a dependency
graph that looks like this:
```
+----------+ transpile +------------+ generate arg parser
| foo.tm.h | <----------- | foo.tm | -------------
+----------+ +------------+ |
| | | transpile |
| | v |
| | +------------+ |
| | | foo.tm.c | +--------------------+
| | +------------+ | main() entry point |
| | | +--------------------+
| | compile v |
| | +------------+ |
| +----------------->| foo.tm.o | |
| +------------+ |
| | link |
| v |
| compile +------------+ compile |
+---------------------> | foo | <------------+
+------------+
```
For a more complicated example, imagine `foo.tm` imports `baz.tm` and both are
being compiled into a shared library, `libfoo.so`:
```
+---------------------------------------+
| |
+----------+ transpile +------------+ |
+- | baz.tm.h | <----------- | baz.tm | -+-------------------------+
| +----------+ +------------+ | |
| | | | |
| | | transpile | |
| | v | |
| | +------------+ | |
| | | baz.tm.c | | |
| | +------------+ | |
| | | | |
| | | compile | |
| | v | |
| | compile +------------+ | |
| +---------------------> | baz.tm.o | | |
| +------------+ | |
| | | |
| | link | compile |
| v v |
| compile +--------------------------------------+ |
| +---------------------> | libfoo.so | |
| | +--------------------------------------+ |
| | ^ |
| | | link |
| | | |
| +----------+ transpile +------------+ | |
| | foo.tm.h | <----------- | foo.tm | | |
| +----------+ +------------+ | |
| | | | |
| | | transpile | |
| | v | |
| | +------------+ | type info |
| | | foo.tm.c | <+-------------------------+
| | +------------+ |
| | | |
| | | compile |
| | v |
| | compile +------------+ |
+----+---------------------> | foo.tm.o | -+
| +------------+
| compile ^
+-------------------------+
```
These dependency graphs are relatively complicated-looking, but here are some
rough takeaways:
1) Header files are a dependency for many parts of the process, so it's
good to transpile them as early as possible.
2) Once all the header files are available,
compiled into their object files in parallel. This is by far the
slowest part of compilation (invoking the C compiler), so it benefits
the most from parallelization.
3) After all object files are compiled, the last step is to link them
all together (fast and simple).
To sastisfy these requirements as efficiently as possible, the approach taken
below is to first transpile all header files sequentially (this could be
parallelized, but is probably faster than the overhead of forking new
processes), then fork a new process for each dependency to transpile and
compile it to an object file. Then, wait for all child processes to finish and
link the resulting object files together.
## Phase 1 (sequential transpilation):
```
+--------+ +--------+
| foo.tm | | baz.tm |
+--------+ +--------+
| | |
+--------------+ |
| |
v v
+----------+ +----------+
| foo.tm.h | | baz.tm.h |
+----------+ +----------+
```
## Phase 2 (parallel transpilation/compilation):
```
################################ ################################
# Process 1 # # Process 2 #
# +--------+ +----------+ # # +----------+ +--------+ #
# | foo.tm | | foo.tm.h | # # | baz.tm.h | | baz.tm | #
# +--------+ | baz.tm.h | # # +----------+ +--------+ #
# | +----+-----+ # # | | #
# v | # # | v #
# +----------+ | # # | +----------+ #
# | foo.tm.c | | # # | | baz.tm.c | #
# +----------+ | # # | +----------+ #
# | | # # | | #
# +------+------+ # # +--------+ #
# | # # | #
# v # # v #
# +----------+ # # +----------+ #
# | foo.tm.o | # # | baz.tm.o | #
# +----------+ # # +----------+ #
################################ ################################
```
## Phase 3 (linking a shared object file library):
```
+----------+ +----------+
| foo.tm.o | | baz.tm.o |
+----------+ +----------+
| |
+--------+--------+
|
v
+-----------+
| libfoo.so |
+-----------+
```
## Phase 3 (linking an executable):
```
+----------+ +----------+ +--------+ +--------+
| foo.tm.o | | baz.tm.o | | foo.tm | | baz.tm |
+----------+ +----------+ +--------+ +--------+
| | | |
+--------+--------+ +----+-----+
| link | Figure out command line args
v v
+-----+ compile +-------------------------+
| foo |<-------------| main() function for exe |
+-----+ +----------+--------------+
| foo.tm.h |
+----------+
| baz.tm.h |
+----------+
```
|
