Significantly reduce compile time for googletest internal tests

[arichardson]

Summary

Clang's optimizer spends a really long time on these tests at -O2, so we now
use -O0 instead. This reduces the -j32 time for lib/googletest/test from 131s
to 29s. Using -O0 also reduces the disk usage from 144MB (at -O2) / 92MB (at
-O1) to 82MB.

[mjg]

Do we even need this in default installs? As in, what happens if this does not get compiled at all?

[arichardson]

Yes I'd also vote for turning this off by default. I have an open review that I need to update: https://reviews.freebsd.org/D26067

[dim]

Might as well go full -O0. :)

[arichardson]

In D26751#599033, @dim wrote:

Might as well go full -O0. :)

Running the tests at -O2 in QEMU amd64 took:
44.52 real 27.28 user 13.96 sys
Changing it to -O1 makes it
91.80 real 73.32 user 14.28 sys
and -O0 results in
109.46 real 90.08 user 14.38 sys

So we might as well use -O0 since it doesn't seem to make much of a run time difference but has a big impact on compile time :)

[ngie]

In D26751#599053, @arichardson wrote:

In D26751#599033, @dim wrote:

Might as well go full -O0. :)

Running the tests at -O2 in QEMU amd64 took:
44.52 real 27.28 user 13.96 sys
Changing it to -O1 makes it
91.80 real 73.32 user 14.28 sys
and -O0 results in
109.46 real 90.08 user 14.38 sys

So we might as well use -O0 since it doesn't seem to make much of a run time difference but has a big impact on compile time :)

What is the disk space size like in each case?

[arichardson]

In D26751#599214, @ngie wrote:

In D26751#599053, @arichardson wrote:

In D26751#599033, @dim wrote:

Might as well go full -O0. :)

Running the tests at -O2 in QEMU amd64 took:
44.52 real 27.28 user 13.96 sys
Changing it to -O1 makes it
91.80 real 73.32 user 14.28 sys
and -O0 results in
109.46 real 90.08 user 14.38 sys

So we might as well use -O0 since it doesn't seem to make much of a run time difference but has a big impact on compile time :)

What is the disk space size like in each case?

O0:
82M /home/alr48/cheri/output/freebsd-amd64/usr/tests/lib/googletest/

O1:
92M /home/alr48/cheri/output/freebsd-amd64/usr/tests/lib/googletest/

O2:
144M /home/alr48/cheri/output/freebsd-amd64/usr/tests/lib/googletest/

So it seems like the aggressive inlining at -O2 also increases the disk space requirements.

[arichardson]

Use -O0 instead and update comment

[ngie]

No blocking concerns.

lib/googletest/tests/Makefile.inc

10–13 ↗

(On Diff #78489)

I'd add "At time of writing" to this statement and mention "amd64"/"arm64" for reference, given that this might change in the future or fluctuate.

15–17 ↗

(On Diff #78489)

What does -g0 do? I really wish the clang manpage/documentation was better about describing this like gcc's is.

[arichardson]

lib/googletest/tests/Makefile.inc

10–13 ↗

(On Diff #78489)

sounds good, will do.

15–17 ↗

(On Diff #78489)

-g0 disables debug info (gcc-compatible flag).