Add zld linker

[CleanCut]

• Add new zld linker for mac.
• Add fatal messages to setup script.

I must be doing something wrong. Even though zld appears to both be installed correctly and the config file appears to be formatted correctly, I see absolutely no difference in compile times on my mac. What am I missing? To test, I'm using this repositories' code with the .add_default_plugins() line commented out so that the app immediately exits after running each system once.

/cc @ashneverdawn @cart @lachlansneff from bevyengine/bevy#312

[ashneverdawn]

The filename should be just config with no extension, rather than config.fast

[ashneverdawn]

Also, as an unrelated side note, you may want to use /usr/local/bin/zld for the path instead of /usr/local/Cellar/zld/1.1.0/bin/zld. (See: bevyengine/bevy#314)

[CleanCut]

The filename should be just config with no extension, rather than config.fast

@ashneverdawn I should clarify that this is after running ./setup which renames .cargo/config.fast to .cargo/config and installs zld. I see no effect whatsoever.

I will update to using the alias, but it's still rather academic if it has no effect. 😢

[CleanCut]

I made the same alias change as in bevyengine/bevy#314

---

I tested again...still not seeing any effect. To avoid confusion, here is my testing procedure:

• Clone the repo: git clone git@github.com:CleanCut/bevy_template
• Checkout the zld branch: pushd bevy_template && git checkout zld && popd
• Make a copy of the repository (I don't test in the original clone): cp -r bevy_template mactest
• Prep the copied repository:
  • cd mactest
  • ./setup
  • Manually verify that .cargo/config is now in place and looks correct.
  • Comment out .add_default_plugins() in src/main.rs so the app exits after running each system once.
• Do the testing in this mactest project, for example:
  • time cargo run (repeat with and without cargo clean)
  • Edit a line in src/main.rs and run time cargo run, rinse & repeat.

Compared to the same commands in another copy of the project without running ./setup (and not having .cargo/config in place), I see no difference in fresh or incremental compile times.

[ashneverdawn]

I cloned the repo and did some tests for incremental compiles:

Case 1: config without zld, without .add_default_plugins()
Case 2: config without zld, with .add_default_plugins()

Case 3: config with zld, without .add_default_plugins()
Case 4: config with zld, with .add_default_plugins()

Case 1	Case 2	Case 3	Case 4
3.05	19.47	2.79	13.97
5.31	17.81	2.16	12.32
3.92	14.70	2.67	13.14
2.37	13.89	2.34	12.45
3.51	16.50	2.27	13.17

I'm running it on a 2014 mac:
2.6 GHz Dual-Core Intel Core i5
8 GB 1600 MHz DDR3
Intel Iris 1536 MB

So, I definitely see a speed improvement on my end. What hardware are you running it on?

[CleanCut]

After discussion with @ashneverdawn on Discord and comparing notes, we discovered that several factors were adding noise to my measurements: 1) using time was adding some startup-time noise, 2) Using time + cargo run was adding some program runtime noise, 3) I am on much higher-end hardware, compressing the total times to begin with, and 4) disabling .add_default_plugins() made my compile sufficiently fast that the noise was dominating the measurements (I was seeing 1.3s-1.7s with and without zld).

By eliminating factors 1, 2 and 4 (only looking at the cargo-reported build time and including .add_default_plugins), I can now see a measurable (though not particularly impressive) difference in my testing:

Case A: Without zld, with .add_default_plugins() (equivalent to Case 2 above) - Average 7.594s
Case B: With zld, with .add_default_plugins() (equivalent to Case 4 above) - Average 6.51s

Case A	Case B
7.54	6.70
7.57	6.44
7.59	6.44
7.60	6.47
7.67	6.50

That's about 15% faster with zld.