Add profile.release to enable link time optimizations

[rawhuul]

Hi, the default profile.release for Cargo.toml is:

[profile.release]
opt-level = 3
debug = false
split-debuginfo = '...'  # Platform-specific.
strip = "none"
debug-assertions = false
overflow-checks = false
lto = false
panic = 'unwind'
incremental = false
codegen-units = 16
rpath = false

It doesn't enable LTO which can be achieved easily by adding:

[profile.release]
opt-level = 3  <--- Can be changed to 's' for further binary size reduction
debug = false
lto = "fat"  <--- Enables LTO
strip = "debuginfo"
panic = 'unwind'
incremental = false
codegen-units = 1  <--- It impacts size of binary
rpath = false

As you can see in this screenshot, the first build binary has release size of 56mb and after applying opt-level='s', the binary size gets down to 32mb and the last build results in 36mb which performs LTO only

[tarkah]

Hey @rawhuul thanks for the suggestion! I'd like to see us create a special profile specifically called packaging that can use these optimizations.

I use release profile a lot while developing and LTO will really kill compile times there, so I think we should only enable when "packaging" the app for release

[rawhuul]

Yup, you are right. This can be achieved easily, this feature is stable from rustc v1.57

[profile.packaging]
inherits = "release"
lto = “fat”