Use twiggy to analyze contract binaries for size optimization opportunities

[cmichi]

Credit for this idea goes to @athei. ink! is currently mostly optimized for speed rather than code size. We can use the twiggy tool to analyze the contract binaries for size optimization opportunities.

We should use the tool to inspect our example contracts to find out where to start optimizing.

1. Install @athei's twiggy fork

cargo install --git https://github.com/athei/twiggy

2. Compile a contract with debug symbols (currently cargo contract master is needed for this)

cargo +nightly contract build --generate code-only --keep-debug-symbols

3. Analyze with twiggy

twiggy dominators target/ink/erc20.wasm
twiggy monos target/ink/erc20.wasm
twiggy top target/ink/erc20.wasm

You can ignore the "name" section in your analysis, those are the debug symbols (function names) which are removed in a real contract.

More info on twiggy can be found here: https://rustwasm.github.io/twiggy/.

[cmichi]

I'm closing this issue, since we've now created a couple of follow-up issues (see paritytech/substrate#9354 for the tracking issue).

As a sidenote I'm adding that

RUSTFLAGS="-Zsymbol-mangling-version=v0" cargo +nightly llvm-lines --release

will show you generics monomorphization bloat (source).