args_info: call get_args_info once per enum variant - #237
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For each variant of a subcommand enum, the generated ArgsInfo::get_args_info previously called <Ty>::get_args_info() twice (once for .name, once for .command), constructing a full CommandInfoWithArgs twice and discarding one. Call it once and reuse for both fields. This halves the per-variant construction work and, since get_args_info is inlined, removes a full duplicated CommandInfoWithArgs construction + drop from the emitted machine code. Behavior is identical.
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Hi there,
I'm experimenting with prompts for LLMs to finding code optimizations (size and speed), and ran it over this crate. It popped up with a few small improvements. This is one.
If inline saves 1,176 bytes
LLM generated below here:
In the derive-generated
ArgsInfo::get_args_info()for subcommand enums, eachvariant previously called
<Ty>::get_args_info()twice — once for.nameand once for
.command— constructing a fullCommandInfoWithArgsvalue twiceand discarding one. This PR calls it once and reuses the value for both fields.
get_args_info()returns a 9-fieldCommandInfoWithArgs<'static>that includesa heap
Vec<SubCommandInfo>(built and dropped). In the test binary this functionis inlined, so the full construction + drop body is emitted at each call site.
Before the change, each enum variant therefore emitted two inlined copies of the
construction; after, one. The redundant second copy is removed per variant.
The runtime benefit (half the construction work, one fewer
Vecallocation pervariant) holds regardless of inlining.