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|
//! Workspace-internal `bench_cell!` implementation for the `mingling_bench`
//! harness (compiled only with the `bench_support` feature).
use proc_macro::TokenStream;
use quote::quote;
use syn::parse::{Parse, ParseStream};
use syn::{Ident, LitStr, Result as SynResult, Token, bracketed};
use crate::systems::dispatch_auto;
use crate::systems::dispatch_list_gen::gen_dispatch_args;
use crate::systems::dispatch_phf_gen::gen_dispatch_args_phf;
use crate::systems::dispatch_tree_gen::gen_dispatch_args_trie;
struct BenchCellInput {
strategy: Ident,
module: Ident,
entries: Vec<(LitStr, Ident)>,
}
impl Parse for BenchCellInput {
fn parse(input: ParseStream<'_>) -> SynResult<Self> {
let strategy = input.parse()?;
input.parse::<Token![,]>()?;
let module = input.parse()?;
input.parse::<Token![,]>()?;
let content;
bracketed!(content in input);
let mut entries = Vec::new();
while !content.is_empty() {
let name = content.parse()?;
content.parse::<Token![=>]>()?;
let disp = content.parse()?;
entries.push((name, disp));
if content.is_empty() {
break;
}
content.parse::<Token![,]>()?;
}
Ok(Self {
strategy,
module,
entries,
})
}
}
pub(crate) fn bench_cell_impl(input: TokenStream) -> TokenStream {
let input = syn::parse_macro_input!(input as BenchCellInput);
let entries: Vec<(String, String, String)> = input
.entries
.iter()
.map(|(name, disp)| (name.value(), disp.to_string(), String::new()))
.collect();
let (dispatch, extra, chosen) = match input.strategy.to_string().as_str() {
"dispatch_linear" => (gen_dispatch_args(&entries), quote! {}, "dispatch_linear"),
"dispatch_tree" => {
let (d, e) = gen_dispatch_args_trie(&entries);
(d, e, "dispatch_tree")
}
"dispatch_phf" => (gen_dispatch_args_phf(&entries), quote! {}, "dispatch_phf"),
"dispatch_auto" => match dispatch_auto::select_strategy(&entries) {
dispatch_auto::DispatchStrategy::Linear => {
(gen_dispatch_args(&entries), quote! {}, "dispatch_linear")
}
dispatch_auto::DispatchStrategy::Trie => {
let (d, e) = gen_dispatch_args_trie(&entries);
(d, e, "dispatch_tree")
}
dispatch_auto::DispatchStrategy::Phf => {
(gen_dispatch_args_phf(&entries), quote! {}, "dispatch_phf")
}
},
other => panic!("bench_cell: unknown strategy `{other}`"),
};
// Keep the generated dispatch out of the harness loop's inline budget:
// the loop calls it once per iteration, and large tables (hundreds of
// arms) would otherwise make LLVM attempt to inline a huge function into
// the 50k-iteration loop, exploding compile time and memory. Production
// codegen would not inline such functions either. The trie generator
// also emits its shared `__trie_fallback` method via `extra`, so parse
// the whole item list (a `syn::File`) and annotate the first function
// (dispatch_args).
let mut file: syn::File = syn::parse2(dispatch)
.unwrap_or_else(|e| panic!("bench_cell: generated dispatch_args failed to parse: {e}"));
if let Some(syn::Item::Fn(dispatch_fn)) = file.items.first_mut() {
dispatch_fn.attrs.push(syn::parse_quote!(#[inline(never)]));
}
let dispatch = quote!(#file);
// The trie fallback is a generic method that must live in an inherent
// impl of the cell type (it references no `Self` associated types).
let extra_impl = if extra.is_empty() {
quote! {}
} else {
quote! {
impl X {
#extra
}
}
};
let module = &input.module;
let name_lits: Vec<proc_macro2::Literal> = input
.entries
.iter()
.map(|(name, _)| proc_macro2::Literal::string(&name.value()))
.collect();
let mut dispatchers = proc_macro2::TokenStream::new();
for (_, disp) in &input.entries {
dispatchers.extend(quote! {
#[derive(Default)]
pub struct #disp;
impl Dispatcher<X> for #disp {
fn begin(&self, _args: Vec<String>) -> ChainProcess<X> {
ChainProcess::Ok((AnyOutput::new(Dummy), NextProcess::Chain))
}
}
});
}
quote! {
pub mod #module {
use ::mingling::{AnyOutput, ChainProcess, Dispatcher, Grouped, NextProcess};
#dispatchers
#[derive(Clone, Copy)]
pub struct X;
unsafe impl Grouped<X> for X {
fn member_id() -> X {
X
}
}
pub struct Dummy;
unsafe impl Grouped<X> for Dummy {
fn member_id() -> X {
X
}
}
pub struct EntryFallback(pub Vec<String>);
unsafe impl Grouped<X> for EntryFallback {
fn member_id() -> X {
X
}
}
impl crate::BenchDispatch for X {
type Enum = X;
fn build_entry_fallback(args: Vec<String>) -> AnyOutput<Self::Enum> {
AnyOutput::new(EntryFallback(args))
}
#dispatch
}
#extra_impl
pub static NAMES: &[&str] = &[#(#name_lits),*];
/// The strategy this cell was generated with (for `dispatch_auto`
/// cells this is the auto-selected strategy).
pub static STRATEGY: &str = #chosen;
/// Time dispatch over a corpus; returns (hit_ns, miss_ns), best of
/// 5 rounds of 50k dispatches.
pub fn measure(hits: &[Vec<String>], misses: &[Vec<String>]) -> (f64, f64) {
let mut acc = 0usize;
for i in 0..2_000 {
let r = <X as crate::BenchDispatch>::dispatch_args(&hits[i % hits.len()]);
acc = acc.wrapping_add(match r {
Ok(_) => 1,
Err(_) => 2,
});
}
std::hint::black_box(acc);
let time = |corpus: &[Vec<String>]| -> f64 {
let mut best = f64::MAX;
for _ in 0..5 {
let start = std::time::Instant::now();
let mut acc = 0usize;
for i in 0..50_000 {
let r = <X as crate::BenchDispatch>::dispatch_args(
&corpus[i % corpus.len()],
);
acc = acc.wrapping_add(match r {
Ok(_) => 1,
Err(_) => 2,
});
}
let el = start.elapsed().as_nanos() as f64 / 50_000.0;
std::hint::black_box(acc);
if el < best {
best = el;
}
}
best
};
(time(hits), time(misses))
}
}
}
.into()
}
|
