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A few micro-optimizations #6

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merged 1 commit into from
Sep 11, 2019
Merged

A few micro-optimizations #6

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33 changes: 12 additions & 21 deletions src/dispatcher.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@ pub(crate) struct Dispatcher {

impl ToTokens for Dispatcher {
fn to_tokens(&self, tokens: &mut TokenStream) {
let function_arguments = &self.signature.inputs.iter();
let function_arguments = self.signature.inputs.iter();
let argument_names = &self
.signature
.inputs
Expand Down Expand Up @@ -48,50 +48,41 @@ impl ToTokens for Dispatcher {
let return_if_detected = self.functions.iter().map(|(target, function)| {
let target_arch = target.target_arch();
let features_detected = target.features_detected();
let function_arguments = function_arguments.clone();
let argument_names = argument_names.clone();
quote! {
#target_arch
{
// wrap the function in an unsafe function with the same signature
unsafe fn unsafe_wrapper(#(#function_arguments),*) #returns {
#function(#(#argument_names),*)
}
if #features_detected {
return unsafe_wrapper
return #function
}
}
}
});
let default = &self.default;
let function_arguments = function_arguments.clone();
let argument_names = argument_names.clone();
quote! {
#(#return_if_detected)*
#[cfg(not(any(#(target_arch = #defaulted_arches),*)))]
{
unsafe fn unsafe_wrapper(#(#function_arguments),*) #returns {
#default(#(#argument_names),*)
}
return unsafe_wrapper
return #default
}
}
};
tokens.extend(quote! {
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::atomic::{AtomicPtr, Ordering};
type __fn_ty = unsafe fn (#(#argument_ty),*) #returns;
#[cold]
fn __get_fn() -> __fn_ty {
#feature_detection
}
static __DISPATCHED_FN: AtomicUsize = AtomicUsize::new(0usize);
let mut __current_ptr = __DISPATCHED_FN.load(Ordering::SeqCst);
if __current_ptr == 0 {
__current_ptr = unsafe { std::mem::transmute(__get_fn()) };
__DISPATCHED_FN.store(__current_ptr, Ordering::SeqCst);
#[cold]
unsafe fn __resolver_fn (#(#function_arguments),*) #returns {
let __current_fn = __get_fn();
__DISPATCHED_FN.store(__current_fn as *mut (), Ordering::SeqCst);
__current_fn(#(#argument_names),*)
}
static __DISPATCHED_FN: AtomicPtr<()> = AtomicPtr::new(__resolver_fn as *mut ());
let __current_ptr = __DISPATCHED_FN.load(Ordering::SeqCst);
unsafe {
let __current_fn = std::mem::transmute::<usize, __fn_ty>(__current_ptr);
let __current_fn = std::mem::transmute::<*mut (), __fn_ty>(__current_ptr);
__current_fn(#(#argument_names),*)
}
});
Expand Down
36 changes: 6 additions & 30 deletions src/target_clones.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ use proc_macro2::{Span, TokenStream};
use quote::{quote, ToTokens};
use syn::parse::{Parse, ParseStream, Result};
use syn::punctuated::Punctuated;
use syn::{token, Attribute, Block, FnArg, Ident, ItemFn, LitStr, Signature, Token, Visibility};
use syn::{token, Attribute, Block, Ident, ItemFn, LitStr, Signature, Token, Visibility};

pub(crate) struct Config {
targets: Vec<Target>,
Expand Down Expand Up @@ -39,36 +39,12 @@ impl ToTokens for FunctionClone<'_> {
.as_ref()
.map_or(TokenStream::new(), |x| x.target_features());
let signature = &self.signature;
let body = &self.body;
tokens.extend(if signature.unsafety.is_some() || self.target.is_none() {
quote! { #target_arch #target_features #signature #body }
} else {
let mut unsafe_signature = signature.clone();
unsafe_signature.unsafety = Some(token::Unsafe {
span: Span::call_site(),
});
unsafe_signature.ident = Ident::new("__unsafe_fn", Span::call_site());
let argument_names = &signature
.inputs
.iter()
.map(|x| {
if let FnArg::Typed(p) = x {
p.pat.as_ref()
} else {
unimplemented!("member fn not supported")
}
})
.collect::<Vec<_>>();
quote! {
#target_arch
#signature {
#target_features #unsafe_signature #body
unsafe {
__unsafe_fn(#(#argument_names),*)
}
}
}
let mut unsafe_signature = signature.clone();
unsafe_signature.unsafety = Some(token::Unsafe {
span: Span::call_site(),
});
let body = &self.body;
tokens.extend(quote! { #target_arch #target_features #unsafe_signature #body });
}
}

Expand Down