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feat: lazily generate instanceFlags #275

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Merged
merged 6 commits into from
Nov 27, 2023
Merged

feat: lazily generate instanceFlags #275

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f4ae669
style: use find_map() instead of filter_map().next()
bnjbvr Nov 24, 2023
53b2ff5
feat: only generate instance flags globals when they're used
bnjbvr Nov 24, 2023
d96e5e6
Merge branch 'main' into dce-instanceflags
Nov 24, 2023
0e7f6a1
Merge branch 'main' into dce-instanceflags
Nov 25, 2023
e151895
Merge branch 'main' into dce-instanceflags
bnjbvr Nov 27, 2023
ce4ef6a
review: rename ensure_instance_flags to instance_flags
bnjbvr Nov 27, 2023
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17 changes: 17 additions & 0 deletions crates/js-component-bindgen/src/source.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,23 @@ impl Source {
}
}

pub fn prepend_str(&mut self, src: &str) {
// Infer the indent at start: it's the difference between the size of the first line, and
// its size if trimmed at the left. That raw difference is in number of spaces, not in
// units of indent; since each indent is 2 spaces, divide by 2 at the end.
let indent = self
.s
.lines()
.next()
.map_or(0, |line| (line.len() - line.trim_start().len()) / 2);
let mut new_start = Source {
s: String::new(),
indent,
};
new_start.push_str(src);
self.s = new_start.s + &self.s;
}

pub fn indent(&mut self, amt: usize) {
self.indent += amt;
}
Expand Down
41 changes: 29 additions & 12 deletions crates/js-component-bindgen/src/transpile_bindgen.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,11 +11,13 @@ use crate::{uwrite, uwriteln};
use base64::{engine::general_purpose, Engine as _};
use heck::*;
use indexmap::IndexMap;
use std::cell::RefCell;
use std::collections::{BTreeMap, BTreeSet, HashMap};
use std::fmt::Write;
use std::mem;
use wasmtime_environ::component::{
ComponentTypes, InterfaceType, TypeDef, TypeFuncIndex, TypeResourceTableIndex,
ComponentTypes, InterfaceType, RuntimeComponentInstanceIndex, TypeDef, TypeFuncIndex,
TypeResourceTableIndex,
};
use wasmtime_environ::{
component,
Expand Down Expand Up @@ -141,6 +143,7 @@ pub fn transpile_bindgen(
lowering_options: Default::default(),
imports_resource_map: Default::default(),
exports_resource_map: Default::default(),
used_instance_flags: Default::default(),
defined_resource_classes: Default::default(),
resource_dtors: Default::default(),
resource_tables_initialized: (0..component.component.num_resource_tables)
Expand All @@ -152,6 +155,7 @@ pub fn transpile_bindgen(
instantiator.instantiate();
instantiator.ensure_resource_tables();
instantiator.destructors();
instantiator.instance_flags();
instantiator.gen.src.js(&instantiator.src.js);
instantiator.gen.src.js_init(&instantiator.src.js_init);

Expand Down Expand Up @@ -353,6 +357,8 @@ struct Instantiator<'a, 'b> {
imports: BTreeMap<String, WorldKey>,
imports_resource_map: ResourceMap,
exports_resource_map: ResourceMap,
/// Instance flags which references have been emitted externally at least once.
used_instance_flags: RefCell<BTreeSet<RuntimeComponentInstanceIndex>>,
defined_resource_classes: BTreeSet<String>,
resource_dtors: BTreeMap<TypeId, CoreDef>,
lowering_options:
Expand Down Expand Up @@ -475,10 +481,6 @@ impl<'a> Instantiator<'a, '_> {
}

fn instantiate(&mut self) {
for i in 0..self.component.num_runtime_component_instances {
uwriteln!(self.src.js_init, "const instanceFlags{i} = new WebAssembly.Global({{ value: \"i32\", mutable: true }}, {});", wasmtime_environ::component::FLAG_MAY_LEAVE | wasmtime_environ::component::FLAG_MAY_ENTER);
}

for (i, trampoline) in self.translation.trampolines.iter() {
let Trampoline::LowerImport {
index,
Expand Down Expand Up @@ -549,11 +551,10 @@ impl<'a> Instantiator<'a, '_> {
.component
.initializers
.iter()
.filter_map(|i| match i {
.find_map(|i| match i {
GlobalInitializer::Resource(r) if r.index == resource_idx => Some(r),
_ => None,
})
.next()
.unwrap();

if let Some(dtor) = &resource_def.dtor {
Expand Down Expand Up @@ -599,6 +600,20 @@ impl<'a> Instantiator<'a, '_> {
}
}

fn instance_flags(&mut self) {
// SAFETY: short-lived borrow, and the refcell isn't mutably borrowed in the loop's body.
let mut instance_flag_defs = String::new();
for used in self.used_instance_flags.borrow().iter() {
let i = used.as_u32();
uwriteln!(
&mut instance_flag_defs,
"const instanceFlags{i} = new WebAssembly.Global({{ value: \"i32\", mutable: true }}, {});",
wasmtime_environ::component::FLAG_MAY_LEAVE
| wasmtime_environ::component::FLAG_MAY_ENTER);
}
self.src.js_init.prepend_str(&instance_flag_defs);
}

fn destructors(&mut self) {
for (ty, dtor) in self.resource_dtors.iter() {
let dtor_name_str = self.core_def(dtor);
Expand Down Expand Up @@ -707,11 +722,10 @@ impl<'a> Instantiator<'a, '_> {
.component
.initializers
.iter()
.filter_map(|i| match i {
.find_map(|i| match i {
GlobalInitializer::Resource(r) if r.index == resource_idx => Some(r),
_ => None,
})
.next()
.unwrap();

if let Some(dtor) = &resource_def.dtor {
Expand Down Expand Up @@ -1054,11 +1068,10 @@ impl<'a> Instantiator<'a, '_> {
.component
.initializers
.iter()
.filter_map(|i| match i {
.find_map(|i| match i {
GlobalInitializer::Resource(r) if r.index == resource_idx => Some(r),
_ => None,
})
.next()
.unwrap();

if let Some(dtor) = &resource_def.dtor {
Expand Down Expand Up @@ -1435,7 +1448,11 @@ impl<'a> Instantiator<'a, '_> {
match def {
CoreDef::Export(e) => self.core_export(e),
CoreDef::Trampoline(i) => format!("trampoline{}", i.as_u32()),
CoreDef::InstanceFlags(i) => format!("instanceFlags{}", i.as_u32()),
CoreDef::InstanceFlags(i) => {
// SAFETY: short-lived borrow-mut.
self.used_instance_flags.borrow_mut().insert(*i);
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These are quite a few hoops just to deal with a u32. I'd suggest rather just cloning it into the set directly to avoid all the other borrow complexity. (it's underlying datatype is just a u32)

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oh it's because I'm mutating the used_instance_flags that I need the inner mutability with RefCell. The alternatives that I've discarded were the following:

  • have core_def take &mut sef: didn't work with existing code where this would cause mutable vs immutable conflicts
  • pass a instance_flags: &mut BTreeSet parameter
    • if that variable lived in self and is mutably borrowed at call sites, we get back to the previous bullet item
    • if not, then I found it a bit invasive to pass it down to all the callers, from the top-level.

Hence the inner mutability. Do you have a preference over how to achieve this?

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Ahh I see, makes sense, thanks for explaining the reasoning here!

format!("instanceFlags{}", i.as_u32())
}
}
}

Expand Down