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Zero out descriptor statics

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This way postprocessing tools like `wasm-opt` can optimize out the data section
altogether, dropping lots of zeros
This commit is contained in:
Alex Crichton 2018-03-14 10:50:12 -07:00
parent 9825b7a7c9
commit 8b2f34b51a
1 changed files with 26 additions and 11 deletions
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37
crates/wasm-bindgen-cli-support/src/lib.rs
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@ -6,7 +6,7 @@ extern crate wasm_gc;
use std::char; use std::char;
use std::fs::File; use std::fs::File;
use std::io::Write; use std::io::Write;
use std::ops::Deref; use std::ops::{Deref, DerefMut};
use std::path::{Path, PathBuf}; use std::path::{Path, PathBuf};
use std::slice; use std::slice;
@ -150,20 +150,22 @@ fn extract_programs(module: &mut Module) -> Vec<shared::Program> {
}; };
for entry in data.entries_mut() { for entry in data.entries_mut() {
let value = bytes_to_u32(entry.value_mut()); let mut value = bytes_to_u32(entry.value_mut());
let mut value = &*value; let mut tmp = &mut *value;
loop { loop {
match value.iter().position(|i| i.0 == 0x30d97887) { let value = tmp;
Some(i) => value = &value[i + 1..], let start = match value.iter().position(|i| i.0 == 0x30d97887) {
Some(i) => i,
None => break, None => break,
} };
if value.get(0).map(|c| c.0) != Some(0xd4182f61) { if value.get(start + 1).map(|c| c.0) != Some(0xd4182f61) {
tmp = &mut value[1..];
continue continue
} }
let cnt = value[1].0 as usize; let cnt = value[start + 2].0 as usize;
let (a, b) = value[2..].split_at(cnt); let (a, b) = value[start..].split_at_mut(cnt + 3);
value = b; tmp = b;
let json = a.iter() let json = a[3..].iter()
.map(|i| char::from_u32(i.0).unwrap()) .map(|i| char::from_u32(i.0).unwrap())
.collect::<String>(); .collect::<String>();
let p: shared::Program = match serde_json::from_str(&json) { let p: shared::Program = match serde_json::from_str(&json) {
@ -198,6 +200,10 @@ to open an issue at https://github.com/alexcrichton/wasm-bindgen/issues!
p.version, version); p.version, version);
} }
ret.push(p); ret.push(p);
for slot in a {
slot.0 = 0;
}
} }
} }
return ret return ret
@ -234,6 +240,15 @@ impl<'a> Deref for FutzWithAlign<'a> {
} }
} }
impl<'a> DerefMut for FutzWithAlign<'a> {
fn deref_mut(&mut self) -> &mut [Unaligned] {
unsafe {
slice::from_raw_parts_mut(self.data.as_mut_ptr() as *mut Unaligned,
self.data.len() / 4)
}
}
}
impl<'a> Drop for FutzWithAlign<'a> { impl<'a> Drop for FutzWithAlign<'a> {
fn drop(&mut self) { fn drop(&mut self) {
self.data.truncate(self.len); self.data.truncate(self.len);