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wasm: fix DCE for signatures and debug names

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Brian Carroll 2022-06-13 00:13:10 +01:00
parent c169815c9e
commit acebdee3dd
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1 changed files with 23 additions and 18 deletions
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41
compiler/gen_wasm/src/wasm_module/mod.rs
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@ -5,6 +5,8 @@ pub mod parse;
pub mod sections;
pub mod serialize;
use std::iter::repeat;
pub use code_builder::{Align, CodeBuilder, LocalId, ValueType, VmSymbolState};
pub use linking::{OffsetRelocType, RelocationEntry, SymInfo};
pub use sections::{ConstExpr, Export, ExportType, Global, GlobalType, Signature};
@ -211,35 +213,38 @@ impl<'a> WasmModule<'a> {
// Remove all unused JS imports
// We don't want to force the web page to provide dummy JS functions, it's a pain!
//
let mut live_import_fns = Vec::with_capacity_in(self.import.imports.len(), arena);
let mut fn_index = 0;
self.import.imports.retain(|import| {
if !matches!(import.description, ImportDesc::Func { .. }) {
true
} else {
let live = live_flags[fn_index];
if live {
live_import_fns.push(fn_index);
}
fn_index += 1;
live
}
});
//
// Update function signatures & debug names for imports that changed index
//
let live_import_fns = Vec::from_iter_in(
live_flags
.iter_ones()
.take_while(|i| *i < self.import.imports.len()),
arena,
);
for (new_index, old_index) in live_import_fns.iter().enumerate() {
// Safe because `old_index >= new_index`
self.function.signatures[new_index] = self.function.signatures[*old_index];
self.names.function_names[new_index] = self.names.function_names[*old_index];
}
let first_dead_import_index = live_import_fns.last().map(|x| x + 1).unwrap_or(0) as u32;
for i in first_dead_import_index..host_fn_min {
self.names.function_names[i as usize] = (i, "unused_host_import");
// signatures
let live_import_count = live_import_fns.len();
let dead_import_count = host_fn_min as usize - live_import_count;
let signature_count = self.function.signatures.len();
self.function
.signatures
.extend(repeat(0).take(dead_import_count));
self.function
.signatures
.copy_within(0..signature_count, dead_import_count);
// debug names
for (new_index, &old_index) in live_import_fns.iter().enumerate() {
let old_name: &str = self.names.function_names[old_index].1;
let new_name: &str = self.names.function_names[new_index].1;
self.names.function_names[new_index].1 = old_name;
self.names.function_names[old_index].1 = new_name;
}
//