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Fix Wasm function indices for generated helpers

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Brian Carroll 2021-12-25 11:36:16 +00:00
parent d08b79295c
commit 1f86ad3438
1 changed files with 25 additions and 14 deletions
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39
compiler/gen_wasm/src/wasm_module/sections.rs
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@ -655,21 +655,35 @@ impl<'a> WasmModule<'a> {
}
/// Re-index internally-defined functions to make room for imported functions.
/// We do this after serialization, when all buffers in all CodeBuilders have been combined.
/// That makes the code simpler and avoids spreading it across multiple impl's and files.
/// Imported functions come first in the index space, but we didn't know how many we needed until now.
/// We do this after serializing the code section, since we have linker data that is literally
/// *designed* for changing function indices in serialized code!
fn finalize_code_fn_indices<T: SerialBuffer>(
&mut self,
buffer: &mut T,
code_section_body_index: usize,
n_imported_fns: u32,
) {
// Modify symbol table entries
let symbol_table = self.linking.symbol_table_mut();
let mut target_symbol_indices = std::vec::Vec::with_capacity(symbol_table.len());
for (i, sym_info) in symbol_table.iter_mut().enumerate() {
if let SymInfo::Function(WasmObjectSymbol::Defined { index, .. }) = sym_info {
target_symbol_indices.push(i as u32);
*index += n_imported_fns;
// Lookup vector of symbol index to new function index
let mut new_index_lookup = std::vec::Vec::with_capacity(symbol_table.len());
// Modify symbol table entries and fill the lookup vector
for sym_info in symbol_table.iter_mut() {
match sym_info {
SymInfo::Function(WasmObjectSymbol::Defined { index, .. }) => {
let new_fn_index = *index + n_imported_fns;
*index = new_fn_index;
new_index_lookup.push(new_fn_index);
}
SymInfo::Function(WasmObjectSymbol::Imported { index, .. }) => {
new_index_lookup.push(*index);
}
_ => {
// Symbol is not a function, so we won't look it up. Use a dummy value.
new_index_lookup.push(u32::MAX);
}
}
}
@ -681,12 +695,9 @@ impl<'a> WasmModule<'a> {
symbol_index,
} = reloc
{
if target_symbol_indices.contains(symbol_index) {
let orig_fn_index = *symbol_index; // trick: we know these were the first symbols we created
let new_fn_index = orig_fn_index + n_imported_fns;
let buffer_index = code_section_body_index + (*offset as usize);
buffer.overwrite_padded_u32(buffer_index, new_fn_index);
}
let new_fn_index = new_index_lookup[*symbol_index as usize];
let buffer_index = code_section_body_index + (*offset as usize);
buffer.overwrite_padded_u32(buffer_index, new_fn_index);
}
}
}