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Wasm: Move code around
This commit is contained in:
Brian Carroll
parent
61d46be923
commit
98400cae1b
2 changed files with 127 additions and 78 deletions
127
compiler/gen_wasm/src/wasm_module/dead_code.rs
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127
compiler/gen_wasm/src/wasm_module/dead_code.rs
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@ -0,0 +1,127 @@
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#[derive(Debug)]
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pub struct DeadCodeMetadata<'a> {
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/// Byte offset (in the module) where each function body can be found
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code_offsets: Vec<'a, u32>,
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/// Vector with one entry per *call*, containing the called function's index
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calls: Vec<'a, u32>,
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/// Vector with one entry per *function*, indicating its offset in `calls`
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calls_offsets: Vec<'a, u32>,
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/// Return types of each function (for making almost-empty dummy replacements)
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ret_types: Vec<'a, u8>,
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}
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impl<'a> DeadCodeMetadata<'a> {
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pub fn new(arena: &'a Bump, func_count: usize) -> Self {
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DeadCodeMetadata {
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code_offsets: Vec::with_capacity_in(func_count, arena),
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ret_types: Vec::with_capacity_in(func_count, arena),
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calls: Vec::with_capacity_in(2 * func_count, arena),
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calls_offsets: Vec::with_capacity_in(1 + func_count, arena),
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}
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}
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}
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/// Parse a Code section, collecting metadata that we can use to figure out
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/// which functions are actually called, and which are not.
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/// This would normally be done in a linker optimisation, but we want to be able to
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/// use this backend without a linker.
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pub fn parse_dead_code_metadata<'a>(
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arena: &'a Bump,
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module_bytes: &[u8],
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cursor: &mut usize,
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) -> DeadCodeMetadata<'a> {
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if module_bytes[*cursor] != SectionId::Code as u8 {
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internal_error!("Expected Code section in object file at offset {}", *cursor);
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}
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*cursor += 1;
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let section_size = parse_u32_or_panic(module_bytes, cursor);
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let count_start = *cursor;
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let section_end = count_start + section_size as usize;
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let func_count = parse_u32_or_panic(module_bytes, cursor);
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let mut metadata = DeadCodeMetadata::new(arena, func_count as usize);
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while *cursor < section_end {
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metadata.code_offsets.push(*cursor as u32);
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metadata.calls_offsets.push(metadata.calls.len() as u32);
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let func_size = parse_u32_or_panic(module_bytes, cursor);
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let func_end = *cursor + func_size as usize;
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// Local variable declarations
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let local_groups_count = parse_u32_or_panic(module_bytes, cursor);
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for _ in 0..local_groups_count {
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let _group_len = parse_u32_or_panic(module_bytes, cursor);
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*cursor += 1; // ValueType
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}
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// Instructions
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while *cursor < func_end {
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let opcode_byte: u8 = module_bytes[*cursor];
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if opcode_byte == OpCode::CALL as u8 {
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*cursor += 1;
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let call_index = parse_u32_or_panic(module_bytes, cursor);
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metadata.calls.push(call_index as u32);
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} else {
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OpCode::skip_bytes(module_bytes, cursor);
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}
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}
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}
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// Extra entries to mark the end of the last function
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metadata.code_offsets.push(*cursor as u32);
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metadata.calls_offsets.push(metadata.calls.len() as u32);
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metadata
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}
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/// Copy used functions (and their dependencies!) from an external module into our Code section
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/// Replace unused functions with very small dummies, to avoid changing any indices
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pub fn copy_used_functions<'a, T: SerialBuffer>(
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arena: &'a Bump,
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buffer: &mut T,
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metadata: DeadCodeMetadata<'a>,
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external_module: &[u8],
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sorted_used_func_indices: &[u32],
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) {
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let [dummy_i32, dummy_i64, dummy_f32, dummy_f64, dummy_nil] = create_dummy_functions(arena);
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}
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/// Create a set of dummy functions that just return a constant of each possible type
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fn create_dummy_functions<'a>(arena: &'a Bump) -> [Vec<'a, u8>; 5] {
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let mut code_builder_i32 = CodeBuilder::new(arena);
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code_builder_i32.i32_const(0);
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let mut code_builder_i64 = CodeBuilder::new(arena);
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code_builder_i64.i64_const(0);
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let mut code_builder_f32 = CodeBuilder::new(arena);
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code_builder_f32.f32_const(0.0);
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let mut code_builder_f64 = CodeBuilder::new(arena);
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code_builder_f64.f64_const(0.0);
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let mut code_builder_nil = CodeBuilder::new(arena);
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code_builder_i32.build_fn_header_and_footer(&[], 0, None);
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code_builder_i64.build_fn_header_and_footer(&[], 0, None);
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code_builder_f32.build_fn_header_and_footer(&[], 0, None);
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code_builder_f64.build_fn_header_and_footer(&[], 0, None);
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code_builder_nil.build_fn_header_and_footer(&[], 0, None);
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let mut dummy_i32 = Vec::with_capacity_in(code_builder_i32.size(), arena);
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let mut dummy_i64 = Vec::with_capacity_in(code_builder_i64.size(), arena);
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let mut dummy_f32 = Vec::with_capacity_in(code_builder_f32.size(), arena);
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let mut dummy_f64 = Vec::with_capacity_in(code_builder_f64.size(), arena);
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let mut dummy_nil = Vec::with_capacity_in(code_builder_nil.size(), arena);
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code_builder_i32.serialize(&mut dummy_i32);
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code_builder_i64.serialize(&mut dummy_i64);
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code_builder_f32.serialize(&mut dummy_f32);
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code_builder_f64.serialize(&mut dummy_f64);
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code_builder_nil.serialize(&mut dummy_nil);
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[dummy_i32, dummy_i64, dummy_f32, dummy_f64, dummy_nil]
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}
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@ -667,29 +667,6 @@ pub struct CodeSection<'a> {
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pub code_builders: Vec<'a, CodeBuilder<'a>>,
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pub code_builders: Vec<'a, CodeBuilder<'a>>,
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}
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}
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#[derive(Debug)]
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pub struct DeadCodeMetadata<'a> {
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/// Byte offset (in the module) where each function body can be found
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code_offsets: Vec<'a, u32>,
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/// Vector with one entry per *call*, containing the called function's index
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calls: Vec<'a, u32>,
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/// Vector with one entry per *function*, indicating its offset in `calls`
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calls_offsets: Vec<'a, u32>,
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/// Return types of each function (for making almost-empty dummy replacements)
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ret_types: Vec<'a, u8>,
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}
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impl<'a> DeadCodeMetadata<'a> {
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pub fn new(arena: &'a Bump, func_count: usize) -> Self {
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DeadCodeMetadata {
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code_offsets: Vec::with_capacity_in(func_count, arena),
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ret_types: Vec::with_capacity_in(func_count, arena),
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calls: Vec::with_capacity_in(2 * func_count, arena),
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calls_offsets: Vec::with_capacity_in(1 + func_count, arena),
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}
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}
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}
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impl<'a> CodeSection<'a> {
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impl<'a> CodeSection<'a> {
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/// Serialize the code builders for all functions, and get code relocations with final offsets
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/// Serialize the code builders for all functions, and get code relocations with final offsets
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pub fn serialize_with_relocs<T: SerialBuffer>(
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pub fn serialize_with_relocs<T: SerialBuffer>(
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@ -727,61 +704,6 @@ impl<'a> CodeSection<'a> {
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code_builders: Vec::with_capacity_in(0, arena),
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code_builders: Vec::with_capacity_in(0, arena),
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}
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}
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}
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}
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/// Parse a Code section, collecting metadata that we can use to figure out
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/// which functions are actually called, and which are not.
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/// This would normally be done in a linker optimisation, but we want to be able to
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/// use this backend without a linker.
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pub fn parse_dead_code_metadata(
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arena: &'a Bump,
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module_bytes: &[u8],
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cursor: &mut usize,
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) -> DeadCodeMetadata<'a> {
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if module_bytes[*cursor] != SectionId::Code as u8 {
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internal_error!("Expected Code section in object file at offset {}", *cursor);
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}
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*cursor += 1;
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let section_size = parse_u32_or_panic(module_bytes, cursor);
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let count_start = *cursor;
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let section_end = count_start + section_size as usize;
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let func_count = parse_u32_or_panic(module_bytes, cursor);
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let mut metadata = DeadCodeMetadata::new(arena, func_count as usize);
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while *cursor < section_end {
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metadata.code_offsets.push(*cursor as u32);
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metadata.calls_offsets.push(metadata.calls.len() as u32);
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let func_size = parse_u32_or_panic(module_bytes, cursor);
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let func_end = *cursor + func_size as usize;
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// Local variable declarations
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let local_groups_count = parse_u32_or_panic(module_bytes, cursor);
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for _ in 0..local_groups_count {
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let _group_len = parse_u32_or_panic(module_bytes, cursor);
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*cursor += 1; // ValueType
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}
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// Instructions
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while *cursor < func_end {
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let opcode_byte: u8 = module_bytes[*cursor];
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if opcode_byte == OpCode::CALL as u8 {
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*cursor += 1;
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let call_index = parse_u32_or_panic(module_bytes, cursor);
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metadata.calls.push(call_index as u32);
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} else {
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OpCode::skip_bytes(module_bytes, cursor);
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}
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}
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}
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// Extra entries to mark the end of the last function
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metadata.code_offsets.push(*cursor as u32);
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metadata.calls_offsets.push(metadata.calls.len() as u32);
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metadata
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}
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}
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}
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impl<'a> Serialize for CodeSection<'a> {
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impl<'a> Serialize for CodeSection<'a> {
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