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gen_wasm: Get rid of individual locals for values in stack memory
All values in stack memory can share the stack frame pointer, with different offsets. This avoids having to generate initialisation code for individual pointers we used to have. It should also make things more efficient when the runtime compiles Wasm to machine code. It can just assign the stack frame pointer to a single CPU register and leave it there. The original idea was to make params and local variables work the same. (A struct param will be passed as a pointer to caller stack memory.) But now I don't think that's worth it. Some match expressions get more awkward this way but we might be able to refactor that to be nicer.
This commit is contained in:
Brian Carroll
parent
4aa2452e01
commit
ffa6ff0a62
3 changed files with 134 additions and 97 deletions
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@ -13,7 +13,7 @@ use roc_mono::layout::{Builtin, Layout};
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use crate::layout::WasmLayout;
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use crate::storage::SymbolStorage;
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use crate::{
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copy_memory, pop_stack_frame, push_stack_frame, round_up_to_alignment, LocalId, PTR_SIZE,
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pop_stack_frame, push_stack_frame, round_up_to_alignment, LocalId, MemoryCopy, PTR_SIZE,
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PTR_TYPE,
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};
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@ -165,7 +165,7 @@ impl<'a> WasmBackend<'a> {
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symbol: Symbol,
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kind: LocalKind,
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) -> SymbolStorage {
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let local_id = LocalId((self.arg_types.len() + self.locals.len()) as u32);
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let next_local_id = LocalId((self.arg_types.len() + self.locals.len()) as u32);
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let storage = match kind {
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LocalKind::Parameter => {
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@ -173,13 +173,13 @@ impl<'a> WasmBackend<'a> {
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self.arg_types.push(wasm_layout.value_type());
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match wasm_layout {
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WasmLayout::LocalOnly(value_type, size) => SymbolStorage::ParamPrimitive {
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local_id,
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local_id: next_local_id,
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value_type,
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size,
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},
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WasmLayout::HeapMemory => SymbolStorage::ParamPrimitive {
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local_id,
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local_id: next_local_id,
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value_type: PTR_TYPE,
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size: PTR_SIZE,
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},
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@ -188,7 +188,7 @@ impl<'a> WasmBackend<'a> {
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size,
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alignment_bytes,
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} => SymbolStorage::ParamStackMemory {
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local_id,
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local_id: next_local_id,
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size,
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alignment_bytes,
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},
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@ -199,12 +199,14 @@ impl<'a> WasmBackend<'a> {
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match wasm_layout {
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WasmLayout::LocalOnly(value_type, size) => SymbolStorage::VarPrimitive {
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local_id,
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local_id: next_local_id,
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value_type,
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size,
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},
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WasmLayout::HeapMemory => SymbolStorage::VarHeapMemory { local_id },
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WasmLayout::HeapMemory => SymbolStorage::VarHeapMemory {
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local_id: next_local_id,
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},
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WasmLayout::StackMemory {
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size,
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@ -216,27 +218,12 @@ impl<'a> WasmBackend<'a> {
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match self.stack_frame_pointer {
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None => {
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// This is the first stack-memory variable in the function
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// That means we can reuse it as the stack frame pointer,
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// and it will get initialised at the start of the function
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self.stack_frame_pointer = Some(local_id);
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}
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Some(frame_ptr_id) => {
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// This local points to the base of a struct, at an offset from the stack frame pointer
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// Having one local per variable means params and locals work the same way in code gen.
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// (alternatively we could use one frame pointer + offset for all struct variables)
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self.instructions.extend([
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GetLocal(frame_ptr_id.0),
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I32Const(offset),
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I32Add,
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SetLocal(local_id.0),
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]);
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self.stack_frame_pointer = Some(next_local_id);
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}
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Some(_) => {}
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};
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SymbolStorage::VarStackMemory {
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local_id,
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size,
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offset: offset as u32,
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alignment_bytes,
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@ -262,12 +249,12 @@ impl<'a> WasmBackend<'a> {
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fn local_id_from_symbol(&self, sym: &Symbol) -> LocalId {
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let storage = self.get_symbol_storage(sym);
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storage.local_id()
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storage.local_id(self.stack_frame_pointer)
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}
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fn load_symbol(&mut self, sym: &Symbol) {
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let storage = self.get_symbol_storage(sym);
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let index: u32 = storage.local_id().0;
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let index: u32 = storage.local_id(self.stack_frame_pointer).0;
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self.instructions.push(GetLocal(index));
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}
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@ -317,7 +304,7 @@ impl<'a> WasmBackend<'a> {
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let wasm_layout = WasmLayout::new(layout);
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let local_id = self
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.insert_local(wasm_layout, *sym, LocalKind::Variable)
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.local_id();
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.local_id(self.stack_frame_pointer);
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self.build_expr(sym, expr, layout)?;
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@ -338,19 +325,35 @@ impl<'a> WasmBackend<'a> {
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match storage {
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VarStackMemory {
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local_id,
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size,
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alignment_bytes,
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..
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offset,
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} => {
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let copy = MemoryCopy {
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from_ptr: self.stack_frame_pointer.unwrap(),
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from_offset: *offset,
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to_ptr: LocalId(0),
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to_offset: 0,
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size: *size,
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alignment_bytes: *alignment_bytes,
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};
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copy.generate(&mut self.instructions);
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}
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| ParamStackMemory {
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ParamStackMemory {
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local_id,
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size,
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alignment_bytes,
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} => {
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let from = *local_id;
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let to = LocalId(0);
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copy_memory(&mut self.instructions, from, to, *size, *alignment_bytes, 0);
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let copy = MemoryCopy {
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from_ptr: *local_id,
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from_offset: 0,
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to_ptr: LocalId(0),
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to_offset: 0,
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size: *size,
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alignment_bytes: *alignment_bytes,
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};
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copy.generate(&mut self.instructions);
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}
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ParamPrimitive { local_id, .. }
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@ -423,7 +426,7 @@ impl<'a> WasmBackend<'a> {
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let wasm_layout = WasmLayout::new(¶meter.layout);
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let local_id = self
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.insert_local(wasm_layout, parameter.symbol, LocalKind::Variable)
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.local_id();
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.local_id(self.stack_frame_pointer);
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jp_parameter_local_ids.push(local_id);
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}
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@ -547,28 +550,27 @@ impl<'a> WasmBackend<'a> {
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let storage = self.get_symbol_storage(sym).to_owned();
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if let Layout::Struct(field_layouts) = layout {
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match storage {
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SymbolStorage::VarStackMemory { local_id, size, .. }
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| SymbolStorage::ParamStackMemory { local_id, size, .. } => {
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if size > 0 {
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let mut relative_offset = 0;
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for (field, _) in fields.iter().zip(field_layouts.iter()) {
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relative_offset += self.copy_symbol_to_pointer_at_offset(
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local_id,
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relative_offset,
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field,
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);
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}
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} else {
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return Err(format!("Not supported yet: zero-size struct at {:?}", sym));
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}
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let (local_id, size) = match storage {
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SymbolStorage::VarStackMemory { size, .. } => {
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(self.stack_frame_pointer.unwrap(), size)
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}
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SymbolStorage::ParamStackMemory { local_id, size, .. } => (local_id, size),
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_ => {
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return Err(format!(
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"Cannot create struct {:?} with storage {:?}",
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sym, storage
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));
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}
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};
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if size > 0 {
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let mut relative_offset = 0;
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for (field, _) in fields.iter().zip(field_layouts.iter()) {
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relative_offset +=
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self.copy_symbol_to_pointer_at_offset(local_id, relative_offset, field);
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}
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} else {
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return Err(format!("Not supported yet: zero-size struct at {:?}", sym));
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}
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} else {
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// Struct expression but not Struct layout => single element. Copy it.
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@ -585,7 +587,12 @@ impl<'a> WasmBackend<'a> {
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from_symbol: &Symbol,
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) -> u32 {
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let from_storage = self.get_symbol_storage(from_symbol).to_owned();
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from_storage.copy_to_memory(&mut self.instructions, to_ptr, to_offset)
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from_storage.copy_to_memory(
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&mut self.instructions,
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to_ptr,
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to_offset,
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self.stack_frame_pointer,
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)
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}
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fn copy_storage(&mut self, to: &SymbolStorage, from: &SymbolStorage) {
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@ -594,18 +601,21 @@ impl<'a> WasmBackend<'a> {
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if !has_stack_memory {
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debug_assert!(from.value_type() == to.value_type());
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self.instructions.push(GetLocal(from.local_id().0));
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self.instructions.push(SetLocal(to.local_id().0));
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self.instructions
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.push(GetLocal(from.local_id(self.stack_frame_pointer).0));
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self.instructions
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.push(SetLocal(to.local_id(self.stack_frame_pointer).0));
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} else {
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let (size, alignment_bytes) = from.stack_size_and_alignment();
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copy_memory(
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&mut self.instructions,
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from.local_id(),
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to.local_id(),
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let copy = MemoryCopy {
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from_ptr: from.local_id(self.stack_frame_pointer),
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to_ptr: to.local_id(self.stack_frame_pointer),
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from_offset: from.address_offset().unwrap(),
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to_offset: to.address_offset().unwrap(),
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size,
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alignment_bytes,
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0,
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);
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};
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copy.generate(&mut self.instructions);
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}
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}
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