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wasm backend call into zig to allocate with refcount correctly

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Brendan Hansknecht 2024-04-12 20:13:45 -07:00
parent 54d0409396
commit 669daad33d
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1 changed files with 16 additions and 37 deletions
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53
crates/compiler/gen_wasm/src/backend.rs
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@ -1562,7 +1562,8 @@ impl<'a, 'r> WasmBackend<'a, 'r> {
// Allocate heap space and store its address in a local variable
let heap_local_id = self.storage.create_anonymous_local(PTR_TYPE);
let heap_alignment = self.layout_interner.alignment_bytes(elem_layout);
self.allocate_with_refcount(Some(size), heap_alignment, 1);
let elems_refcounted = self.layout_interner.contains_refcounted(elem_layout);
self.allocate_with_refcount(size, heap_alignment, elems_refcounted);
self.code_builder.set_local(heap_local_id);
let (stack_local_id, stack_offset) =
@ -1676,13 +1677,13 @@ impl<'a, 'r> WasmBackend<'a, 'r> {
}
self.code_builder.else_();
{
self.allocate_with_refcount(Some(data_size), data_alignment, 1);
self.allocate_with_refcount(data_size, data_alignment, false);
self.code_builder.set_local(*local_id);
}
self.code_builder.end();
} else {
// Call the allocator to get a memory address.
self.allocate_with_refcount(Some(data_size), data_alignment, 1);
self.allocate_with_refcount(data_size, data_alignment, false);
self.code_builder.set_local(*local_id);
}
(*local_id, 0)
@ -1965,53 +1966,31 @@ impl<'a, 'r> WasmBackend<'a, 'r> {
* Refcounting & Heap allocation
*******************************************************************/
/// Allocate heap space and write an initial refcount
/// If the data size is known at compile time, pass it in comptime_data_size.
/// If size is only known at runtime, push *data* size to the VM stack first.
/// Allocates heap space and write an initial refcount of 1.
/// Leaves the *data* address on the VM stack
///
/// elements_refcounted should only ever be set for lists.
fn allocate_with_refcount(
&mut self,
comptime_data_size: Option<u32>,
data_size: u32,
alignment_bytes: u32,
initial_refcount: u32,
elements_refcounted: bool,
) {
if !self.can_relocate_heap {
// This will probably only happen for test hosts.
panic!("The app tries to allocate heap memory but the host doesn't support that. It needs to export symbols __heap_base and __heap_end");
}
// Add extra bytes for the refcount
let extra_bytes = alignment_bytes.max(PTR_SIZE);
if let Some(data_size) = comptime_data_size {
// Data size known at compile time and passed as an argument
self.code_builder
.i32_const((data_size + extra_bytes) as i32);
} else {
// Data size known only at runtime and is on top of VM stack
self.code_builder.i32_const(extra_bytes as i32);
self.code_builder.i32_add();
}
// Zig arguments Wasm types
// data_bytes: usize i32
// element_alignment: u32 i32
// element_refcounted: bool i32
// Provide a constant for the alignment argument
self.code_builder.i32_const(data_size as i32);
self.code_builder.i32_const(alignment_bytes as i32);
self.code_builder.i32_const(elements_refcounted as i32);
// Call the foreign function. (Zig and C calling conventions are the same for this signature)
self.call_host_fn_after_loading_args("roc_alloc");
// Save the allocation address to a temporary local variable
let local_id = self.storage.create_anonymous_local(ValueType::I32);
self.code_builder.tee_local(local_id);
// Write the initial refcount
let refcount_offset = extra_bytes - PTR_SIZE;
let encoded_refcount = (initial_refcount as i32) - 1 + i32::MIN;
self.code_builder.i32_const(encoded_refcount);
self.code_builder.i32_store(Align::Bytes4, refcount_offset);
// Put the data address on the VM stack
self.code_builder.get_local(local_id);
self.code_builder.i32_const(extra_bytes as i32);
self.code_builder.i32_add();
self.call_host_fn_after_loading_args(bitcode::UTILS_ALLOCATE_WITH_REFCOUNT);
}
fn expr_reset(&mut self, argument: Symbol, ret_symbol: Symbol, ret_storage: &StoredValue) {