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Fixes #7065 in List.dropAt, author: @bhansconnect

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Aurélien Geron 2024-09-19 10:43:05 +12:00
parent 14bfa91ff3
commit c10b25cf6e
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1 changed files with 18 additions and 17 deletions
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27
crates/compiler/builtins/bitcode/src/list.zig
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@ -618,6 +618,16 @@ pub fn listDropAt(
) callconv(.C) RocList { ) callconv(.C) RocList {
const size = list.len(); const size = list.len();
const size_u64 = @as(u64, @intCast(size)); const size_u64 = @as(u64, @intCast(size));
// NOTE
// we need to return an empty list explicitly,
// because we rely on the pointer field being null if the list is empty
// which also requires duplicating the utils.decref call to spend the RC token
if (size <= 1) {
list.decref(alignment, element_width, elements_refcounted, dec);
return RocList.empty();
}
// If droping the first or last element, return a seamless slice. // If droping the first or last element, return a seamless slice.
// For simplicity, do this by calling listSublist. // For simplicity, do this by calling listSublist.
// In the future, we can test if it is faster to manually inline the important parts here. // In the future, we can test if it is faster to manually inline the important parts here.
@ -638,25 +648,16 @@ pub fn listDropAt(
// were >= than `size`, and we know `size` fits in usize. // were >= than `size`, and we know `size` fits in usize.
const drop_index: usize = @intCast(drop_index_u64); const drop_index: usize = @intCast(drop_index_u64);
if (list.isUnique()) {
if (elements_refcounted) { if (elements_refcounted) {
const element = source_ptr + drop_index * element_width; const element = source_ptr + drop_index * element_width;
dec(element); dec(element);
} }
// NOTE const copy_target = source_ptr + (drop_index * element_width);
// we need to return an empty list explicitly,
// because we rely on the pointer field being null if the list is empty
// which also requires duplicating the utils.decref call to spend the RC token
if (size < 2) {
list.decref(alignment, element_width, elements_refcounted, dec);
return RocList.empty();
}
if (list.isUnique()) {
var i = drop_index;
const copy_target = source_ptr;
const copy_source = copy_target + element_width; const copy_source = copy_target + element_width;
std.mem.copyForwards(u8, copy_target[i..size], copy_source[i..size]); const copy_size = (size - drop_index - 1) * element_width;
std.mem.copyForwards(u8, copy_target[0..copy_size], copy_source[0..copy_size]);
var new_list = list; var new_list = list;