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stop aliasing in dictWalk

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Folkert 2021-02-20 04:25:21 +01:00
parent 1a39fa201c
commit 48dee993d0
1 changed files with 16 additions and 9 deletions
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25
compiler/builtins/bitcode/src/dict.zig
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@ -761,28 +761,35 @@ pub fn setFromList(list: RocList, alignment: Alignment, key_width: usize, value_
const StepperCaller = fn (?[*]u8, ?[*]u8, ?[*]u8, ?[*]u8, ?[*]u8) callconv(.C) void; const StepperCaller = fn (?[*]u8, ?[*]u8, ?[*]u8, ?[*]u8, ?[*]u8) callconv(.C) void;
pub fn dictWalk(dict: RocDict, stepper: Opaque, stepper_caller: StepperCaller, accum: Opaque, alignment: Alignment, key_width: usize, value_width: usize, accum_width: usize, inc_key: Inc, inc_value: Inc, output: Opaque) callconv(.C) void { pub fn dictWalk(dict: RocDict, stepper: Opaque, stepper_caller: StepperCaller, accum: Opaque, alignment: Alignment, key_width: usize, value_width: usize, accum_width: usize, inc_key: Inc, inc_value: Inc, output: Opaque) callconv(.C) void {
@memcpy(output orelse unreachable, accum orelse unreachable, accum_width); // allocate space to write the result of the stepper into
// experimentally aliasing the accum and output pointers is not a good idea
const alloc: [*]u8 = @ptrCast([*]u8, std.heap.c_allocator.alloc(u8, accum_width) catch unreachable);
var b1 = output orelse unreachable;
var b2 = alloc;
@memcpy(b2, accum orelse unreachable, accum_width);
var i: usize = 0; var i: usize = 0;
const size = dict.capacity(); const size = dict.capacity();
while (i < size) : (i += 1) { while (i < size) : (i += 1) {
switch (dict.getSlot(i, key_width, value_width)) { switch (dict.getSlot(i, key_width, value_width)) {
Slot.Filled => { Slot.Filled => {
if (value_width == 0) { const key = dict.getKey(i, alignment, key_width, value_width);
const key = dict.getKey(i, alignment, key_width, value_width); const value = dict.getValue(i, alignment, key_width, value_width);
stepper_caller(stepper, key, null, output, output); stepper_caller(stepper, key, value, b2, b1);
} else {
const key = dict.getKey(i, alignment, key_width, value_width);
const value = dict.getValue(i, alignment, key_width, value_width);
stepper_caller(stepper, key, value, output, output); const temp = b1;
} b2 = b1;
b1 = temp;
}, },
else => {}, else => {},
} }
} }
@memcpy(output orelse unreachable, b2, accum_width);
std.heap.c_allocator.free(alloc[0..accum_width]);
const data_bytes = dict.capacity() * slotSize(key_width, value_width); const data_bytes = dict.capacity() * slotSize(key_width, value_width);
decref(std.heap.c_allocator, alignment, dict.dict_bytes, data_bytes); decref(std.heap.c_allocator, alignment, dict.dict_bytes, data_bytes);
} }