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Make Str equality faster

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Brian Carroll 2021-12-13 15:57:54 +00:00
parent 3c74acafa4
commit ad8fa483d2
1 changed files with 18 additions and 15 deletions
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33
compiler/builtins/bitcode/src/str.zig
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@ -105,11 +105,8 @@ pub const RocStr = extern struct {
}
pub fn eq(self: RocStr, other: RocStr) bool {
const self_bytes_ptr: ?[*]const u8 = self.str_bytes;
const other_bytes_ptr: ?[*]const u8 = other.str_bytes;
// If they are byte-for-byte equal, they're definitely equal!
if (self_bytes_ptr == other_bytes_ptr and self.str_len == other.str_len) {
if (self.str_bytes == other.str_bytes and self.str_len == other.str_len) {
return true;
}
@ -121,21 +118,27 @@ pub const RocStr = extern struct {
return false;
}
const self_u8_ptr: [*]const u8 = @ptrCast([*]const u8, &self);
const other_u8_ptr: [*]const u8 = @ptrCast([*]const u8, &other);
const self_bytes: [*]const u8 = if (self.isSmallStr() or self.isEmpty()) self_u8_ptr else self_bytes_ptr orelse unreachable;
const other_bytes: [*]const u8 = if (other.isSmallStr() or other.isEmpty()) other_u8_ptr else other_bytes_ptr orelse unreachable;
// Now we have to look at the string contents
const self_bytes = self.asU8ptr();
const other_bytes = other.asU8ptr();
var index: usize = 0;
// TODO rewrite this into a for loop
const length = self.len();
while (index < length) {
if (self_bytes[index] != other_bytes[index]) {
// It's faster to compare pointer-sized words rather than bytes, as far as possible
// The bytes are always pointer-size aligned due to the refcount
const self_words = @ptrCast([*]const usize, @alignCast(@alignOf(usize), self_bytes));
const other_words = @ptrCast([*]const usize, @alignCast(@alignOf(usize), other_bytes));
var w: usize = 0;
while (w < self_len / @sizeOf(usize)) : (w += 1) {
if (self_words[w] != other_words[w]) {
return false;
}
}
index = index + 1;
// Compare the leftover bytes
var b = w * @sizeOf(usize);
while (b < self_len) : (b += 1) {
if (self_bytes[b] != other_bytes[b]) {
return false;
}
}
return true;