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std: slightly improve codegen of std.unicode.utf8ValidateSlice

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Jacob Young 2023-10-21 13:43:06 -04:00 committed by Andrew Kelley
parent b4d4d19958
commit ccc9ebf0bd
1 changed files with 8 additions and 11 deletions
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19
lib/std/unicode.zig
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@ -201,21 +201,18 @@ pub fn utf8CountCodepoints(s: []const u8) !usize {
pub fn utf8ValidateSlice(input: []const u8) bool {
var remaining = input;
const V_len = std.simd.suggestVectorSize(usize) orelse 1;
const V = @Vector(V_len, usize);
const u8s_in_vector = @sizeOf(usize) * V_len;
const chunk_len = std.simd.suggestVectorSize(u8) orelse 1;
const Chunk = @Vector(chunk_len, u8);
// Fast path. Check for and skip ASCII characters at the start of the input.
while (remaining.len >= u8s_in_vector) {
const chunk: V = @bitCast(remaining[0..u8s_in_vector].*);
const swapped = mem.littleToNative(V, chunk);
const reduced = @reduce(.Or, swapped);
const mask: usize = @bitCast([1]u8{0x80} ** @sizeOf(usize));
if (reduced & mask != 0) {
// Found a non ASCII byte
while (remaining.len >= chunk_len) {
const chunk: Chunk = remaining[0..chunk_len].*;
const mask: Chunk = @splat(0x80);
if (@reduce(.Or, chunk & mask == mask)) {
// found a non ASCII byte
break;
}
remaining = remaining[u8s_in_vector..];
remaining = remaining[chunk_len..];
}
// default lowest and highest continuation byte