faster Buffer.byteLength("latin1")

1 files changed, 28 insertions, 36 deletions

diff --git a/src/string_immutable.zig b/src/string_immutable.zig
index e012b6e5a..5f5b943d6 100644
--- a/src/string_immutable.zig
+++ b/src/string_immutable.zig
@@ -1729,48 +1729,40 @@ pub fn elementLengthLatin1IntoUTF8(comptime Type: type, latin1_: Type) usize {
 
     const latin1_last = latin1.ptr + latin1.len;
     if (latin1.ptr != latin1_last) {
-        const wrapped_len = latin1.len - (latin1.len % ascii_vector_size);
+
         // reference the pointer directly because it improves codegen
         var ptr = latin1.ptr;
-        const latin1_vec_end = ptr + wrapped_len;
-
-        while (ptr != latin1_vec_end) {
-            const vec: AsciiVector = ptr[0..ascii_vector_size].*;
 
-            if (@reduce(.Max, vec) > 127) {
-                const Int = u64;
-                const size = @sizeOf(Int);
-
-                const bytes = [2]Int{
-                    @bitCast(Int, ptr[0..size].*) & 0x8080808080808080,
-                    @bitCast(Int, ptr[size .. 2 * size].*) & 0x8080808080808080,
-                };
-
-                total_non_ascii_count += @popCount(bytes[0]) + @popCount(bytes[1]);
+        if (comptime Environment.enableSIMD) {
+            const wrapped_len = latin1.len - (latin1.len % ascii_vector_size);
+            const latin1_vec_end = ptr + wrapped_len;
+            while (ptr != latin1_vec_end) {
+                const vec: AsciiVector = ptr[0..ascii_vector_size].*;
+                const cmp = vec & @splat(ascii_vector_size, @as(u8, 0x80));
+                total_non_ascii_count += @reduce(.Add, cmp);
+                ptr += ascii_vector_size;
+            }
+        } else {
+            while (@ptrToInt(ptr + 8) < @ptrToInt(latin1_last)) {
+                if (comptime Environment.allow_assert) std.debug.assert(@ptrToInt(ptr) <= @ptrToInt(latin1_last) and @ptrToInt(ptr) >= @ptrToInt(latin1_.ptr));
+                const bytes = @bitCast(u64, ptr[0..8].*) & 0x8080808080808080;
+                total_non_ascii_count += @popCount(bytes);
+                ptr += 8;
             }
 
-            ptr += ascii_vector_size;
-        }
-
-        if (@ptrToInt(ptr + 8) < @ptrToInt(latin1_last)) {
-            if (comptime Environment.allow_assert) std.debug.assert(@ptrToInt(ptr) <= @ptrToInt(latin1_last) and @ptrToInt(ptr) >= @ptrToInt(latin1_.ptr));
-            const bytes = @bitCast(u64, ptr[0..8].*) & 0x8080808080808080;
-            total_non_ascii_count += @popCount(bytes);
-            ptr += 8;
-        }
-
-        if (@ptrToInt(ptr + 4) < @ptrToInt(latin1_last)) {
-            if (comptime Environment.allow_assert) std.debug.assert(@ptrToInt(ptr) <= @ptrToInt(latin1_last) and @ptrToInt(ptr) >= @ptrToInt(latin1_.ptr));
-            const bytes = @bitCast(u32, ptr[0..4].*) & 0x80808080;
-            total_non_ascii_count += @popCount(bytes);
-            ptr += 4;
-        }
+            if (@ptrToInt(ptr + 4) < @ptrToInt(latin1_last)) {
+                if (comptime Environment.allow_assert) std.debug.assert(@ptrToInt(ptr) <= @ptrToInt(latin1_last) and @ptrToInt(ptr) >= @ptrToInt(latin1_.ptr));
+                const bytes = @bitCast(u32, ptr[0..4].*) & 0x80808080;
+                total_non_ascii_count += @popCount(bytes);
+                ptr += 4;
+            }
 
-        if (@ptrToInt(ptr + 2) < @ptrToInt(latin1_last)) {
-            if (comptime Environment.allow_assert) std.debug.assert(@ptrToInt(ptr) <= @ptrToInt(latin1_last) and @ptrToInt(ptr) >= @ptrToInt(latin1_.ptr));
-            const bytes = @bitCast(u16, ptr[0..2].*) & 0x8080;
-            total_non_ascii_count += @popCount(bytes);
-            ptr += 2;
+            if (@ptrToInt(ptr + 2) < @ptrToInt(latin1_last)) {
+                if (comptime Environment.allow_assert) std.debug.assert(@ptrToInt(ptr) <= @ptrToInt(latin1_last) and @ptrToInt(ptr) >= @ptrToInt(latin1_.ptr));
+                const bytes = @bitCast(u16, ptr[0..2].*) & 0x8080;
+                total_non_ascii_count += @popCount(bytes);
+                ptr += 2;
+            }
         }
 
         while (ptr != latin1_last) {