| ... | ... | @@ -1126,63 +1126,6 @@ pub const indexOfSentinel = findSentinel; |
| 1126 | 1126 | /// Linear search through memory until the sentinel is found. |
| 1127 | 1127 | pub fn findSentinel(comptime T: type, comptime sentinel: T, p: [*:sentinel]const T) usize { |
| 1128 | 1128 | var i: usize = 0; |
| 1129 | | |
| 1130 | | if (use_vectors_for_comparison and |
| 1131 | | !std.debug.inValgrind() and // https://github.com/ziglang/zig/issues/17717 |
| 1132 | | !@inComptime() and |
| 1133 | | (@typeInfo(T) == .int or @typeInfo(T) == .float) and std.math.isPowerOfTwo(@bitSizeOf(T))) |
| 1134 | | { |
| 1135 | | switch (@import("builtin").cpu.arch) { |
| 1136 | | // The below branch assumes that reading past the end of the buffer is valid, as long |
| 1137 | | // as we don't read into a new page. This should be the case for most architectures |
| 1138 | | // which use paged memory, however should be confirmed before adding a new arch below. |
| 1139 | | .aarch64, .x86, .x86_64 => if (std.simd.suggestVectorLength(T)) |block_len| { |
| 1140 | | const page_size = std.heap.page_size_min; |
| 1141 | | const block_size = @sizeOf(T) * block_len; |
| 1142 | | const Block = @Vector(block_len, T); |
| 1143 | | const mask: Block = @splat(sentinel); |
| 1144 | | |
| 1145 | | comptime assert(std.heap.page_size_min % @sizeOf(Block) == 0); |
| 1146 | | assert(page_size % @sizeOf(Block) == 0); |
| 1147 | | |
| 1148 | | // First block may be unaligned |
| 1149 | | const start_addr = @intFromPtr(&p[i]); |
| 1150 | | const offset_in_page = start_addr & (page_size - 1); |
| 1151 | | if (offset_in_page <= page_size - @sizeOf(Block)) { |
| 1152 | | // Will not read past the end of a page, full block. |
| 1153 | | const block: Block = p[i..][0..block_len].*; |
| 1154 | | const matches = block == mask; |
| 1155 | | if (@reduce(.Or, matches)) { |
| 1156 | | return i + std.simd.firstTrue(matches).?; |
| 1157 | | } |
| 1158 | | |
| 1159 | | i += @divExact(std.mem.alignForward(usize, start_addr, block_size) - start_addr, @sizeOf(T)); |
| 1160 | | } else { |
| 1161 | | @branchHint(.unlikely); |
| 1162 | | // Would read over a page boundary. Per-byte at a time until aligned or found. |
| 1163 | | // 0.39% chance this branch is taken for 4K pages at 16b block length. |
| 1164 | | // |
| 1165 | | // An alternate strategy is to do read a full block (the last in the page) and |
| 1166 | | // mask the entries before the pointer. |
| 1167 | | while ((@intFromPtr(&p[i]) & (block_size - 1)) != 0) : (i += 1) { |
| 1168 | | if (p[i] == sentinel) return i; |
| 1169 | | } |
| 1170 | | } |
| 1171 | | |
| 1172 | | std.debug.assertAligned(&p[i], .fromByteUnits(block_size)); |
| 1173 | | while (true) { |
| 1174 | | const block: Block = p[i..][0..block_len].*; |
| 1175 | | const matches = block == mask; |
| 1176 | | if (@reduce(.Or, matches)) { |
| 1177 | | return i + std.simd.firstTrue(matches).?; |
| 1178 | | } |
| 1179 | | i += block_len; |
| 1180 | | } |
| 1181 | | }, |
| 1182 | | else => {}, |
| 1183 | | } |
| 1184 | | } |
| 1185 | | |
| 1186 | 1129 | while (p[i] != sentinel) { |
| 1187 | 1130 | i += 1; |
| 1188 | 1131 | } |
Alex Rønne Petersen <alex@alexrp.com> 2026-03-19 18:53:12+01:00
Andrew Kelley <andrew@ziglang.org> 2026-03-23 05:35:04+01:00
lib