| ... | @@ -327,6 +327,97 @@ pub const FixedBufferAllocator = struct { | ... | @@ -327,6 +327,97 @@ pub const FixedBufferAllocator = struct { |
| 327 | } | 327 | } |
| 328 | }; | 328 | }; |
| 329 | | 329 | |
| | 330 | // FIXME: Exposed LLVM intrinsics is a bug |
| | 331 | // See: https://github.com/ziglang/zig/issues/2291 |
| | 332 | extern fn @"llvm.wasm.memory.size.i32"(u32) u32; |
| | 333 | extern fn @"llvm.wasm.memory.grow.i32"(u32, u32) i32; |
| | 334 | |
| | 335 | pub const wasm_allocator = &wasm_allocator_state.allocator; |
| | 336 | var wasm_allocator_state = WasmAllocator{ |
| | 337 | .allocator = Allocator{ |
| | 338 | .reallocFn = WasmAllocator.realloc, |
| | 339 | .shrinkFn = WasmAllocator.shrink, |
| | 340 | }, |
| | 341 | .start_ptr = undefined, |
| | 342 | .num_pages = 0, |
| | 343 | .end_index = 0, |
| | 344 | }; |
| | 345 | |
| | 346 | const WasmAllocator = struct { |
| | 347 | allocator: Allocator, |
| | 348 | start_ptr: [*]u8, |
| | 349 | num_pages: usize, |
| | 350 | end_index: usize, |
| | 351 | |
| | 352 | fn alloc(allocator: *Allocator, size: usize, alignment: u29) ![]u8 { |
| | 353 | const self = @fieldParentPtr(WasmAllocator, "allocator", allocator); |
| | 354 | |
| | 355 | const addr = @ptrToInt(self.start_ptr) + self.end_index; |
| | 356 | const adjusted_addr = mem.alignForward(addr, alignment); |
| | 357 | const adjusted_index = self.end_index + (adjusted_addr - addr); |
| | 358 | const new_end_index = adjusted_index + size; |
| | 359 | |
| | 360 | if (new_end_index > self.num_pages * os.page_size) { |
| | 361 | const required_memory = new_end_index - (self.num_pages * os.page_size); |
| | 362 | |
| | 363 | var num_pages: u32 = required_memory / os.page_size; |
| | 364 | if (required_memory % os.page_size != 0) { |
| | 365 | num_pages += 1; |
| | 366 | } |
| | 367 | |
| | 368 | const prev_page = @"llvm.wasm.memory.grow.i32"(0, num_pages); |
| | 369 | if (prev_page == -1) { |
| | 370 | return error.OutOfMemory; |
| | 371 | } |
| | 372 | |
| | 373 | self.num_pages += num_pages; |
| | 374 | } |
| | 375 | |
| | 376 | const result = self.start_ptr[adjusted_index..new_end_index]; |
| | 377 | self.end_index = new_end_index; |
| | 378 | |
| | 379 | return result; |
| | 380 | } |
| | 381 | |
| | 382 | // Check if memory is the last "item" and is aligned correctly |
| | 383 | fn is_last_item(allocator: *Allocator, memory: []u8, alignment: u29) bool { |
| | 384 | const self = @fieldParentPtr(WasmAllocator, "allocator", allocator); |
| | 385 | return memory.ptr == self.start_ptr + self.end_index - memory.len and mem.alignForward(@ptrToInt(memory.ptr), alignment) == @ptrToInt(memory.ptr); |
| | 386 | } |
| | 387 | |
| | 388 | fn realloc(allocator: *Allocator, old_mem: []u8, old_align: u29, new_size: usize, new_align: u29) ![]u8 { |
| | 389 | const self = @fieldParentPtr(WasmAllocator, "allocator", allocator); |
| | 390 | |
| | 391 | // Initialize start_ptr at the first realloc |
| | 392 | if (self.num_pages == 0) { |
| | 393 | self.start_ptr = @intToPtr([*]u8, @intCast(usize, @"llvm.wasm.memory.size.i32"(0)) * os.page_size); |
| | 394 | } |
| | 395 | |
| | 396 | if (is_last_item(allocator, old_mem, new_align)) { |
| | 397 | const start_index = self.end_index - old_mem.len; |
| | 398 | const new_end_index = start_index + new_size; |
| | 399 | |
| | 400 | if (new_end_index > self.num_pages * os.page_size) { |
| | 401 | _ = try alloc(allocator, new_end_index - self.end_index, new_align); |
| | 402 | } |
| | 403 | const result = self.start_ptr[start_index..new_end_index]; |
| | 404 | |
| | 405 | self.end_index = new_end_index; |
| | 406 | return result; |
| | 407 | } else if (new_size <= old_mem.len and new_align <= old_align) { |
| | 408 | return error.OutOfMemory; |
| | 409 | } else { |
| | 410 | const result = try alloc(allocator, new_size, new_align); |
| | 411 | mem.copy(u8, result, old_mem); |
| | 412 | return result; |
| | 413 | } |
| | 414 | } |
| | 415 | |
| | 416 | fn shrink(allocator: *Allocator, old_mem: []u8, old_align: u29, new_size: usize, new_align: u29) []u8 { |
| | 417 | return old_mem[0..new_size]; |
| | 418 | } |
| | 419 | }; |
| | 420 | |
| 330 | pub const ThreadSafeFixedBufferAllocator = blk: { | 421 | pub const ThreadSafeFixedBufferAllocator = blk: { |
| 331 | if (builtin.single_threaded) { | 422 | if (builtin.single_threaded) { |
| 332 | break :blk FixedBufferAllocator; | 423 | break :blk FixedBufferAllocator; |
Andrew Kelley <andrew@ziglang.org> 2019-04-16 13:27:56-04:00
GitHub <noreply@github.com> 2019-04-16 13:27:56-04:00