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Use raw PackedIo to shave ~150b

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This commit is contained in:
Benjamin Feng 2019-12-04 21:21:54 -06:00
parent a910a6c871
commit 5784985bb8
1 changed files with 18 additions and 13 deletions
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31
lib/std/heap.zig
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@ -257,24 +257,28 @@ const WasmPageAllocator = struct {
var heap_base_wannabe: [256]u8 align(16) = undefined;
const FreeBlock = struct {
packed_data: std.PackedIntSlice(u1) = std.PackedIntSlice(u1).init(&[_]u8{}, 0),
block_data: []u128 = &[_]u128{},
const Io = std.packed_int_array.PackedIntIo(u1, .Little);
fn initData(self: *FreeBlock, data: []align(16) u8) void {
bytes: []align(16) u8,
fn initData(self: *FreeBlock, bytes: []align(16) u8) void {
// 0 == used, 1 == free
std.mem.set(u8, data, 0);
self.packed_data = std.PackedIntSlice(u1).init(data, data.len * 8);
self.block_data = @bytesToSlice(u128, data);
std.mem.set(u8, bytes, 0);
self.bytes = bytes;
}
fn totalPages(self: FreeBlock) usize {
return self.packed_data.int_count;
return self.bytes.len * 8;
}
fn getBit(self: *FreeBlock, idx: usize) u1 {
return Io.get(self.bytes, idx, 0);
}
fn setBits(self: *FreeBlock, start_idx: usize, len: usize, val: u1) void {
var i: usize = 0;
while (i < len) : (i += 1) {
self.packed_data.set(i + start_idx, val);
Io.set(self.bytes, start_idx + i, 0, val);
}
}
@ -282,14 +286,15 @@ const WasmPageAllocator = struct {
// This saves ~50 bytes compared to returning a nullable
// We can guarantee that conventional memory never gets this big,
// and wasm32 would not be able to address this block (32 GB > usize).
// and wasm32 would not be able to address this memory (32 GB > usize).
// Revisit if this is settled: https://github.com/ziglang/zig/issues/3806
const not_found = std.math.maxInt(usize);
fn useRecycled(self: *FreeBlock, num_pages: usize) usize {
@setCold(true);
for (self.block_data) |segment, i| {
const segments = @bytesToSlice(u128, self.bytes);
for (segments) |segment, i| {
const spills_into_next = @bitCast(i128, segment) < 0;
const has_enough_bits = @popCount(u128, segment) >= num_pages;
@ -298,7 +303,7 @@ const WasmPageAllocator = struct {
var j: usize = i * 128;
while (j < (i + 1) * 128) : (j += 1) {
var count: usize = 0;
while (j + count < self.packed_data.int_count and self.packed_data.get(j + count) == 1) {
while (j + count < self.totalPages() and self.getBit(j + count) == 1) {
count += 1;
if (count >= num_pages) {
self.setBits(j, num_pages, 0);
@ -316,8 +321,8 @@ const WasmPageAllocator = struct {
}
};
var conventional = FreeBlock{};
var extended = FreeBlock{};
var conventional = FreeBlock{ .bytes = &[_]u8{} };
var extended = FreeBlock{ .bytes = &[_]u8{} };
fn extendedOffset() usize {
return conventional.totalPages();