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Add local and offset free lists

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This commit is contained in:
Jakub Konka 2020-10-10 21:39:29 +02:00
parent ea45ee5484
commit 0b77152faa
1 changed files with 37 additions and 0 deletions
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37
src/link/MachO.zig
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@ -116,7 +116,9 @@ global_symbols: std.ArrayListUnmanaged(macho.nlist_64) = .{},
/// Table of all undefined symbols
undef_symbols: std.ArrayListUnmanaged(macho.nlist_64) = .{},
local_symbol_free_list: std.ArrayListUnmanaged(u32) = .{},
global_symbol_free_list: std.ArrayListUnmanaged(u32) = .{},
offset_table_free_list: std.ArrayListUnmanaged(u32) = .{},
dyld_stub_binder_index: ?u16 = null,
@ -153,6 +155,12 @@ const LIB_SYSTEM_NAME: [*:0]const u8 = "System";
/// TODO we should search for libSystem and fail if it doesn't exist, instead of hardcoding it
const LIB_SYSTEM_PATH: [*:0]const u8 = DEFAULT_LIB_SEARCH_PATH ++ "/libSystem.B.dylib";
/// In order for a slice of bytes to be considered eligible to keep metadata pointing at
/// it as a possible place to put new symbols, it must have enough room for this many bytes
/// (plus extra for reserved capacity).
const minimum_text_block_size = 64;
const min_text_capacity = minimum_text_block_size * alloc_num / alloc_den;
pub const TextBlock = struct {
/// Each decl always gets a local symbol with the fully qualified name.
/// The vaddr and size are found here directly.
@ -179,6 +187,33 @@ pub const TextBlock = struct {
.prev = null,
.next = null,
};
/// Returns how much room there is to grow in virtual address space.
/// File offset relocation happens transparently, so it is not included in
/// this calculation.
fn capacity(self: TextBlock, macho_file: MachO) u64 {
const self_sym = macho_file.local_symbols.items[self.local_sym_index];
if (self.next) |next| {
const next_sym = macho_file.local_symbols.items[next.local_sym_index];
return next_sym.n_value - self_sym.n_value;
} else {
// We are the last block.
// The capacity is limited only by virtual address space.
return std.math.maxInt(u64) - self_sym.n_value;
}
}
fn freeListEligible(self: TextBlock, macho_file: MachO) bool {
// No need to keep a free list node for the last block.
const next = self.next orelse return false;
const self_sym = macho_file.local_symbols.items[self.local_sym_index];
const next_sym = macho_file.local_symbols.items[next.local_sym_index];
const cap = next_sym.n_value - self_sym.n_value;
const ideal_cap = self.size * alloc_num / alloc_den;
if (cap <= ideal_cap) return false;
const surplus = cap - ideal_cap;
return surplus >= min_text_capacity;
}
};
pub const Export = struct {
@ -721,11 +756,13 @@ fn darwinArchString(arch: std.Target.Cpu.Arch) []const u8 {
pub fn deinit(self: *MachO) void {
self.offset_table.deinit(self.base.allocator);
self.offset_table_free_list.deinit(self.base.allocator);
self.string_table.deinit(self.base.allocator);
self.undef_symbols.deinit(self.base.allocator);
self.global_symbols.deinit(self.base.allocator);
self.global_symbol_free_list.deinit(self.base.allocator);
self.local_symbols.deinit(self.base.allocator);
self.local_symbol_free_list.deinit(self.base.allocator);
self.sections.deinit(self.base.allocator);
self.load_commands.deinit(self.base.allocator);
}