Commit f95549ddc71f75f3bf15f54f8d03a1a367d0db37 | zig

author	Luuk de Gram <luuk@degram.dev> 2022-12-14 16:55:23+01:00
committer	Luuk de Gram <luuk@degram.dev> 2022-12-14 16:55:23+01:00
log	f95549ddc71f75f3bf15f54f8d03a1a367d0db37
tree	5d043b4c9df3a85a467f767d9542a4f5cc94ad3b
parent	41199bba4bae4783634ee52ecd8d111f8f82fd4c
signature	Commit is signed but in an unrecognized format.

wasm-linker: Export data symbols as global

When a data symbol is required to be exported, we instead generate
a global that will be exported. This global is immutable and contains
the address of the data symbol.

2 files changed, 39 insertions(+), 4 deletions(-)

src
- link
  - Wasm.zig
  - Wasm
    Symbol.zig

src/link/Wasm.zig+38-3

...	...	@@ -112,6 +112,8 @@ func_types: std.ArrayListUnmanaged(std.wasm.Type) = .{},
112	112	functions: std.AutoArrayHashMapUnmanaged(struct { file: ?u16, index: u32 }, std.wasm.Func) = .{},
113	113	/// Output global section
114	114	wasm_globals: std.ArrayListUnmanaged(std.wasm.Global) = .{},
	115	/// Global symbols for exported data symbols
	116	address_globals: std.ArrayListUnmanaged(SymbolLoc) = .{},
115	117	/// Memory section
116	118	memories: std.wasm.Memory = .{ .limits = .{ .min = 0, .max = null } },
117	119	/// Output table section
...	...	@@ -839,6 +841,7 @@ pub fn deinit(wasm: *Wasm) void {
839	841	wasm.func_types.deinit(gpa);
840	842	wasm.functions.deinit(gpa);
841	843	wasm.wasm_globals.deinit(gpa);
	844	wasm.address_globals.deinit(gpa);
842	845	wasm.function_table.deinit(gpa);
843	846	wasm.tables.deinit(gpa);
844	847	wasm.exports.deinit(gpa);
...	...	@@ -1804,7 +1807,15 @@ fn setupExports(wasm: *Wasm) !void {
1804	1807	if (sym_loc.file == null) break :blk symbol.name;
1805	1808	break :blk try wasm.string_table.put(wasm.base.allocator, sym_name);
1806	1809	};
1807		const exp: types.Export = .{
	1810	const exp: types.Export = if (symbol.tag == .data) exp: {
	1811	const global_index = @intCast(u32, wasm.wasm_globals.items.len + wasm.address_globals.items.len);
	1812	try wasm.address_globals.append(wasm.base.allocator, sym_loc);
	1813	break :exp .{
	1814	.name = export_name,
	1815	.kind = .global,
	1816	.index = global_index,
	1817	};
	1818	} else .{
1808	1819	.name = export_name,
1809	1820	.kind = symbol.tag.externalType(),
1810	1821	.index = symbol.index,
...	...	@@ -2473,10 +2484,22 @@ fn linkWithZld(wasm: Wasm, comp: Compilation, prog_node: *std.Progress.Node) l
2473	2484	if (wasm.wasm_globals.items.len > 0) {
2474	2485	const header_offset = try reserveVecSectionHeader(&binary_bytes);
2475	2486
	2487	var global_count: u32 = 0;
2476	2488	for (wasm.wasm_globals.items) \|global\| {
2477	2489	try binary_writer.writeByte(std.wasm.valtype(global.global_type.valtype));
2478	2490	try binary_writer.writeByte(@boolToInt(global.global_type.mutable));
2479	2491	try emitInit(binary_writer, global.init);
	2492	global_count += 1;
	2493	}
	2494
	2495	for (wasm.address_globals.items) \|sym_loc\| {
	2496	const atom = wasm.symbol_atom.get(sym_loc).?;
	2497	try binary_writer.writeByte(std.wasm.valtype(.i32));
	2498	try binary_writer.writeByte(0); // immutable
	2499	try emitInit(binary_writer, .{
	2500	.i32_const = @bitCast(i32, atom.offset),
	2501	});
	2502	global_count += 1;
2480	2503	}
2481	2504
2482	2505	try writeVecSectionHeader(
...	...	@@ -2484,7 +2507,7 @@ fn linkWithZld(wasm: Wasm, comp: Compilation, prog_node: *std.Progress.Node) l
2484	2507	header_offset,
2485	2508	.global,
2486	2509	@intCast(u32, binary_bytes.items.len - header_offset - header_size),
2487		@intCast(u32, wasm.wasm_globals.items.len),
	2510	@intCast(u32, global_count),
2488	2511	);
2489	2512	section_count += 1;
2490	2513	}
...	...	@@ -2990,10 +3013,22 @@ pub fn flushModule(wasm: Wasm, comp: Compilation, prog_node: *std.Progress.Nod
2990	3013	if (wasm.wasm_globals.items.len > 0) {
2991	3014	const header_offset = try reserveVecSectionHeader(&binary_bytes);
2992	3015
	3016	var global_count: u32 = 0;
2993	3017	for (wasm.wasm_globals.items) \|global\| {
2994	3018	try binary_writer.writeByte(std.wasm.valtype(global.global_type.valtype));
2995	3019	try binary_writer.writeByte(@boolToInt(global.global_type.mutable));
2996	3020	try emitInit(binary_writer, global.init);
	3021	global_count += 1;
	3022	}
	3023
	3024	for (wasm.address_globals.items) \|sym_loc\| {
	3025	const atom = wasm.symbol_atom.get(sym_loc).?;
	3026	try binary_writer.writeByte(std.wasm.valtype(.i32));
	3027	try binary_writer.writeByte(0); // immutable
	3028	try emitInit(binary_writer, .{
	3029	.i32_const = @bitCast(i32, atom.offset),
	3030	});
	3031	global_count += 1;
2997	3032	}
2998	3033
2999	3034	try writeVecSectionHeader(
...	...	@@ -3001,7 +3036,7 @@ pub fn flushModule(wasm: Wasm, comp: Compilation, prog_node: *std.Progress.Nod
3001	3036	header_offset,
3002	3037	.global,
3003	3038	@intCast(u32, binary_bytes.items.len - header_offset - header_size),
3004		@intCast(u32, wasm.wasm_globals.items.len),
	3039	@intCast(u32, global_count),
3005	3040	);
3006	3041	section_count += 1;
3007	3042	}

src/link/Wasm/Symbol.zig+1-1

...	...	@@ -38,7 +38,7 @@ pub const Tag = enum {
38	38	return switch (tag) {
39	39	.function => .function,
40	40	.global => .global,
41		.data => .memory,
	41	.data => unreachable, // Data symbols will generate a global
42	42	.section => unreachable, // Not an external type
43	43	.event => unreachable, // Not an external type
44	44	.dead => unreachable, // Dead symbols should not be referenced