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wasm-linker: Export data symbols as global

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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.
This commit is contained in:
Luuk de Gram 2022-12-14 16:55:23 +01:00
parent 41199bba4b
commit f95549ddc7
No known key found for this signature in database
GPG Key ID: A8CFE58E4DC7D664
2 changed files with 39 additions and 4 deletions
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41
src/link/Wasm.zig
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@ -112,6 +112,8 @@ func_types: std.ArrayListUnmanaged(std.wasm.Type) = .{},
functions: std.AutoArrayHashMapUnmanaged(struct { file: ?u16, index: u32 }, std.wasm.Func) = .{},
/// Output global section
wasm_globals: std.ArrayListUnmanaged(std.wasm.Global) = .{},
/// Global symbols for exported data symbols
address_globals: std.ArrayListUnmanaged(SymbolLoc) = .{},
/// Memory section
memories: std.wasm.Memory = .{ .limits = .{ .min = 0, .max = null } },
/// Output table section
@ -839,6 +841,7 @@ pub fn deinit(wasm: *Wasm) void {
wasm.func_types.deinit(gpa);
wasm.functions.deinit(gpa);
wasm.wasm_globals.deinit(gpa);
wasm.address_globals.deinit(gpa);
wasm.function_table.deinit(gpa);
wasm.tables.deinit(gpa);
wasm.exports.deinit(gpa);
@ -1804,7 +1807,15 @@ fn setupExports(wasm: *Wasm) !void {
if (sym_loc.file == null) break :blk symbol.name;
break :blk try wasm.string_table.put(wasm.base.allocator, sym_name);
};
const exp: types.Export = .{
const exp: types.Export = if (symbol.tag == .data) exp: {
const global_index = @intCast(u32, wasm.wasm_globals.items.len + wasm.address_globals.items.len);
try wasm.address_globals.append(wasm.base.allocator, sym_loc);
break :exp .{
.name = export_name,
.kind = .global,
.index = global_index,
};
} else .{
.name = export_name,
.kind = symbol.tag.externalType(),
.index = symbol.index,
@ -2473,10 +2484,22 @@ fn linkWithZld(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Node) l
if (wasm.wasm_globals.items.len > 0) {
const header_offset = try reserveVecSectionHeader(&binary_bytes);
var global_count: u32 = 0;
for (wasm.wasm_globals.items) |global| {
try binary_writer.writeByte(std.wasm.valtype(global.global_type.valtype));
try binary_writer.writeByte(@boolToInt(global.global_type.mutable));
try emitInit(binary_writer, global.init);
global_count += 1;
}
for (wasm.address_globals.items) |sym_loc| {
const atom = wasm.symbol_atom.get(sym_loc).?;
try binary_writer.writeByte(std.wasm.valtype(.i32));
try binary_writer.writeByte(0); // immutable
try emitInit(binary_writer, .{
.i32_const = @bitCast(i32, atom.offset),
});
global_count += 1;
}
try writeVecSectionHeader(
@ -2484,7 +2507,7 @@ fn linkWithZld(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Node) l
header_offset,
.global,
@intCast(u32, binary_bytes.items.len - header_offset - header_size),
@intCast(u32, wasm.wasm_globals.items.len),
@intCast(u32, global_count),
);
section_count += 1;
}
@ -2990,10 +3013,22 @@ pub fn flushModule(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Nod
if (wasm.wasm_globals.items.len > 0) {
const header_offset = try reserveVecSectionHeader(&binary_bytes);
var global_count: u32 = 0;
for (wasm.wasm_globals.items) |global| {
try binary_writer.writeByte(std.wasm.valtype(global.global_type.valtype));
try binary_writer.writeByte(@boolToInt(global.global_type.mutable));
try emitInit(binary_writer, global.init);
global_count += 1;
}
for (wasm.address_globals.items) |sym_loc| {
const atom = wasm.symbol_atom.get(sym_loc).?;
try binary_writer.writeByte(std.wasm.valtype(.i32));
try binary_writer.writeByte(0); // immutable
try emitInit(binary_writer, .{
.i32_const = @bitCast(i32, atom.offset),
});
global_count += 1;
}
try writeVecSectionHeader(
@ -3001,7 +3036,7 @@ pub fn flushModule(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Nod
header_offset,
.global,
@intCast(u32, binary_bytes.items.len - header_offset - header_size),
@intCast(u32, wasm.wasm_globals.items.len),
@intCast(u32, global_count),
);
section_count += 1;
}

2
src/link/Wasm/Symbol.zig
View File

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