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Ensure function indices are correct and fix a memory leak

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This commit is contained in:
Luuk de Gram 2021-02-04 21:08:19 +01:00
parent aa3e0ff454
commit 36df6a008f
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GPG Key ID: A002B174963DBB7D
3 changed files with 73 additions and 49 deletions
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2
lib/std/wasm.zig
View File

@ -263,7 +263,7 @@ pub const ExternalKind = enum(u8) {
};
/// Returns the integer value of a given `ExternalKind`
pub fn kind(val: ExternalKind) u8 {
pub fn externalKind(val: ExternalKind) u8 {
return @enumToInt(val);
}

2
src/codegen/wasm.zig
View File

@ -161,7 +161,6 @@ pub const Context = struct {
pub fn gen(self: *Context) InnerError!void {
assert(self.code.items.len == 0);
try self.genFunctype();
const writer = self.code.writer();
// Write instructions
// TODO: check for and handle death of instructions
@ -194,6 +193,7 @@ pub const Context = struct {
}
}
const writer = self.code.writer();
try writer.writeByte(wasm.opcode(.end));
// Fill in the size of the generated code to the reserved space at the

118
src/link/Wasm.zig
View File

@ -33,9 +33,18 @@ base: link.File,
/// List of all function Decls to be written to the output file. The index of
/// each Decl in this list at the time of writing the binary is used as the
/// function index.
/// function index. In the event where ext_funcs' size is not 0, the index of
/// each function is added on top of the ext_funcs' length.
/// TODO: can/should we access some data structure in Module directly?
funcs: std.ArrayListUnmanaged(*Module.Decl) = .{},
/// List of all extern function Decls to be written to the `import` section of the
/// wasm binary. The positin in the list defines the function index
ext_funcs: std.ArrayListUnmanaged(*Module.Decl) = .{},
/// When importing objects from the host environment, a name must be supplied.
/// LLVM uses "env" by default when none is given. This would be a good default for Zig
/// to support existing code.
/// TODO: Allow setting this through a flag?
host_name: []const u8 = "env",
pub fn openPath(allocator: *Allocator, sub_path: []const u8, options: link.Options) !*Wasm {
assert(options.object_format == .wasm);
@ -76,7 +85,13 @@ pub fn deinit(self: *Wasm) void {
decl.fn_link.wasm.?.code.deinit(self.base.allocator);
decl.fn_link.wasm.?.idx_refs.deinit(self.base.allocator);
}
for (self.ext_funcs.items) |decl| {
decl.fn_link.wasm.?.functype.deinit(self.base.allocator);
decl.fn_link.wasm.?.code.deinit(self.base.allocator);
decl.fn_link.wasm.?.idx_refs.deinit(self.base.allocator);
}
self.funcs.deinit(self.base.allocator);
self.ext_funcs.deinit(self.base.allocator);
}
// Generate code for the Decl, storing it in memory to be later written to
@ -92,7 +107,12 @@ pub fn updateDecl(self: *Wasm, module: *Module, decl: *Module.Decl) !void {
fn_data.idx_refs.items.len = 0;
} else {
decl.fn_link.wasm = .{};
try self.funcs.append(self.base.allocator, decl);
// dependent on function type, appends it to the correct list
switch (decl.typed_value.most_recent.typed_value.val.tag()) {
.function => try self.funcs.append(self.base.allocator, decl),
.extern_fn => try self.ext_funcs.append(self.base.allocator, decl),
else => return error.TODOImplementNonFnDeclsForWasm,
}
}
const fn_data = &decl.fn_link.wasm.?;
@ -141,7 +161,12 @@ pub fn updateDeclExports(
pub fn freeDecl(self: *Wasm, decl: *Module.Decl) void {
// TODO: remove this assert when non-function Decls are implemented
assert(decl.typed_value.most_recent.typed_value.ty.zigTypeTag() == .Fn);
_ = self.funcs.swapRemove(self.getFuncidx(decl).?);
const func_idx = self.getFuncidx(decl).?;
switch (decl.typed_value.most_recent.typed_value.val.tag()) {
.function => _ = self.funcs.swapRemove(func_idx),
.extern_fn => _ = self.ext_funcs.swapRemove(func_idx),
else => unreachable,
}
decl.fn_link.wasm.?.functype.deinit(self.base.allocator);
decl.fn_link.wasm.?.code.deinit(self.base.allocator);
decl.fn_link.wasm.?.idx_refs.deinit(self.base.allocator);
@ -170,15 +195,18 @@ pub fn flushModule(self: *Wasm, comp: *Compilation) !void {
// Type section
{
const header_offset = try reserveVecSectionHeader(file);
for (self.funcs.items) |decl| {
try file.writeAll(decl.fn_link.wasm.?.functype.items);
}
// extern functions are defined in the wasm binary first through the `import`
// section, so define their func types first
for (self.ext_funcs.items) |decl| try file.writeAll(decl.fn_link.wasm.?.functype.items);
for (self.funcs.items) |decl| try file.writeAll(decl.fn_link.wasm.?.functype.items);
try writeVecSectionHeader(
file,
header_offset,
.type,
@intCast(u32, (try file.getPos()) - header_offset - header_size),
@intCast(u32, self.funcs.items.len),
@intCast(u32, self.ext_funcs.items.len + self.funcs.items.len),
);
}
@ -187,28 +215,18 @@ pub fn flushModule(self: *Wasm, comp: *Compilation) !void {
// TODO: implement non-functions imports
const header_offset = try reserveVecSectionHeader(file);
const writer = file.writer();
var count: u32 = 0;
for (self.funcs.items) |decl, typeidx| {
if (decl.typed_value.most_recent.typed_value.val.tag() != .extern_fn) {
continue;
}
for (self.ext_funcs.items) |decl, typeidx| {
try leb.writeULEB128(writer, @intCast(u32, self.host_name.len));
try writer.writeAll(self.host_name);
// TODO: can we set/save the module name somewhere?
// For now, emit "env" like LLVM does
const module_name = "env";
try leb.writeULEB128(writer, @intCast(u32, module_name.len));
try writer.writeAll(module_name);
// wasm requires the length of the import name and doesn't require a null-termination
// wasm requires the length of the import name with no null-termination
const decl_len = mem.len(decl.name);
try leb.writeULEB128(writer, @intCast(u32, decl_len));
try writer.writeAll(decl.name[0..decl_len]);
// emit kind and the function type
try writer.writeByte(wasm.kind(.function));
try writer.writeByte(wasm.externalKind(.function));
try leb.writeULEB128(writer, @intCast(u32, typeidx));
count += 1;
}
try writeVecSectionHeader(
@ -216,7 +234,7 @@ pub fn flushModule(self: *Wasm, comp: *Compilation) !void {
header_offset,
.import,
@intCast(u32, (try file.getPos()) - header_offset - header_size),
count,
@intCast(u32, self.ext_funcs.items.len),
);
}
@ -224,21 +242,17 @@ pub fn flushModule(self: *Wasm, comp: *Compilation) !void {
{
const header_offset = try reserveVecSectionHeader(file);
const writer = file.writer();
var count: u32 = 0;
for (self.funcs.items) |decl, typeidx| {
// Extern functions only have a type, so skip the function signature section
if (decl.typed_value.most_recent.typed_value.val.tag() != .function) {
continue;
}
try leb.writeULEB128(writer, @intCast(u32, typeidx));
count += 1;
for (self.funcs.items) |_, typeidx| {
const func_idx = @intCast(u32, self.getFuncIdxOffset() + typeidx);
try leb.writeULEB128(writer, func_idx);
}
try writeVecSectionHeader(
file,
header_offset,
.function,
@intCast(u32, (try file.getPos()) - header_offset - header_size),
count,
@intCast(u32, self.funcs.items.len),
);
}
@ -256,9 +270,9 @@ pub fn flushModule(self: *Wasm, comp: *Compilation) !void {
switch (exprt.exported_decl.typed_value.most_recent.typed_value.ty.zigTypeTag()) {
.Fn => {
// Type of the export
try writer.writeByte(0x00);
try writer.writeByte(wasm.externalKind(.function));
// Exported function index
try leb.writeULEB128(writer, self.getFuncidx(exprt.exported_decl).? + 1);
try leb.writeULEB128(writer, self.getFuncidx(exprt.exported_decl).?);
},
else => return error.TODOImplementNonFnDeclsForWasm,
}
@ -279,13 +293,7 @@ pub fn flushModule(self: *Wasm, comp: *Compilation) !void {
{
const header_offset = try reserveVecSectionHeader(file);
const writer = file.writer();
var count: u32 = 0;
for (self.funcs.items) |decl| {
// Do not emit any code for extern functions
if (decl.typed_value.most_recent.typed_value.val.tag() != .function) {
std.debug.print("Skipping decl: {s}\n", .{decl.name});
continue;
}
const fn_data = &decl.fn_link.wasm.?;
// Write the already generated code to the file, inserting
@ -297,20 +305,18 @@ pub fn flushModule(self: *Wasm, comp: *Compilation) !void {
// Use a fixed width here to make calculating the code size
// in codegen.wasm.gen() simpler.
var buf: [5]u8 = undefined;
std.debug.print("idx_ref: {s} - {d}\n", .{ idx_ref.decl.name, self.getFuncidx(idx_ref.decl).? });
leb.writeUnsignedFixed(5, &buf, self.getFuncidx(idx_ref.decl).? - 1);
leb.writeUnsignedFixed(5, &buf, self.getFuncidx(idx_ref.decl).?);
try writer.writeAll(&buf);
}
try writer.writeAll(fn_data.code.items[current..]);
count += 1;
}
try writeVecSectionHeader(
file,
header_offset,
.code,
@intCast(u32, (try file.getPos()) - header_offset - header_size),
count,
@intCast(u32, self.funcs.items.len),
);
}
}
@ -575,13 +581,31 @@ fn linkWithLLD(self: *Wasm, comp: *Compilation) !void {
}
/// Get the current index of a given Decl in the function list
/// TODO: we could maintain a hash map to potentially make this
/// This will correctly provide the index, regardless whether the function is extern or not
/// TODO: we could maintain a hash map to potentially make this simpler
fn getFuncidx(self: Wasm, decl: *Module.Decl) ?u32 {
return for (self.funcs.items) |func, idx| {
if (func == decl) break @intCast(u32, idx);
var offset: u32 = 0;
const slice = switch (decl.typed_value.most_recent.typed_value.val.tag()) {
.function => blk: {
// when the target is a regular function, we have to calculate
// the offset of where the index starts
offset += self.getFuncIdxOffset();
break :blk self.funcs.items;
},
.extern_fn => self.ext_funcs.items,
else => return null,
};
return for (slice) |func, idx| {
if (func == decl) break @intCast(u32, offset + idx);
} else null;
}
/// Based on the size of `ext_funcs` returns the
/// offset of the function indices
fn getFuncIdxOffset(self: Wasm) u32 {
return @intCast(u32, self.ext_funcs.items.len);
}
fn reserveVecSectionHeader(file: fs.File) !u64 {
// section id + fixed leb contents size + fixed leb vector length
const header_size = 1 + 5 + 5;