Commit c2316c5228

Jacob Young <jacobly0@users.noreply.github.com>
2024-07-11 03:39:11
InternPool: make `global_error_set` thread-safe
1 parent 98f3a26
src/arch/wasm/CodeGen.zig
@@ -3304,7 +3304,7 @@ fn lowerConstant(func: *CodeGen, val: Value, ty: Type) InnerError!WValue {
             }
         },
         .err => |err| {
-            const int = try mod.getErrorValue(err.name);
+            const int = try pt.getErrorValue(err.name);
             return WValue{ .imm32 = int };
         },
         .error_union => |error_union| {
@@ -3452,30 +3452,25 @@ fn emitUndefined(func: *CodeGen, ty: Type) InnerError!WValue {
 /// Returns a `Value` as a signed 32 bit value.
 /// It's illegal to provide a value with a type that cannot be represented
 /// as an integer value.
-fn valueAsI32(func: *const CodeGen, val: Value, ty: Type) i32 {
+fn valueAsI32(func: *const CodeGen, val: Value) i32 {
     const pt = func.pt;
     const mod = pt.zcu;
+    const ip = &mod.intern_pool;
 
-    switch (val.ip_index) {
-        .none => {},
+    switch (val.toIntern()) {
         .bool_true => return 1,
         .bool_false => return 0,
-        else => return switch (mod.intern_pool.indexToKey(val.ip_index)) {
-            .enum_tag => |enum_tag| intIndexAsI32(&mod.intern_pool, enum_tag.int, pt),
+        else => return switch (ip.indexToKey(val.ip_index)) {
+            .enum_tag => |enum_tag| intIndexAsI32(ip, enum_tag.int, pt),
             .int => |int| intStorageAsI32(int.storage, pt),
             .ptr => |ptr| {
                 assert(ptr.base_addr == .int);
                 return @intCast(ptr.byte_offset);
             },
-            .err => |err| @as(i32, @bitCast(@as(Zcu.ErrorInt, @intCast(mod.global_error_set.getIndex(err.name).?)))),
+            .err => |err| @bitCast(ip.getErrorValueIfExists(err.name).?),
             else => unreachable,
         },
     }
-
-    return switch (ty.zigTypeTag(mod)) {
-        .ErrorSet => @as(i32, @bitCast(val.getErrorInt(mod))),
-        else => unreachable, // Programmer called this function for an illegal type
-    };
 }
 
 fn intIndexAsI32(ip: *const InternPool, int: InternPool.Index, pt: Zcu.PerThread) i32 {
@@ -4098,7 +4093,7 @@ fn airSwitchBr(func: *CodeGen, inst: Air.Inst.Index) InnerError!void {
 
         for (items, 0..) |ref, i| {
             const item_val = (try func.air.value(ref, pt)).?;
-            const int_val = func.valueAsI32(item_val, target_ty);
+            const int_val = func.valueAsI32(item_val);
             if (lowest_maybe == null or int_val < lowest_maybe.?) {
                 lowest_maybe = int_val;
             }
@@ -7454,7 +7449,7 @@ fn airErrorSetHasValue(func: *CodeGen, inst: Air.Inst.Index) InnerError!void {
     var lowest: ?u32 = null;
     var highest: ?u32 = null;
     for (0..names.len) |name_index| {
-        const err_int: Zcu.ErrorInt = @intCast(mod.global_error_set.getIndex(names.get(ip)[name_index]).?);
+        const err_int = ip.getErrorValueIfExists(names.get(ip)[name_index]).?;
         if (lowest) |*l| {
             if (err_int < l.*) {
                 l.* = err_int;
src/arch/x86_64/CodeGen.zig
@@ -16435,7 +16435,7 @@ fn airErrorName(self: *Self, inst: Air.Inst.Index) !void {
                 .size = .dword,
                 .index = err_reg.to64(),
                 .scale = .@"4",
-                .disp = 4,
+                .disp = (1 - 1) * 4,
             } },
         },
     );
@@ -16448,7 +16448,7 @@ fn airErrorName(self: *Self, inst: Air.Inst.Index) !void {
                 .size = .dword,
                 .index = err_reg.to64(),
                 .scale = .@"4",
-                .disp = 8,
+                .disp = (2 - 1) * 4,
             } },
         },
     );
src/codegen/c.zig
@@ -2622,10 +2622,11 @@ pub fn genErrDecls(o: *Object) !void {
 
     var max_name_len: usize = 0;
     // do not generate an invalid empty enum when the global error set is empty
-    if (zcu.global_error_set.keys().len > 1) {
+    const names = ip.global_error_set.getNamesFromMainThread();
+    if (names.len > 0) {
         try writer.writeAll("enum {\n");
         o.indent_writer.pushIndent();
-        for (zcu.global_error_set.keys()[1..], 1..) |name_nts, value| {
+        for (names, 1..) |name_nts, value| {
             const name = name_nts.toSlice(ip);
             max_name_len = @max(name.len, max_name_len);
             const err_val = try pt.intern(.{ .err = .{
@@ -2644,7 +2645,7 @@ pub fn genErrDecls(o: *Object) !void {
     defer o.dg.gpa.free(name_buf);
 
     @memcpy(name_buf[0..name_prefix.len], name_prefix);
-    for (zcu.global_error_set.keys()) |name| {
+    for (names) |name| {
         const name_slice = name.toSlice(ip);
         @memcpy(name_buf[name_prefix.len..][0..name_slice.len], name_slice);
         const identifier = name_buf[0 .. name_prefix.len + name_slice.len];
@@ -2674,7 +2675,7 @@ pub fn genErrDecls(o: *Object) !void {
     }
 
     const name_array_ty = try pt.arrayType(.{
-        .len = zcu.global_error_set.count(),
+        .len = 1 + names.len,
         .child = .slice_const_u8_sentinel_0_type,
     });
 
@@ -2688,9 +2689,9 @@ pub fn genErrDecls(o: *Object) !void {
         .complete,
     );
     try writer.writeAll(" = {");
-    for (zcu.global_error_set.keys(), 0..) |name_nts, value| {
+    for (names, 1..) |name_nts, val| {
         const name = name_nts.toSlice(ip);
-        if (value != 0) try writer.writeByte(',');
+        if (val > 1) try writer.writeAll(", ");
         try writer.print("{{" ++ name_prefix ++ "{}, {}}}", .{
             fmtIdent(name),
             try o.dg.fmtIntLiteral(try pt.intValue(Type.usize, name.len), .StaticInitializer),
@@ -6873,7 +6874,7 @@ fn airErrorName(f: *Function, inst: Air.Inst.Index) !CValue {
 
     try writer.writeAll(" = zig_errorName[");
     try f.writeCValue(writer, operand, .Other);
-    try writer.writeAll("];\n");
+    try writer.writeAll(" - 1];\n");
     return local;
 }
 
src/codegen/llvm.zig
@@ -1036,20 +1036,21 @@ pub const Object = struct {
 
         const pt = o.pt;
         const mod = pt.zcu;
+        const ip = &mod.intern_pool;
 
-        const error_name_list = mod.global_error_set.keys();
-        const llvm_errors = try mod.gpa.alloc(Builder.Constant, error_name_list.len);
+        const error_name_list = ip.global_error_set.getNamesFromMainThread();
+        const llvm_errors = try mod.gpa.alloc(Builder.Constant, 1 + error_name_list.len);
         defer mod.gpa.free(llvm_errors);
 
         // TODO: Address space
         const slice_ty = Type.slice_const_u8_sentinel_0;
         const llvm_usize_ty = try o.lowerType(Type.usize);
         const llvm_slice_ty = try o.lowerType(slice_ty);
-        const llvm_table_ty = try o.builder.arrayType(error_name_list.len, llvm_slice_ty);
+        const llvm_table_ty = try o.builder.arrayType(1 + error_name_list.len, llvm_slice_ty);
 
         llvm_errors[0] = try o.builder.undefConst(llvm_slice_ty);
-        for (llvm_errors[1..], error_name_list[1..]) |*llvm_error, name| {
-            const name_string = try o.builder.stringNull(name.toSlice(&mod.intern_pool));
+        for (llvm_errors[1..], error_name_list) |*llvm_error, name| {
+            const name_string = try o.builder.stringNull(name.toSlice(ip));
             const name_init = try o.builder.stringConst(name_string);
             const name_variable_index =
                 try o.builder.addVariable(.empty, name_init.typeOf(&o.builder), .default);
@@ -1085,7 +1086,7 @@ pub const Object = struct {
         // If there is no such function in the module, it means the source code does not need it.
         const name = o.builder.strtabStringIfExists(lt_errors_fn_name) orelse return;
         const llvm_fn = o.builder.getGlobal(name) orelse return;
-        const errors_len = o.pt.zcu.global_error_set.count();
+        const errors_len = o.pt.zcu.intern_pool.global_error_set.mutate.list.len;
 
         var wip = try Builder.WipFunction.init(&o.builder, .{
             .function = llvm_fn.ptrConst(&o.builder).kind.function,
@@ -1096,12 +1097,12 @@ pub const Object = struct {
 
         // Example source of the following LLVM IR:
         // fn __zig_lt_errors_len(index: u16) bool {
-        //     return index < total_errors_len;
+        //     return index <= total_errors_len;
         // }
 
         const lhs = wip.arg(0);
         const rhs = try o.builder.intValue(try o.errorIntType(), errors_len);
-        const is_lt = try wip.icmp(.ult, lhs, rhs, "");
+        const is_lt = try wip.icmp(.ule, lhs, rhs, "");
         _ = try wip.ret(is_lt);
         try wip.finish();
     }
@@ -3820,7 +3821,7 @@ pub const Object = struct {
                 return lowerBigInt(o, ty, bigint);
             },
             .err => |err| {
-                const int = try mod.getErrorValue(err.name);
+                const int = try pt.getErrorValue(err.name);
                 const llvm_int = try o.builder.intConst(try o.errorIntType(), int);
                 return llvm_int;
             },
@@ -9658,7 +9659,7 @@ pub const FuncGen = struct {
         defer wip_switch.finish(&self.wip);
 
         for (0..names.len) |name_index| {
-            const err_int = mod.global_error_set.getIndex(names.get(ip)[name_index]).?;
+            const err_int = ip.getErrorValueIfExists(names.get(ip)[name_index]).?;
             const this_tag_int_value = try o.builder.intConst(try o.errorIntType(), err_int);
             try wip_switch.addCase(this_tag_int_value, valid_block, &self.wip);
         }
src/codegen/spirv.zig
@@ -963,7 +963,7 @@ const DeclGen = struct {
                     break :cache result_id;
                 },
                 .err => |err| {
-                    const value = try mod.getErrorValue(err.name);
+                    const value = try pt.getErrorValue(err.name);
                     break :cache try self.constInt(ty, value, repr);
                 },
                 .error_union => |error_union| {
src/link/Wasm/ZigObject.zig
@@ -652,13 +652,22 @@ fn populateErrorNameTable(zig_object: *ZigObject, wasm_file: *Wasm, tid: Zcu.Per
     // Addend for each relocation to the table
     var addend: u32 = 0;
     const pt: Zcu.PerThread = .{ .zcu = wasm_file.base.comp.module.?, .tid = tid };
-    for (pt.zcu.global_error_set.keys()) |error_name| {
-        const atom = wasm_file.getAtomPtr(atom_index);
+    const slice_ty = Type.slice_const_u8_sentinel_0;
+    const atom = wasm_file.getAtomPtr(atom_index);
+    {
+        // TODO: remove this unreachable entry
+        try atom.code.appendNTimes(gpa, 0, 4);
+        try atom.code.writer(gpa).writeInt(u32, 0, .little);
+        atom.size += @intCast(slice_ty.abiSize(pt));
+        addend += 1;
 
-        const error_name_slice = error_name.toSlice(&pt.zcu.intern_pool);
+        try names_atom.code.append(gpa, 0);
+    }
+    const ip = &pt.zcu.intern_pool;
+    for (ip.global_error_set.getNamesFromMainThread()) |error_name| {
+        const error_name_slice = error_name.toSlice(ip);
         const len: u32 = @intCast(error_name_slice.len + 1); // names are 0-terminated
 
-        const slice_ty = Type.slice_const_u8_sentinel_0;
         const offset = @as(u32, @intCast(atom.code.items.len));
         // first we create the data for the slice of the name
         try atom.code.appendNTimes(gpa, 0, 4); // ptr to name, will be relocated
@@ -677,7 +686,7 @@ fn populateErrorNameTable(zig_object: *ZigObject, wasm_file: *Wasm, tid: Zcu.Per
         try names_atom.code.ensureUnusedCapacity(gpa, len);
         names_atom.code.appendSliceAssumeCapacity(error_name_slice[0..len]);
 
-        log.debug("Populated error name: '{}'", .{error_name.fmt(&pt.zcu.intern_pool)});
+        log.debug("Populated error name: '{}'", .{error_name.fmt(ip)});
     }
     names_atom.size = addend;
     zig_object.error_names_atom = names_atom_index;
@@ -1042,7 +1051,7 @@ fn setupErrorsLen(zig_object: *ZigObject, wasm_file: *Wasm) !void {
     const gpa = wasm_file.base.comp.gpa;
     const sym_index = zig_object.findGlobalSymbol("__zig_errors_len") orelse return;
 
-    const errors_len = wasm_file.base.comp.module.?.global_error_set.count();
+    const errors_len = 1 + wasm_file.base.comp.module.?.intern_pool.global_error_set.mutate.list.len;
     // overwrite existing atom if it already exists (maybe the error set has increased)
     // if not, allcoate a new atom.
     const atom_index = if (wasm_file.symbol_atom.get(.{ .file = zig_object.index, .index = sym_index })) |index| blk: {
src/link/Dwarf.zig
@@ -2698,7 +2698,7 @@ pub fn flushModule(self: *Dwarf, pt: Zcu.PerThread) !void {
         try addDbgInfoErrorSetNames(
             pt,
             Type.anyerror,
-            pt.zcu.global_error_set.keys(),
+            pt.zcu.intern_pool.global_error_set.getNamesFromMainThread(),
             target,
             &dbg_info_buffer,
         );
@@ -2867,7 +2867,7 @@ fn addDbgInfoErrorSetNames(
     mem.writeInt(u64, dbg_info_buffer.addManyAsArrayAssumeCapacity(8), 0, target_endian);
 
     for (error_names) |error_name| {
-        const int = try pt.zcu.getErrorValue(error_name);
+        const int = try pt.getErrorValue(error_name);
         const error_name_slice = error_name.toSlice(&pt.zcu.intern_pool);
         // DW.AT.enumerator
         try dbg_info_buffer.ensureUnusedCapacity(error_name_slice.len + 2 + @sizeOf(u64));
src/link/SpirV.zig
@@ -227,9 +227,9 @@ pub fn flushModule(self: *SpirV, arena: Allocator, tid: Zcu.PerThread.Id, prog_n
     var error_info = std.ArrayList(u8).init(self.object.gpa);
     defer error_info.deinit();
 
-    try error_info.appendSlice("zig_errors");
-    const mod = self.base.comp.module.?;
-    for (mod.global_error_set.keys()) |name| {
+    try error_info.appendSlice("zig_errors:");
+    const ip = &self.base.comp.module.?.intern_pool;
+    for (ip.global_error_set.getNamesFromMainThread()) |name| {
         // Errors can contain pretty much any character - to encode them in a string we must escape
         // them somehow. Easiest here is to use some established scheme, one which also preseves the
         // name if it contains no strange characters is nice for debugging. URI encoding fits the bill.
@@ -238,7 +238,7 @@ pub fn flushModule(self: *SpirV, arena: Allocator, tid: Zcu.PerThread.Id, prog_n
         try error_info.append(':');
         try std.Uri.Component.percentEncode(
             error_info.writer(),
-            name.toSlice(&mod.intern_pool),
+            name.toSlice(ip),
             struct {
                 fn isValidChar(c: u8) bool {
                     return switch (c) {
src/Zcu/PerThread.zig
@@ -2287,6 +2287,17 @@ pub fn allocateNewDecl(pt: Zcu.PerThread, namespace: Zcu.Namespace.Index) !Zcu.D
     return decl_index;
 }
 
+pub fn getErrorValue(
+    pt: Zcu.PerThread,
+    name: InternPool.NullTerminatedString,
+) Allocator.Error!Zcu.ErrorInt {
+    return pt.zcu.intern_pool.getErrorValue(pt.zcu.gpa, pt.tid, name);
+}
+
+pub fn getErrorValueFromSlice(pt: Zcu.PerThread, name: []const u8) Allocator.Error!Zcu.ErrorInt {
+    return pt.getErrorValue(try pt.zcu.intern_pool.getOrPutString(pt.zcu.gpa, name));
+}
+
 pub fn initNewAnonDecl(
     pt: Zcu.PerThread,
     new_decl_index: Zcu.Decl.Index,
src/codegen.zig
@@ -137,10 +137,10 @@ pub fn generateLazySymbol(
 
     if (lazy_sym.ty.isAnyError(pt.zcu)) {
         alignment.* = .@"4";
-        const err_names = pt.zcu.global_error_set.keys();
+        const err_names = ip.global_error_set.getNamesFromMainThread();
         mem.writeInt(u32, try code.addManyAsArray(4), @intCast(err_names.len), endian);
         var offset = code.items.len;
-        try code.resize((1 + err_names.len + 1) * 4);
+        try code.resize((err_names.len + 1) * 4);
         for (err_names) |err_name_nts| {
             const err_name = err_name_nts.toSlice(ip);
             mem.writeInt(u32, code.items[offset..][0..4], @intCast(code.items.len), endian);
@@ -243,13 +243,13 @@ pub fn generateSymbol(
             int_val.writeTwosComplement(try code.addManyAsSlice(abi_size), endian);
         },
         .err => |err| {
-            const int = try mod.getErrorValue(err.name);
+            const int = try pt.getErrorValue(err.name);
             try code.writer().writeInt(u16, @intCast(int), endian);
         },
         .error_union => |error_union| {
             const payload_ty = ty.errorUnionPayload(mod);
             const err_val: u16 = switch (error_union.val) {
-                .err_name => |err_name| @intCast(try mod.getErrorValue(err_name)),
+                .err_name => |err_name| @intCast(try pt.getErrorValue(err_name)),
                 .payload => 0,
             };
 
@@ -1058,7 +1058,7 @@ pub fn genTypedValue(
         },
         .ErrorSet => {
             const err_name = ip.indexToKey(val.toIntern()).err.name;
-            const error_index = zcu.global_error_set.getIndex(err_name).?;
+            const error_index = try pt.getErrorValue(err_name);
             return GenResult.mcv(.{ .immediate = error_index });
         },
         .ErrorUnion => {
src/Compilation.zig
@@ -2943,7 +2943,7 @@ pub fn totalErrorCount(comp: *Compilation) u32 {
             }
         }
 
-        if (zcu.global_error_set.entries.len - 1 > zcu.error_limit) {
+        if (zcu.intern_pool.global_error_set.mutate.list.len > zcu.error_limit) {
             total += 1;
         }
     }
@@ -3072,7 +3072,7 @@ pub fn getAllErrorsAlloc(comp: *Compilation) !ErrorBundle {
             try addModuleErrorMsg(zcu, &bundle, value.*, &all_references);
         }
 
-        const actual_error_count = zcu.global_error_set.entries.len - 1;
+        const actual_error_count = zcu.intern_pool.global_error_set.mutate.list.len;
         if (actual_error_count > zcu.error_limit) {
             try bundle.addRootErrorMessage(.{
                 .msg = try bundle.printString("ZCU used more errors than possible: used {d}, max {d}", .{
src/InternPool.zig
@@ -6,6 +6,8 @@ locals: []Local = &.{},
 /// Length must be a power of two and represents the number of simultaneous
 /// writers that can mutate any single sharded data structure.
 shards: []Shard = &.{},
+/// Key is the error name, index is the error tag value. Index 0 has a length-0 string.
+global_error_set: GlobalErrorSet = GlobalErrorSet.empty,
 /// Cached number of active bits in a `tid`.
 tid_width: if (single_threaded) u0 else std.math.Log2Int(u32) = 0,
 /// Cached shift amount to put a `tid` in the top bits of a 31-bit value.
@@ -10129,10 +10131,10 @@ pub fn getOrPutTrailingString(
     defer shard.mutate.string_map.len += 1;
     const map_header = map.header().*;
     if (shard.mutate.string_map.len < map_header.capacity * 3 / 5) {
+        strings.appendAssumeCapacity(.{0});
         const entry = &map.entries[map_index];
         entry.hash = hash;
         entry.release(@enumFromInt(@intFromEnum(value)));
-        strings.appendAssumeCapacity(.{0});
         return value;
     }
     const arena_state = &ip.getLocal(tid).mutate.arena;
@@ -10171,12 +10173,12 @@ pub fn getOrPutTrailingString(
         map_index &= new_map_mask;
         if (map.entries[map_index].value == .none) break;
     }
+    strings.appendAssumeCapacity(.{0});
     map.entries[map_index] = .{
         .value = @enumFromInt(@intFromEnum(value)),
         .hash = hash,
     };
     shard.shared.string_map.release(new_map);
-    strings.appendAssumeCapacity(.{0});
     return value;
 }
 
@@ -10942,3 +10944,159 @@ fn ptrsHaveSameAlignment(ip: *InternPool, a_ty: Index, a_info: Key.PtrType, b_ty
     return a_info.flags.alignment == b_info.flags.alignment and
         (a_info.child == b_info.child or a_info.flags.alignment != .none);
 }
+
+const GlobalErrorSet = struct {
+    shared: struct {
+        names: Names,
+        map: Shard.Map(GlobalErrorSet.Index),
+    } align(std.atomic.cache_line),
+    mutate: Local.MutexListMutate align(std.atomic.cache_line),
+
+    const Names = Local.List(struct { NullTerminatedString });
+
+    const empty: GlobalErrorSet = .{
+        .shared = .{
+            .names = Names.empty,
+            .map = Shard.Map(GlobalErrorSet.Index).empty,
+        },
+        .mutate = Local.MutexListMutate.empty,
+    };
+
+    const Index = enum(Zcu.ErrorInt) {
+        none = 0,
+        _,
+    };
+
+    /// Not thread-safe, may only be called from the main thread.
+    pub fn getNamesFromMainThread(ges: *const GlobalErrorSet) []const NullTerminatedString {
+        return ges.shared.names.view().items(.@"0")[0..ges.mutate.list.len];
+    }
+
+    fn getErrorValue(
+        ges: *GlobalErrorSet,
+        gpa: Allocator,
+        arena_state: *std.heap.ArenaAllocator.State,
+        name: NullTerminatedString,
+    ) Allocator.Error!GlobalErrorSet.Index {
+        if (name == .empty) return .none;
+        const hash = std.hash.uint32(@intFromEnum(name));
+        var map = ges.shared.map.acquire();
+        const Map = @TypeOf(map);
+        var map_mask = map.header().mask();
+        const names = ges.shared.names.acquire();
+        var map_index = hash;
+        while (true) : (map_index += 1) {
+            map_index &= map_mask;
+            const entry = &map.entries[map_index];
+            const index = entry.acquire();
+            if (index == .none) break;
+            if (entry.hash != hash) continue;
+            if (names.view().items(.@"0")[@intFromEnum(index) - 1] == name) return index;
+        }
+        ges.mutate.mutex.lock();
+        defer ges.mutate.mutex.unlock();
+        if (map.entries != ges.shared.map.entries) {
+            map = ges.shared.map;
+            map_mask = map.header().mask();
+            map_index = hash;
+        }
+        while (true) : (map_index += 1) {
+            map_index &= map_mask;
+            const entry = &map.entries[map_index];
+            const index = entry.value;
+            if (index == .none) break;
+            if (entry.hash != hash) continue;
+            if (names.view().items(.@"0")[@intFromEnum(index) - 1] == name) return index;
+        }
+        const mutable_names: Names.Mutable = .{
+            .gpa = gpa,
+            .arena = arena_state,
+            .mutate = &ges.mutate.list,
+            .list = &ges.shared.names,
+        };
+        try mutable_names.ensureUnusedCapacity(1);
+        const map_header = map.header().*;
+        if (ges.mutate.list.len < map_header.capacity * 3 / 5) {
+            mutable_names.appendAssumeCapacity(.{name});
+            const index: GlobalErrorSet.Index = @enumFromInt(mutable_names.mutate.len);
+            const entry = &map.entries[map_index];
+            entry.hash = hash;
+            entry.release(index);
+            return index;
+        }
+        var arena = arena_state.promote(gpa);
+        defer arena_state.* = arena.state;
+        const new_map_capacity = map_header.capacity * 2;
+        const new_map_buf = try arena.allocator().alignedAlloc(
+            u8,
+            Map.alignment,
+            Map.entries_offset + new_map_capacity * @sizeOf(Map.Entry),
+        );
+        const new_map: Map = .{ .entries = @ptrCast(new_map_buf[Map.entries_offset..].ptr) };
+        new_map.header().* = .{ .capacity = new_map_capacity };
+        @memset(new_map.entries[0..new_map_capacity], .{ .value = .none, .hash = undefined });
+        const new_map_mask = new_map.header().mask();
+        map_index = 0;
+        while (map_index < map_header.capacity) : (map_index += 1) {
+            const entry = &map.entries[map_index];
+            const index = entry.value;
+            if (index == .none) continue;
+            const item_hash = entry.hash;
+            var new_map_index = item_hash;
+            while (true) : (new_map_index += 1) {
+                new_map_index &= new_map_mask;
+                const new_entry = &new_map.entries[new_map_index];
+                if (new_entry.value != .none) continue;
+                new_entry.* = .{
+                    .value = index,
+                    .hash = item_hash,
+                };
+                break;
+            }
+        }
+        map = new_map;
+        map_index = hash;
+        while (true) : (map_index += 1) {
+            map_index &= new_map_mask;
+            if (map.entries[map_index].value == .none) break;
+        }
+        mutable_names.appendAssumeCapacity(.{name});
+        const index: GlobalErrorSet.Index = @enumFromInt(mutable_names.mutate.len);
+        map.entries[map_index] = .{ .value = index, .hash = hash };
+        ges.shared.map.release(new_map);
+        return index;
+    }
+
+    fn getErrorValueIfExists(
+        ges: *const GlobalErrorSet,
+        name: NullTerminatedString,
+    ) ?GlobalErrorSet.Index {
+        if (name == .empty) return .none;
+        const hash = std.hash.uint32(@intFromEnum(name));
+        const map = ges.shared.map.acquire();
+        const map_mask = map.header().mask();
+        const names_items = ges.shared.names.acquire().view().items(.@"0");
+        var map_index = hash;
+        while (true) : (map_index += 1) {
+            map_index &= map_mask;
+            const entry = &map.entries[map_index];
+            const index = entry.acquire();
+            if (index == .none) return null;
+            if (entry.hash != hash) continue;
+            if (names_items[@intFromEnum(index) - 1] == name) return index;
+        }
+    }
+};
+
+pub fn getErrorValue(
+    ip: *InternPool,
+    gpa: Allocator,
+    tid: Zcu.PerThread.Id,
+    name: NullTerminatedString,
+) Allocator.Error!Zcu.ErrorInt {
+    return @intFromEnum(try ip.global_error_set.getErrorValue(gpa, &ip.getLocal(tid).mutate.arena, name));
+}
+
+pub fn getErrorValueIfExists(ip: *const InternPool, name: NullTerminatedString) ?Zcu.ErrorInt {
+    return @intFromEnum(ip.global_error_set.getErrorValueIfExists(name) orelse return null);
+}
src/Sema.zig
@@ -3473,7 +3473,7 @@ fn zirErrorSetDecl(
         const name_index: Zir.NullTerminatedString = @enumFromInt(sema.code.extra[extra_index]);
         const name = sema.code.nullTerminatedString(name_index);
         const name_ip = try mod.intern_pool.getOrPutString(gpa, pt.tid, name, .no_embedded_nulls);
-        _ = try mod.getErrorValue(name_ip);
+        _ = try pt.getErrorValue(name_ip);
         const result = names.getOrPutAssumeCapacity(name_ip);
         assert(!result.found_existing); // verified in AstGen
     }
@@ -8705,7 +8705,7 @@ fn zirErrorValue(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!
         inst_data.get(sema.code),
         .no_embedded_nulls,
     );
-    _ = try pt.zcu.getErrorValue(name);
+    _ = try pt.getErrorValue(name);
     // Create an error set type with only this error value, and return the value.
     const error_set_type = try pt.singleErrorSetType(name);
     return Air.internedToRef((try pt.intern(.{ .err = .{
@@ -8735,7 +8735,7 @@ fn zirIntFromError(sema: *Sema, block: *Block, extended: Zir.Inst.Extended.InstD
         const err_name = ip.indexToKey(val.toIntern()).err.name;
         return Air.internedToRef((try pt.intValue(
             err_int_ty,
-            try mod.getErrorValue(err_name),
+            try pt.getErrorValue(err_name),
         )).toIntern());
     }
 
@@ -8746,10 +8746,7 @@ fn zirIntFromError(sema: *Sema, block: *Block, extended: Zir.Inst.Extended.InstD
             const names = ip.indexToKey(err_set_ty_index).error_set_type.names;
             switch (names.len) {
                 0 => return Air.internedToRef((try pt.intValue(err_int_ty, 0)).toIntern()),
-                1 => {
-                    const int: Module.ErrorInt = @intCast(mod.global_error_set.getIndex(names.get(ip)[0]).?);
-                    return pt.intRef(err_int_ty, int);
-                },
+                1 => return pt.intRef(err_int_ty, ip.getErrorValueIfExists(names.get(ip)[0]).?),
                 else => {},
             }
         },
@@ -8765,6 +8762,7 @@ fn zirErrorFromInt(sema: *Sema, block: *Block, extended: Zir.Inst.Extended.InstD
 
     const pt = sema.pt;
     const mod = pt.zcu;
+    const ip = &mod.intern_pool;
     const extra = sema.code.extraData(Zir.Inst.UnNode, extended.operand).data;
     const src = block.nodeOffset(extra.node);
     const operand_src = block.builtinCallArgSrc(extra.node, 0);
@@ -8774,11 +8772,16 @@ fn zirErrorFromInt(sema: *Sema, block: *Block, extended: Zir.Inst.Extended.InstD
 
     if (try sema.resolveDefinedValue(block, operand_src, operand)) |value| {
         const int = try sema.usizeCast(block, operand_src, try value.toUnsignedIntSema(pt));
-        if (int > mod.global_error_set.count() or int == 0)
+        if (int > len: {
+            const mutate = &ip.global_error_set.mutate;
+            mutate.mutex.lock();
+            defer mutate.mutex.unlock();
+            break :len mutate.list.len;
+        } or int == 0)
             return sema.fail(block, operand_src, "integer value '{d}' represents no error", .{int});
         return Air.internedToRef((try pt.intern(.{ .err = .{
             .ty = .anyerror_type,
-            .name = mod.global_error_set.keys()[int],
+            .name = ip.global_error_set.shared.names.acquire().view().items(.@"0")[int - 1],
         } })));
     }
     try sema.requireRuntimeBlock(block, src, operand_src);
@@ -14005,7 +14008,7 @@ fn zirRetErrValueCode(sema: *Sema, inst: Zir.Inst.Index) CompileError!Air.Inst.R
         inst_data.get(sema.code),
         .no_embedded_nulls,
     );
-    _ = try mod.getErrorValue(name);
+    _ = try pt.getErrorValue(name);
     const error_set_type = try pt.singleErrorSetType(name);
     return Air.internedToRef((try pt.intern(.{ .err = .{
         .ty = error_set_type.toIntern(),
@@ -19564,7 +19567,7 @@ fn zirRetErrValue(
         inst_data.get(sema.code),
         .no_embedded_nulls,
     );
-    _ = try mod.getErrorValue(err_name);
+    _ = try pt.getErrorValue(err_name);
     // Return the error code from the function.
     const error_set_type = try pt.singleErrorSetType(err_name);
     const result_inst = Air.internedToRef((try pt.intern(.{ .err = .{
@@ -21607,7 +21610,7 @@ fn zirReify(
                 const name = try sema.sliceToIpString(block, src, name_val, .{
                     .needed_comptime_reason = "error set contents must be comptime-known",
                 });
-                _ = try mod.getErrorValue(name);
+                _ = try pt.getErrorValue(name);
                 const gop = names.getOrPutAssumeCapacity(name);
                 if (gop.found_existing) {
                     return sema.fail(block, src, "duplicate error '{}'", .{
@@ -27485,7 +27488,7 @@ fn fieldVal(
                         },
                         .simple_type => |t| {
                             assert(t == .anyerror);
-                            _ = try mod.getErrorValue(field_name);
+                            _ = try pt.getErrorValue(field_name);
                         },
                         else => unreachable,
                     }
@@ -27725,7 +27728,7 @@ fn fieldPtr(
                         },
                         .simple_type => |t| {
                             assert(t == .anyerror);
-                            _ = try mod.getErrorValue(field_name);
+                            _ = try pt.getErrorValue(field_name);
                         },
                         else => unreachable,
                     }
src/Value.zig
@@ -417,7 +417,7 @@ pub fn writeToMemory(val: Value, ty: Type, pt: Zcu.PerThread, buffer: []u8) erro
             var bigint_buffer: BigIntSpace = undefined;
             const bigint = BigIntMutable.init(
                 &bigint_buffer.limbs,
-                mod.global_error_set.getIndex(name).?,
+                ip.getErrorValueIfExists(name).?,
             ).toConst();
             bigint.writeTwosComplement(buffer[0..byte_count], endian);
         },
@@ -427,7 +427,7 @@ pub fn writeToMemory(val: Value, ty: Type, pt: Zcu.PerThread, buffer: []u8) erro
                 if (val.unionTag(mod)) |union_tag| {
                     const union_obj = mod.typeToUnion(ty).?;
                     const field_index = mod.unionTagFieldIndex(union_obj, union_tag).?;
-                    const field_type = Type.fromInterned(union_obj.field_types.get(&mod.intern_pool)[field_index]);
+                    const field_type = Type.fromInterned(union_obj.field_types.get(ip)[field_index]);
                     const field_val = try val.fieldValue(pt, field_index);
                     const byte_count: usize = @intCast(field_type.abiSize(pt));
                     return writeToMemory(field_val, field_type, pt, buffer[0..byte_count]);
@@ -1455,9 +1455,9 @@ pub fn getErrorName(val: Value, mod: *const Module) InternPool.OptionalNullTermi
     };
 }
 
-pub fn getErrorInt(val: Value, mod: *const Module) Module.ErrorInt {
-    return if (getErrorName(val, mod).unwrap()) |err_name|
-        @intCast(mod.global_error_set.getIndex(err_name).?)
+pub fn getErrorInt(val: Value, zcu: *Zcu) Module.ErrorInt {
+    return if (getErrorName(val, zcu).unwrap()) |err_name|
+        zcu.intern_pool.getErrorValueIfExists(err_name).?
     else
         0;
 }
src/Zcu.zig
@@ -141,9 +141,6 @@ failed_exports: std.AutoArrayHashMapUnmanaged(u32, *ErrorMsg) = .{},
 /// are stored here.
 cimport_errors: std.AutoArrayHashMapUnmanaged(AnalUnit, std.zig.ErrorBundle) = .{},
 
-/// Key is the error name, index is the error tag value. Index 0 has a length-0 string.
-global_error_set: GlobalErrorSet = .{},
-
 /// Maximum amount of distinct error values, set by --error-limit
 error_limit: ErrorInt,
 
@@ -2399,7 +2396,6 @@ pub const CompileError = error{
 pub fn init(mod: *Module, thread_count: usize) !void {
     const gpa = mod.gpa;
     try mod.intern_pool.init(gpa, thread_count);
-    try mod.global_error_set.put(gpa, .empty, {});
 }
 
 pub fn deinit(zcu: *Zcu) void {
@@ -2471,8 +2467,6 @@ pub fn deinit(zcu: *Zcu) void {
     zcu.single_exports.deinit(gpa);
     zcu.multi_exports.deinit(gpa);
 
-    zcu.global_error_set.deinit(gpa);
-
     zcu.potentially_outdated.deinit(gpa);
     zcu.outdated.deinit(gpa);
     zcu.outdated_ready.deinit(gpa);
@@ -3108,22 +3102,6 @@ pub fn addUnitReference(zcu: *Zcu, src_unit: AnalUnit, referenced_unit: AnalUnit
     gop.value_ptr.* = @intCast(ref_idx);
 }
 
-pub fn getErrorValue(
-    mod: *Module,
-    name: InternPool.NullTerminatedString,
-) Allocator.Error!ErrorInt {
-    const gop = try mod.global_error_set.getOrPut(mod.gpa, name);
-    return @as(ErrorInt, @intCast(gop.index));
-}
-
-pub fn getErrorValueFromSlice(
-    mod: *Module,
-    name: []const u8,
-) Allocator.Error!ErrorInt {
-    const interned_name = try mod.intern_pool.getOrPutString(mod.gpa, name);
-    return getErrorValue(mod, interned_name);
-}
-
 pub fn errorSetBits(mod: *Module) u16 {
     if (mod.error_limit == 0) return 0;
     return std.math.log2_int_ceil(ErrorInt, mod.error_limit + 1); // +1 for no error