From 967a299c346937316158f58f3d3ae1be7ee0f551 Mon Sep 17 00:00:00 2001 From: Luuk de Gram Date: Sun, 23 May 2021 16:43:44 +0200 Subject: [PATCH] wasm: Add support for error union as return type - This currently uses the multi-value feature to return both the possible error, and its payload. - Also genAlloc and the logic to allocate the locals itself have been seperated, so we can create more locals whenever needed, and not only when `genAlloc` is called. --- src/codegen/wasm.zig | 145 +++++++++++++++++++++++-------------------- 1 file changed, 79 insertions(+), 66 deletions(-) diff --git a/src/codegen/wasm.zig b/src/codegen/wasm.zig index 88bb6ec5a0..5c902ea703 100644 --- a/src/codegen/wasm.zig +++ b/src/codegen/wasm.zig @@ -580,7 +580,7 @@ pub const Context = struct { .Pointer, .ErrorSet, => wasm.Valtype.i32, - .Struct, .ErrorUnion => unreachable, // Multi typed, must be handled individually by genAlloc(). + .Struct, .ErrorUnion => unreachable, // Multi typed, must be handled individually. else => self.fail(src, "TODO - Wasm valtype for type '{s}'", .{ty.zigTypeTag()}), }; } @@ -614,6 +614,55 @@ pub const Context = struct { } } + /// Creates one or multiple locals for a given `Type`. + /// Returns a corresponding `Wvalue` that can either be of tag + /// local or multi_value + fn allocLocal(self: *Context, ty: Type) InnerError!WValue { + const initial_index = self.local_index; + switch (ty.zigTypeTag()) { + .Struct => { + // for each struct field, generate a local + const struct_data: *Module.Struct = ty.castTag(.@"struct").?.data; + try self.locals.ensureCapacity(self.gpa, self.locals.items.len + struct_data.fields.count()); + for (struct_data.fields.items()) |entry| { + const val_type = try self.genValtype( + .{ .node_offset = struct_data.node_offset }, + entry.value.ty, + ); + self.locals.appendAssumeCapacity(val_type); + self.local_index += 1; + } + return WValue{ .multi_value = .{ + .index = initial_index, + .count = @intCast(u32, struct_data.fields.count()), + } }; + }, + .ErrorUnion => { + // generate a local for both the error and the payload. + const payload_type = ty.errorUnionChild(); + + // we emit the payload value as the first local, and the error as the second + // The first local is also used to find the index of the error. + try self.locals.ensureCapacity(self.gpa, self.locals.items.len + 2); + const val_type = try self.genValtype(.{ .node_offset = 0 }, payload_type); + self.locals.appendAssumeCapacity(val_type); + self.locals.appendAssumeCapacity(wasm.valtype(.i32)); // error values are always i32 + self.local_index += 2; + + return WValue{ .multi_value = .{ + .index = initial_index, + .count = 2, + } }; + }, + else => { + const valtype = try self.genValtype(.{ .node_offset = 0 }, ty); + try self.locals.append(self.gpa, valtype); + self.local_index += 1; + return WValue{ .local = initial_index }; + }, + } + } + fn genFunctype(self: *Context) InnerError!void { assert(self.decl.has_tv); const ty = self.decl.ty; @@ -636,8 +685,19 @@ pub const Context = struct { // return type const return_type = ty.fnReturnType(); - switch (return_type.tag()) { - .void, .noreturn => try leb.writeULEB128(writer, @as(u32, 0)), + switch (return_type.zigTypeTag()) { + .Void, .NoReturn => try leb.writeULEB128(writer, @as(u32, 0)), + .Struct => return self.fail(.{ .node_offset = 0 }, "TODO: Implement struct as return type for wasm", .{}), + .Optional => return self.fail(.{ .node_offset = 0 }, "TODO: Implement optionals as return type for wasm", .{}), + .ErrorUnion => { + try leb.writeULEB128(writer, @as(u32, 2)); + const val_type = try self.genValtype( + .{ .node_offset = 0 }, + return_type.errorUnionChild(), + ); + try writer.writeByte(val_type); + try writer.writeByte(wasm.valtype(.i32)); // error code is always an i32 integer. + }, else => |ret_type| { try leb.writeULEB128(writer, @as(u32, 1)); // Can we maybe get the source index of the return type? @@ -763,6 +823,7 @@ pub const Context = struct { .switchbr => self.genSwitchBr(inst.castTag(.switchbr).?), .unreach => self.genUnreachable(inst.castTag(.unreach).?), .unwrap_errunion_payload => self.genUnwrapErrUnionPayload(inst.castTag(.unwrap_errunion_payload).?), + .wrap_errunion_payload => self.genWrapErrUnionPayload(inst.castTag(.wrap_errunion_payload).?), .xor => self.genBinOp(inst.castTag(.xor).?, .xor), else => self.fail(.{ .node_offset = 0 }, "TODO: Implement wasm inst: {s}", .{inst.tag}), }; @@ -787,7 +848,7 @@ pub const Context = struct { const func_inst = inst.func.castTag(.constant).?; const func_val = inst.func.value().?; - const target = blk: { + const target: *Decl = blk: { if (func_val.castTag(.function)) |func| { break :blk func.data.owner_decl; } else if (func_val.castTag(.extern_fn)) |ext_fn| { @@ -815,50 +876,7 @@ pub const Context = struct { fn genAlloc(self: *Context, inst: *Inst.NoOp) InnerError!WValue { const elem_type = inst.base.ty.elemType(); - const initial_index = self.local_index; - - switch (elem_type.zigTypeTag()) { - .Struct => { - // for each struct field, generate a local - const struct_data: *Module.Struct = elem_type.castTag(.@"struct").?.data; - try self.locals.ensureCapacity(self.gpa, self.locals.items.len + struct_data.fields.count()); - for (struct_data.fields.items()) |entry| { - const val_type = try self.genValtype( - .{ .node_offset = struct_data.node_offset }, - entry.value.ty, - ); - self.locals.appendAssumeCapacity(val_type); - self.local_index += 1; - } - return WValue{ .multi_value = .{ - .index = initial_index, - .count = @intCast(u32, struct_data.fields.count()), - } }; - }, - .ErrorUnion => { - // generate a local for both the error and the payload. - const payload_type = elem_type.errorUnionChild(); - - // we emit the payload value as the first local, and the error as the second - // The first local is also used to find the index of the error. - try self.locals.ensureCapacity(self.gpa, self.locals.items.len + 2); - const val_type = try self.genValtype(.{ .node_offset = 0 }, payload_type); - self.locals.appendAssumeCapacity(val_type); - self.locals.appendAssumeCapacity(wasm.valtype(.i32)); // error values are always i32 - self.local_index += 2; - - return WValue{ .multi_value = .{ - .index = initial_index, - .count = 2, - } }; - }, - else => { - const valtype = try self.genValtype(inst.base.src, elem_type); - try self.locals.append(self.gpa, valtype); - self.local_index += 1; - return WValue{ .local = initial_index }; - }, - } + return self.allocLocal(elem_type); } fn genStore(self: *Context, inst: *Inst.BinOp) InnerError!WValue { @@ -867,21 +885,6 @@ pub const Context = struct { const lhs = self.resolveInst(inst.lhs); const rhs = self.resolveInst(inst.rhs); - // switch (lhs) { - // // When assigning a value to a multi_value such as a struct, - // // we simply assign the local_index to the rhs one. - // // This allows us to update struct fields without having to individually - // // set each local as each field's index will be calculated off the struct's base index - // .multi_value => self.values.put(self.gpa, inst.lhs, rhs) catch unreachable, // Instruction does not dominate all uses! - // .local => |local| { - // try self.emitWValue(rhs); - // try writer.writeByte(wasm.opcode(.local_set)); - // try leb.writeULEB128(writer, lhs.local); - // }, - // else => unreachable, - // } - // return .none; - switch (lhs) { .multi_value => |multi_value| switch (rhs) { // When assigning a value to a multi_value such as a struct, @@ -889,8 +892,8 @@ pub const Context = struct { // This allows us to update struct fields without having to individually // set each local as each field's index will be calculated off the struct's base index .multi_value => self.values.put(self.gpa, inst.lhs, rhs) catch unreachable, // Instruction does not dominate all uses! - .constant => { - // emit all values onto the stack + .constant, .none => { + // emit all values onto the stack if constant try self.emitWValue(rhs); // for each local, pop the stack value into the local @@ -1037,8 +1040,14 @@ pub const Context = struct { const payload_type = ty.errorUnionChild(); if (value.getError()) |_| { // no payload, so write a '0' const - try writer.writeByte(wasm.opcode(.i32_const)); + const opcode: wasm.Opcode = buildOpcode(.{ + .op = .@"const", + .valtype1 = try self.typeToValtype(src, payload_type), + }); + try writer.writeByte(wasm.opcode(opcode)); try leb.writeULEB128(writer, @as(u32, 0)); + + // write the error value try self.emitConstant(src, data, error_type); } else { // payload first @@ -1287,4 +1296,8 @@ pub const Context = struct { // payload's local index is that of its multi_value index, so convert it to a `WValue.local` return WValue{ .local = operand.multi_value.index }; } + + fn genWrapErrUnionPayload(self: *Context, inst: *Inst.UnOp) InnerError!WValue { + return self.resolveInst(inst.operand); + } };