pub const Index = enum(u32) {
    none = std.math.maxInt(u31),
    _,

    pub fn name(self: Instruction.Index, function: *const Function) String {
        return function.names[@intFromEnum(self)];
    }

    pub fn valueIndex(self: Instruction.Index, function: *const Function) u32 {
        return function.value_indices[@intFromEnum(self)];
    }

    pub fn toValue(self: Instruction.Index) Value {
        return @enumFromInt(@intFromEnum(self));
    }

    pub fn isTerminatorWip(self: Instruction.Index, wip: *const WipFunction) bool {
        return switch (wip.instructions.items(.tag)[@intFromEnum(self)]) {
            .br,
            .br_cond,
            .indirectbr,
            .ret,
            .@"ret void",
            .@"switch",
            .@"unreachable",
            => true,
            else => false,
        };
    }

    pub fn hasResultWip(self: Instruction.Index, wip: *const WipFunction) bool {
        return switch (wip.instructions.items(.tag)[@intFromEnum(self)]) {
            .br,
            .br_cond,
            .fence,
            .indirectbr,
            .ret,
            .@"ret void",
            .store,
            .@"store atomic",
            .@"switch",
            .@"unreachable",
            .block,
            => false,
            .call,
            .@"call fast",
            .@"musttail call",
            .@"musttail call fast",
            .@"notail call",
            .@"notail call fast",
            .@"tail call",
            .@"tail call fast",
            => self.typeOfWip(wip) != .void,
            else => true,
        };
    }

    pub fn typeOfWip(self: Instruction.Index, wip: *const WipFunction) Type {
        const instruction = wip.instructions.get(@intFromEnum(self));
        return switch (instruction.tag) {
            .add,
            .@"add nsw",
            .@"add nuw",
            .@"add nuw nsw",
            .@"and",
            .ashr,
            .@"ashr exact",
            .fadd,
            .@"fadd fast",
            .fdiv,
            .@"fdiv fast",
            .fmul,
            .@"fmul fast",
            .frem,
            .@"frem fast",
            .fsub,
            .@"fsub fast",
            .lshr,
            .@"lshr exact",
            .mul,
            .@"mul nsw",
            .@"mul nuw",
            .@"mul nuw nsw",
            .@"or",
            .sdiv,
            .@"sdiv exact",
            .shl,
            .@"shl nsw",
            .@"shl nuw",
            .@"shl nuw nsw",
            .srem,
            .sub,
            .@"sub nsw",
            .@"sub nuw",
            .@"sub nuw nsw",
            .udiv,
            .@"udiv exact",
            .urem,
            .xor,
            => wip.extraData(Binary, instruction.data).lhs.typeOfWip(wip),
            .addrspacecast,
            .bitcast,
            .fpext,
            .fptosi,
            .fptoui,
            .fptrunc,
            .inttoptr,
            .ptrtoint,
            .sext,
            .sitofp,
            .trunc,
            .uitofp,
            .zext,
            => wip.extraData(Cast, instruction.data).type,
            .alloca,
            .@"alloca inalloca",
            => wip.builder.ptrTypeAssumeCapacity(
                wip.extraData(Alloca, instruction.data).info.addr_space,
            ),
            .arg => wip.function.typeOf(wip.builder)
                .functionParameters(wip.builder)[instruction.data],
            .atomicrmw => wip.extraData(AtomicRmw, instruction.data).val.typeOfWip(wip),
            .block => .label,
            .br,
            .br_cond,
            .fence,
            .indirectbr,
            .ret,
            .@"ret void",
            .store,
            .@"store atomic",
            .@"switch",
            .@"unreachable",
            => .none,
            .call,
            .@"call fast",
            .@"musttail call",
            .@"musttail call fast",
            .@"notail call",
            .@"notail call fast",
            .@"tail call",
            .@"tail call fast",
            => wip.extraData(Call, instruction.data).ty.functionReturn(wip.builder),
            .cmpxchg,
            .@"cmpxchg weak",
            => wip.builder.structTypeAssumeCapacity(.normal, &.{
                wip.extraData(CmpXchg, instruction.data).cmp.typeOfWip(wip),
                .i1,
            }),
            .extractelement => wip.extraData(ExtractElement, instruction.data)
                .val.typeOfWip(wip).childType(wip.builder),
            .extractvalue => {
                var extra = wip.extraDataTrail(ExtractValue, instruction.data);
                const indices = extra.trail.next(extra.data.indices_len, u32, wip);
                return extra.data.val.typeOfWip(wip).childTypeAt(indices, wip.builder);
            },
            .@"fcmp false",
            .@"fcmp fast false",
            .@"fcmp fast oeq",
            .@"fcmp fast oge",
            .@"fcmp fast ogt",
            .@"fcmp fast ole",
            .@"fcmp fast olt",
            .@"fcmp fast one",
            .@"fcmp fast ord",
            .@"fcmp fast true",
            .@"fcmp fast ueq",
            .@"fcmp fast uge",
            .@"fcmp fast ugt",
            .@"fcmp fast ule",
            .@"fcmp fast ult",
            .@"fcmp fast une",
            .@"fcmp fast uno",
            .@"fcmp oeq",
            .@"fcmp oge",
            .@"fcmp ogt",
            .@"fcmp ole",
            .@"fcmp olt",
            .@"fcmp one",
            .@"fcmp ord",
            .@"fcmp true",
            .@"fcmp ueq",
            .@"fcmp uge",
            .@"fcmp ugt",
            .@"fcmp ule",
            .@"fcmp ult",
            .@"fcmp une",
            .@"fcmp uno",
            .@"icmp eq",
            .@"icmp ne",
            .@"icmp sge",
            .@"icmp sgt",
            .@"icmp sle",
            .@"icmp slt",
            .@"icmp uge",
            .@"icmp ugt",
            .@"icmp ule",
            .@"icmp ult",
            => wip.extraData(Binary, instruction.data).lhs.typeOfWip(wip)
                .changeScalarAssumeCapacity(.i1, wip.builder),
            .fneg,
            .@"fneg fast",
            => @as(Value, @enumFromInt(instruction.data)).typeOfWip(wip),
            .getelementptr,
            .@"getelementptr inbounds",
            => {
                var extra = wip.extraDataTrail(GetElementPtr, instruction.data);
                const indices = extra.trail.next(extra.data.indices_len, Value, wip);
                const base_ty = extra.data.base.typeOfWip(wip);
                if (!base_ty.isVector(wip.builder)) for (indices) |index| {
                    const index_ty = index.typeOfWip(wip);
                    if (!index_ty.isVector(wip.builder)) continue;
                    return index_ty.changeScalarAssumeCapacity(base_ty, wip.builder);
                };
                return base_ty;
            },
            .insertelement => wip.extraData(InsertElement, instruction.data).val.typeOfWip(wip),
            .insertvalue => wip.extraData(InsertValue, instruction.data).val.typeOfWip(wip),
            .load,
            .@"load atomic",
            => wip.extraData(Load, instruction.data).type,
            .phi,
            .@"phi fast",
            => wip.extraData(Phi, instruction.data).type,
            .select,
            .@"select fast",
            => wip.extraData(Select, instruction.data).lhs.typeOfWip(wip),
            .shufflevector => {
                const extra = wip.extraData(ShuffleVector, instruction.data);
                return extra.lhs.typeOfWip(wip).changeLengthAssumeCapacity(
                    extra.mask.typeOfWip(wip).vectorLen(wip.builder),
                    wip.builder,
                );
            },
            .va_arg => wip.extraData(VaArg, instruction.data).type,
        };
    }

    pub fn typeOf(
        self: Instruction.Index,
        function_index: Function.Index,
        builder: *Builder,
    ) Type {
        const function = function_index.ptrConst(builder);
        const instruction = function.instructions.get(@intFromEnum(self));
        return switch (instruction.tag) {
            .add,
            .@"add nsw",
            .@"add nuw",
            .@"add nuw nsw",
            .@"and",
            .ashr,
            .@"ashr exact",
            .fadd,
            .@"fadd fast",
            .fdiv,
            .@"fdiv fast",
            .fmul,
            .@"fmul fast",
            .frem,
            .@"frem fast",
            .fsub,
            .@"fsub fast",
            .lshr,
            .@"lshr exact",
            .mul,
            .@"mul nsw",
            .@"mul nuw",
            .@"mul nuw nsw",
            .@"or",
            .sdiv,
            .@"sdiv exact",
            .shl,
            .@"shl nsw",
            .@"shl nuw",
            .@"shl nuw nsw",
            .srem,
            .sub,
            .@"sub nsw",
            .@"sub nuw",
            .@"sub nuw nsw",
            .udiv,
            .@"udiv exact",
            .urem,
            .xor,
            => function.extraData(Binary, instruction.data).lhs.typeOf(function_index, builder),
            .addrspacecast,
            .bitcast,
            .fpext,
            .fptosi,
            .fptoui,
            .fptrunc,
            .inttoptr,
            .ptrtoint,
            .sext,
            .sitofp,
            .trunc,
            .uitofp,
            .zext,
            => function.extraData(Cast, instruction.data).type,
            .alloca,
            .@"alloca inalloca",
            => builder.ptrTypeAssumeCapacity(
                function.extraData(Alloca, instruction.data).info.addr_space,
            ),
            .arg => function.global.typeOf(builder)
                .functionParameters(builder)[instruction.data],
            .atomicrmw => function.extraData(AtomicRmw, instruction.data)
                .val.typeOf(function_index, builder),
            .block => .label,
            .br,
            .br_cond,
            .fence,
            .indirectbr,
            .ret,
            .@"ret void",
            .store,
            .@"store atomic",
            .@"switch",
            .@"unreachable",
            => .none,
            .call,
            .@"call fast",
            .@"musttail call",
            .@"musttail call fast",
            .@"notail call",
            .@"notail call fast",
            .@"tail call",
            .@"tail call fast",
            => function.extraData(Call, instruction.data).ty.functionReturn(builder),
            .cmpxchg,
            .@"cmpxchg weak",
            => builder.structTypeAssumeCapacity(.normal, &.{
                function.extraData(CmpXchg, instruction.data)
                    .cmp.typeOf(function_index, builder),
                .i1,
            }),
            .extractelement => function.extraData(ExtractElement, instruction.data)
                .val.typeOf(function_index, builder).childType(builder),
            .extractvalue => {
                var extra = function.extraDataTrail(ExtractValue, instruction.data);
                const indices = extra.trail.next(extra.data.indices_len, u32, function);
                return extra.data.val.typeOf(function_index, builder)
                    .childTypeAt(indices, builder);
            },
            .@"fcmp false",
            .@"fcmp fast false",
            .@"fcmp fast oeq",
            .@"fcmp fast oge",
            .@"fcmp fast ogt",
            .@"fcmp fast ole",
            .@"fcmp fast olt",
            .@"fcmp fast one",
            .@"fcmp fast ord",
            .@"fcmp fast true",
            .@"fcmp fast ueq",
            .@"fcmp fast uge",
            .@"fcmp fast ugt",
            .@"fcmp fast ule",
            .@"fcmp fast ult",
            .@"fcmp fast une",
            .@"fcmp fast uno",
            .@"fcmp oeq",
            .@"fcmp oge",
            .@"fcmp ogt",
            .@"fcmp ole",
            .@"fcmp olt",
            .@"fcmp one",
            .@"fcmp ord",
            .@"fcmp true",
            .@"fcmp ueq",
            .@"fcmp uge",
            .@"fcmp ugt",
            .@"fcmp ule",
            .@"fcmp ult",
            .@"fcmp une",
            .@"fcmp uno",
            .@"icmp eq",
            .@"icmp ne",
            .@"icmp sge",
            .@"icmp sgt",
            .@"icmp sle",
            .@"icmp slt",
            .@"icmp uge",
            .@"icmp ugt",
            .@"icmp ule",
            .@"icmp ult",
            => function.extraData(Binary, instruction.data).lhs.typeOf(function_index, builder)
                .changeScalarAssumeCapacity(.i1, builder),
            .fneg,
            .@"fneg fast",
            => @as(Value, @enumFromInt(instruction.data)).typeOf(function_index, builder),
            .getelementptr,
            .@"getelementptr inbounds",
            => {
                var extra = function.extraDataTrail(GetElementPtr, instruction.data);
                const indices = extra.trail.next(extra.data.indices_len, Value, function);
                const base_ty = extra.data.base.typeOf(function_index, builder);
                if (!base_ty.isVector(builder)) for (indices) |index| {
                    const index_ty = index.typeOf(function_index, builder);
                    if (!index_ty.isVector(builder)) continue;
                    return index_ty.changeScalarAssumeCapacity(base_ty, builder);
                };
                return base_ty;
            },
            .insertelement => function.extraData(InsertElement, instruction.data)
                .val.typeOf(function_index, builder),
            .insertvalue => function.extraData(InsertValue, instruction.data)
                .val.typeOf(function_index, builder),
            .load,
            .@"load atomic",
            => function.extraData(Load, instruction.data).type,
            .phi,
            .@"phi fast",
            => function.extraData(Phi, instruction.data).type,
            .select,
            .@"select fast",
            => function.extraData(Select, instruction.data).lhs.typeOf(function_index, builder),
            .shufflevector => {
                const extra = function.extraData(ShuffleVector, instruction.data);
                return extra.lhs.typeOf(function_index, builder).changeLengthAssumeCapacity(
                    extra.mask.typeOf(function_index, builder).vectorLen(builder),
                    builder,
                );
            },
            .va_arg => function.extraData(VaArg, instruction.data).type,
        };
    }

    const FormatData = struct {
        instruction: Instruction.Index,
        function: Function.Index,
        builder: *Builder,
    };
    fn format(
        data: FormatData,
        comptime fmt_str: []const u8,
        _: std.fmt.FormatOptions,
        writer: anytype,
    ) @TypeOf(writer).Error!void {
        if (comptime std.mem.indexOfNone(u8, fmt_str, ", %")) |_|
            @compileError("invalid format string: '" ++ fmt_str ++ "'");
        if (comptime std.mem.indexOfScalar(u8, fmt_str, ',') != null) {
            if (data.instruction == .none) return;
            try writer.writeByte(',');
        }
        if (comptime std.mem.indexOfScalar(u8, fmt_str, ' ') != null) {
            if (data.instruction == .none) return;
            try writer.writeByte(' ');
        }
        if (comptime std.mem.indexOfScalar(u8, fmt_str, '%') != null) try writer.print(
            "{%} ",
            .{data.instruction.typeOf(data.function, data.builder).fmt(data.builder)},
        );
        assert(data.instruction != .none);
        try writer.print("%{}", .{
            data.instruction.name(data.function.ptrConst(data.builder)).fmt(data.builder),
        });
    }
    pub fn fmt(
        self: Instruction.Index,
        function: Function.Index,
        builder: *Builder,
    ) std.fmt.Formatter(format) {
        return .{ .data = .{ .instruction = self, .function = function, .builder = builder } };
    }
}