zeroInitConstAssumeCapacity

fn zeroInitConstAssumeCapacity(self: *Builder, ty: Type) Constant {
    switch (ty) {
        inline .half,
        .bfloat,
        .float,
        .double,
        .fp128,
        .x86_fp80,
        => |tag| return @field(Builder, @tagName(tag) ++ "ConstAssumeCapacity")(self, 0.0),
        .ppc_fp128 => return self.ppc_fp128ConstAssumeCapacity(.{ 0.0, 0.0 }),
        .token => return .none,
        .i1 => return .false,
        else => switch (self.type_items.items[@backingInt(ty)].tag) {
            .simple,
            .function,
            .vararg_function,
            => unreachable,
            .integer => {
                var limbs: [std.math.big.int.calcLimbLen(0)]std.math.big.Limb = undefined;
                const bigint = std.math.big.int.Mutable.init(&limbs, 0);
                return self.bigIntConstAssumeCapacity(ty, bigint.toConst()) catch unreachable;
            },
            .pointer => return self.nullConstAssumeCapacity(ty),
            .target,
            .vector,
            .scalable_vector,
            .small_array,
            .array,
            .structure,
            .packed_structure,
            .named_structure,
            => {},
        },
    }
    const result = self.getOrPutConstantNoExtraAssumeCapacity(
        .{ .tag = .zeroinitializer, .data = @backingInt(ty) },
    );
    return result.constant;
}