gepConstAssumeCapacity

fn gepConstAssumeCapacity(
    self: *Builder,
    comptime kind: Constant.GetElementPtr.Kind,
    ty: Type,
    base: Constant,
    inrange: ?u16,
    indices: []const Constant,
) Constant {
    const tag: Constant.Tag = switch (kind) {
        .normal => .getelementptr,
        .inbounds => .@"getelementptr inbounds",
    };
    const base_ty = base.typeOf(self);
    const base_is_vector = base_ty.isVector(self);

    const VectorInfo = struct {
        kind: Type.Vector.Kind,
        len: u32,

        fn init(vector_ty: Type, builder: *const Builder) @This() {
            return .{ .kind = vector_ty.vectorKind(builder), .len = vector_ty.vectorLen(builder) };
        }
    };
    var vector_info: ?VectorInfo = if (base_is_vector) VectorInfo.init(base_ty, self) else null;
    for (indices) |index| {
        const index_ty = index.typeOf(self);
        switch (index_ty.tag(self)) {
            .integer => {},
            .vector, .scalable_vector => {
                const index_info = VectorInfo.init(index_ty, self);
                if (vector_info) |info|
                    assert(std.meta.eql(info, index_info))
                else
                    vector_info = index_info;
            },
            else => unreachable,
        }
    }
    if (!base_is_vector) if (vector_info) |info| switch (info.kind) {
        inline else => |vector_kind| _ = self.vectorTypeAssumeCapacity(vector_kind, info.len, base_ty),
    };

    const Key = struct {
        type: Type,
        base: Constant,
        inrange: Constant.GetElementPtr.InRangeIndex,
        indices: []const Constant,
    };
    const Adapter = struct {
        builder: *const Builder,
        pub fn hash(_: @This(), key: Key) u32 {
            var hasher = std.hash.Wyhash.init(comptime std.hash.int(@backingInt(tag)));
            hasher.update(std.mem.asBytes(&key.type));
            hasher.update(std.mem.asBytes(&key.base));
            hasher.update(std.mem.asBytes(&key.inrange));
            hasher.update(std.mem.sliceAsBytes(key.indices));
            return @truncate(hasher.final());
        }
        pub fn eql(ctx: @This(), lhs_key: Key, _: void, rhs_index: usize) bool {
            if (ctx.builder.constant_items.items(.tag)[rhs_index] != tag) return false;
            const rhs_data = ctx.builder.constant_items.items(.data)[rhs_index];
            var rhs_extra = ctx.builder.constantExtraDataTrail(Constant.GetElementPtr, rhs_data);
            const rhs_indices =
                rhs_extra.trail.next(rhs_extra.data.info.indices_len, Constant, ctx.builder);
            return lhs_key.type == rhs_extra.data.type and lhs_key.base == rhs_extra.data.base and
                lhs_key.inrange == rhs_extra.data.info.inrange and
                std.mem.eql(Constant, lhs_key.indices, rhs_indices);
        }
    };
    const data: Key = .{
        .type = ty,
        .base = base,
        .inrange = if (inrange) |index| @fromBackingInt(index) else .none,
        .indices = indices,
    };
    const gop = self.constant_map.getOrPutAssumeCapacityAdapted(data, Adapter{ .builder = self });
    if (!gop.found_existing) {
        gop.key_ptr.* = {};
        gop.value_ptr.* = {};
        self.constant_items.appendAssumeCapacity(.{
            .tag = tag,
            .data = self.addConstantExtraAssumeCapacity(Constant.GetElementPtr{
                .type = ty,
                .base = base,
                .info = .{ .indices_len = @intCast(indices.len), .inrange = data.inrange },
            }),
        });
        self.constant_extra.appendSliceAssumeCapacity(@ptrCast(indices));
    }
    return @fromBackingInt(@intCast(gop.index));
}