It is said that that was all that he said.

第一个that是that从句
第二个that是代词吧，应该是“那些（话）”的意思
第三个that是all that=what

第一个that是that从句
第二个that是代词
第三个that是all that

1.宾语从句
2.代词,代他讲的话
3.定语从句

第一个that是It is said that句式的引导词。
第二个that是指示代词，代替sth.
第三个that是关系代词，引导定语从句，修饰all 。