Add some comments to compiler.h
Add some comments to compiler.h

pengli09/Paddle,baidu/Paddle,QiJune/Paddle,PaddlePaddle/Paddle,jacquesqiao/Paddle,QiJune/Paddle,cxysteven/Paddle,cxysteven/Paddle,lispc/Paddle,QiJune/Paddle,pengli09/Paddle,lispc/Paddle,gangliao/Paddle,lcy-seso/Paddle,yu239/Paddle,livc/Paddle,lispc/Paddle,PaddlePaddle/Paddle,livc/Paddle,pengli09/Paddle,Canpio/Paddle,PaddlePaddle/Paddle,hedaoyuan/Paddle,pkuyym/Paddle,QiJune/Paddle,hedaoyuan/Paddle,tensor-tang/Paddle,gangliao/Paddle,emailweixu/Paddle,baidu/Paddle,lispc/Paddle,lcy-seso/Paddle,cxysteven/Paddle,wen-bo-yang/Paddle,pengli09/Paddle,tensor-tang/Paddle,gangliao/Paddle,pkuyym/Paddle,chengduoZH/Paddle,hedaoyuan/Paddle,pengli09/Paddle,emailweixu/Paddle,jacquesqiao/Paddle,putcn/Paddle,Canpio/Paddle,baidu/Paddle,hedaoyuan/Paddle,chengduoZH/Paddle,gangliao/Paddle,cxysteven/Paddle,pengli09/Paddle,luotao1/Paddle,livc/Paddle,reyoung/Paddle,luotao1/Paddle,pkuyym/Paddle,pkuyym/Paddle,wen-bo-yang/Paddle,putcn/Paddle,pengli09/Paddle,livc/Paddle,jacquesqiao/Paddle,Canpio/Paddle,yu239/Paddle,luotao1/Paddle,pkuyym/Paddle,cxysteven/Paddle,luotao1/Paddle,QiJune/Paddle,putcn/Paddle,Canpio/Paddle,gangliao/Paddle,wen-bo-yang/Paddle,tensor-tang/Paddle,yu239/Paddle,lcy-seso/Paddle,hedaoyuan/Paddle,jacquesqiao/Paddle,cxysteven/Paddle,hedaoyuan/Paddle,PaddlePaddle/Paddle,livc/Paddle,PaddlePaddle/Paddle,yu239/Paddle,baidu/Paddle,putcn/Paddle,wen-bo-yang/Paddle,emailweixu/Paddle,Canpio/Paddle,luotao1/Paddle,lispc/Paddle,luotao1/Paddle,wen-bo-yang/Paddle,yu239/Paddle,cxysteven/Paddle,Canpio/Paddle,livc/Paddle,yu239/Paddle,PaddlePaddle/Paddle,lcy-seso/Paddle,reyoung/Paddle,reyoung/Paddle,yu239/Paddle,Canpio/Paddle,jacquesqiao/Paddle,wen-bo-yang/Paddle,emailweixu/Paddle,tensor-tang/Paddle,livc/Paddle,lispc/Paddle,jacquesqiao/Paddle,pengli09/Paddle,luotao1/Paddle,lcy-seso/Paddle,wen-bo-yang/Paddle,chengduoZH/Paddle,lcy-seso/Paddle,reyoung/Paddle,hedaoyuan/Paddle,chengduoZH/Paddle,emailweixu/Paddle,lispc/Paddle,lispc/Paddle,QiJune/Paddle,gangliao/Paddle,putcn/Paddle,emailweixu/Paddle,pkuyym/Paddle,reyoung/Paddle,chengduoZH/Paddle,emailweixu/Paddle,yu239/Paddle,putcn/Paddle,baidu/Paddle,PaddlePaddle/Paddle,gangliao/Paddle,tensor-tang/Paddle,Canpio/Paddle,hedaoyuan/Paddle,reyoung/Paddle