style(decode): add comments and small modification on code style

[Squareless-XD]

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[XiangShanRobot]

[Generated by IPC robot]
commit: 1d94032

commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
1d94032	1.926	0.451	2.705	1.192	2.824	2.464	2.401	0.920	1.390	1.616	3.413	2.734	2.419	3.275

master branch:

commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
bb94c7b	1.926			1.192	2.824	2.464		0.920		1.616	3.413		2.419	3.275
e11ec86	1.926	0.451	2.705	1.192	2.824	2.464	2.401	0.920	1.394	1.616	3.413	2.734	2.419	3.275
2574292	1.926	0.451	2.705	1.192	2.824	2.464	2.401	0.920	1.390	1.616	3.413	2.734	2.419	3.275
78f118b	1.926	0.451	2.705	1.192	2.824	2.464	2.401	0.920	1.394	1.616	3.413	2.734	2.419	3.275
ddb4906	1.926	0.451	2.705	1.192	2.824	2.464	2.401	0.920	1.394	1.616	3.413	2.734	2.419	3.275
e76e9e5	1.926	0.451	2.705	1.192	2.824	2.464	2.401	0.920	1.394	1.616	3.413	2.734	2.419	3.275
4c5e04f	1.926	0.451	2.705	1.192	2.824	2.464	2.401	0.920	1.394	1.616	3.413	2.734	2.419	3.275
c3d1dc2	1.926	0.451	2.705	1.192	2.824	2.464	2.401	0.920	1.394	1.616	3.413	2.734	2.419	3.275
a8db6d3	1.926	0.451	2.705	1.192	2.824	2.464	2.401	0.920	1.394	1.616	3.413	2.734	2.419	3.275
8ab9d9d	1.926	0.451	2.705	1.192	2.824	2.464	2.401	0.920	1.394	1.616	3.413	2.734	2.419	3.275