引自
https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html：
-falign-labels
-falign-labels=n
Align all branch targets to a power-of-two boundary,skipping up to n bytes like -falign-functions. This option can easily@H_301_9@ make code slower,because it must insert dummy operations for when the@H_301_9@ branch target is reached in the usual flow of the code.
-fno-align-labels and -falign-labels=1 are equivalent and mean that labels are not aligned.
If -falign-loops or -falign-jumps are applicable and are greater than@H_301_9@ this value,then their values are used instead.
If n is not specified or is zero,use a machine-dependent default@H_301_9@ which is very likely to be ‘1’,meaning no alignment.
Enabled at levels -O2,-O3.
考虑这个标志会使它失去更多意义……有引发代码缓存未命中的后果,甚至启用意味着何时参数采用数值(1 ..)？
