Branch taken rate of Linux kernel compiled with GCC 4.9

[Pengfei Yuan]

Actually GCC does not help reduce branch misprediction rate on modern
X86 processors.
Reducing branch taken rate is more important.
Related discussion: https://gcc.gnu.org/ml/gcc/2014-12/msg00000.html

Yuan

2015-01-13 22:13 GMT+08:00  <Paul_Koning@dell.com>:
> Depending on what the processor hardware can do, the data you need is the branch mispredict rate.  A lot of processors will predict forward branches not taken, reverse branches taken, and I believe GCC optimizes that way.  (Some processors are different: MC68040 predicts all branches taken no matter what direction!)  If the mispredict rate is unreasonably high, then that might indeed suggest missed optimizations.
>
>         paul