[llvm] [RISCV] Add branch folding before branch relaxation (PR #134760)

[Mikhail R. Gadelha via llvm-commits]

mikhailramalho wrote:

Updated numbers with blender:
```
Benchmark                       DirA            DirB   Diff (%)
============================================================
500.perlbench_r         165826196167    166357789074      0.32%
502.gcc_r               219399420992    219803323636      0.18%
505.mcf_r               156797058571    157114468160      0.20%
508.namd_r              217322414517    217333387648      0.01%
510.parest_r            143264868963    143516815618      0.18%
511.povray_r             30514506955     30467500922     -0.15%
519.lbm_r                95279677707     95782257905      0.53%
520.omnetpp_r           141462225575    141696999927      0.17%
523.xalancbmk_r         282306179988    284057163151      0.62%
525.x264_r              183580253187    183653095365      0.04%
526.blender_r           660276542155    660835589453      0.08%
531.deepsjeng_r         350577788863    351478176840      0.26%
538.imagick_r           238460281809    247684328639      3.87%
541.leela_r             405842310516    406313280179      0.12%
544.nab_r               396838566663    398308105312      0.37%
557.xz_r                124382811159    124798965273      0.33%


https://github.com/llvm/llvm-project/pull/134760