[llvm] [RISCV] Add late optimization pass for RISC-V to optimize branch instructions (PR #131728)

[Mikhail R. Gadelha via llvm-commits]

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@@ -567,6 +568,7 @@ void RISCVPassConfig::addPreEmitPass() {
     addPass(createMachineCopyPropagationPass(true));
   addPass(&BranchRelaxationPassID);
   addPass(createRISCVMakeCompressibleOptPass());
+  addPass(createRISCVLatePeepholeOptPass());
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mikhailramalho wrote:

I'm checking my notes here and the pattern that generates the branch, i.e.:
```
bb.2:
  renamable $x10 = XORI killed renamable $x10, -1
  renamable $x10 = BEXTI killed renamable $x10, 13
  BNE killed renamable $x10, $x0, %bb.5
```
Seems to be formed by `MachineBlockPlacementPass`, so maybe we can move this change to the beginning of `addPreEmitPass` and still be able to optimize it.

https://github.com/llvm/llvm-project/pull/131728