[llvm] [RISCV][GlobalISel] Vector Extension vadd Legalizer (PR #71400)

[Luke Lau via llvm-commits]

lukel97 wrote:

> ```
> 0. Program arguments: ../../../../../../build/bin/llc -mtriple=riscv32 -mattr=+v -debug-only=isel -view-legalize-dags ./rv32/legalize-vadd.mir
> 1. Running pass 'Function Pass Manager' on module './rv32/legalize-vadd.mir'.
> 2. Running pass 'Live Variable Analysis' on function '@test_vadd'
> gio: file:///tmp/dag.test_vadd-e7c028.dot: No application is registered as handling this file
> ```
> 
> Is there any obvious mistake I made?

That `-view-legalize-dags` argument will generate a .dot file and try to open it with a graphviz viewer, it's mainly useful for debugging. Looks like it's complaining that you don't have a viewer installed, [you can install one](https://packages.debian.org/stable/graphviz) or just omit the argument!

https://github.com/llvm/llvm-project/pull/71400