[llvm] [GlobalISel][AArch64] Legalize G_FABS and G_FNEG for SVE (PR #114784)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

This PR is somewhere between proposal and template. The market share of fneg and fabs won't be that high. The cost of lowering fneg in the DAG for AArch64 with C++ is so low that pattens would introduce overhead or more work. For GlobalISel the situation is the opposite.

https://github.com/llvm/llvm-project/pull/114784