[llvm] [WIP] [AMDGPU] [GlobalIsel] Combine Fmul with Select into ldexp instruction. (PR #120104)

[Vikash Gupta via llvm-commits]

vg0204 wrote:

> TO DO :
> 
> 1. Identify the most ideal place to invoke this combine (pre or post legalization or BOTH).
> 2. Update the test cases following it.

Addressed this!!!!

https://github.com/llvm/llvm-project/pull/120104