[llvm] [GVN] Fold scalar mul/fmul of extracts into vector extract reuse (PR #186259)

[Vedant Neve via llvm-commits]

0bVdnt wrote:

@arsenm Thanks for the feedback! I've made the said changes. Note: I kept the tests using `fmul` rather than switching to `fdiv`, because this specific fold is currently gated to `mul` and `fmul` to match the scope of the original issue. If you think it's valuable, I would be happy to add `fdiv` support in quick follow-up PR!

https://github.com/llvm/llvm-project/pull/186259