[llvm-branch-commits] [SPARC] Use op-then-neg instructions when we have VIS3 (PR #135717)

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koachan wrote:

> Not sure isFNegFree is doing anything in this patch, would be best to drop it and separately test the combines it enables

It prevents the multiplication tests from being rewritten into `a*-b`, a pattern that we currently don't handle.
Without it, the codegen wouldn't issue `fnmuls`/`fnmuls`/`fnsmuld` instructions.

https://github.com/llvm/llvm-project/pull/135717