[clang] [llvm] [X86] Fix x87 excess precision escaping into f32/f64 values (PR #215104)

[Dennis Duda via cfe-commits]

seritools wrote:

@tgross35 Oh, I don't mind squashing after the review process, or splitting it up into separate PRs at that point, whatever the maintainers prefer :). Probably better to keep it in one PR until then, though?

https://github.com/llvm/llvm-project/pull/215104