[compiler-rt] [builtins] Start to refactor int to fp conversion functions to use a common implementation (PR #66903)

[Alex Bradbury via llvm-commits]

asb wrote:

> @asb This seems to have broken some things for -target arm64-apple-ios11.0-simulator #69779
> 
> /int_to_fp_impl.inc:60:29: error: shift count is negative [-Werror,-Wshift-count-negative] 60 | const int dstExpBias = (1 << (dstExpBits - 1)) - 1; | ^ ~~~~~~~~~~~~~~~~ 1 error generated.

Thank you and apologies for breaking your build, commented there with what I think the problem is.

https://github.com/llvm/llvm-project/pull/66903