[libclc] [libclc] Reduce bithacking in CLC frexp (PR #129871)

[Fraser Cormack via cfe-commits]

frasercrmck wrote:

It strikes me as a swiftshader bug. If `x` is a denormal/subnormal number and it is being untouched by this function and really reaching this comparison as `0x1.008p-140` then I don't believe it should ever compare true against `0.0`.

My reading of flush-to-zero ([here](https://registry.khronos.org/OpenCL/specs/3.0-unified/html/OpenCL_C.html#inf-nan-and-denormalized-numbers)) is that it only applies to certain functions and in-built operations but not comparison operators.

I don't have any definitive source to prove this, though.

https://github.com/llvm/llvm-project/pull/129871