Docs: Update Math API page

[adeljo-amd]

The goal of this PR is to improve the usability of the Math API page, by providing information about each function's maximum ULP error when compared against the C++ standard library (if applicable). It also highlights specific math functions which are unsupported too.

[randyh62]

Looks good to me, except for the missing data related to the functions that don't run on GPUs.

[neon60]

@adeljo-amd Could you please rebase the branch?

[adeljo-amd]

@adeljo-amd Could you please rebase the branch?

Done

[adeljo-amd]

@neon60 Updated and added test ranges too

[g-h-c]

I find the explanation of ffs() might lack information. ffs() returns 0 if the integer has no bit set to 1. i.e.

• ffs(0) returns 0
• ffs(x) returns the position of the first bit set in x +1

Also should we warn that fns() calls are potentially slower? (as the compiler does not have a intrinsic for them, unlike ffs()):

• ffs() uses the ff1 instruction present both in RDNA and CDNA. See https://godbolt.org/z/3ncG3E99o
• fns() has no equivalent intrinsic, and it is implemented with a loop in the CLR.

[adeljo-amd]

I find the explanation of ffs() might lack information. ffs() returns 0 if the integer has no bit set to 1. i.e.

• ffs(0) returns 0
• ffs(x) returns the position of the first bit set in x +1

Also should we warn that fns() calls are potentially slower? (as the compiler does not have a intrinsic for them, unlike ffs()):

• ffs() uses the ff1 instruction present both in RDNA and CDNA. See https://godbolt.org/z/3ncG3E99o
• fns() has no equivalent intrinsic, and it is implemented with a loop in the CLR.

@g-h-c These are fair suggestions - it probably won't be necessary to mention that ffs() calls ff1, but it would be good to highlight that fns() is implemented via software rather than via hardware intrinsics.

Besides updating the ffs() description, I think it would be good to align this with ffsll(), which I imagine has the same behavior

[adeljo-amd]

@g-h-c Fixed, let me know what you think