Added the right file for sin_div_tan.ll test case (incorrect was added in previous commit).

In D41659#965699, @davide wrote:

Meta point: It's unclear to me whether this is something profitable to implement.
Sure, you can probably take a textbook and implement all the possible identities written there, but, what's the point?

I looked and it seems other compilers (most notably, GCC) don't implement at least the first transformation you implemented (I didn't bother to check the others).
https://godbolt.org/g/kKP5PW

tl;dr: what's your motivation?

In D41659#965696, @rengolin wrote:

This may need special guard with fast-math flags (precision, etc), no?

In D41659#965694, @fhahn wrote:

Thanks for your patch!

Usually it is easier to review smaller patches. Splitting it up into 4 patches for the 4 different cases you implemented would make it slightly easier to reason about the 4 unrelated transformation in isolation.

In D41659#965688, @asb wrote:

As mentioned in llvm-dev, it looks like David Majnemer and Craig Topper might be appropriate reviewers for this patch (or can perhaps help to suggest other reviewers).

Hi, thanks for the comment. Thanks for adding appropriate reviewers for the patch.

Updates made: