[PATCH] D127964: [DCE] Eliminate no-op atan and atan2 calls

[Rainer Orth via Phabricator via llvm-commits]

ro added a comment.

I've looked around some more and it seems the Solaris `libm` acts within the C standard: all of C99, p.219, C11, p.239, and C17, p.147 state

  A domain error may occur if both arguments are zero.

I've also found the atan2 docs on cppreference.com <https://en.cppreference.com/w/c/numeric/math/atan2> which says the same, adding

  If the implementation supports IEEE floating-point arithmetic (IEC 60559),
  
      If x and y are both zero, domain error does not occur
      If x and y are both zero, range error does not occur either 

IEC 60559 support thus seems to be lacking on Solaris and, given that's it's optional, the LLVM testsuite should cope either way.


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