[SimplifyLibCalls] Inline calls to cabs when it's safe to do so

When unsafe algerbra is allowed calls to cabs(r) can be replaced by:

  sqrt(creal(r)*creal(r) + cimag(r)*cimag(r))

Patch by Paul Walker, thanks!

Differential Revision: https://reviews.llvm.org/D40069

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@320901 91177308-0d34-0410-b5e6-96231b3b80d8
7 files changed