[InstSimplify] loosen FMF for sqrt(X) * sqrt(X) --> X

As shown in the code comment, we don't need all of 'fast', 
but we do need reassoc + nsz + nnan.

Differential Revision: https://reviews.llvm.org/D43765


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@327796 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed