[x86] limit transform for select-of-fp-constants

This should likely be adjusted to limit this transform
further, but these diffs should be clear wins.

If we have blendv/conditional move, then we should assume 
those are cheap ops. The loads become independent of the
compare, so those can be speculated before we need to use 
the values in the blend/mov.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@347526 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed