AMDGPU: Fold undef fcanonicalize to qNaN

We could choose a free 0 for this, but this
matches the behavior for fmul undef, 1.0. Also,
the NaN use is more useful for folding use operations
although if it's not eliminated it is more expensive
in terms of code size.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@338376 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed