[InstCombine] canonicalize fcmp+select to fabs
This is complicated by -0.0 and nan. This is based on the DAG patterns
as shown in D44091. I'm hoping that we can just remove those DAG folds
and always rely on IR canonicalization to handle the matching to fabs.
We would still need to delete the broken code from DAGCombiner to fix
PR36600:
https://bugs.llvm.org/show_bug.cgi?id=36600
Differential Revision: https://reviews.llvm.org/D44550
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@327858
91177308-0d34-0410-b5e6-
96231b3b80d8
OSDN Git Service
