This removes the after the fact FMF handling from D46854 in favor of passing fast math flags to getNode. This should be a superset of D87130.
This required adding a SDNodeFlags to SelectionDAG::getSetCC.
Now we manage to contant fold some stuff undefs during the
initial getNode that we don't do in later DAG combines.
Differential Revision: https://reviews.llvm.org/D87200
As discussed in the commit thread for rGa253a2a and D73978, we can do more undef folding for FP ops.
The nnan and ninf fast-math-flags specify that if an operand is the disallowed value, the result is
poison, so we can produce an undef result.
But this doesn't work as expected (the undef operand cases remain) because of a Flags propagation
problem in SelectionDAGBuilder.
I've added DAGCombiner calls to enable these for the other cases because we've shown in other
patches that (because of the limited way that SDAG iterates), it is possible to miss simplifications
like this if they are done only at node creation time.
Several potential follow-ups to expand on this patch are possible.
Differential Revision: https://reviews.llvm.org/D75576
We don't have FP exception limits in the IR constant folder for the binops (apart from strict ops),
so it does not make sense to have them here in the DAG either. Nothing else in the backend tries
to preserve exceptions (again outside of strict ops), so I don't see how this could have ever
worked for real code that cares about FP exceptions.
There are still cases (examples: unary opcodes in SDAG, FMA in IR) where we are trying (at least
partially) to preserve exceptions without even asking if the target supports FP exceptions. Those
should be corrected in subsequent patches.
Real support for FP exceptions requires several changes to handle the constrained/strict FP ops.
Differential Revision: https://reviews.llvm.org/D61331
llvm-svn: 359791
We don't have this restriction in IR, so it should not be here
either simply out of consistency. Code that wants to handle FP
exceptions is expected to use the 'strict' variants of these
nodes.
We don't get the frem case because frem by 0.0 produces NaN (invalid),
and that's the remaining check here (so the removed check for frem
was dead code AFAIK).
This is the only place in SDAG that uses "HasFPExceptions", so I
think we should remove that entirely as a follow-up patch.
llvm-svn: 359566
Craig Topper