Commit Graph

4 Commits

Author SHA1 Message Date
Sanjay Patel 284472be6d [SelectionDAG] remove constant folding limitations based on FP exceptions
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
2019-05-02 14:47:59 +00:00
Sanjay Patel 3ec1c51716 [AArch64] add more tests for constant folding failures; NFC
llvm-svn: 359592
2019-04-30 18:15:18 +00:00
Sanjay Patel 0387bf5269 [SelectionDAG] remove div-by-zero constant folding restriction
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
2019-04-30 14:37:15 +00:00
Sanjay Patel c16fd75e44 [AArch64] add tests for fdiv/frem constant folding (PR41668); NFC
llvm-svn: 359561
2019-04-30 13:43:17 +00:00