Commit Graph

3 Commits

Author SHA1 Message Date
Piotr Sobczak d1a7bfca74 [AMDGPU] Fix AMDGPUUnifyDivergentExitNodes
Summary:
For the case where "done" bits on existing exports are removed
by unifyReturnBlockSet(), unify all return blocks - even the
uniformly reached ones. We do not want to end up with a non-unified,
uniformly reached block containing a normal export with the "done"
bit cleared.

That case is believed to be rare - possible with infinite loops
in pixel shaders.

This is a fix for D71192.

Subscribers: arsenm, kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, hiraditya, kerbowa, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D76364
2020-03-18 16:49:30 +01:00
Connor Abbott ce06d50756 AMDGPU: Fix AMDGPUUnifyDivergentExitNodes with no normal returns
Summary:
The code was assuming in a few places that if there was only one exit
from the function that it was a normal return, which is invalid. It
could be an infinite loop, in which case we still need to insert the
usual fake edge so that the null export happens. This fixes shaders that
end with an infinite loop that discards.

Reviewers: arsenm, nhaehnle, critson

Subscribers: kzhuravl, jvesely, wdng, yaxunl, dstuttard, tpr, t-tye, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D71192
2020-01-30 10:55:02 +01:00
Diego Novillo 688afeb884 Update phis in AMDGPUUnifyDivergentExitNodes
Original patch https://reviews.llvm.org/D63659 from
Steven Perron <stevenperron@google.com>

The pass AMDGPUUnifyDivergentExitNodes does not update the phi nodes in
the successors of blocks that is splits. This is fixed by calling
BasicBlock::splitBasicBlock to split the block instead of doing it
manually. This does extra work because a new conditional branch is
created in BB which is immediately replaced, but I think the simplicity
is worth it. It also helps make the code more future proof in case other
things need to be updated.

llvm-svn: 364342
2019-06-25 18:55:16 +00:00