If some of gc live value are not used in gc.relocate we can remove them
from gc-live bundle of statepoint instruction.
Also the CL removes duplicated Values in gc-live bundle.
Reviewers: reames, dantrushin
Reviewed By: dantrushin
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D85959
The "gc-live" operand bundles were recently added, and all tests have been updated to use that format. A migration period was provided, though it's worth noting these intrinsics are experimental, so formally there is no compatibile requirement.
This is an extension to a96fc46. "gc-live" hadn't been implemented at the point that patch was initially posted.
InstCombine adds users of transformed instruction to working list to
process on the same iteration. However gc.relocate may have a hidden
user (next gc.relocate) which is connected through gc.statepoint intrinsic and
there is no direct def-use chain between them.
In this case if the next gc.relocation is already processed it will not be added
to worklist and will not be able to be processed on the same iteration.
Let's we have the following case:
A = gc.relocate(null)
B = statepoint(A)
C = gc.relocate(B, hidden(A))
If C is already considered then after replacement of A with null, statepoint B
instruction will be added to the queue but not C.
C can be processed only on the next iteration.
If the chain of relocation is pretty long the many iteration may be required.
This change is to reduce the number of iteration to meet the latest changes
related to reducing infinite loop threshold.
This is a quick (not best) fix. In the follow up patches I plan to move gc relocation
handling into statepoint handler. This should also help to remove unused gc live
entries in statepoint bundle.
Reviewers: reames, dantrushin
Reviewed By: reames
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D75598
Serguei Katkov