With the addition of the `willreturn` attribute, functions that may
not return (e.g. due to an infinite loop) are well defined, if they are
not marked as `willreturn`.
This patch updates `wouldInstructionBeTriviallyDead` to not consider
calls that may not return as dead.
This patch still provides an escape hatch for intrinsics, which are
still assumed as willreturn unconditionally. It will be removed once
all intrinsics definitions have been reviewed and updated.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D94106
D70365 allows us to make attributes default. This is a follow up to
actually make nosync, nofree and willreturn default. The approach we
chose, for now, is to opt-in to default attributes to avoid introducing
problems to target specific intrinsics. Intrinsics with default
attributes can be created using `DefaultAttrsIntrinsic` class.
This patch moves the tests for the old MemDepAnalysis based DSE
implementation to the MemDepAnalysis subdirectory and updates them to
pass -enable-dse-memoryssa=false.
This is in preparation for the switch to MemorySSA-backed DSE.
