The legacy PM is deprecated, so update a bunch of lit tests running
opt to use the new PM syntax when specifying the pipeline.
In this patch focus has been put on test cases for ConstantMerge,
ConstraintElimination, CorrelatedValuePropagation, GlobalDCE,
GlobalOpt, SCCP, TailCallElim and PredicateInfo.
Differential Revision: https://reviews.llvm.org/D114516
Reapply with DTU update moved after CFG update, which is a
requirement of the API.
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Non-feasible control-flow edges are currently removed by replacing
the branch condition with a constant and then calling
ConstantFoldTerminator. This happens in a rather roundabout manner,
by inspecting the users (effectively: predecessors) of unreachable
blocks, and further complicated by the need to explicitly materialize
the condition for "forced" edges. I would like to extend SCCP to
discard switch conditions that are non-feasible based on range
information, but this is incompatible with the current approach
(as there is no single constant we could use.)
Instead, this patch explicitly removes non-feasible edges. It
currently only needs to handle the case where there is a single
feasible edge. The llvm_unreachable() branch will need to be
implemented for the aforementioned switch improvement.
Differential Revision: https://reviews.llvm.org/D84264
