This step removes redundant instance-at-offset-0, collapsing the child
into the parent, whenever this operation does not induce instance-loops
on the graph.
This is intended to reduce the number of shallow wrapper structs and
unions.
Before this commit there was a single pass removing equality SCC and
inheritance SCC.
This commit splits the removal of each kind of SCC in a separate
DLAStep, and adds handling of instance-at-offset-0 SCCs that were not
considered before.
Before this commit, DLAMakeModelTypes was generating broken types in
several corner cases involving unions with children at offset different
than zero, and strided accesses.
This commit fixes these issues and reworks the pass to also consider
strides and model::Qualifiers in the correct order.
Nested SCEVAddRecs are not guaranteed to have strides that go from
larger to smaller. Both cases are valid and can convey interesting
information to DLA. But DLA assumes that the outermost strides are
always larger than the innermost, because this is the only scenario
allowed by well-nested types.
This commit re-orders the strides (and the associated trip counts) so
that they always go from larger to smaller sizes.
The linkOrderLess comparison function is used for sorting the children
edges of a node.
Before this commit, it could not handle the case of comparing an edge
with itself, yielding wrong results (or assertion failure if assertions
were compiled in).
This commit fixes linkOrderLess to handle that case without asserting,
and adds an early return for it, without requiring to inspect the edges
in depth.
DeduplicateUnionFields does not depend on CollapseSingleChild, but can
break if CollapseSingleChild has not run.
However, we don't want to introduce an explicit dependency between the
two steps, because CollapseSingleChild could soon become obsolete on
its own, superseeded by a more powerful and costly step.
This commit changes DeduplicateUnionFields with an additional
pre-processing that runs CollapseSingleChild on each node at step one,
to ensure the step does not fail if CollapseSingleChild child is not
executed.
In order to enable the optimizer to strip dead calls, ModelGEP,
SerializationMarker and AddressOf functions are marked as
`ReadNone` instead of `InaccessibleMemOnly`.
This DLAStep was moving edges improperly before this commit.
In particular, edges were detected solely looking at source and target
edge, not looking at the edge itself. This was leading to wrong results
whenever a node N1 had many outgoing edges to a child node N2, at
different offsets, where all the edges were moved instead of just the
correct ones.
In order to fix this, this commit:
- reworks the logic of `moveEdges`, switching to iterator-based logic
- reworks the struct OrderedChild used internally by
DLAComputeNonInterferingComponents, so that it is also iterator-based
- re-uses common code for field size computation
This commit moves the logic for the computation of field sizes to a
separate .cpp file.
At the moment this is only used by DLAComputeUpperMemberAccess, but in
the future it will also be re-used DLAComputeNonInterferingComponents,
which at the moment employs very similar code.
Pietro Fezzardi