This allows for using the llvm namespace cast methods instead of the ones on the Value class. The Value class method are kept for now, but we'll want to remove these eventually (with a really long lead time).
Related change: https://reviews.llvm.org/D134327
Differential Revision: https://reviews.llvm.org/D135870
The previous impl densely scanned the entire region starting with an op
when dominators were created, creating a DominatorTree for every region.
This is extremely expensive up front -- particularly for clients like
Linalg/Transforms/Fusion.cpp that construct DominanceInfo for a single
query. It is also extremely memory wasteful for IRs that use single
block regions commonly (e.g. affine.for) because it's making a
dominator tree for a region that has trivial dominance. The
implementation also had numerous unnecessary minor efficiencies, e.g.
doing multiple walks of the region tree or tryGetBlocksInSameRegion
building a DenseMap that it didn't need.
This patch switches to an approach where [Post]DominanceInfo is free
to construct, and which lazily constructs DominatorTree's for any
multiblock regions that it needs. This avoids the up-front cost
entirely, making its runtime proportional to the complexity of the
region tree instead of # ops in a region. This also avoids the memory
and time cost of creating DominatorTree's for single block regions.
Finally this rewrites the implementation for simplicity and to avoids
the constant factor problems the old implementation had.
Differential Revision: https://reviews.llvm.org/D103384
This avoids trying to find the RegionKindInterface for every
operation in the program, we only need it if they have regions.
Differential Revision: https://reviews.llvm.org/D103367
If block A and B are in different regions and region of A is not an ancestor of
B, either A is included in region of B or the two regions are disjoint. In both
case A doesn't post-dominate B.
Differential Revision: https://reviews.llvm.org/D91225
Some dialects have semantics which is not well represented by common
SSA structures with dominance constraints. This patch allows
operations to declare the 'kind' of their contained regions.
Currently, two kinds are allowed: "SSACFG" and "Graph". The only
difference between them at the moment is that SSACFG regions are
required to have dominance, while Graph regions are not required to
have dominance. The intention is that this Interface would be
generated by ODS for existing operations, although this has not yet
been implemented. Presumably, if someone were interested in code
generation, we might also have a "CFG" dialect, which defines control
flow, but does not require SSA.
The new behavior is mostly identical to the previous behavior, since
registered operations without a RegionKindInterface are assumed to
contain SSACFG regions. However, the behavior has changed for
unregistered operations. Previously, these were checked for
dominance, however the new behavior allows dominance violations, in
order to allow the processing of unregistered dialects with Graph
regions. One implication of this is that regions in unregistered
operations with more than one op are no longer CSE'd (since it
requires dominance info).
I've also reorganized the LangRef documentation to remove assertions
about "sequential execution", "SSA Values", and "Dominance". Instead,
the core IR is simply "ordered" (i.e. totally ordered) and consists of
"Values". I've also clarified some things about how control flow
passes between blocks in an SSACFG region. Control Flow must enter a
region at the entry block and follow terminator operation successors
or be returned to the containing op. Graph regions do not define a
notion of control flow.
see discussion here:
https://llvm.discourse.group/t/rfc-allowing-dialects-to-relax-the-ssa-dominance-condition/833/53
Differential Revision: https://reviews.llvm.org/D80358
It is possible for optimizations to create SSA code which violates
the dominance property in unreachable blocks. Equivalently, dominance
computed using normal mechanisms is undefined in unreachable blocks.
See discussion here: https://llvm.discourse.group/t/rfc-allowing-dialects-to-relax-the-ssa-dominance-condition/833/51
This patch only checks the dominance condition inside blocks which are
reachable from the the entry block of their region. Note that the
dominance conditions of regions contained in an unreachable block are
still checked.
Differential Revision: https://reviews.llvm.org/D79922
These libraries are distinct from other things in Analysis in that they
operate only on core IR concepts. This also simplifies dependencies
so that Dialect -> Analysis -> Parser -> IR. Previously, the parser depended
on portions of the the Analysis directory as well, which sometimes
caused issues with the way the cmake makefile generator discovers
dependencies on generated files during compilation.
Differential Revision: https://reviews.llvm.org/D79240
