Commit Graph

3 Commits

Author SHA1 Message Date
Tobias Grosser 6e6264c142 [tests] Force invariant load hoisting for test cases that need it
This will make it easier to switch the default of Polly's invariant load
hoisting strategy and also makes it very clear that these test cases
indeed require invariant code hoisting to work.

llvm-svn: 278667
2016-08-15 13:27:49 +00:00
Johannes Doerfert 4ba65a5622 [GSoC 2016]New function pass ScopInfoWrapperPass
This patch adds a new function pass ScopInfoWrapperPass so that the
polyhedral description of a region, the SCoP, can be constructed and
used in a function pass.

Patch by Utpal Bora <cs14mtech11017@iith.ac.in>

Differential Revision: http://reviews.llvm.org/D20962

llvm-svn: 273856
2016-06-27 09:32:30 +00:00
Johannes Doerfert 09e3697f44 Allow invariant loads in the SCoP description
This patch allows invariant loads to be used in the SCoP description,
  e.g., as loop bounds, conditions or in memory access functions.

  First we collect "required invariant loads" during SCoP detection that
  would otherwise make an expression we care about non-affine. To this
  end a new level of abstraction was introduced before
  SCEVValidator::isAffineExpr() namely ScopDetection::isAffine() and
  ScopDetection::onlyValidRequiredInvariantLoads(). Here we can decide
  if we want a load inside the region to be optimistically assumed
  invariant or not. If we do, it will be marked as required and in the
  SCoP generation we bail if it is actually not invariant. If we don't
  it will be a non-affine expression as before. At the moment we
  optimistically assume all "hoistable" (namely non-loop-carried) loads
  to be invariant. This causes us to expand some SCoPs and dismiss them
  later but it also allows us to detect a lot we would dismiss directly
  if we would ask e.g., AliasAnalysis::canBasicBlockModify(). We also
  allow potential aliases between optimistically assumed invariant loads
  and other pointers as our runtime alias checks are sound in case the
  loads are actually invariant. Together with the invariant checks this
  combination allows to handle a lot more than LICM can.

  The code generation of the invariant loads had to be extended as we
  can now have dependences between parameters and invariant (hoisted)
  loads as well as the other way around, e.g.,
    test/Isl/CodeGen/invariant_load_parameters_cyclic_dependence.ll
  First, it is important to note that we cannot have real cycles but
  only dependences from a hoisted load to a parameter and from another
  parameter to that hoisted load (and so on). To handle such cases we
  materialize llvm::Values for parameters that are referred by a hoisted
  load on demand and then materialize the remaining parameters. Second,
  there are new kinds of dependences between hoisted loads caused by the
  constraints on their execution. If a hoisted load is conditionally
  executed it might depend on the value of another hoisted load. To deal
  with such situations we sort them already in the ScopInfo such that
  they can be generated in the order they are listed in the
  Scop::InvariantAccesses list (see compareInvariantAccesses). The
  dependences between hoisted loads caused by indirect accesses are
  handled the same way as before.

llvm-svn: 249607
2015-10-07 20:17:36 +00:00