The logic added in 3771310eed was placed sub-optimally. Applying the
transform in ::getConstraint meant that it would also impact conditions
that are added to the system by the signed <-> unsigned transfer logic.
This meant we failed to add some signed facts to the signed system. To
make sure we still add as many useful facts to the signed/unsigned
systems, move the logic to the point where we query the system.
Make sure conditions with constant operands come before conditions
without constant operands. This increases the effectiveness of the
current signed <-> unsigned fact transfer logic.
Recent improvements to the code structure mean we don't need to reset
the condition's predicate in the IR and later restore it. Remove the
restorer logic.
Interestingly, MathExtras.h doesn't use <cmath> declaration, so move it out of
that header and include it when needed.
No functional change intended, but there's no longer a transitive include
fromMathExtras.h to cmath.
f213128b292d didn't account for the possibility that the result of
decompose may be empty. Fix that by explicitly checking. Use a newly
introduced helper to also reduce some duplication.
Thanks @bjope for finding the issue!
Keep track if variables are known positive during constraint
decomposition, aggregate the information when building the constraint
object and encode the extra information as constraints to be used during
reasoning.
Instead of checking if any of the new indices has a non-zero coefficient
before using the constraint, do this directly when constructing the
constraint.
If there are multiple constraints in the same block, at the moment the
order they are processed may be different depending on the sort
implementation.
Use stable_sort to ensure consistent ordering.
This patch adds a new transferToOtherSystem helper that tries to
transfer information from signed predicates to the unsigned system and
vice versa.
The initial version adds A >=u B for A >=s B && B >=s 0
https://alive2.llvm.org/ce/z/8b6F9i
Remove the early exit if both constraints contain no variables. This
restriction is unnecessayr for correctness and removing it simplifies
handling of trivial constant conditions in follow-up changes.
A first patch to use the reasoning in ConstraintElimination to simplify
sub with overflow to a regular sub, if the operation is guaranteed to
not overflow.
Reviewed By: spatel
Differential Revision: https://reviews.llvm.org/D125264
This refactor makes it easier to extend the logic to collect information
from blocks in the future, without even further increasing the size of
eliminateConstriants.
After moving the CanAdd check in c60cdb44f7ecb4b02ed and using it for
the assume cases as well, the passed in block may not have a branch
instruction as terminator. This can trigger the assertion. Given the new
use case, it doesn't add value any longer and can be removed.
Fixes https://github.com/llvm/llvm-project/issues/54281
When decomposing constraints for unsigned conditions, we can use
negative values by zero-extending them, as long as they are less than
the maximum constraint value.
Fixes https://github.com/llvm/llvm-project/issues/54224
Add missing CanAdd check before adding a condition from an assume
to the successor blocks. When adding information from assume to
successor blocks we need to perform the same CanAdd as we do for adding
a condition from a branch.
Fixes https://github.com/llvm/llvm-project/issues/54217
This patch extends ConstraintElimination to also remove dead variables
when removing a constraint. When a constraint is removed because it is
out of scope, all new variables added for this constraint can also be
removed.
This keeps the total size of the systems much smaller, because it
reduces the number of variables drastically.
It also fixes a bug where variables where removed incorrectly.
Fixes https://github.com/llvm/llvm-project/issues/54228
This patch simplifies constraint handling by removing the
ConstraintListTy wrapper struct and moving the Preconditions directly
into ConstraintTy. This reduces the amount of memory needed for managing
constraints.
The only use case for ConstraintListTy was adding 2 constraints to model
ICMP_EQ conditions. But this can be handled by adding an IsEq flag. When
adding an equality constraint, we need to add the constraint and the
inverted constraint.
