urem x, n: result < n (remainder is always less than divisor)
urem x, n: result <= x (remainder is at most the dividend)
udiv x, n: result <= x (quotient is at most the dividend)
https://alive2.llvm.org/ce/z/ezzsjQ
At this stage I'm just opportunistically deleting any code using
debug-intrinsic types, largely adjacent to calls to findDbgUsers. I'll
get to deleting that in probably one or more two commits.
It took me some time to fully understand the implementation of
Fourier–Motzkin elimination in the Constraint System, so I added an
example in the comments. Hopefully future developers can understand the
algorithm more easily with the example.
As part of the "RemoveDIs" project, BasicBlock::iterator now carries a
debug-info bit that's needed when getFirstNonPHI and similar feed into
instruction insertion positions. Call-sites where that's necessary were
updated a year ago; but to ensure some type safety however, we'd like to
have all calls to moveBefore use iterators.
This patch adds a (guaranteed dereferenceable) iterator-taking
moveBefore, and changes a bunch of call-sites where it's obviously safe
to change to use it by just calling getIterator() on an instruction
pointer. A follow-up patch will contain less-obviously-safe changes.
We'll eventually deprecate and remove the instruction-pointer
insertBefore, but not before adding concise documentation of what
considerations are needed (very few).
Facts of eq/ne were added to unsigned system only, causing some missing
optimizations. This patch adds eq/ne facts to both signed & unsigned
constraint system.
Fixes#117961.
This patch does following things,
- prefer early exits;
- add missing std::move;
- avoid duplicate map lookups;
- prefer emplace_back to avoid unnecessary copies.
When the samesign flag is present on an icmp, we can transfer all the
facts on the unsigned system to the signed system, and vice-versa: we do
this by specializing transferToOtherSystem when samesign is present.
With the introduction of CmpPredicate in 51a895a (IR: introduce struct
with CmpInst::Predicate and samesign), PatternMatch is one of the first
key pieces of infrastructure that must be updated to match a CmpInst
respecting samesign information. Implement this change to Cmp-matchers.
This is a preparatory step in migrating the codebase over to
CmpPredicate. Since we no functional changes are desired at this stage,
we have chosen not to migrate CmpPredicate::operator==(CmpPredicate)
calls to use CmpPredicate::getMatching(), as that would have visible
impact on tests that are not yet written: instead, we call
CmpPredicate::operator==(Predicate), preserving the old behavior, while
also inserting a few FIXME comments for follow-ups.
ConstraintElimination currently only supports decomposing gep nusw with
non-negative indices (with "non-negative" possibly being enforced via
pre-condition).
Add support for gep nuw, which directly gives us the necessary
guarantees for the decomposition.
Check for nusw instead of inbounds when decomposing GEPs.
In this particular case, we can also look through multiple nusw
flags, because we will ultimately be working in the unsigned
constraint system.
De-duplicate the functions getSignedPredicate and getUnsignedPredicate,
nearly identical versions of which were present in CmpInst and ICmpInst,
creating less confusion.
getContextInst currently returns an invalid union field, when it is
called with a ConditionFact, although existing callers don't do this. In
order to error out early and serve as documentation for future callers,
add an assert forbidding the behavior.
This replaces some of the most frequent offenders of using a DenseMap that
cause a malloc, where the typical element-count is small enough to fit in
an initial stack allocation.
Most of these are fairly obvious, one to highlight is the collectOffset
method of GEP instructions: if there's a GEP, of course it's going to have
at least one offset, but every time we've called collectOffset we end up
calling malloc as well for the DenseMap in the MapVector.
Don't call raw_string_ostream::flush(), which is essentially a no-op.
As specified in the docs, raw_string_ostream is always unbuffered.
( 65b13610a5226b84889b923bae884ba395ad084d for further reference )
For loops, we can use the condition in the loop header as upper bound on
the compared induction in the unique exit block, if it exists. This can
be done even if there are multiple in-loop edges to the unique exit
block, as any other exit may only exit earlier.
More generally, we could add the OR of all exit conditions to the exit,
but that's a possible future extension.
PR: https://github.com/llvm/llvm-project/pull/94610
Uses the new InsertPosition class (added in #94226) to simplify some of
the IRBuilder interface, and removes the need to pass a BasicBlock
alongside a BasicBlock::iterator, using the fact that we can now get the
parent basic block from the iterator even if it points to the sentinel.
This patch removes the BasicBlock argument from each constructor or call
to setInsertPoint.
This has no functional effect, but later on as we look to remove the
`Instruction *InsertBefore` argument from instruction-creation
(discussed
[here](https://discourse.llvm.org/t/psa-instruction-constructors-changing-to-iterator-only-insertion/77845)),
this will simplify the process by allowing us to deprecate the
InsertPosition constructor directly and catch all the cases where we use
instructions rather than iterators.
