This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated. The intent is to reduce
the amount of manual work required in migrating from Optional to
std::optional.
This is part of an effort to migrate from llvm::Optional to
std::optional:
https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716
This can't make use of TestBinaryOpExhaustive, but it can make use
of the general TestRange approach that collects the precise elements
in a bit vector.
This allows us to remove the obsolete "op range gatherer" infrastructure.
Signed one bit values can only be -1 or 0, not positive. The code
was interpreting the 1 as -1 and intersecting with a full range
rather than an empty one.
Fixes https://github.com/llvm/llvm-project/issues/56333.
This diff adjusts binaryOr to take advantage of the analysis
based on KnownBits.
Differential revision: https://reviews.llvm.org/D125933
Test plan:
1/ ninja check-llvm
2/ ninja check-llvm-unit
This diff adjusts binaryAnd to take advantage of the analysis
based on KnownBits.
Differential revision: https://reviews.llvm.org/D125603
Test plan:
1/ ninja check-llvm
2/ ninja check-llvm-unit
Checking whether two KnownBits are the same is somewhat common,
mainly in test code.
I don't think there is a lot of room for confusion with "determine
what the KnownBits for an icmp eq would be", as that has a
different result type (this is what the eq() method implements,
which returns Optional<bool>).
Differential Revision: https://reviews.llvm.org/D125692
Add toKnownBits() method to mirror fromKnownBits(). We know the
top bits that are constant between min and max.
The return value for an empty range is chosen to be conservative.
For some optimizations on comparisons it's necessary that the
union/intersect is exact and not a superset. Add methods that
return Optional<ConstantRange> only if the result is exact.
For the sake of simplicity this is implemented by comparing
the subset and superset approximations for now, but it should be
possible to do this more directly, as unionWith() and intersectWith()
already distinguish the cases where the result is imprecise for the
preferred range type functionality.
Add a variant of getEquivalentICmp() that produces an optional
offset. This allows us to create an equivalent icmp for all ranges.
Use this in the with.overflow folding code, which was doing this
adjustment separately -- this clarifies that the fold will indeed
always apply.
By default `llvm::seq` would happily iterate over enums, which may be unsafe if the enum values are not continuous. This patch disable enum iteration with `llvm::seq` and `llvm::seq_inclusive` and adds two new functions: `enum_seq` and `enum_seq_inclusive`.
To make sure enum iteration is safe, we require users to declare their enum types as iterable by specializing `enum_iteration_traits<SomeEnum>`. Because it's not always possible to add these traits next to enum definition (e.g., for enums defined in external libraries), we provide an escape hatch to allow iteration on per-callsite basis by passing `force_iteration_on_noniterable_enum`.
The main benefit of this approach is that these global declarations via traits can appear just next to enum definitions, making easy to spot when enums are miss-labeled, e.g., after introducing new enum values, whereas `force_iteration_on_noniterable_enum` should stand out and be easy to grep for.
This emerged from a discussion with gchatelet@ about reusing llvm's `Sequence.h` in lieu of https://github.com/GPUOpen-Drivers/llpc/blob/dev/lgc/interface/lgc/EnumIterator.h.
Reviewed By: dblaikie, gchatelet, aaron.ballman
Differential Revision: https://reviews.llvm.org/D107378
For certain combination of LHS and RHS constant ranges,
the signedness of the relational comparison predicate is irrelevant.
This implements complete and precise model for all predicates,
as confirmed by the brute-force tests. I'm not sure if there are
some more cases that we can handle here.
In a follow-up, CVP will make use of this.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D90924
As noted in https://reviews.llvm.org/D90924#inline-1076197
apparently this is a pretty common pattern,
let's not repeat it yet again, but have it in a common place.
There may be some more places where it could be used,
but these are the most obvious ones.
The multiply() implementation is very slow -- it performs six
multiplications in double the bitwidth, which means that it will
typically work on allocated APInts and bypass fast-path
implementations. Add an additional implementation that doesn't
try to produce anything better than a full range if overflow is
possible. At least for the BasicAA use-case, we really don't care
about more precise modeling of overflow behavior. The current
use of multiply() is fine while the implementation is limited to
a single index, but extending it to the multiple-index case makes
the compile-time impact untenable.
For the common case where the shift amount is constant (a single
element range) we can easily compute a precise range (up to
unsigned envelope), so do that.
We always want to check correctness, but for some operations we
can only guarantee optimality for a subset of inputs. Accept an
additional predicate that determines whether optimality for a
given pair of ranges should be checked.
Print a friendly error message including the inputs, result and
not-contained element if an exhaustive correctness test fails,
same as we do if the optimality test fails.
Stop using APInt constructors and methods that were soft-deprecated in
D109483. This fixes all the uses I found in llvm, except for the APInt
unit tests which should still test the deprecated methods.
Differential Revision: https://reviews.llvm.org/D110807
This renames the primary methods for creating a zero value to `getZero`
instead of `getNullValue` and renames predicates like `isAllOnesValue`
to simply `isAllOnes`. This achieves two things:
1) This starts standardizing predicates across the LLVM codebase,
following (in this case) ConstantInt. The word "Value" doesn't
convey anything of merit, and is missing in some of the other things.
2) Calling an integer "null" doesn't make any sense. The original sin
here is mine and I've regretted it for years. This moves us to calling
it "zero" instead, which is correct!
APInt is widely used and I don't think anyone is keen to take massive source
breakage on anything so core, at least not all in one go. As such, this
doesn't actually delete any entrypoints, it "soft deprecates" them with a
comment.
Included in this patch are changes to a bunch of the codebase, but there are
more. We should normalize SelectionDAG and other APIs as well, which would
make the API change more mechanical.
Differential Revision: https://reviews.llvm.org/D109483
This patch allows iterating typed enum via the ADT/Sequence utility.
It also changes the original design to better separate concerns:
- `StrongInt` only deals with safe `intmax_t` operations,
- `SafeIntIterator` presents the iterator and reverse iterator
interface but only deals with safe `StrongInt` internally.
- `iota_range` only deals with `SafeIntIterator` internally.
This design ensures that operations are always valid. In particular,
"Out of bounds" assertions fire when:
- the `value_type` is not representable as an `intmax_t`
- iterator operations make internal computation underflow/overflow
- the internal representation cannot be converted back to `value_type`
Differential Revision: https://reviews.llvm.org/D106279
"Does the predicate hold between two ranges?"
Not very surprisingly, some places were already doing this check,
without explicitly naming the algorithm, cleanup them all.
"Does the predicate hold between two ranges?"
Not very surprisingly, some places were already doing this check,
without explicitly naming the algorithm, cleanup them all.
When one of the inputs is a wrapping range, intersect with the
union of the two inputs. The union of the two inputs corresponds
to the result we would get if we treated the min/max as a simple
select.
This fixes PR48643.
We don't need any special handling for wrapping ranges (or empty
ranges for that matter). The sub() call will already compute a
correct and precise range.
We only need to adjust the test expectation: We're now computing
an optimal result, rather than an unsigned envelope.
When the optimality check fails, print the inputs, the computed
range and the better range that was found. This makes it much
simpler to identify the cause of the failure.
Make sure that full ranges (which, unlikely all the other cases,
have multiple ways to construct them that all result in the same
range) only print one message by handling them separately.
The current infrastructure for exhaustive ConstantRange testing is
somewhat confusing in what exactly it tests and currently cannot even
be used for operations that produce smallest-size results, rather than
signed/unsigned envelopes.
This patch makes the testing more principled by collecting the exact
set of results of an operation into a bit set and then comparing it
against the range approximation by:
* Checking conservative correctness: All elements in the set must be
in the range.
* Checking optimality under a given preference function: None of the
(slack-free) ranges that can be constructed from the set are
preferred over the computed range.
Implemented preference functions are:
* PreferSmallest: Smallest range regardless of signed/unsigned wrapping
behavior. Probably what we would call "optimal" without further
qualification.
* PreferSmallestUnsigned/Signed: Smallest range that has no
unsigned/signed wrapping. We use this if our calculation is precise
only up to signed/unsigned envelope.
* PreferSmallestNonFullUnsigned/Signed: Smallest range that has no
unsigned/signed wrapping -- but preferring a smaller wrapping range
over a (non-wrapping) full range. We use this if we have a fully
precise calculation but apply a sign preference to the result
(union/intersection). Even with a sign preference, returning a
wrapping range is still "strictly better" than returning a full one.
This also addresses PR49273 by replacing the fragile manual range
construction logic in testBinarySetOperationExhaustive() with generic
code that isn't specialized to the particular form of ranges that set
operations can produces.
Differential Revision: https://reviews.llvm.org/D88356
I have long complained that while we have exhaustive tests
for ConstantRange, they are, uh, not good.
The approach of groking our own constant range
via exhaustive enumeration is, mysterious.
It neither tells us without doubt that the result is
conservatively correct, nor the precise match to the ConstantRange
result tells us that the result is precise.
But yeah, it's fast, i give it that.
In short, there are three things that we need to check:
1. That ConstantRange result is conservatively correct
2. That ConstantRange range is reasonable
3. That ConstantRange result is reasonably precise
So let's not just check the middle one, but all three.
This provides precision test coverage for D88178.
Similar to the ConstantRange::getActiveBits(), and to similarly-named
methods in APInt, returns the bitwidth needed to represent
the given signed constant range
Much like APInt::getActiveBits(), computes how many bits are needed
to be able to represent every value in this constant range,
treating the values as unsigned.
Use the fact that `~X` is equivalent to `-1 - X`, which gives us
fully-precise answer, and we only need to special-handle the wrapped case.
This fires ~16k times for vanilla llvm test-suite + RawSpeed.
The initial implementation just delegates to APInt's implementation of
XOR for single element ranges and conservatively returns the full set
otherwise.
Reviewers: nikic, spatel, lebedev.ri
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D76453
We returning a full set, we should use ResultBitWidth. Otherwise we might
it assertions when the resulting constant ranges are used later on.
Reviewers: nikic, spatel, reames
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D71937
Summary:
To be used in `ConstantRange::mulWithNoOverflow()`,
may in future be useful for when saturating shift/mul ops are added.
These are precise as far as i can tell.
I initially though i will need `APInt::[us]mul_sat()` for these,
but it turned out much simpler to do what `ConstantRange::multiply()`
does - perform multiplication in twice the bitwidth, and then truncate.
Though here we want saturating signed truncation.
Reviewers: nikic, reames, spatel
Reviewed By: nikic
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69994
Summary:
To be used in `ConstantRange::shlWithNoOverflow()`,
may in future be useful for when saturating shift/mul ops are added.
Unlike `ConstantRange::shl()`, these are precise.
Reviewers: nikic, spatel, reames
Reviewed By: nikic
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69960
Summary:
Much like D67339, adds ConstantRange handling for
when we know no-wrap behavior of the `sub`.
Unlike addWithNoWrap(), we only get lucky re returning empty set
for signed wrap. For unsigned, we must perform overflow check manually.
A patch that makes use of this in LVI (CVP) to be posted later.
Reviewers: nikic, shchenz, efriedma
Reviewed By: nikic
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69918
Fangrui Song