This patch extends the support added in #158088 to loops where the
assignment is non-speculatable (e.g. a conditional load or divide).
For example, the following loop can now be vectorized:
```
int simple_csa_int_load(
int* a, int* b, int default_val, int N, int threshold)
{
int result = default_val;
for (int i = 0; i < N; ++i)
if (a[i] > threshold)
result = b[i];
return result;
}
```
It does this by extending the recurrence matching from only looking for
selects, to include phis where all operands are the header phi, except
for one which can be an arbitrary value outside the recurrence.
---
Reverts llvm/llvm-project#180275 (original PR: #178862)
Additional type legalization for `ISD::VECTOR_FIND_LAST_ACTIVE` was
added in #180290, which should resolve the backend crashes on x86.
When `-pass-remarks=loop-vectorize` is specified, the subsequent logic
is executed to display detailed debug messages even if no PreHeader
exists in the loop.
Therefore, an assert occurs when the `getLoopPreHeader()` function is
called. This commit resolves that issue.
Fixed: #165377
This patch extends the support added in #158088 to loops where the
assignment is non-speculatable (e.g. a conditional load or divide).
For example, the following loop can now be vectorized:
```
int simple_csa_int_load(
int* a, int* b, int default_val, int N, int threshold)
{
int result = default_val;
for (int i = 0; i < N; ++i)
if (a[i] > threshold)
result = b[i];
return result;
}
```
It does this by extending the recurrence matching from only looking for
selects, to include phis where all operands are the header phi, except
for one which can be an arbitrary value outside the recurrence.
This patch restructures Find(First|Last)IV handling. Instead of
differentiating between FindLast, FindFirstIV and FindLastIV up front,
this patch simplifies the logic in IVDescriptor to just identify the
FindLast pattern up-front.
It then adds a new VPlan transformation to optimize FindLast reductions
to FindIV reductions if there is a suitable sentinel value.
Find(Last|First)IV recurrence kinds to a single FindIV kind.
This is simpler and more accurate, given selecting the first/last
induction of the final IV reduction is directly controlled by the
corresponding recurrence kind of the ComputeReductionResult.
The new structure also allows further optimizations, like vectorizing
FindLastIV with another boolean reduction that tracks if the condition
in the loop was ever true, if there is no suitable sentinel value.
PR: https://github.com/llvm/llvm-project/pull/177870
Based on Michael Maitland's previous work:
https://github.com/llvm/llvm-project/pull/121222
This PR uses the existing recurrences code instead of introducing a
new pass just for CSA autovec. I've also made recipes that are more
generic.
ConstantRange::getNonEmpty was excluding MAX and MAX - 1 in FindFirstIV
vectorization, and this was discovered in an i1 miscompile, where it
returns the full range: fix it to exclude MAX only. The change has also
necessitated fixing a test that's not supposed to be vectorized.
Fixes#173459.
Co-authored-by: Nikita Popov <npopov@redhat.com>
Add support for vectorizing loops that select the index of the minimum
or maximum element. The patch implements vectorizing those patterns by
combining Min/Max and FindFirstIV reductions.
It extends matching Min/Max reductions to allow in-loop users that are
FindLastIV reductions. It records a flag indicating that the Min/Max
reduction is used by another reduction. The extra user is then check as
part of the new `handleMultiUseReductions` VPlan transformation.
It processes any reduction that has other reduction users. The reduction
using the min/max reduction currently must be a FindLastIV reduction,
which needs adjusting to compute the correct result:
1. We need to find the last IV for which the condition based on the
min/max reduction is true,
2. Compare the partial min/max reduction result to its final value and,
3. Select the lanes of the partial FindLastIV reductions which
correspond to the lanes matching the min/max reduction result.
Depends on https://github.com/llvm/llvm-project/pull/140451
PR: https://github.com/llvm/llvm-project/pull/141431
Currently, in-loop reductions for AnyOf and FindIV are not supported.
They were implicitly blocked. This happened because
RecurrenceDescriptor::getReductionOpChain could not detect their
recurrence chain. The reason is that RecurrenceDescriptor::getOpcode was
set to Instruction::Or, but the recurrence chains of AnyOf and FindIV do
not actually contain an Instruction::Or.
This patch explicitly disables in-loop reductions for AnyOf and FindIV
instead of relying on getReductionOpChain to implicitly prevent them.
Update LV to vectorize maxnum/minnum reductions without fast-math flags,
by adding an extra check in the loop if any inputs to maxnum/minnum are
NaN, due to maxnum/minnum behavior w.r.t to signaling NaNs. Signed-zeros
are already handled consistently by maxnum/minnum.
If any input is NaN,
*exit the vector loop,
*compute the reduction result up to the vector iteration that contained
NaN inputs and
* resume in the scalar loop
New recurrence kinds are added for reductions using maxnum/minnum
without fast-math flags.
PR: https://github.com/llvm/llvm-project/pull/148239
Similar to FindLastIV, add FindFirstIVSMin to support select (icmp(), x, y)
reductions where one of x or y is a decreasing induction, producing a SMin
reduction. It uses signed max as sentinel value.
PR: https://github.com/llvm/llvm-project/pull/140451
Having a finite Depth (or recursion limit) for computeKnownBits is very
limiting, but is currently a load-bearing necessity, as all KnownBits
are recomputed on each call and there is no caching. As a prerequisite
for an effort to remove the recursion limit altogether, either using a
clever caching technique, or writing a easily-invalidable KnownBits
analysis, make the Depth argument in APIs in ValueTracking uniformly the
last argument with a default value. This would aid in removing the
argument when the time comes, as many callers that currently pass 0
explicitly are now updated to omit the argument altogether.
Non-arithmetic reductions do not require the binary opcodes.
As a first step toward removing the dependency of non-arithmetic
reductions on `getOpcode` function, this patch refactors the
`getReductionOpChain` function.
In the future, once all users of `getOpcode` function are refactored, an
assertion can be added to `getOpcode` function to ensure that only
arithmetic reductions rely on it.
Add a new reduction recurrence kind for reductions with
minimumnum/maximumnum. Such reductions can be vectorized without
nsz/nnans, same as reductions with maximum/minimum intrinsics.
Note that a new reduction kind is needed to make sure partial reductions
are also combined with minimumnum/maximumnum.
Note that the final reduction to a scalar value is performed with
vector.reduce.fmin/fmax. This should be fine, as the results of the
partial reductions with maximumnum/minimumnum silences any sNaNs.
In-loop and reductions in SLP are not supported yet, as there's no
reduction version of maximumnum/minimumnum yet and fmax may be
incorrect.
PR: https://github.com/llvm/llvm-project/pull/137335
There are other types of recurrences with an icmp/fcmp opcode, AnyOf and
FindLastIV, so don't rely on the opcode to detect them.
This makes adding support for AnyOf in #131830 easier.
Note that these currently fail the ExpectedUses/isCorrectOpcode checks
anyway, so there shouldn't be any functional change.
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.
Consider the following loop:
```
int rdx = init;
for (int i = 0; i < n; ++i)
rdx = (a[i] > b[i]) ? i : rdx;
```
We can vectorize this loop if `i` is an increasing induction variable.
The final reduced value will be the maximum of `i` that the condition
`a[i] > b[i]` is satisfied, or the start value `init`.
This patch added new RecurKind enums - IFindLastIV and FFindLastIV.
---------
Co-authored-by: Alexey Bataev <5361294+alexey-bataev@users.noreply.github.com>
Today, InstCombine can fold fcmp+select patterns to minnum/maxnum
intrinsics when the nnan and nsz flags are set. The ordering of the
operands in both the fcmp and select instructions is important for the
folding to occur.
maxnum patterns:
1. (a op b) ? a : b -> maxnum(a, b), where op is one of {ogt, oge}
2. (a op b) ? b : a -> maxnum(a, b), where op is one of {ule, ult}
The second pattern is supposed to make the order of the operands in the
select instruction irrelevant. However, the pattern matching code uses
the CmpInst::getInversePredicate method to invert the comparison
predicate. This method doesn't take into account the fast-math flags,
which can lead missing the folding opportunity.
The patch extends the pattern matching code to handle unordered fcmp
instructions. This allows the folding to occur even when the select
instruction has the operands in the inverse order.
New maxnum patterns:
1. (a op b) ? a : b -> maxnum(a, b), where op is one of {ugt, uge}
2. (a op b) ? b : a -> maxnum(a, b), where op is one of {ole, olt}
The same changes are applied to the minnum intrinsic.
This change merges the three different places (at the IR layer) for
finding the identity value of a reduction into a single copy. This
depends on several prior commits which fix ommissions and bugs in
the distinct copies, but this patch itself should be fully
non-functional.
As the new comments and naming try to make clear, the identity value
is a property of the @llvm.vector.reduce.* intrinsic, not of e.g.
the recurrence descriptor. (We still provide an interface for
clients using recurrence descriptors, but the implementation simply
translates to the intrinsic which each corresponds to.)
As a note, the getIntrinsicIdentity API does not support fminnum/fmaxnum
or fminimum/fmaximum which is why we still need manual logic (but at
least only one copy of manual logic) for those cases.
Analogous to 2c7786e94a1058bd4f96794a1d4f70dcb86e5cc5, cleanup a case
where the vectorizer is emitting a non-canonical identity value given
the available flags. We use largest/smallest value during ISEL, and VP
expansion, but not during vectorization.
Since the fmin/fmax/fminimum/fmaximum intrinsics don't require a start
value, this difference is only visible when masking of inactive lanes is
required.
Primary motivation of this change is simply to remove a difference
between version of code which reason about the identity value of a
reduction so I can kill all but one off.
In review, it was pointed out that this is actually a functional fix as well.
The old code used inf on a noinf reduction instruction - whose
result is poison! That wasn't the intent of the code.
These recurrence types don't have a meaningful identity, and the
routine was abused to return the start value instead. Out of the
three callers to this routine, only one actually wants this
behavior. This is a prep change for removing the routine entirely
and commoning it with other copies of the same logic.
getSCEV will assert unless the operand is SCEVable. Replace an instance
of the implementation of ScalarEvolution::isSCEVable (which checks that
the operand is either integer or pointer type) with a call to the
function, to make it clear that the subsequent use of getSCEV will not
fail.
This change allows to consider compare instructions in the loop with
multiple use inside the loop and outside.
This change allows to vectorise this loop:
int foo(float* a, int n) {
_Bool any = 0;
_Bool all = 1;
for (int i = 0; i < n; i++) {
if (a[i] < 0.0f) {
any = 1;
} else {
all = 0;
}
}
return all ? 1 : any ? 2 : 3;
}
This is a helper to avoid writing `getModule()->getDataLayout()`. I
regularly try to use this method only to remember it doesn't exist...
`getModule()->getDataLayout()` is also a common (the most common?)
reason why code has to include the Module.h header.
{mini|maxi}mum intrinsics are different from {min|max}num intrinsics in
the propagation of NaN and signed zero. Also, the minnum/maxnum
intrinsics require the presence of nsz flags to be valid reductions in
vectorizer. In this regard, we introduce a new recurrence kind and also
add support for identifying reduction patterns using these intrinsics.
The reduction intrinsics and lowering was introduced here: 26bfbec5d2.
There are tests added which show how this interacts across chains of
min/max patterns.
Differential Revision: https://reviews.llvm.org/D151482
Phis that are present inside loop headers can only be Induction Phis
legally. This patch adds an assertion to isInductionPhi which checks for
the said legality and it also updates the docs of the said function to
reflect the given legality.
Differential Revision: https://reviews.llvm.org/D149041
