This is already done within InstCombine:
https://alive2.llvm.org/ce/z/MiGE22
...but leaving it out of analysis makes it
harder to avoid infinite loops there.
(cherry picked from commit e260e10c4a21784c146c94a2a14b7e78b09a9cf7)
Users, especially the Attributor, might replace multiple operands at
once. The actual implementation of simplifyWithOpReplaced is able to
handle that just fine, the interface was simply not allowing to replace
more than one operand at a time. This is exposing a more generic
interface without intended changes for existing code.
Differential Revision: https://reviews.llvm.org/D106189
Currently InstructionSimplify.cpp knows how to simplify floating point
instructions that have a NaN operand. It does not know how to handle the
matching constrained FP intrinsic.
This patch teaches it how to simplify so long as the exception handling
is not "fpexcept.strict".
Differential Revision: https://reviews.llvm.org/D103169
If any operand of a math op is poison, that takes
precedence over general undef/NaN.
This should not be visible with binary ops because
it requires 2 constant operands to trigger (and if
both operands of a binop are constant, that should
get handled first in ConstantFolding).
We already have a fold for variable index with constant vector,
but if we can determine a scalar splat value, then it does not
matter whether that value is constant or not.
We overlooked this fold in D102404 and earlier patches,
but the fixed vector variant is shown in:
https://llvm.org/PR50817
Alive2 agrees on that:
https://alive2.llvm.org/ce/z/HpijPC
The same logic applies to scalable vectors.
Differential Revision: https://reviews.llvm.org/D104867
This is the cause of the miscompile in:
https://llvm.org/PR50944
The problem has likely existed for some time, but it was made visible with:
5af8bacc94024 ( D104661 )
handleOtherCmpSelSimplifications() assumed it can convert select of
constants to bool logic ops, but that does not work with poison.
We had a very similar construct in InstCombine, so the fix here
mimics the fix there.
The bug is in instsimplify, but I'm not sure how to reproduce it outside of
instcombine. The reason this is visible in instcombine is because we have a
hack (FIXME) to bypass simplification of a select when it has an icmp user:
955f125899/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp (L2632)
So we get to an unusual case where we are trying to simplify an instruction
that has an operand that would have already simplified if we had processed
it in normal order.
Differential Revision: https://reviews.llvm.org/D105298
This adds more poison folding optimizations to InstSimplify.
Since all binary operators propagate poison, these are fine.
Also, the precondition of `select cond, undef, x` -> `x` is relaxed to allow the case when `x` is undef.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D104661
We already have this fold:
fadd float poison, 1.0 --> poison
...via ConstantFolding, so this makes the behavior consistent
if the other operand(s) are non-constant.
The fold for undef was added before poison existed as a
value/type in IR.
This came up in D102673 / D103169
because we're trying to sort out the more complicated handling
for constrained math ops.
We should have the handling for the regular instructions done
first, so we can build on that (or diverge as needed).
Differential Revision: https://reviews.llvm.org/D104383
We can look through invariant group intrinsics for the purposes of
simplifying the result of a load.
Since intrinsics can't be constants, but we also don't want to
completely rewrite load constant folding, we convert the load operand to
a constant. For GEPs and bitcasts we just treat them as constants. For
invariant group intrinsics, we treat them as a bitcast.
Relanding with a check for self-referential values.
Reviewed By: lebedev.ri
Differential Revision: https://reviews.llvm.org/D101103
This patch allows that scalable vector can also use the fold that already
exists for fixed vector, only when the lane index is lower than the minimum
number of elements of the vector.
Differential Revision: https://reviews.llvm.org/D102404
We can look through invariant group intrinsics for the purposes of
simplifying the result of a load.
Since intrinsics can't be constants, but we also don't want to
completely rewrite load constant folding, we convert the load operand to
a constant. For GEPs and bitcasts we just treat them as constants. For
invariant group intrinsics, we treat them as a bitcast.
Reviewed By: lebedev.ri
Differential Revision: https://reviews.llvm.org/D101103
This is similar to the fix in c590a9880d7a ( PR49832 ), but
we missed handling the pattern for select of bools (no compare
inst).
We can't substitute a vector value because the equality condition
replacement that we are attempting requires that the condition
is true/false for the entire value. Vector select can be partly
true/false.
I added an assert for vector types, so we shouldn't hit this again.
Fixed formatting while auditing the callers.
https://llvm.org/PR50500
The semantics of select with undefined/poison condition
are not explicitly stated in the LangRef, but this matches
comments in the code and Alive2 appears to concur:
https://alive2.llvm.org/ce/z/KXytmd
We can find this pattern after demanded elements transforms.
As noted in D101191, fuzzers are finding infinite loops because
we may not account for this pattern in other passes.
The previous rule:
(insert_vector _, (extract_vector X, 0), 0) -> X
is not quite correct. The correct fold should be:
(insert_vector Y, (extract_vector X, 0), 0) -> X
where: Y is X, or Y is undef
This commit updates the pattern.
Reviewed By: peterwaller-arm, paulwalker-arm
Differential Revision: https://reviews.llvm.org/D102699
This commit removes some redundant {insert,extract}_vector intrinsic
chains by implementing the following patterns as instsimplifies:
(insert_vector _, (extract_vector X, 0), 0) -> X
(extract_vector (insert_vector _, X, 0), 0) -> X
Reviewed By: peterwaller-arm
Differential Revision: https://reviews.llvm.org/D101986
This reverts commit ea1a0d7c9ae3e5232a4163fc67efad4aabd51f2b.
While this is strictly more powerful, it is also strictly slower.
InstSimplify intentionally does not perform many folds that it
is allowed to perform, if doing so requires a KnownBits calculation
that will be repeated in InstCombine.
Maybe it's worthwhile to do this here, but that needs a more
explicitly stated motivation, evaluated in a review.
We already special-cased a few interesting patterns,
but that is strictly less powerful than using KnownBits.
So instead get the known bits for the operand of `and`,
and iff all the unset bits of the `and`-mask are known to be zeros
in the operand, we can omit said `and`.
Stepping through callstacks in the example from D99759 reveals
this potential compile-time improvement.
The savings come from avoiding ValueTracking's computing known
bits if we have already dealt with special-case patterns.
Further improvements in this direction seem possible.
This makes a degenerate test based on PR49785 about 40x faster
(25 sec -> 0.6 sec), but it does not address the larger question
of how to limit computeKnownBitsFromAssume(). Ie, the original
test there is still infinite-time for all practical purposes.
Differential Revision: https://reviews.llvm.org/D100408
"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.
The current code does not properly handle vector indices unless they are
the first index.
At the moment LangRef gives the impression that the vector index must be
the one and only index (https://llvm.org/docs/LangRef.html#getelementptr-instruction).
But vector indices can appear at any position and according to the
verifier there may be multiple vector indices. If that's the case, the
number of elements must match.
This patch updates SimplifyGEPInst to properly handle those additional
cases.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D99961
This is the sibling fix to c590a9880d7a -
as there, we can't subsitute a vector value the equality
compare replacement that we are trying requires that the
comparison is true for the entire value. Vector select
can be partly true/false.
In order to bring up scalable vector support in LLVM incrementally,
we introduced behaviour to emit a warning, instead of an error, when
asking the wrong question of a scalable vector, like asking for the
fixed number of elements.
This patch puts that behaviour under a flag. The default behaviour is
that the compiler will always error, which means that all LLVM unit
tests and regression tests will now fail when a code-path is taken that
still uses the wrong interface.
The behaviour to demote an error to a warning can be individually enabled
for tools that want to support experimental use of scalable vectors.
This patch enables that behaviour when driving compilation from Clang.
This means that for users who want to try out scalable-vector support,
fixed-width codegen support, or build user-code with scalable vector
intrinsics, Clang will not crash and burn when the compiler encounters
such a case.
This allows us to do away with the following pattern in many of the SVE tests:
RUN: .... 2>%t
RUN: cat %t | FileCheck --check-prefix=WARN
WARN-NOT: warning: ...
The behaviour to emit warnings is only temporary and we expect this flag
to be removed in the future when scalable vector support is more stable.
This patch also has fixes the following tests:
unittests:
ScalableVectorMVTsTest.SizeQueries
SelectionDAGAddressAnalysisTest.unknownSizeFrameObjects
AArch64SelectionDAGTest.computeKnownBitsSVE_ZERO_EXTEND_VECTOR_INREG
regression tests:
Transforms/InstCombine/vscale_gep.ll
Reviewed By: paulwalker-arm, ctetreau
Differential Revision: https://reviews.llvm.org/D98856
This relands 07c3b97e184d5bd828b8a680cdce46e73f3db9fc (D96945) which was reverted by
commit f49354838e526671e616d16199ebdee653b9f6fa.
The two-stage compilation successfully tests passes on my machine.
This is an alternative to D98391/D98585, playing things more
conservatively. If AllowRefinement == false, then we don't use
InstSimplify methods at all, and instead explicitly implement a
small number of non-refining folds. Most cases are handled by
constant folding, and I only had to add three folds to cover
our unit tests / test-suite. While this may lose some optimization
power, I think it is safer to approach from this direction, given
how many issues this code has already caused.
Differential Revision: https://reviews.llvm.org/D99027
This is a follow-up to D98588, and fixes the inline `FIXME` about a GEP-related simplification not
preserving the provenance.
https://alive2.llvm.org/ce/z/qbQoAY
Additional tests were added in {rGf125f28afdb59eba29d2491dac0dfc0a7bf1b60b}
Depends on D98672
Reviewed By: lebedev.ri
Differential Revision: https://reviews.llvm.org/D98611
In preparation for D98611, the upcoming change will need to apply additional checks to `P` and `V`,
and so this refactor paves the way for adding additional checks in a less awkward way.
Reviewed By: lebedev.ri
Differential Revision: https://reviews.llvm.org/D98672
The motivating pattern was handled in 0a2d69480d ,
but we should have this for symmetry.
But this really highlights that we could generalize for
any shifted constant if we match this in instcombine.
https://alive2.llvm.org/ce/z/MrmVNt
Add simplification of smul.fix and smul.fix.sat according to
X * 0 -> 0
X * undef -> 0
X * (1 << scale) -> X
This includes the commuted patterns and splatted vectors.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D98299
This is a patch that adds folding of two logical and/ors that share one variable:
a && (a && b) -> a && b
a && (a & b) -> a && b
...
This is towards removing the poison-unsafe select optimization (D93065 has more context).
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D96945
Pulled out from D90479 - this recognises invalid nsw shl patterns with signbit changes that result in poison.
Differential Revision: https://reviews.llvm.org/D97305
This patch adds a new intrinsic experimental.vector.reduce that takes a single
vector and returns a vector of matching type but with the original lane order
reversed. For example:
```
vector.reverse(<A,B,C,D>) ==> <D,C,B,A>
```
The new intrinsic supports fixed and scalable vectors types.
The fixed-width vector relies on shufflevector to maintain existing behaviour.
Scalable vector uses the new ISD node - VECTOR_REVERSE.
This new intrinsic is one of the named shufflevector intrinsics proposed on the
mailing-list in the RFC at [1].
Patch by Paul Walker (@paulwalker-arm).
[1] https://lists.llvm.org/pipermail/llvm-dev/2020-November/146864.html
Differential Revision: https://reviews.llvm.org/D94883
