This issue reproduces in the context of LoopDeletion, because the
bitcast does not get simplified away there. For a plain -inst-simplify
run the bitcast would get folded away first.
Fixes https://github.com/llvm/llvm-project/issues/54615.
If a constrained intrinsic call was replaced by some value, it was not
removed in some cases. The dangling instruction resulted in useless
instructions executed in runtime. It happened because constrained
intrinsics usually have side effect, it is used to model the interaction
with floating-point environment. In some cases side effect is actually
absent or can be ignored.
This change adds specific treatment of constrained intrinsics so that
their side effect can be removed if it actually absents.
Differential Revision: https://reviews.llvm.org/D118426
Currently the fsub optimizations in InstSimplify don't know how to fold
-0.0 - (-X) to X when the constrained intrinsics are used. This adds partial
support. The rest of the support will come later with work on the IR
matchers.
This review is split out from D107285.
Differential Revision: https://reviews.llvm.org/D123396
In D111530, I suggested that we add some relatively basic pattern-matching
folds for shifts and funnel shifts and avoid a more specialized solution
if possible.
We can start by implementing at least one of these in IR because it's
easier to write the code and verify with Alive2:
https://alive2.llvm.org/ce/z/qHpmNn
This will need to be adapted/extended for SDAG to handle the motivating
bug ( #49541 ) because the patterns only appear later with that example
(added some tests: bb850d422b)
This can be extended within InstSimplify to handle cases where we 'and'
with a shift too (in that case, kill the funnel shift).
We could also handle patterns where the shift and funnel shift directions
are inverted, but I think it's better to canonicalize that instead to
avoid pattern-match case explosion.
Differential Revision: https://reviews.llvm.org/D120253
The code was using exact sizing only, but since what we really need is just to make sure the offsets are in bounds, a minimum bound on the object size is sufficient.
To demonstrate the difference, support computing minimum sizes from obects of scalable vector type.
Remove some code which tried to handle the case of comparing two allocas where an object size could not be precisely computed. This code had zero coverage in tree, and at least one nasty bug.
The bug comes from the fact that the code uses the size of the result pointer as a proxy for whether the alloca can be of size zero. Since the result of an alloca is *always* a pointer type, and a pointer type can *never* be empty, this check was a nop. As a result, we blindly consider a zero offset from two allocas to never be equal. They can in fact be equal when one or more of the allocas is zero sized.
This is particularly ugly because instcombine contains the exact opposite rule. If instcombine reaches the allocas first, it combines them into one (making them equal). If instsimplify reaches the compare first, it would consider them not equal. This creates all kinds of fun scenarios for order of optimization reaching different and contradictory conclusions.
In a prior review I was asked to move the helper function canIgnoreSNaN()
out to FPEnv.h. This wasn't possible at the time because that function
needs the fast math flags, and including them includes lots of other stuff
that isn't needed.
This patch moves the fast math flags out into a new FMF.h file unchanged,
and moves the helper function out to FPEnv.h also unchanged. This ticket
only moves code around.
Differential Revision: https://reviews.llvm.org/D119752
Currently the fsub optimizations in InstSimplify don't know how to fold
X - -0.0 to X when we know X is not zero and the constrained intrinsics
are used. This adds the support.
This review is split out from D107285.
Differential Revision: https://reviews.llvm.org/D119746
Instead of doing an inbounds strip first and another non-inbounds
strip afterward for equality comparisons, directly do a single
inbounds or non-inbounds strip based on whether we have an equality
predicate or not.
This is NFC-ish in that the alloca equality codepath is the only
part that sees additional non-inbounds offsets now, and for that
codepath it doesn't matter whether or not the GEP is inbounds, as
it does a stronger check itself. InstCombine would infer inbounds
for such GEPs.
Currently the fsub optimizations in InstSimplify don't know how to fold X
- +0.0 to X when using the constrained intrinsics. This adds the support.
This review is split out from D107285.
Differential Revision: https://reviews.llvm.org/D118928
This doesn't require callers to put the pointer operand and the indices
in a container like a vector when calling the function. This is not
really an issue with the existing callers. But when using it from
IRBuilder the inputs are available as separate pointer value and indices
ArrayRef.
Reviewed By: lebedev.ri
Differential Revision: https://reviews.llvm.org/D117038
We could use knownbits on both operands for even more folds (and there are
already tests in place for that), but this is enough to recover the example
from:
https://github.com/llvm/llvm-project/issues/51934
(the tests are derived from the code in that example)
I am assuming no noticeable compile-time impact from this because udiv/urem
are rare opcodes.
Differential Revision: https://reviews.llvm.org/D116616
Alternative to D116817.
This introduces a new value-based folding interface for Or (FoldOr),
which takes 2 values and returns an existing Value or a constant if the
Or can be simplified. Otherwise nullptr is returned. This replaces the
more restrictive CreateOr which takes 2 constants.
This is the used to implement a folder that uses InstructionSimplify.
The logic to simplify `Or` instructions is moved there. Subsequent
patches are going to transition other CreateXXX to the more general
FoldXXX interface.
Reviewed By: nikic, lebedev.ri
Differential Revision: https://reviews.llvm.org/D116935
D92270 updated constant expression folding to fold inbounds GEP to
poison if the base is undef. Apply the same logic to SimplifyGEPInst.
The justification is that we can choose an out-of-bounds pointer as base
pointer.
Reviewed By: nikic, lebedev.ri
Differential Revision: https://reviews.llvm.org/D117015
We should not lose analysis precision if an 'add' has both no-wrap
flags (nsw and nuw) compared to just one or the other.
This patch is modeled on a similar construct that was added with
D59386.
I don't think it is possible to expose a problem with an unsigned
compare because of the way this was coded (nuw is handled first).
InstCombine has an assert that fires with the example from:
https://github.com/llvm/llvm-project/issues/52884
...because it was expecting InstSimplify to handle this kind of
pattern with an smax.
Fixes#52884
Differential Revision: https://reviews.llvm.org/D116322
Adding following fold opportunity:
((A | B) ^ A) & ((A | B) ^ B) --> 0
Reviewed By: spatel, rampitec
Differential Revision: https://reviews.llvm.org/D115755
Refer to https://llvm.org/PR52546.
Simplifies the following cases:
not(X) == 0 -> X != 0 -> X
not(X) <=u 0 -> X >u 0 -> X
not(X) >=s 0 -> X <s 0 -> X
not(X) != 1 -> X == 1 -> X
not(X) <=u 1 -> X >=u 1 -> X
not(X) >s 1 -> X <=s -1 -> X
Differential Revision: https://reviews.llvm.org/D114666
Reduce code duplication for commutative pattern matching
and fix a miscompile.
We can't safely propagate an undef element in this transform:
https://alive2.llvm.org/ce/z/s5xy55
We needed a stricter version of m_Not for D114462, but I wasn't
sure if that was going to be required anywhere else, so I didn't bother
to make that reusable.
It turns out we have one more existing simplification that needs
this (currently miscompiles):
https://alive2.llvm.org/ce/z/9-nTKi
And there's at least one more fold in that family that we could add.
Differential Revision: https://reviews.llvm.org/D114882
https://alive2.llvm.org/ce/z/4PaPDy
There's a related fold where the inner 'or' is replaced by 'and',
but that needs to be more careful about matching a 'not'.
Reduce duplication for handling the top-level commuted operands.
There are several other folds that should be moved in here, but
we need to make sure there's good test coverage.
(~a & b) ^ (a | b) --> a
This is the swapped and/or (Demorgan?) sibling fold for
the fold added with D114462 ( 892648b18a ).
This case is easier to specify because we are returning
a root value, not a 'not':
https://alive2.llvm.org/ce/z/SRzj4f
(a & b) ^ (~a | b) --> ~a
I was looking for a shortcut to reduce some of the complex logic
folds that are currently up for review (D113216
and others in that stack), and I found this missing from
instcombine/instsimplify.
There is a trade-off in putting it into instsimplify: because
we can't create new values here, we need a strict 'not' op (no
undef elements). Otherwise, the fold is not valid:
https://alive2.llvm.org/ce/z/k_AGGj
If this was in instcombine instead, we could create the proper
'not'. But having the fold here benefits other passes like GVN
that use instsimplify as an analysis.
There is a related fold where 'and' and 'or' are swapped, and
that is planned as a follow-up commit.
Differential Revision: https://reviews.llvm.org/D114462
As described in https://bugs.llvm.org/show_bug.cgi?id=52429 this
fold is incorrect, because inbounds only guarantees that the
pointers don't wrap in the unsigned space: It is possible that
the sign boundary is crossed by an object.
I'm dropping the fold entirely rather than adjusting it, because
computePointerICmp() fully subsumes it (just with correct predicate
handling).
Differential Revision: https://reviews.llvm.org/D113343
Nikita Popov