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
We can fold x*C1/C2 <= x to true if C1 <= C2. This is valid even
if the multiplication is not nuw: https://alive2.llvm.org/ce/z/vULors
The multiplication or division can be replaced by shifts. We don't
handle the case where both are shifts, as that should get folded
away by InstCombine.
This is a partial fix for https://bugs.llvm.org/show_bug.cgi?id=44403.
Folding gep p, q-p to q is only legal if p and q have the same
provenance. This fold should probably be guarded by something like
getUnderlyingObject(p) == getUnderlyingObject(q).
This patch is a partial fix that removes the special handling for
gep p, 0-p, which will fold to a null pointer, which would certainly
not pass an underlying object check (unless p is also null, in which
case this would fold trivially anyway). Folding to a null pointer
is particularly problematic due to the special handling it receives
in many places, making end-to-end miscompiles more likely.
Differential Revision: https://reviews.llvm.org/D93820
I don't believe this has an observable effect, because the only
thing we care about here is replacing the operand with a constant
so following folds can apply. This change is just to make the
representation follow canonical unary shuffle form.
Calling null or undef results in immediate undefined behavior.
Return poison instead of undef in this case, similar to what
we do for immediate UB due to division by zero.
Make InstSimplify return poison rather than undef for out-of-bounds
shifts, as specified by LandRef:
> If op2 is (statically or dynamically) equal to or larger than the
> number of bits in op1, this instruction returns a poison value.
Differential Revision: https://reviews.llvm.org/D93998
As the comment already indicates, performing an operation with
nnan/ninf flags on a nan/inf or undef results in poison. Now that
we have a proper poison value, we no longer need to relax it to
undef.
Div/rem by zero is immediate undefined behavior and anything goes.
Currently we fold it to undef, this patch changes it to fold to
poison instead, which is slightly stronger.
Differential Revision: https://reviews.llvm.org/D93995
This is the same change as D93990, but for extractelement rather
than insertelement.
> If idx exceeds the length of val for a fixed-length vector, the
> result is a poison value. For a scalable vector, if the value of
> idx exceeds the runtime length of the vector, the result is a
> poison value.
This is a simple patch that updates InstSimplify to return poison if the index is/can be out-of-bounds
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D93990
The last use of the function, located in RemovePredecessorAndSimplify,
was removed on Dec 25, 2020 in commit
46bea9b29714ba77010612b04ba13aff56d62e7b.
The last use of RemovePredecessorAndSimplify was removed on Sep 29,
2010 in commit 99c985c37dd45dd0fbd03863037d8e93153783e6.
The transform wasn't checking that the LHS of the comparison
*is* the `X` in question...
This is the miscompile that was holding up D87188.
Thanks to Dave Green for producing an actionable reproducer!
Folding a select of vector constants that include undef elements only
applies to fixed vectors, but there's no earlier check the type is not
scalable so it crashes for scalable vectors. This adds a check so this
optimization is only attempted for fixed vectors.
Reviewed By: sdesmalen
Differential Revision: https://reviews.llvm.org/D92046
This extends D78430 to solve cases like:
https://llvm.org/PR47858
There are still missed opportunities shown in the tests,
and as noted in the earlier patches, we have related
functionality in InstCombine, so we may want to extend
other folds in a similar way.
A semi-random sampling of test diff proofs in this patch:
https://rise4fun.com/Alive/sS4C
This improves simplifications for pattern `icmp (X+Y), (X+Z)` -> `icmp Y,Z`
if only one of the operands has NSW set, e.g.:
icmp slt (x + 0), (x +nsw 1)
We can still safely rewrite this to:
icmp slt 0, 1
because we know that the LHS can't overflow if the RHS has NSW set and
C1 < C2 && C1 >= 0, or C2 < C1 && C1 <= 0
This simplification is useful because ScalarEvolutionExpander which is used to
generate code for SCEVs in different loop optimisers is not always able to put
back NSW flags across control-flow, thus inhibiting CFG simplifications.
Differential Revision: https://reviews.llvm.org/D89317
