I think what we need is the least Log2(EltSize) significant bits are known to be ones.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D130251
Optimizing (a * 0 + b) to (b) requires assuming that a is finite and not
NaN. DAGCombiner will do this optimization when the reassoc fast math
flag is set, which is not correct. Change DAGCombiner to only consider
UnsafeMath for this optimization.
Differential Revision: https://reviews.llvm.org/D130232
Co-authored-by: Andrea Faulds <andrea.faulds@arm.com>
This will fix the SystemZ v3i31 memcpy regression in D77804 (with the help of D129765 as well....).
It should also allow us to /bend/ the oneuse limitation for cases where we can use demanded bits to safely peek though multiple uses of the AND ops.
We were looking for loads or any_extend+load. reduceLoadWidth
hasn't known how to look through such an any_extend to find the
load since D40667 almost 5 years ago.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D130333
When determining if an `and` should be merged into an extending load
the constant argument to the `and` is currently not checked if the
argument requires truncation. This prevents the combine happening when
the vector width is half the normal available vector width for SVE VLA
vectors.
Reviewed By: c-rhodes
Differential Revision: https://reviews.llvm.org/D129281
This revision supports to scalarize a binary operation of two scalable splat vectors.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D122791
The DAG Combiner unnecessarily restricts commutative CSE
to nodes with a single result value. This commit removes
that restriction.
Signed-off-by: Itay Bookstein <ibookstein@gmail.com>
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D129666
trunc (sign_ext_inreg X, iM) to iN --> sign_ext_inreg (trunc X to iN), iM
There are improvements on existing tests from this, and there are a pair
of large regressions in D127115 for Thumb2 caused by not folding this
pattern.
Differential Revision: https://reviews.llvm.org/D129890
D127595 added the ability to recurse up a (one-use) INSERT_VECTOR_ELT chain to create a BUILD_VECTOR before other combines manage to break the chain, something that is particularly bad in D127115.
The patch generalises this so it doesn't have to build the chain starting from the last element insertion, instead it can now start from any insertion and will recurse up the chain until it finds all elements or finds a UNDEF/BUILD_VECTOR/SCALAR_TO_VECTOR which represents that start of the chain.
Fixes several regressions in D127115
As mentioned on D127115, this patch that attempts to recognise shuffle masks that could be simplified to a AND mask - we already have a similar transform that will fold AND -> 'clear mask' shuffle, but this patch handles cases where the referenced elements are not from the same lane indices but are known to be zero.
Differential Revision: https://reviews.llvm.org/D129150
combineShiftAnd1ToBitTest already matches "and (not (srl X, C)), 1 --> (and X, 1<<C) == 0" patterns, but we can end up with situations where the not is before the shift.
Part of some yak shaving for D127115 to generalise the "xor (X >> ShiftC), XorC --> (not X) >> ShiftC" fold.
SimplifyDemandedBits is called slightly later which allows the not(sext(x)) -> sext(not(x)) fold to occur via foldLogicOfShifts
As mentioned on D127115, we should be able to further generalise this based off the demanded bits.
We have the same fold in InstCombine - though implemented via OrZero flag on isKnownToBePowerOfTwo. The reasoning here is that either a) the result of the lshr is a power-of-two, or b) we have a div-by-zero triggering UB which we can ignore.
Differential Revision: https://reviews.llvm.org/D129606
As suggested in the post-commit feedback for D128123,
we can ease the mask constraint to ignore the MSB
(and make the code easier to read by adjusting the check).
https://alive2.llvm.org/ce/z/bbvqWv
This patch restores calls to has_value to make it clear that we are
checking the presence of an optional value, not the underlying value.
This patch partially reverts d08f34b592ff06ccb1f36da88ec09aa926427a4d.
Differential Revision: https://reviews.llvm.org/D129454
We already handled this case for add with a constant RHS. A
similar pattern can occur for sub with a constant left hand side.
Test cases use add and a mul representing (neg (shl X, C)) because
that's what I saw in the wild. The mul will be decomposed and then
the new transform can kick in.
Tests have not been committed, but this patch shows the changes.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D128769
This is almost the same as the abandoned D48529, but it
allows splat vector constants too.
This replaces the x86-specific code that was added with
the alternate patch D48557 with the original generic
combine.
This transform is a less restricted form of an existing
InstCombine and the proposed SDAG equivalent for that
in D128080:
https://alive2.llvm.org/ce/z/OUm6N_
Differential Revision: https://reviews.llvm.org/D128123
Similar to the existing (shl (srl x, c1), c2) fold
Part of the work to fix the regressions in D77804
Differential Revision: https://reviews.llvm.org/D125836
The VT we want to shrink to may not be legal especially after type
legalization.
Fixes PR56110.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D128135
Another issue unearthed by D127115
We take a long time to canonicalize an insert_vector_elt chain before being able to convert it into a build_vector - even if they are already in ascending insertion order, we fold the nodes one at a time into the build_vector 'seed', leaving plenty of time for other folds to alter it (in particular recognising when they come from extract_vector_elt resulting in a shuffle_vector that is much harder to fold with).
D127115 makes this particularly difficult as we're almost guaranteed to have the lost the sequence before all possible insertions have been folded.
This patch proposes to begin at the last insertion and attempt to collect all the (oneuse) insertions right away and create the build_vector before its too late.
Differential Revision: https://reviews.llvm.org/D127595
