This is an enhancement motivated by https://llvm.org/PR16739
(see D92858 for another).
We can look through a GEP to find a base pointer that may be
safe to use for a vector load. If so, then we shuffle (shift)
the necessary vector element over to index 0.
Alive2 proof based on 1 of the regression tests:
https://alive2.llvm.org/ce/z/yPJLkh
The vector translation is independent of endian (verify by
changing to leading 'E' in the datalayout string).
Differential Revision: https://reviews.llvm.org/D93229
Here's another minimal step suggested by D93229 / D93397 .
(I'm trying to be extra careful in these changes because
load transforms are easy to get wrong.)
We can optimistically choose the greater alignment of a
load and its pointer operand. As the test diffs show, this
can improve what would have been unaligned vector loads
into aligned loads.
When we enhance with gep offsets, we will need to adjust
the alignment calculation to include that offset.
Differential Revision: https://reviews.llvm.org/D93406
As discussed in D93229, we only need a minimal alignment constraint
when querying whether a hypothetical vector load is safe. We still
pass/use the potentially stronger alignment attribute when checking
costs and creating the new load.
There's already a test that changes with the minimum code change,
so splitting this off as a preliminary commit independent of any
gep/offset enhancements.
Differential Revision: https://reviews.llvm.org/D93397
As noted in D93229, the transform from scalar load to vector load
potentially leaks poison from the extra vector elements that are
being loaded.
We could use freeze here (and x86 codegen at least appears to be
the same either way), but we already have a shuffle in this logic
to optionally change the vector size, so let's allow that
instruction to serve both purposes.
Differential Revision: https://reviews.llvm.org/D93238
This is an enhancement to load vectorization that is motivated by
a pattern in https://llvm.org/PR16739.
Unfortunately, it's still not enough to make a difference there.
We will have to handle multi-use cases in some better way to avoid
creating multiple overlapping loads.
Differential Revision: https://reviews.llvm.org/D92858
As discussed in:
https://llvm.org/PR47558
...there are several potential fixes/follow-ups visible
in the test case, but this is the quickest and safest
fix of the perf regression.
Similar to the tsan suppression in
`Utils/VNCoercion.cpp:getLoadLoadClobberFullWidthSize` (rL175034; load widening used by GVN),
the D81766 optimization should be suppressed under tsan due to potential
spurious data race reports:
struct A {
int i;
const short s; // the load cannot be vectorized because
int modify; // it overlaps with bytes being concurrently modified
long pad1, pad2;
};
// __tsan_read16 does not know that some bytes are undef and accessing is safe
Similarly, under asan, users can mark memory regions with
`__asan_poison_memory_region`. A widened load can lead to a spurious
use-after-poison error. hwasan/memtag should be similarly suppressed.
`mustSuppressSpeculation` suppresses asan/hwasan/tsan but not memtag, so
we need to exclude memtag in `vectorizeLoadInsert`.
Note, memtag suppression can be relaxed if the load is aligned to the
its granule (usually 16), but that is out of scope of this patch.
Reviewed By: spatel, vitalybuka
Differential Revision: https://reviews.llvm.org/D87538
This is an enhancement to D81766 to allow loading the minimum target
vector type into an IR vector with a different number of elements.
In one of the motivating tests from PR16739, SLP creates <2 x float>
load ops mixed with <4 x float> insert ops, so we want to handle that
pattern in addition to potential oversized vectors created by the
vectorizers.
For now, we are assuming the insert/extract subvector with undef is
free because there is no exact corresponding TTI modeling for that.
Differential Revision: https://reviews.llvm.org/D86160
This is a fixup to commit 43bdac2906, to make sure the
address space from the original load pointer is retained in the
vector pointer.
Resolves problem with
Assertion `castIsValid(op, S, Ty) && "Invalid cast!"' failed.
due to address space mismatch.
Reviewed By: spatel
Differential Revision: https://reviews.llvm.org/D85912
This patch was adjusted to match the most basic pattern that starts with an insertelement
(so there's no extract created here). Hopefully, that removes any concern about
interfering with other passes. Ie, the transform should almost always be profitable.
We could make an argument that this could be part of canonicalization, but we
conservatively try not to create vector ops from scalar ops in passes like instcombine.
If the transform is not profitable, the backend should be able to re-scalarize the load.
Differential Revision: https://reviews.llvm.org/D81766
Sanjay Patel