The loop vectorizer will currently assume a large trip count when
calculating which of several vectorization factors are more profitable.
That is often not a terrible assumption to make as small trip count
loops will usually have been fully unrolled. There are cases however
where we will try to vectorize them, and especially when folding the
tail by masking can incorrectly choose to vectorize loops that are not
beneficial, due to the folded tail rounding the iteration count up for
the vectorized loop.
The motivating example here has a trip count of 5, so either performs 5
scalar iterations or 2 vector iterations (with VF=4). At a high enough
trip count the vectorization becomes profitable, but the rounding up to
2 vector iterations vs only 5 scalar makes it unprofitable.
This adds an alternative cost calculation when we know the max trip
count and are folding tail by masking, rounding the iteration count up
to the correct number for the vector width. We still do not account for
anything like setup cost or the mixture of vector and scalar loops, but
this is at least an improvement in a few cases that we have had
reported.
Differential Revision: https://reviews.llvm.org/D101726
Adds support for scalable vectorization of loops containing first-order recurrences, e.g:
```
for(int i = 0; i < n; i++)
b[i] = a[i] + a[i - 1]
```
This patch changes fixFirstOrderRecurrence for scalable vectors to take vscale into
account when inserting into and extracting from the last lane of a vector.
CreateVectorSplice has been added to construct a vector for the recurrence, which
returns a splice intrinsic for scalable types. For fixed-width the behaviour
remains unchanged as CreateVectorSplice will return a shufflevector instead.
The tests included here are the same as test/Transform/LoopVectorize/first-order-recurrence.ll
Reviewed By: david-arm, fhahn
Differential Revision: https://reviews.llvm.org/D101076
This is a patch that disables the poison-unsafe select -> and/or i1 folding.
It has been blocking D72396 and also has been the source of a few miscompilations
described in llvm.org/pr49688 .
D99674 conditionally blocked this folding and successfully fixed the latter one.
The former one was still blocked, and this patch addresses it.
Note that a few test functions that has `_logical` suffix are now deoptimized.
These are created by @nikic to check the impact of disabling this optimization
by copying existing original functions and replacing and/or with select.
I can see that most of these are poison-unsafe; they can be revived by introducing
freeze instruction. I left comments at fcmp + select optimizations (or-fcmp.ll, and-fcmp.ll)
because I think they are good targets for freeze fix.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D101191
LoopVectorize has a fairly deeply baked in design problem where it will try to query analysis (primarily SCEV, but also ValueTracking) in the midst of mutating IR. In particular, the intermediate IR state does not represent the semantics of the original (or final) program.
Fixing this for real is hard, but all of the cases seen so far share a common symptom. In cases seen to date, the analysis being queried is the computation of the original loop's trip count. We can fix this particular instance of the issue by simply computing the trip count early, and caching it.
I want to be really clear that this is nothing but a workaround. It does nothing to fix the root issue, and at best, delays the time until we have to fix this for real. Florian and I have discussed an eventual solution in the review comments for https://reviews.llvm.org/D100663, but it's a lot of work.
Test taken from https://reviews.llvm.org/D100663.
Differential Revision: https://reviews.llvm.org/D101487
This patch updates the code that sinks recipes required for first-order
recurrences to properly handle replicate-regions. At the moment, the
code would just move the replicate recipe out of its replicate-region,
producing an invalid VPlan.
When sinking a recipe in a replicate-region, we have to sink the whole
region. To do that, we first need to split the block at the target
recipe and move the region in between.
This patch also adds a splitAt helper to VPBasicBlock to split a
VPBasicBlock at a given iterator.
Fixes PR50009.
Reviewed By: Ayal
Differential Revision: https://reviews.llvm.org/D100751
This patch is to address https://bugs.llvm.org/show_bug.cgi?id=49916.
When the size of an alloca is 0, it will trigger an assertion in OptimizedStructLayout when being added to the frame.
Fix it by not adding it at all. We return index 0 (beginning of the frame) for all 0-sized allocas.
Differential Revision: https://reviews.llvm.org/D101841
We need to use a logical or instead of a bitwise or to preserve
poison behavior. Poison from the second condition should not
propagate if the first condition is true.
We were already handling this correctly in FoldBranchToCommonDest(),
but not in this fold. (There are still other folds with this issue.)
This fixes https://llvm.org/PR48900 , but as seen in the
regression tests prevents some optimizations.
There are a few options to restore those (switch to min/max
intrinsics, add larger pattern matching for select with
dominating condition, improve CVP), but we need to prevent
the bug 1st.
This patch updates the code handling reduction recipes to also keep
track of the incoming value from the latch in the recipe. This is needed
to model the def-use chains completely in VPlan, so that it is possible
to replace the incoming value with an arbitrary VPValue.
Reviewed By: Ayal
Differential Revision: https://reviews.llvm.org/D99294
We were missing bitreverse matches in cases where InstCombine had seen a byte-level rotation at the end of a bitreverse sequence (replacing or() with fshl()), hindering the exhaustive bitreverse matching in CodeGenPrepare later on.
This reverts commit fd18547e0721983dcb273670d16341921f831e50. Need to
add a check for the size of the vectorization tree to avoid some extra
vectorization.
Instruction has mayHaveSideEffects method that returns true if mayThrow return true because this is called internally in the first method. As such, the call being removed is redundant.
Patch By: vdsered (Daniil Seredkin)
Differential Revision: https://reviews.llvm.org/D101685
Summary:
Add the AAExecutionDomainInfo attributor instance to OpenMPOpt.
This will infer information relating to domain information that an
instruction might be expecting in. Right now this only includes a very
crude check for instructions that will be executed by the master thread
by comparing a thread-id function with a constant zero.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D101578
When passingValueIsAlwaysUndefined scans for an instruction between an
inst with a null or undef argument and its first use, it was checking
for instructions that may have side effects, which is a superset of the
instructions it intended to find (as per the comments, control flow
changing instructions that would prevent reaching the uses). Switch
to using isGuaranteedToTransferExecutionToSuccessor() instead.
Without this change, when enabling -fwhole-program-vtables, which causes
assumes to be inserted by clang, we can get different simplification
decisions. In particular, when building with instrumentation FDO it can
affect the optimizations decisions before FDO matching, leading to some
mismatches.
I had to modify d83507-knowledge-retention-bug.ll since this fix enables
more aggressive optimization of that code such that it no longer tested
the original bug it was meant to test. I removed the undef which still
provokes the original failure (confirmed by temporarily reverting the
fix) and also changed it to just invoke the passes of interest to narrow
the testing.
Similarly I needed to adjust code for UnreachableEliminate.ll to avoid
an undef which was causing the function body to get optimized away with
this fix.
Differential Revision: https://reviews.llvm.org/D101507
Need to check if target allows/supports masked gathers before trying to
estimate its cost, otherwise we may fail to vectorize some of the
patterns because of too pessimistic cost model.
Part of D57059.
Differential Revision: https://reviews.llvm.org/D101297
Need to check if target allows/supports masked gathers before trying to
estimate its cost, otherwise we may fail to vectorize some of the
patterns because of too pessimistic cost model.
Part of D57059.
Differential Revision: https://reviews.llvm.org/D101297
As we gradually move more elements of LV to VPlan, we are trying to
reduce the number of places that still has to check IR of the original
loop.
This patch adjusts the code to fix cross iteration phis to get the PHIs
to fix directly from the VPlan that is executed. We still need the
original PHI to check for first-order recurrences, but we can get rid of
that once we model that explicitly in VPlan as well.
Reviewed By: Ayal
Differential Revision: https://reviews.llvm.org/D99293
Add address sanitizer instrumentation support for accesses to global
and constant address spaces in AMDGPU. It strictly avoids instrumenting
the stack and assumes x86 as the host.
Reviewed by: vitalybuka
Differential Revision: https://reviews.llvm.org/D99071
This patch introduces a helper to obtain an iterator range for the
PHI-like recipes in a block.
Reviewed By: Ayal
Differential Revision: https://reviews.llvm.org/D100101
The problem is the following. With fast8, we broke an important
invariant when loading shadows. A wide shadow of 64 bits used to
correspond to 4 application bytes with fast16; so, generating a single
load was okay since those 4 application bytes would share a single
origin. Now, using fast8, a wide shadow of 64 bits corresponds to 8
application bytes that should be backed by 2 origins (but we kept
generating just one).
Let’s say our wide shadow is 64-bit and consists of the following:
0xABCDEFGH. To check if we need the second origin value, we could do
the following (on the 64-bit wide shadow) case:
- bitwise shift the wide shadow left by 32 bits (yielding 0xEFGH0000)
- push the result along with the first origin load to the shadow/origin vectors
- load the second 32-bit origin of the 64-bit wide shadow
- push the wide shadow along with the second origin to the shadow/origin vectors.
The combineOrigins would then select the second origin if the wide
shadow is of the form 0xABCDE0000. The tests illustrate how this
change affects the generated bitcode.
Reviewed By: stephan.yichao.zhao
Differential Revision: https://reviews.llvm.org/D101584
If the extracts from the non-power-2 vectors are recognized as shuffles,
need some extra checks to not crash cost calculations if trying to gext
the ecost for subvector extracts. In this case need to check carefully
that we do not exit out of bounds of the original vector, otherwise the
TTI's cost model will crash on assert.
Differential Revision: https://reviews.llvm.org/D101477
Previous attempt to fix infinite recursion in min/max reassociation was not fully successful (D100170). Newly discovered failing case is due to not properly handled when there is a single use. It should be processed separately from 2 uses case.
Reviewed By: mkazantsev
Differential Revision: https://reviews.llvm.org/D101359
Hoisting and sinking instructions out of conditional blocks enables
additional vectorization by:
1. Executing memory accesses unconditionally.
2. Reducing the number of instructions that need predication.
After disabling early hoisting / sinking, we miss out on a few
vectorization opportunities. One of those is causing a ~10% performance
regression in one of the Geekbench benchmarks on AArch64.
This patch tires to recover the regression by running hoisting/sinking
as part of a SimplifyCFG run after LoopRotate and before LoopVectorize.
Note that in the legacy pass-manager, we run LoopRotate just before
vectorization again and there's no SimplifyCFG run in between, so the
sinking/hoisting may impact the later run on LoopRotate. But the impact
should be limited and the benefit of hosting/sinking at this stage
should outweigh the risk of not rotating.
Compile-time impact looks slightly positive for most cases.
http://llvm-compile-time-tracker.com/compare.php?from=2ea7fb7b1c045a7d60fcccf3df3ebb26aa3699e5&to=e58b4a763c691da651f25996aad619cb3d946faf&stat=instructions
NewPM-O3: geomean -0.19%
NewPM-ReleaseThinLTO: geoman -0.54%
NewPM-ReleaseLTO-g: geomean -0.03%
With a few benchmarks seeing a notable increase, but also some
improvements.
Alternative to D101290.
Reviewed By: lebedev.ri
Differential Revision: https://reviews.llvm.org/D101468
Added an extra analysis for better choosing of shuffle kind in
getShuffleCost functions for better cost estimation if mask was
provided.
Differential Revision: https://reviews.llvm.org/D100865
Sanjay Patel