If the parameter had been annotated as nonnull because of the null
check, we want to remove the attribute, since it may no longer apply and
could result in miscompiles if left. Similarly, we also want to remove
undef-implying attributes, since they may not apply anymore either.
Fixes PR52110.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D111515
This extends the foldOpIntoPhi code used when visiting a freeze user of a phi to allow any non-undef/poison operand as opposed to only non-undef/poison constants. This lets us hoist a freeze in the increment of an IV into the preheader in many cases.
Differential Revision: https://reviews.llvm.org/D111744
Even if there are no interesting functions, the SCCP solver would still run
before bailing. Now bail earlier, avoid running the solver for nothing.
Differential Revision: https://reviews.llvm.org/D111645
This is NFC-intended for scalar code. There are still unnecessary
m_ConstantInt restrictions in surrounding code, so this is not a
complete fix.
This prevents regressions seen with a planned follow-on to D111410.
If we have an instruction which produces poison only when flags are specified on the instruction, then we know that freezing the operands and dropping flags is equivalent to freezing the result. If we know those flags don't result in any undefined behavior being executed, then there's no point in preserving the flags as we gain no knowledge by having them.
This patch extends the existing propagation logic which sinks freeze to single potential non-poison operands to allow dropping of flags when we know the freeze is the sole use of the instruction with poison flags.
The main value is that we tend to sink freezes towards the phi in IV cycles where the incoming value to the phi is the freeze of an IV increment. This will in turn (in a future patch), let us fold the freeze through the phi into the loop preheader. Motivated by eliminating need for CanonicalizeFreezeInLoops for the clearly profitable cases from onephi.ll test case in the test directory.
Differential Revision: https://reviews.llvm.org/D111675
This patch fixes another crash revealed by PR51614:
when *deciding* to vectorize with masked interleave groups, check if the access
is reverse (which is currently not supported).
Differential Revision: https://reviews.llvm.org/D108900
If another inlining session came after a ModuleInlinerWrapperPass, the
advisor alanysis would still be cached, but its Result would be cleared.
We need to clear both.
This addresses PR52118
Differential Revision: https://reviews.llvm.org/D111586
This may not be obvious, but Alive2 agrees:
https://alive2.llvm.org/ce/z/Ld9qNT
If the mul has "nsw", then -1 * INT_MIN is poison, so the
negate can also have "nsw" because 0 - INT_MIN is poison.
If the mul has "nuw", then that means the "OtherOp" can only
be 0 or 1 (anything else multiplied by 0xfff... would wrap).
So the replacement negate must be "nsw" because it is either
"0-0" or "0-1".
This is another regression noticed with a planned follow-up
to D111410.
This patch continues unblocking optimizations that are blocked by pseudo probe instrumentation.
Not exactly like DbgIntrinsics, PseudoProbe intrinsic has other attributes (such as mayread, maywrite, mayhaveSideEffect) that can block optimizations. The issues fixed are:
- Flipped default param of getFirstNonPHIOrDbg API to skip pseudo probes
- Unblocked CSE by avoiding pseudo probe from clobbering memory SSA
- Unblocked induction variable simpliciation
- Allow empty loop deletion by treating probe intrinsic isDroppable
- Some refactoring.
Reviewed By: wenlei
Differential Revision: https://reviews.llvm.org/D110847
collectLoopScalars collects pointer induction updates in ScalarPtrs, assuming
that the instruction will be scalar after vectorization. This may crash later
in VPReplicateRecipe::execute() if there there is another user of the instruction
other than the Phi node which needs to be widened.
This changes collectLoopScalars so that if there are any other users of
Update other than a Phi node, it is not added to ScalarPtrs.
Reviewed By: david-arm, fhahn
Differential Revision: https://reviews.llvm.org/D111294
This is a follow up of D110529 that disallowed constexprs. That change
introduced a regression as this also disallowed constexprs that are function
pointers, which is actually one of the motivating use cases that we do want to
support.
Differential Revision: https://reviews.llvm.org/D111567
This patch adds a new cost heuristic that allows peeling a single
iteration off read-only loops, if the loop contains a load that
1. is feeding an exit condition,
2. dominates the latch,
3. is not already known to be dereferenceable,
4. and has a loop invariant address.
If all non-latch exits are terminated with unreachable, such loads
in the loop are guaranteed to be dereferenceable after peeling,
enabling hoisting/CSE'ing them.
This enables vectorization of loops with certain runtime-checks, like
multiple calls to `std::vector::at` if the vector is passed as pointer.
Reviewed By: mkazantsev
Differential Revision: https://reviews.llvm.org/D108114
LoopSimplifyCFG does not need MSSA, but should preserve it if it's available.
This is a legacy PM change, aimed to denoise the test changes in D109958.
Differential Revision: https://reviews.llvm.org/D111578
There may be some other patterns like this or a generalization,
but this is an example that I noticed would definitely regress
with a planned follow-up to D111410.
https://alive2.llvm.org/ce/z/GVpQDb
At the moment, a VPValue is created for the backedge-taken count, which
is used by some recipes. To make it easier to identify the operands of
recipes using the backedge-taken count, print it at the beginning of the
VPlan if it is used.
Reviewed By: a.elovikov
Differential Revision: https://reviews.llvm.org/D111298
As a brief reminder, an "exit count" is the number of times the backedge executes before some event. It can be zero if we exit before the backedge is reached. A "trip count" is the number of times the loop header is entered if we branch into the loop. In general, TC = BTC + 1 and thus a zero trip count is ill defined
There is a cornercases which we don't handle well. Let's assume i8 for our examples to keep things simple. If BTC = 255, then the correct trip count is 256. However, 256 is not representable in i8.
In theory, code which needs to reason about trip counts is responsible for checking for this cornercase, and either bailing out, or handling it correctly. Historically, we don't have a great track record about actually doing so.
When reviewing D109676, I found myself asking a basic question. Was there any good reason to preserve the current wrap-to-zero behavior when converting from backedge taken counts to trip counts? After reviewing existing code, I could not find a single case which appears to correctly and precisely handle the overflow case.
This patch changes the default behavior to extend instead of wrap. That is, if the result might be 256, we return a value of i9 type to ensure we interpret the count correctly. I did leave the legacy behavior as an option since a) loop-flatten stops triggering if I extend due to weirdly specific pattern matching I didn't understand and b) we could reasonably use the mode if we'd externally established a lack of overflow.
I want to emphasize that this change is *not* NFC. There are two call sites (one in ScalarEvolution.cpp, one in LoopCacheAnalysis.cpp) which are switched to the extend semantics. The former appears imprecise (but correct) for a constant 255 BTC. The later appears incorrect, though I don't have a test case.
Differential Revision: https://reviews.llvm.org/D110587
https://bugs.llvm.org/show_bug.cgi?id=27506https://bugs.llvm.org/show_bug.cgi?id=31652https://bugs.llvm.org/show_bug.cgi?id=51043
Problems with SimpleLoopUnswitch cause the bug reports above.
```
while (...) {
if (C) { A }
else { B }
}
Into:
C' = freeze(C)
if (C') {
while (...) { A }
} else {
while (...) { B }
}
```
This problem can be solved by adding a freeze on hoisted branches(above transform) and has been solved by D29015.
However, D29015 is now reverted by performance regression(2b5a897651)
It is not the first time that an added freeze has caused performance regression.
SimplifyCFG also had a problem with UB caused by branching-on-undef, which was solved by adding freeze to the branching condition. (D104569)
Performance regression occurred in D104569, and patches such as D105344 and D105392 were written to minimize it.
This patch will correct the SimpleLoopUnswitch as D104569 handles the SimplyCFG while minimizing performance loss by introducing patches like D105344 and D105392(This patch was rebased with the author's permission)
Reviewed By: reames
Differential Revision: https://reviews.llvm.org/D106041
This patch adds further support for vectorisation of loops that involve
selecting an integer value based on a previous comparison. Consider the
following C++ loop:
int r = a;
for (int i = 0; i < n; i++) {
if (src[i] > 3) {
r = b;
}
src[i] += 2;
}
We should be able to vectorise this loop because all we are doing is
selecting between two states - 'a' and 'b' - both of which are loop
invariant. This just involves building a vector of values that contain
either 'a' or 'b', where the final reduced value will be 'b' if any lane
contains 'b'.
The IR generated by clang typically looks like this:
%phi = phi i32 [ %a, %entry ], [ %phi.update, %for.body ]
...
%pred = icmp ugt i32 %val, i32 3
%phi.update = select i1 %pred, i32 %b, i32 %phi
We already detect min/max patterns, which also involve a select + cmp.
However, with the min/max patterns we are selecting loaded values (and
hence loop variant) in the loop. In addition we only support certain
cmp predicates. This patch adds a new pattern matching function
(isSelectCmpPattern) and new RecurKind enums - SelectICmp & SelectFCmp.
We only support selecting values that are integer and loop invariant,
however we can support any kind of compare - integer or float.
Tests have been added here:
Transforms/LoopVectorize/AArch64/sve-select-cmp.ll
Transforms/LoopVectorize/select-cmp-predicated.ll
Transforms/LoopVectorize/select-cmp.ll
Differential Revision: https://reviews.llvm.org/D108136
We were using the type of the loop back edge count to represent the
store size. This failed for small loop counts (e.g. in the added test,
the loop count was an i2).
Use the index type instead.
Fixes PR52104.
Differential Revision: https://reviews.llvm.org/D111401
Transformation from malloc+memset to calloc is always correct and in many situations
it brings significant observable benefits in terms of execution speed and memory consumption [1][2].
Unfortunately there are cases when producing calloc cause performance drops [3].
As discussed here: https://reviews.llvm.org/D103009 it's possible to differentiate between those 2 scenarios.
If optimizer is able to prove that after malloc call it's _very_ likely to reach memset branch then after
calloc emission we shouldn't observe any performance hits. Therefore finding "null pointer check" pattern
before memset basic block sounds like good justification for performing transformation.
Also that method was already suggested by GCC folks [4]. Main reason for change is that for now
to be safe we check for post dominance relation which is way too conservative approach making transformation
"almost" disabled in practice. This patch tends to enable transformation again but with extra care.
[1] https://stackoverflow.com/questions/2688466/why-mallocmemset-is-slower-than-calloc
[2] https://vorpus.org/blog/why-does-calloc-exist/
[3] http://smalldatum.blogspot.com/2017/11/a-new-optimization-in-gcc-5x-and-mysql.html
[4] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83022
Differential Revision: https://reviews.llvm.org/D110021
The test diffs show that we have better analysis/folds for 'add'
(although we should at least have the simplifications
independently, so we don't have the one-use restriction).
This is related to solving regressions that would appear in
transforms related to D111410, and that is part of a series
of enhancements that may eventually helpi solve PR34047.
https://alive2.llvm.org/ce/z/3tB9KG
define i1 @src(i8 %x, i8 %C, i8 %C2) {
%sub = sub nuw i8 %C2, %x
%r = icmp slt i8 %sub, %C
ret i1 %r
}
define i1 @tgt(i8 %x, i8 %C, i8 %C2) {
%Cnot = xor i8 %C, -1
%C2not = xor i8 %C2, -1
%add = add nuw i8 %x, %C2not
%r = icmp sgt i8 %add, %Cnot
ret i1 %r
}
There were 2 related but over-specified folds for:
C1 - X == C
One allowed multi-use but was limited to equal constants.
The other allowed different constants but disallowed multi-use.
This combines the 2 folds into a more general match.
The test diffs show the multi-use cases that were falling
through the cracks.
https://alive2.llvm.org/ce/z/4_hEt2
define i1 @src(i8 %x, i8 %subC, i8 %C) {
%s = sub i8 %subC, %x
%r = icmp eq i8 %s, %C
ret i1 %r
}
define i1 @tgt(i8 %x, i8 %subC, i8 %C) {
%newC = sub i8 %subC, %C
%isneg = icmp eq i8 %x, %newC
ret i1 %isneg
}
If a loop is flattened, the inner loop is removed and the LPM
should be informed of this fact, so it can invalidate associated
analyses. To support this, we relax an assertion in LPMUpdater to
allow invalidating non-top-level loops when running in LoopNestMode,
as the pass does not know how exactly it will get scheduled.
Differential Revision: https://reviews.llvm.org/D111350
This factors out utilities for scanning a bounded block of instructions since we have this code repeated in a bunch of places. The change to InlineFunction isn't strictly NFC as the limit mechanism there didn't handle debug instructions correctly.
Removed obsolete DT verification that should not be there because the
strategy of DT updates has changed.
Differential Revision: https://reviews.llvm.org/D110922
Added support for peeling loops with "deoptimizing" exits -
such exits that it or any of its children (or any of their
children, etc) either has a @llvm.experimental.deoptimize call
prior to the terminating return instruction of this basic block
or is terminated with unreachable. All blocks in the the
sequence must have a single successor, maybe except for the last
one.
Previously we only checked the exit block for being deoptimizing.
Now we check if the last reachable block from the exit is deoptimizing.
Patch by Dmitry Makogon!
Differential Revision: https://reviews.llvm.org/D110922
Reviewed By: mkazantsev
LoopFlatten does preserve loop analyses (DT, LI and SCEV), but
currently doesn't mark them as preserved in the NewPM (they are
marked as preserved in the LegacyPM). I think this doesn't really
have an effect in the end because the loop pass adaptor will just
assume they're preserved anyway, but let's be explicit about this
for the sake of clarity.
Differential Revision: https://reviews.llvm.org/D111328
This patch fixes problems reported in PR51981.
When rotating a loop it isn't enough to just forget SCEV for that
loop nest. When rotating we might clone some instructions from the
old header into the preheader, and insert new PHI nodes to merge
values together. There could be users of the original value that are
updated to use the PHI result. And those users were not necessarily
depending on a PHI node earlier, so they weren't cleaned up when just
forgetting all SCEV:s for the loop nest. So we need to explicitly
forget those values to avoid invalid cached SCEV expressions.
Reviewed By: fhahn, mkazantsev
Differential Revision: https://reviews.llvm.org/D110813
SCEV-based salvaging will use excessive resources if it encounters
very long SCEV expressions. This patch places a limit on the length of
SCEV expression that salvaging will attempt to translate.
Reviewed by: Orlando
Differential Revision: https://reviews.llvm.org/D110558
To better reflect the meaning of the now-disambiguated {GlobalValue,
GlobalAlias}::getBaseObject after breaking off GlobalIFunc::getResolverFunction
(D109792), the function is renamed to getAliaseeObject.
