The LangRef clearly states that branching on a undef or poison value is immediate undefined behavior, but historically, we have not been consistent about implementing that interpretation in the optimizer. Historically, we used (in some cases) a more relaxed model which essentially looked for provable UB along both paths which was control dependent on the condition. However, we've never been 100% consistent here. For instance SCEV uses the strong model for increments which form AddRecs (and only addrecs).
At the moment, the last big blocker for finally making this switch is enabling the fix landed in D106041. Loop unswitching (in it's classic form) is incorrect as it creates many "branch on poisons" when unswitching conditions originally unreachable within the loop.
This change adds a flag to value tracking which allows to easily test the optimization potential of treating branch on poison as immediate UB. It's intended to help ease work on getting us finally through this transition and avoid multiple independent rediscovers of the same issues.
Differential Revision: https://reviews.llvm.org/D112026
As this API is now internally offset-based, we can accept a starting
offset and remove the need to create a temporary bitcast+gep
sequence to perform an offset load. The API now mirrors the
ConstantFoldLoadFromConst() API.
The functionality of this method is already covered by
computeExitCountExhaustively() in a more general fashion. It was
added at a time when exhaustive exit count calculation did not
support constant folding loads yet. I double checked that dropping
this code causes no binary changes in test-suite.
Differential Revision: https://reviews.llvm.org/D112343
GEP indices larger than the GEP index size are implicitly truncated
to the index size. BasicAA currently doesn't model this, resulting
in incorrect alias analysis results.
Fix this by explicitly modelling truncation in CastedValue in the
same way we do zext and sext. Additionally we need to disable a
number of optimizations for truncated values, in particular
"non-zero" and "non-equal" may no longer hold after truncation.
I believe the constant offset heuristic is also not necessarily
correct for truncated values, but wasn't able to come up with a
test for that one.
A possible followup here would be to use the new mechanism to
model explicit trunc as well (which should be much more common,
as it is the canonical form). This is straightforward, but omitted
here to separate the correctness fix from the analysis improvement.
(Side note: While I say "index size" above, BasicAA currently uses
the pointer size instead. Something for another day...)
Differential Revision: https://reviews.llvm.org/D110977
This follows up on D111023 by exporting the generic "load value
from constant at given offset as given type" and using it in the
store to load forwarding code. We now need to make sure that the
load size is smaller than the store size, previously this was
implicitly ensured by ConstantFoldLoadThroughBitcast().
Differential Revision: https://reviews.llvm.org/D112260
As discussed in D112016, our current requirement of speculatability
for ephemeral is overly strict: What we really care about is that
the instruction will be DCEd once the assume is dropped. For that
it is sufficient that the instruction is side-effect free and not
a terminator.
In particular, this allows non-dereferenceable loads to be ephemeral
values.
Differential Revision: https://reviews.llvm.org/D112179
This change restructures the cache used in IPT to point not to the first special instruction, but to the first instruction which *could* be special. That is, the cached reference is always equal to the first special, or comes before it in the block.
This avoids expensive block scans when we are removing special instructions from the beginning of the block. At the moment, this case is not heavily used, though it does trigger in GVN when doing CSE of calls. The main motivation was a change I'm no longer planning to move forward with, but the cache optimization seemed worthwhile as a minor perf win at low cost.
Differential Revision: https://reviews.llvm.org/D111768
As seen in PR51869 the ScalarEvolution::isImpliedCond function might
end up spending lots of time when doing the isKnownPredicate checks.
Calling isKnownPredicate for example result in isKnownViaInduction
being called, which might result in isLoopBackedgeGuardedByCond being
called, and then we might get one or more new calls to isImpliedCond.
Even if the scenario described here isn't an infinite loop, using
some random generated C programs as input indicates that those
isKnownPredicate checks quite often returns true. On the other hand,
the third condition that needs to be fulfilled in order to "prove
implications via truncation", i.e. the isImpliedCondBalancedTypes
check, is rarely fulfilled.
I also made some similar experiments to look at how often we would
get the same result when using isKnownViaNonRecursiveReasoning instead
of isKnownPredicate. So far I haven't seen a single case when codegen
is negatively impacted by using isKnownViaNonRecursiveReasoning. On
the other hand, it seems like we get rid of the compile time explosion
seen in PR51869 that way. Hence this patch.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D112080
The goal is to allow grafting an inline tree from Clang or GCC into a new compilation without affecting other functions. For GCC, we're doing this by extracting the inline tree from dwarf information and generating the equivalent remarks.
This allows easier side-by-side asm analysis and a trial way to see if a particular inlining setup provides benefits by itself.
Testing:
ninja check-all
Reviewed By: wenlei, mtrofin
Differential Revision: https://reviews.llvm.org/D110658
This is NFC-intended for the callers. Posting in case there are
other potential users that I missed.
I would also use this from VectorCombine in a patch for:
https://llvm.org/PR52178 ( D111901 )
Differential Revision: https://reviews.llvm.org/D111891
The multiply() implementation is very slow -- it performs six
multiplications in double the bitwidth, which means that it will
typically work on allocated APInts and bypass fast-path
implementations. Add an additional implementation that doesn't
try to produce anything better than a full range if overflow is
possible. At least for the BasicAA use-case, we really don't care
about more precise modeling of overflow behavior. The current
use of multiply() is fine while the implementation is limited to
a single index, but extending it to the multiple-index case makes
the compile-time impact untenable.
This patch teaches SCEV two implication rules:
x <u y && y >=s 0 --> x <s y,
x <s y && y <s 0 --> x <u y.
And all equivalents with signs/parts swapped.
Differential Revision: https://reviews.llvm.org/D110517
Reviewed By: nikic
Current implementations of DFS in SCEV check unique-visited of traversed
values on pop, and not on push. As result, the same value may be pushed
multiple times just to be thrown away when popped. These operations are
meaningless and only waste time and increase memory footprint of the
worklist.
This patch reworks the DFS strategy to check uniqueness before push.
Should be NFC.
Differential Revision: https://reviews.llvm.org/D111774
Reviewed By: nikic, reames
Fix a bug when getInlineCost incorrectly returns a
cost/threshold pair instead of an explicit never inline.
Reviewed By: mtrofin
Differential Revision: https://reviews.llvm.org/D111687
Rather than checking for loop nest preheaders upfront in IVUsers,
move this requirement into isSafeToExpand() from SCEVExpander.
Historically, LSR did not check whether SCEVs are safe to expand
and fully relied on IVUsers to validate this. Later, support for
non-expandable SCEVs was added via rigid formulas.
Checking this in isSafeToExpand() makes it more obvious what
exactly this check is guarding against, and avoids the awkward
loop nest scan.
This is a followup to https://reviews.llvm.org/D111493#3055286.
Differential Revision: https://reviews.llvm.org/D111681
Currently, DecomposeGEP() bails out on the whole decomposition if
it encounters a scalable GEP type anywhere. However, it is fine to
still analyze other GEPs that we look through before hitting the
scalable GEP. This does mean that the decomposed GEP base is no
longer required to be the same as the underlying object. However,
I don't believe this property is necessary for correctness anymore.
This allows us to compute slightly more precise aliasing results
for GEP chains containing scalable vectors, though my primary
interest here is simplifying the code.
Differential Revision: https://reviews.llvm.org/D110511
Currently the fadd optimizations in InstSimplify don't know how to do this
NoSignedZeros "X + 0.0 ==> X" fold when using the constrained intrinsics.
This adds the support.
This review is derived from D106362 with some improvements from D107285
and is a follow-on to D111085.
Differential Revision: https://reviews.llvm.org/D111450
Replace check with
if ((ExitIfTrue && CI->isZero()) || (!ExitIfTrue && CI->isOne()))
with equivalent and simpler version
if (ExitIfTrue == CI->isZero())
The tests that exercise the 'release' mode, where the model is AOT-ed,
check the output has certain properties, to validate that, indeed, a
different policy from the default one was exercised. For determinism, we
can't reliably check that output for an arbitrary learned policy, since
it could be that policy happens to mimic the default one in that
particular case.
This patch adds a requirement that those tests run only when the model
is autogenerated (e.g. on build bots).
Differential Revision: https://reviews.llvm.org/D111747
This is a follow on for D111675 which implements the gep case. I'd originally left it out because I was hoping to actually implement the inrange todo, but after a bit of staring at the code, decided to leave it as is since it doesn't effect this use case (i.e. instcombine requires the op to freeze to be an instruction).
Differential Revision: https://reviews.llvm.org/D111691
The newly introduced API for checking whether poison comes solely from flags which can be dropped was out of sync. This was noticed by a reviewer post commit.
For the moment, disable the floating point flags. In a follow up change, I plan to add support in dropPoisonGeneratingFlags, but that deserves to be a change of it's own.
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 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
IVUsers currently makes sure that all loops dominating a user are
in loop simplify form, because SCEVExpander needs a preheader to
insert into. However, loop simplify form requires much more than
that. In particular, it requires dedicated exits, which means that
exits need to be found and walked. For large functions with many
nested loops, this can result in pathological compile-time explosion.
Fix this by only checking the property we're actually interested in,
which is incidentally cheap to check.
Differential Revision: https://reviews.llvm.org/D111493
The CFG being changed and the overall call graph are not related, we can introduce/remove calls without changing the CFG.
Resolves one of the issues in PR51946.
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D111275
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
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
llvm.is.constant* intrinsics are evaluated to 0 or 1 integral values.
A common use case for llvm.is.constant comes from the higher level
__builtin_constant_p. A common usage pattern of __builtin_constant_p in
the Linux kernel is:
void foo (int bar) {
if (__builtin_constant_p(bar)) {
// lots of code that will fold away to a constant.
} else {
// a little bit of code, usually a libcall.
}
}
A minor issue in InlineCost calculations is when `bar` is _not_ Constant
and still will not be after inlining, we don't discount the true branch
and the inline cost of `foo` ends up being the cost of both branches
together, rather than just the false branch.
This leads to code like the above where inlining will not help prove bar
Constant, but it still would be beneficial to inline foo, because the
"true" branch is irrelevant from a cost perspective.
For example, IPSCCP can sink a passed constant argument to foo:
const int x = 42;
void bar (void) { foo(x); }
This improves our inlining decisions, and fixes a few head scratching
cases were the disassembly shows a relatively small `foo` not inlined
into a lone caller.
We could further improve this modeling by tracking whether the argument
to llvm.is.constant* is a parameter of the function, and if inlining
would allow that parameter to become Constant. This idea is noted in a
FIXME comment.
Link: https://github.com/ClangBuiltLinux/linux/issues/1302
Reviewed By: kazu
Differential Revision: https://reviews.llvm.org/D111272
We only need to invalidate if the instruction being removed is the cached "first special instruction". If the instruction is before that one, it can't (by assumption) be special. If it is after that one, it wasn't the first.
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.
DecompGEP.Base and UnderlyingV are currently always the same.
However, logically DecompGEP.Base is the right value to use here,
because the decomposed offset is relative to that base.
To better reflect the meaning of the now-disambiguated {GlobalValue,
GlobalAlias}::getBaseObject after breaking off GlobalIFunc::getResolverFunction
(D109792), the function is renamed to getAliaseeObject.
When checking to see if we can apply IR flags to a SCEV, we need to identify a bound on the defining scope of the SCEV to be produced. We'd previously added support for a couple SCEVExpr types which trivially imply bounds, but hadn't handled types such as umax where the bounds come from the bounds of the operands. This does the obvious thing, and recurses through operands searching for a tighter bound on the defining scope.
I'm honestly surprised by how little this seems to mater on existing tests, but it's worth doing for completeness sake alone.
Differential Revision: https://reviews.llvm.org/D111191
When determining the defining scope, avoid repeatedly querying
dominationg against the function entry instruction. This ends up
begin a very common case that we can handle more efficiently.
This does for readability of returns within said function as what we do for the caller side when reasoning about what might be poison.
Differential Revision: https://reviews.llvm.org/D111180
This patch removes a compile time restriction from isSCEVExprNeverPoison. We've strengthened our ability to reason about flags on scopes other than addrecs, and this bailout prevents us from using it. The comment is also suspect as well in that we're in the middle of constructing a SCEV for I. As such, we're going to visit all operands *anyways*.
Differential Revision: https://reviews.llvm.org/D111186
Currently the fadd optimizations in InstSimplify don't know how to do this
"X + -0.0 ==> X" fold when using the constrained intrinsics. This adds the
support.
This commit is derived from D106362 with some improvements from D107285.
Differential Revision: https://reviews.llvm.org/D111085
BasicAA GEP decomposition currently performs all calculation on the
maximum pointer size, but at least 64-bit, with an option to double
the size. The code comment claims that this improves analysis power
when working with uint64_t indices on 32-bit systems. However, I don't
see how this can be, at least while maintaining correctness:
When working on canonical code, the GEP indices will have GEP index
size. If the original code worked on uint64_t with a 32-bit size_t,
then there will be truncs inserted before use as a GEP index. Linear
expression decomposition does not look through truncs, so this will
be an opaque value as far as GEP decomposition is concerned. Working
on a wider pointer size does not help here (or have any effect at all).
When working on non-canonical code (before first InstCombine), the
GEP indices are implicitly truncated to GEP index size. The BasicAA
code currently just ignores this fact completely, and pretends that
this truncation doesn't happen. This is incorrect and will be
addressed by D110977.
I believe that for correctness reasons, it is important to work on
the actual GEP index size to properly model potential overflow.
BasicAA tries to patch over the fact that it uses the wrong size
(see adjustToPointerSize), but it only does that in limited cases
(only for constant values, and not all of them either). I'd like to
move this code towards always working on the correct size, and
dropping these artificial pointer size adjustments is the first step
towards that.
Differential Revision: https://reviews.llvm.org/D110657
https://alive2.llvm.org/ce/z/QagQMn
This fold is handled by instcombine via SimplifyUsingDistributiveLaws(),
but we are missing the sibliing fold for 'logical and' (implemented with
'select'). Retrofitting the code in instcombine looks much harder
than just adding a small adjustment here, and this is potentially more
efficient and beneficial to other passes.
This also removes the need to disable the mandatory inlining phase in
tests.
In a departure from the previous remark, we don't output a 'cost' in
this case, because there's no such thing. We just report that inlining
happened because of the attribute.
Differential Revision: https://reviews.llvm.org/D110891
Behavior wise, this patch should be mostly NFC. The only behavior difference known is that on the isSCEVExprNeverPoison path we'll consider a bound imposed by the SCEVable operands (if any).
Algorithmically, it's an invert of the existing code. Previously, we checked for each operand if we could find a bound, then checked for must-execute given that bound. With the patch, we use dominance to refine the innermost bound, then check must execute once. The interesting case is when we have multiple unknowns within a single basic block. While both dominance and must-execute are worst-case linear walks within the block, only dominance is cached. As such, refining based on dominance should be more efficient.
This refactors load folding to happen in two cleanly separated
steps: ConstantFoldLoadFromConstPtr() takes a pointer to load from
and decomposes it into a constant initializer base and an offset.
Then ConstantFoldLoadFromConst() loads from that initializer at
the given offset. This makes the core logic independent of having
actual GEP expressions (and those GEP expressions having certain
structure) and will allow exposing ConstantFoldLoadFromConst() as
an independent API in the future.
This is mostly only a refactoring, but it does make the folding
logic slightly more powerful.
Differential Revision: https://reviews.llvm.org/D111023
When determining NoAlias based on object size and dereferenceability
information, we can ignore frees for the same reason we can ignore
possible null pointers (if null is not a valid pointer): Actually
accessing the null pointer / freed pointer would be immediate UB,
and AA results are only valid under the assumption of an access.
This addresses a minor regression from D110745.
Differential Revision: https://reviews.llvm.org/D111028
In TargetLibraryInfoImpl::isValidProtoForLibFunc we no longer
need the IsSizeTTy lambda function and the SizeTTy object. Instead
we just follow the regular structure of checking for integer types
given an exepected number of bits.
Stop using APInt constructors and methods that were soft-deprecated in
D109483. This fixes all the uses I found in llvm, except for the APInt
unit tests which should still test the deprecated methods.
Differential Revision: https://reviews.llvm.org/D110807
This addresses a comment from review on D109845. The concern was raised that an unbounded scan would be expensive. Long term plan is to cache this search - likely reusing the existing mechanism for loop side effects - but let's be simple and conservative for now.
This addresses a comment from review on D109845. Even for SCEVs which we can't find true bounds without recursing through operands, entry to the function forms a trivial upper bound. In some cases, this trivial bound is enough to prove safety of flag inference.
This is a followon to D109845. With that landed, we will have fixed all known instances of pr51817, and can thus start inferring flags more aggressively with greatly reduced risk of miscompiles. This patch simply applies the same inference logic used in that patch to our other major flag inference path.
We can still do much better here (on both paths), but this is our first step.
Differential Revision: https://reviews.llvm.org/D111003
This fixes a violation of the wrap flag rules introduced in c4048d8f. This is an alternate fix to D106852.
The basic problem being fixed is that we infer a set of flags which is valid at some inner scope S1 (usually by correctly propagating them from IR), and then (incorrectly) extend them to a SCEV in scope S2 where S1 != S2. This is not in general safe per the wrap flags semantics recently defined.
In this patch, I include a simple inference step to handle the case where we can prove that S2 is the preheader of the loop S1, and that entry into S2 implies execution of S1. See the code for a more detailed explanation.
One worry I have with this patch is that I might be over-fitting what shows up in tests - and thus hiding negative impact we'd see in the real world. My best defense is that the rule used here very closely follows the one used to propagate the flags from IR to the inner add to start with, and thus if one is reasonable, so probably is the other. Curious what others think about that piece.
The test diffs are roughly as expected. Mostly analysis only, with two transform changes. Oddly, the result looks better in the loop-idiom test, and I don't understand the PPC output enough to have tell. Nothing terrible looking though. (For context, without the scope inference peephole, the test delta includes a couple of vectorization tests. Again, not super concerning, but slightly more so.)
Differential Revision: https://reviews.llvm.org/D109845
This fixes a violation of the wrap flag rules introduced in c4048d8f. This was also noted in the (very old) PR23527.
The issue being fixed is that we assume the inbound flag on any GEP assumes that all users of *any* gep (or add) which happens to map to that SCEV would also be UB if the (other) gep overflowed. That's simply not true.
In terms of the test diffs, I don't see anything seriously problematic. The lost flags are expected (given the semantic restriction on when its legal to tag the SCEV), and there are several cases where the previously inferred flags are unsound per the new semantics.
The only common trend I noticed when looking at the deltas is that by not considering branch on poison as immediate UB in ValueTracking, we do miss a few cases we could reclaim. We may be able to claw some of these back with the follow ideas mentioned in PR51817.
It's worth noting that most of the changes are analysis result only changes. The two transform changes are pretty minimal. In one case, we miss the opportunity to infer a nuw (correctly). In the other, we fail to fold an exit and produce a loop invariant form instead. This one is probably over-reduced as the program appears to be undefined in practice, and neither before or after exploits that.
Differential Revision: https://reviews.llvm.org/D109789
This code is attempting to prove that I must execute if we enter the defining scope of the SCEV which will be created from I. In the case where it found a defining addrec scope, it had a rather odd restriction that all of the other operands must be loop invariant in that addrec's loop.
As near as I can tell here, we really only need a upper bound on the defining scope. If we can prove the stronger property, then we must also have proven the property on the exact defining scope as well.
In practice, the actual effect of this change is narrow. The compile time restriction at the top of the routine basically limits us to I being an arithmetic in some loop L with both an addrec operand in L, and a unknown operands in L. Possible to demonstrate, but the main value of the change is removing unneeded code.
Differential Revision: https://reviews.llvm.org/D110892
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
Add methods to appropriately extend KnownBits/ConstantRange there,
same as with APInt. Also clean up the known bits handling by
actually doing that extension rather than checking ZExtBits. This
doesn't matter now, but becomes relevant once truncation is
involved.
The information can be implicit (from `ValueTracking`) or explicit.
This implements the backend part of the following RFC
https://groups.google.com/g/llvm-dev/c/T9o51zB1JY.
We still need to settle on how to best represent the information in the
IR, but this is a separate discussion.
Differential Revision: https://reviews.llvm.org/D109746
Rather than separately handling subtraction of offset and variable
indices, make this one operation. Also rewrite the implementation
to use range-based for loops.
There are two sets of new/delete functions, one with Windows/MSVC
mangling and one with Itanium mangling. Mark one set or the other
as unavailable depending on the target.
Split the test malloc-free-delete.ll into three parts: malloc-free.dll
for the C API tests, new-delete-itanium.ll and new-delete-msvc.ll for
the target-specific new/delete tests.
Differential Revision: https://reviews.llvm.org/D110419
I was looking at some missed optimizations in CHERI-enabled targets and
noticed that we weren't removing vtable indirection for calls via known
pointers-to-members. The underlying reason for this is that we represent
pointers-to-function-members as {i8 addrspace(200)*, i64} and generate the
constant offsets using (gep i8 null, <index>). We use a constant GEP here
since inttoptr should be avoided for CHERI capabilities. The pointer-to-member
call uses ptrtoint to extract the index, and due to this missing fold we can't
infer the actual value loaded from the vtable.
This is the initial constant folding change for this pattern, I will add
an InstCombine fold as a follow-up.
We could fold all inbounds GEP to null (and therefore the ptrtoint to
zero) since zero is the only valid offset for an inbounds GEP. If the
offset is not zero, that GEP is poison and therefore returning 0 is valid
(https://alive2.llvm.org/ce/z/Gzb5iH). However, Clang currently generates
inbounds GEPs on NULL for hand-written offsetof() expressions, so this
could lead to miscompilations.
Reviewed By: lebedev.ri
Differential Revision: https://reviews.llvm.org/D110245
When using a datalayout that has pointer index width != pointer size this
code triggers an assertion in Value::stripAndAccumulateConstantOffsets().
I encountered this this while compiling FreeBSD for CHERI-RISC-V.
Also update LoadsTest.cpp to use a DataLayout with index width != pointer
width to ensure this case is tested.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D110406
When TargetLibraryInfoImpl::isValidProtoForLibFunc is checking
function signatures to detect lib calls it may check that a parameter
or return value matches with the "size_t" type. For this to work it
has to derive the IR type matching with "size_t". Depending on if
a DataLayout is provided or not, this has been done in two different
way. Either a more strict check being based on IntPtrType (which is
given by the DataLayout) or a more relaxed check assuming that any
integer type matches with "size_t".
Given that the stricter approach exist it seems like we do not want
to trigger rewrites etc if we aren't sure that a function calls
actually match with the library function. Therefore it was questioned
why we actually have the more relaxed approach when not being able
to derive an IR type for "size_t". This patch will take a more
defensive approach, requiring that a DataLayout is passed to
isValidProtoForLibFunc.
Differential Revision: https://reviews.llvm.org/D110584
Philip Reames