This pattern was repeated a few times, and for some reason always
using insert or try_emplace, even though we know in advance that
we're looking for an existing entry and not trying to create a
new one.
Function isNonEscapingLocalObject is a static one within BasicAliasAnalysis.cpp.
It wraps around PointerMayBeCaptured of CaptureTracking, checking whether a pointer
is to a function-local object, which never escapes from the function.
Although at the moment, isNonEscapingLocalObject is used only by BasicAliasAnalysis,
its functionality can be used by other pass(es), one of which I will put up for review
very soon. Instead of copying the contents of this static function, I move it to llvm
scope, and place it amongst other functions with similar functionality in CaptureTracking.
The rationale for the location are:
- Pointer escape and pointer being captured are actually two sides of the same coin
- isNonEscapingLocalObject is wrapping around another function in CaptureTracking
Reviewed By: jdoerfert (Johannes Doerfert)
Differential Revision: https://reviews.llvm.org/D89465
This adjusts the description of `llvm.memcpy` to also allow operands
to be equal. This is in line with what Clang currently expects.
This change is intended to be temporary and followed by re-introduce
a variant with the non-overlapping guarantee for cases where we can
actually ensure that property in the front-end.
See the links below for more details:
http://lists.llvm.org/pipermail/cfe-dev/2020-August/066614.html
and PR11763.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D86815
This option was added a while back, to help improve AA around pointer
phi loops. It looks for phi(gep(phi, const), x) loops, checking if x can
then prove more precise aliasing info.
Differential Revision: https://reviews.llvm.org/D82998
As shown in D82998, the basic-aa-recphi option can cause miscompiles for
gep's with negative constants. The option checks for recursive phi, that
recurse through a contant gep. If it finds one, it performs aliasing
calculations using the other phi operands with an unknown size, to
specify that an unknown number of elements after the initial value are
potentially accessed. This works fine expect where the constant is
negative, as the size is still considered to be positive. So this patch
expands the check to make sure that the constant is also positive.
Differential Revision: https://reviews.llvm.org/D83576
This option was added a while back, to help improve AA around pointer
phi loops. It looks for phi(gep(phi, const), x) loops, checking if x can
then prove more precise aliasing info.
Differential Revision: https://reviews.llvm.org/D82998
With the option -basic-aa-recphi we can detect recursive phis that loop
through constant geps, which allows us to detect more no-alias case for
pointer IV's. If the other phi operand and the other alias value are
MustAlias though, we cannot presume that every element in the loop is
also MustAlias. We need to instead be conservative and return MayAlias.
Differential Revision: https://reviews.llvm.org/D82987
Summary:
BasicAA under the new pass manager is called "basic-aa", which fits more
with the other AA names which almost always contain a dash.
Keep an alias from basicaa -> basic-aa.
Will change all references of "basicaa" to "basic-aa", then remove the
alias.
Makes check-llvm failures under NPM go from 2307 to 1867.
Reviewers: asbirlea, ychen
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D82607
GetUnderlyingObject() (and by required symmetry
DecomposeGEPExpression()) will call SimplifyInstruction() on the
passed value if other checks fail. This simplification is very
expensive, but has little effect in practice. This patch removes
the SimplifyInstruction call(), and replaces it with a check for
single-argument phis (which can occur in canonical IR in LCSSA
form), which is the only useful simplification case I was able to
identify.
At O3 the geomean CTMark improvement is -1.7%. The largest
improvement is SPASS with ThinLTO at -6%.
In test-suite, I see only two tests with a hash difference and
no code size difference (PAQ8p, Ptrdist), which indicates that
the simplification only ends up being useful very rarely. (I would
have liked to figure out which simplification is responsible here,
but wasn't able to spot it looking at transformation logs.)
The AMDGPU test case that is update was using two selects with
undef condition, in which case GetUnderlyingObject will return
the first select operand as the underlying object. This will of
course not happen with non-undef conditions, so this was not
testing anything realistic. Additionally this illustrates potential
unsoundness: While GetUnderlyingObject will pick the first operand,
the select might be later replaced by the second operand, resulting
in inconsistent assumptions about the undef value.
Differential Revision: https://reviews.llvm.org/D82261
Currently, BasicAA does not exploit information about value ranges of
indexes. For example, consider the 2 pointers %a = %base and
%b = %base + %stride below, assuming they are used to access 4 elements.
If we know that %stride >= 4, we know the accesses do not alias. If
%stride is a constant, BasicAA currently gets that. But if the >= 4
constraint is encoded using an assume, it misses the NoAlias.
This patch extends DecomposedGEP to include an additional MinOtherOffset
field, which tracks the constant offset similar to the existing
OtherOffset, which the difference that it also includes non-negative
lower bounds on the range of the index value. When checking if the
distance between 2 accesses exceeds the access size, we can use this
improved bound.
For now this is limited to using non-negative lower bounds for indices,
as this conveniently skips cases where we do not have a useful lower
bound (because it is not constrained). We potential miss out in cases
where the lower bound is constrained but negative, but that can be
exploited in the future.
Reviewers: sanjoy, hfinkel, reames, asbirlea
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D76194
Summary:
Don't attempt to analyze the decomposed GEP for scalable type.
GEP index scale is not compile-time constant for scalable type.
Be conservative, return MayAlias.
Explicitly call TypeSize::getFixedSize() to assert on places where
scalable type doesn't make sense.
Add unit tests to check functionality of -basicaa for scalable type.
This patch is needed for D76944.
Reviewers: sdesmalen, efriedma, spatel, bjope, ctetreau
Reviewed By: efriedma
Subscribers: tschuett, hiraditya, rkruppe, psnobl, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D77828
Now that we have scalable vectors, there's a distinction that isn't
getting captured in the original SequentialType: some vectors don't have
a known element count, so counting the number of elements doesn't make
sense.
In some cases, there's a better way to express the commonality using
other methods. If we're dealing with GEPs, there's GEP methods; if we're
dealing with a ConstantDataSequential, we can query its element type
directly.
In the relatively few remaining cases, I just decided to write out
the type checks. We're talking about relatively few places, and I think
the abstraction doesn't really carry its weight. (See thread "[RFC]
Refactor class hierarchy of VectorType in the IR" on llvmdev.)
Differential Revision: https://reviews.llvm.org/D75661
Aligned_alloc is a standard lib function and has been in glibc since
2.16 and in the C11 standard. It has semantics similar to malloc/calloc
for several analyses/transforms. This patch introduces aligned_alloc
in target library info and memory builtins. Subsequent ones will
make other passes aware and fix https://bugs.llvm.org/show_bug.cgi?id=44062
This change will also be useful to LLVM generators that need to allocate
buffers of vector elements larger than 16 bytes (for eg. 256-bit ones),
element boundary alignment for which is not typically provided by glibc malloc.
Signed-off-by: Uday Bondhugula <uday@polymagelabs.com>
Differential Revision: https://reviews.llvm.org/D76970
Summary:
Part of the changes in D44564 made BasicAA not CFG only due to it using
PhiAnalysisValues which may have values invalidated.
Subsequent patches (rL340613) appear to have addressed this limitation.
BasicAA should not be invalidated by non-CFG-altering passes.
A concrete example is MemCpyOpt which preserves CFG, but we are testing
it invalidates BasicAA.
llvm-dev RFC: https://groups.google.com/forum/#!topic/llvm-dev/eSPXuWnNfzM
Reviewers: john.brawn, sebpop, hfinkel, brzycki
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D74353
Previously, the enums didn't account for all the possible cases, which
could cause misleading results (particularly for a "switch" on
FunctionModRefBehavior).
Fixes regression in polly from recent patch to add writeonly to memset.
While I'm here, also fix a few dubious uses of the FMRB_* enum values.
Differential Revision: https://reviews.llvm.org/D73154
In order to use assumptions, computeKnownBits needs a context
instruction. We can use the GEP, if it is an instruction. We already
pass the assumption cache, but it cannot be used without a context
instruction.
Reviewers: anemet, asbirlea, hfinkel, spatel
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D71264
This file lists every pass in LLVM, and is included by Pass.h, which is
very popular. Every time we add, remove, or rename a pass in LLVM, it
caused lots of recompilation.
I found this fact by looking at this table, which is sorted by the
number of times a file was changed over the last 100,000 git commits
multiplied by the number of object files that depend on it in the
current checkout:
recompiles touches affected_files header
342380 95 3604 llvm/include/llvm/ADT/STLExtras.h
314730 234 1345 llvm/include/llvm/InitializePasses.h
307036 118 2602 llvm/include/llvm/ADT/APInt.h
213049 59 3611 llvm/include/llvm/Support/MathExtras.h
170422 47 3626 llvm/include/llvm/Support/Compiler.h
162225 45 3605 llvm/include/llvm/ADT/Optional.h
158319 63 2513 llvm/include/llvm/ADT/Triple.h
140322 39 3598 llvm/include/llvm/ADT/StringRef.h
137647 59 2333 llvm/include/llvm/Support/Error.h
131619 73 1803 llvm/include/llvm/Support/FileSystem.h
Before this change, touching InitializePasses.h would cause 1345 files
to recompile. After this change, touching it only causes 550 compiles in
an incremental rebuild.
Reviewers: bkramer, asbirlea, bollu, jdoerfert
Differential Revision: https://reviews.llvm.org/D70211
Summary:
This is the first change to enable the TLI to be built per-function so
that -fno-builtin* handling can be migrated to use function attributes.
See discussion on D61634 for background. This is an enabler for fixing
handling of these options for LTO, for example.
This change should not affect behavior, as the provided function is not
yet used to build a specifically per-function TLI, but rather enables
that migration.
Most of the changes were very mechanical, e.g. passing a Function to the
legacy analysis pass's getTLI interface, or in Module level cases,
adding a callback. This is similar to the way the per-function TTI
analysis works.
There was one place where we were looking for builtins but not in the
context of a specific function. See FindCXAAtExit in
lib/Transforms/IPO/GlobalOpt.cpp. I'm somewhat concerned my workaround
could provide the wrong behavior in some corner cases. Suggestions
welcome.
Reviewers: chandlerc, hfinkel
Subscribers: arsenm, dschuff, jvesely, nhaehnle, mehdi_amini, javed.absar, sbc100, jgravelle-google, eraman, aheejin, steven_wu, george.burgess.iv, dexonsmith, jfb, asbirlea, gchatelet, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D66428
llvm-svn: 371284
Summary:
We already use the fact that an object with known size X does not alias
another objection of size Y > X before. With this commit, we use
dereferenceability information to determine a lower bound for Y and not
only rely on the user provided query size.
The result for @global_and_deref_arg_2() and @local_and_deref_ret_2()
in test/Analysis/BasicAA/dereferenceable.ll improved with this patch.
Reviewers: asbirlea, chandlerc, hfinkel, sanjoy
Subscribers: hiraditya, bollu, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D66157
llvm-svn: 369786
Some uses of getArgumentAliasingToReturnedPointer and
isIntrinsicReturningPointerAliasingArgumentWithoutCapturing require the
calls/intrinsics to preserve the nullness of the argument.
For alias analysis, the nullness property does not really come into
play.
This patch explicitly sets it to true. In D61669, the alias analysis
uses will be switched to not require preserving nullness.
Reviewers: nlopes, efriedma, hfinkel, sanjoy, aqjune, jdoerfert
Reviewed By: jdoerfert
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D64150
llvm-svn: 368993
Summary:
Adding contained caching to AliasAnalysis. BasicAA is currently the only one using it.
AA changes:
- This patch is pulling the caches from BasicAAResults to AAResults, meaning the getModRefInfo call benefits from the IsCapturedCache as well when in "batch mode".
- All AAResultBase implementations add the QueryInfo member to all APIs. AAResults APIs maintain wrapper APIs such that all alias()/getModRefInfo call sites are unchanged.
- AA now provides a BatchAAResults type as a wrapper to AAResults. It keeps the AAResults instance and a QueryInfo instantiated to batch mode. It delegates all work to the AAResults instance with the batched QueryInfo. More API wrappers may be needed in BatchAAResults; only the minimum needed is currently added.
MemorySSA changes:
- All walkers are now templated on the AA used (AliasAnalysis=AAResults or BatchAAResults).
- At build time, we optimize uses; now we create a local walker (lives only as long as OptimizeUses does) using BatchAAResults.
- All Walkers have an internal AA and only use that now, never the AA in MemorySSA. The Walkers receive the AA they will use when built.
- The walker we use for queries after the build is instantiated on AliasAnalysis and is built after building MemorySSA and setting AA.
- All static methods doing walking are now templated on AliasAnalysisType if they are used both during build and after. If used only during build, the method now only takes a BatchAAResults. If used only after build, the method now takes an AliasAnalysis.
Subscribers: sanjoy, arsenm, jvesely, nhaehnle, jlebar, george.burgess.iv, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59315
llvm-svn: 356783
Summary:
This is a refactoring patch.
- Reduce the number of map searches by reusing the iterator.
- Add asserts to check that the entry is in the cache, as this is something BasicAA relies on to avoid infinite recursion.
Reviewers: chandlerc, aschwaighofer
Subscribers: sanjoy, jlebar, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59151
llvm-svn: 356644
Summary:
Use a small cache for Values tested by nonEscapingLocalObject().
Since the calls to PointerMayBeCaptured are fairly expensive, this saves
a good amount of compile time for anything relying heavily on
BasicAA.alias() calls.
This uses the same approach as the AliasCache, i.e. the cache is reset
after each alias() call. The cache is not used or updated by modRefInfo
calls since it's harder to know when to reset the cache.
Testcases that show improvements with this patch are too large to
include. Example compile time improvement: 7s to 6s.
Reviewers: chandlerc, sunfish
Subscribers: sanjoy, jlebar, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D57627
llvm-svn: 353245
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
minted `CallBase` class instead of the `CallSite` wrapper.
This moves the largest interwoven collection of APIs that traffic in
`CallSite`s. While a handful of these could have been migrated with
a minorly more shallow migration by converting from a `CallSite` to
a `CallBase`, it hardly seemed worth it. Most of the APIs needed to
migrate together because of the complex interplay of AA APIs and the
fact that converting from a `CallBase` to a `CallSite` isn't free in its
current implementation.
Out of tree users of these APIs can fairly reliably migrate with some
combination of `.getInstruction()` on the `CallSite` instance and
casting the resulting pointer. The most generic form will look like `CS`
-> `cast_or_null<CallBase>(CS.getInstruction())` but in most cases there
is a more elegant migration. Hopefully, this migrates enough APIs for
users to fully move from `CallSite` to the base class. All of the
in-tree users were easily migrated in that fashion.
Thanks for the review from Saleem!
Differential Revision: https://reviews.llvm.org/D55641
llvm-svn: 350503
Motivated by the discussion in D38499, this patch updates BasicAA to support
arbitrary pointer sizes by switching most remaining non-APInt calculations to
use APInt. The size of these APInts is set to the maximum pointer size (maximum
over all address spaces described by the data layout string).
Most of this translation is straightforward, but this patch contains a fix for
a bug that revealed itself during this translation process. In order for
test/Analysis/BasicAA/gep-and-alias.ll to pass, which is run with 32-bit
pointers, the intermediate calculations must be performed using 64-bit
integers. This is because, as noted in the patch, when GetLinearExpression
decomposes an expression into C1*V+C2, and we then multiply this by Scale, and
distribute, to get (C1*Scale)*V + C2*Scale, it can be the case that, even
through C1*V+C2 does not overflow for relevant values of V, (C2*Scale) can
overflow. If this happens, later logic will draw invalid conclusions from the
(base) offset value. Thus, when initially applying the APInt conversion,
because the maximum pointer size in this test is 32 bits, it started failing.
Suspicious, I created a 64-bit version of this test (included here), and that
failed (miscompiled) on trunk for a similar reason (the multiplication can
overflow).
After fixing this overflow bug, the first test case (at least) in
Analysis/BasicAA/q.bad.ll started failing. This is also a 32-bit test, and was
relying on having 64-bit intermediate values to have BasicAA return an accurate
result. In order to fix this problem, and because I believe that it is not
uncommon to use i64 indexing expressions in 32-bit code (especially portable
code using int64_t), it seems reasonable to always use at least 64-bit
integers. In this way, we won't regress our analysis capabilities (and there's
a command-line option added, so experimenting with this should be easy).
As pointed out by Eli during the review, there are other potential overflow
conditions that this patch does not address. Fixing those is left to follow-up
work.
Patch by me with contributions from Michael Ferguson (mferguson@cray.com).
Differential Revision: https://reviews.llvm.org/D38662
llvm-svn: 350220
Summary:
BasicAA has special logic for unescaped allocas, which normally applies
equally well to dynamic and static allocas. However, llvm.stackrestore
has the power to end the lifetime of dynamic allocas, without referring
to them directly.
stackrestore is already marked with the most conservative memory
modification attributes, but because the alloca is not escaped, the
normal logic produces incorrect results. I think BasicAA needs a special
case here to teach it about the relationship between dynamic allocas and
stackrestore.
Fixes PR40118
Reviewers: gbiv, efriedma, george.burgess.iv
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D55969
llvm-svn: 349945
Moving away from UnknownSize is part of the effort to migrate us to
LocationSizes (e.g. the cleanup promised in D44748).
This doesn't entirely remove all of the uses of UnknownSize; some uses
require tweaks to assume that UnknownSize isn't just some kind of int.
This patch is intended to just be a trivial replacement for all places
where LocationSize::unknown() will Just Work.
llvm-svn: 344186
There are places where we need to merge multiple LocationSizes of
different sizes into one, and get a sensible result.
There are other places where we want to optimize aggressively based on
the value of a LocationSizes (e.g. how can a store of four bytes be to
an area of storage that's only two bytes large?)
This patch makes LocationSize hold an 'imprecise' bit to note whether
the LocationSize can be treated as an upper-bound and lower-bound for
the size of a location, or just an upper-bound.
This concludes the series of patches leading up to this. The most recent
of which is r344108.
Fixes PR36228.
Differential Revision: https://reviews.llvm.org/D44748
llvm-svn: 344114
This is the second in a series of changes intended to make
https://reviews.llvm.org/D44748 more easily reviewable. Please see that
patch for more context. The first change being r344012.
Since I was requested to do all of this with post-commit review, this is
about as small as I can make this patch.
This patch makes LocationSize into an actual type that wraps a uint64_t;
users are required to call getValue() in order to get the size now. If
the LocationSize has an Unknown size (e.g. if LocSize ==
MemoryLocation::UnknownSize), getValue() will assert.
This also adds DenseMap specializations for LocationInfo, which required
taking two more values from the set of values LocationInfo can
represent. Hence, heavy users of multi-exabyte arrays or structs may
observe slightly lower-quality code as a result of this change.
The intent is for getValue()s to be very close to a corresponding
hasValue() (which is often spelled `!= MemoryLocation::UnknownSize`).
Sadly, small diff context appears to crop that out sometimes, and the
last change in DSE does require a bit of nonlocal reasoning about
control-flow. :/
This also removes an assert, since it's now redundant with the assert in
getValue().
llvm-svn: 344013
This is one of a series of changes intended to make
https://reviews.llvm.org/D44748 more easily reviewable. Please see that
patch for more context.
Since I was requested to do all of this with post-commit review, this is
about as small as I can make it (beyond committing changes to these few
files separately, but they're incredibly similar in spirit, so...)
On its own, this change doesn't make a great deal of sense. I plan on
having a follow-up Real Soon Now(TM) to make the bits here make more
sense. :)
In particular, the next change in this series is meant to make
LocationSize an actual type, which you have to call .getValue() on in
order to get at the uint64_t inside. Hence, this change refactors code
so that:
- we only need to call the soon-to-come getValue() once in most cases,
and
- said call to getValue() happens very closely to a piece of code that
checks if the LocationSize has a value (e.g. if it's != UnknownSize).
llvm-svn: 344012
Summary:
Calls marked 'tail' cannot read or write allocas from the current frame
because the current frame might be destroyed by the time they run.
However, a tail call may use an alloca with byval. Calling with byval
copies the contents of the alloca into argument registers or stack
slots, so there is no lifetime issue. Tail calls never modify allocas,
so we can return just ModRefInfo::Ref.
Fixes PR38466, a longstanding bug.
Reviewers: hfinkel, nlewycky, gbiv, george.burgess.iv
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D50679
llvm-svn: 339636
By using PhiValuesAnalysis we can get all the values reachable from a phi, so
we can be more precise instead of giving up when a phi has phi operands. We
can't make BaseicAA directly use PhiValuesAnalysis though, as the user of
BasicAA may modify the function in ways that PhiValuesAnalysis can't cope with.
For this optional usage to work correctly BasicAAWrapperPass now needs to be not
marked as CFG-only (i.e. it is now invalidated even when CFG is preserved) due
to how the legacy pass manager handles dependent passes being invalidated,
namely the depending pass still has a pointer to the now-dead dependent pass.
Differential Revision: https://reviews.llvm.org/D44564
llvm-svn: 338242
Summary:
Support for this option is needed for building Linux kernel.
This is a very frequently requested feature by kernel developers.
More details : https://lkml.org/lkml/2018/4/4/601
GCC option description for -fdelete-null-pointer-checks:
This Assume that programs cannot safely dereference null pointers,
and that no code or data element resides at address zero.
-fno-delete-null-pointer-checks is the inverse of this implying that
null pointer dereferencing is not undefined.
This feature is implemented in LLVM IR in this CL as the function attribute
"null-pointer-is-valid"="true" in IR (Under review at D47894).
The CL updates several passes that assumed null pointer dereferencing is
undefined to not optimize when the "null-pointer-is-valid"="true"
attribute is present.
Reviewers: t.p.northover, efriedma, jyknight, chandlerc, rnk, srhines, void, george.burgess.iv
Reviewed By: efriedma, george.burgess.iv
Subscribers: eraman, haicheng, george.burgess.iv, drinkcat, theraven, reames, sanjoy, xbolva00, llvm-commits
Differential Revision: https://reviews.llvm.org/D47895
llvm-svn: 336613
Summary:
This patch introduce new intrinsic -
strip.invariant.group that was described in the
RFC: Devirtualization v2
Reviewers: rsmith, hfinkel, nlopes, sanjoy, amharc, kuhar
Subscribers: arsenm, nhaehnle, JDevlieghere, hiraditya, xbolva00, llvm-commits
Differential Revision: https://reviews.llvm.org/D47103
Co-authored-by: Krzysztof Pszeniczny <krzysztof.pszeniczny@gmail.com>
llvm-svn: 336073
Summary:
A simple change to derive mod/ref info from the atomic memcpy
intrinsic in the same way as from the regular memcpy intrinsic.
llvm-svn: 333454
The uint64_ts that we pass around AA to represent MemoryLocation sizes
are logically an Optional<uint64_t>. In D44748, we want to add an extra
'imprecise' bit to this Optional<uint64_t> to represent whether a given
MemoryLocation size is an upper-bound or an exact size. For more context
on why, please see D44748.
That patch is quite large, but reviewers seem to be OK with the
approach. In D45581 (my first attempt to split 'noise' out of D44748),
reames asked that I land a precursor that is solely replacing uint64_t
with LocationSize, which starts out as `using LocationSize = uint64_t;`.
He also gave me the OK to submit this rename without further review.
llvm-svn: 333314
Summary:
Patch for capture tracking broke
bootstrap of clang with -fstict-vtable-pointers
which resulted in debbugging nightmare. It was fixed
https://reviews.llvm.org/D46900 but as it turned
out, there were other parts like inliner (computing of
noalias metadata) that I found after bootstraping with enabled
assertions.
Reviewers: hfinkel, rsmith, chandlerc, amharc, kuhar
Subscribers: JDevlieghere, eraman, llvm-commits, hiraditya
Differential Revision: https://reviews.llvm.org/D47088
llvm-svn: 333070
Summary:
A recent patch ([[ https://reviews.llvm.org/rL331587 | rL331587 ]]) to Capture Tracking taught it that the `launder_invariant_group` intrinsic captures its argument only by returning it. Unfortunately, BasicAA still considered every call instruction as a possible escape source and hence concluded that the result of a `launder_invariant_group` call cannot alias any local non-escaping value. This led to [[ https://bugs.llvm.org/show_bug.cgi?id=37458 | bug 37458 ]].
This patch updates the relevant check for escape sources in BasicAA.
Reviewers: Prazek, kuhar, rsmith, hfinkel, sanjoy, xbolva00
Reviewed By: hfinkel, xbolva00
Subscribers: JDevlieghere, hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D46900
llvm-svn: 332466
Summary:
In ModRefInfo "Must" was introduced to track presence of MustAlias, but we still want to return NoModRef when there is neither Mod or Ref, even when MustAlias is found. Patch has small fixes to ensure this happens.
Minor cleanup to remove nesting for 2 if statements when calling getModRefInfo for 2 ImmutableCallSites.
Reviewers: sanjoy
Subscribers: jlebar, llvm-commits
Differential Revision: https://reviews.llvm.org/D42209
llvm-svn: 322932
An alternative (and probably better) fix would be that of
making `Scale` an APInt, and there's a patch floating around
to do this. As we're still discussing it, at least stop crashing
in the meanwhile (added bonus, we now have a regression test for
this situation).
Fixes PR35843.
Thanks to Eli for suggesting the fix and Simon for reporting and
reducing the bug.
llvm-svn: 322467
Summary:
Add an additional bit to ModRefInfo, ModRefInfo::Must, to be cleared for known must aliases.
Shift existing Mod/Ref/ModRef values to include an additional most
significant bit. Update wrappers that modify ModRefInfo values to
reflect the change.
Notes:
* ModRefInfo::Must is almost entirely cleared in the AAResults methods, the remaining changes are trying to preserve it.
* Only some small changes to make custom AA passes set ModRefInfo::Must (BasicAA).
* GlobalsModRef already declares a bit, who's meaning overlaps with the most significant bit in ModRefInfo (MayReadAnyGlobal). No changes to shift the value of MayReadAnyGlobal (see AlignedMap). FunctionInfo.getModRef() ajusts most significant bit so correctness is preserved, but the Must info is lost.
* There are cases where the ModRefInfo::Must is not set, e.g. 2 calls that only read will return ModRefInfo::NoModRef, though they may read from exactly the same location.
Reviewers: dberlin, hfinkel, george.burgess.iv
Subscribers: llvm-commits, sanjoy
Differential Revision: https://reviews.llvm.org/D38862
llvm-svn: 321309
Summary:
Make enum ModRefInfo an enum class. Changes to ModRefInfo values should
be done using inline wrappers.
This should prevent future bit-wise opearations from being added, which can be more error-prone.
Reviewers: sanjoy, dberlin, hfinkel, george.burgess.iv
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D40933
llvm-svn: 320107
Summary:
The aim is to make ModRefInfo checks and changes more intuitive
and less error prone using inline methods that abstract the bit operations.
Ideally ModRefInfo would become an enum class, but that change will require
a wider set of changes into FunctionModRefBehavior.
Reviewers: sanjoy, george.burgess.iv, dberlin, hfinkel
Subscribers: nlopes, llvm-commits
Differential Revision: https://reviews.llvm.org/D40749
llvm-svn: 319821
My fix is conservative and will make us return may-alias instead.
The test case is:
check(gep(x, 0), n, gep(x, n), -1) with n == sizeof(x)
Here, the first value accesses the whole object, but the second access
doesn't access anything. The semantics of -1 is read until the end of the
object, which in this case means read nothing.
No test case, since isn't trivial to exploit this one, but I've proved it correct.
llvm-svn: 317680
Remove code that assumed that a nullptr of address space != 0 couldnt alias with a non-null pointer. This is incorrect, since nothing can be concluded about a null pointer in an address space != 0.
This code was written before address spaces were introduced
Differential Revision: https://reviews.llvm.org/D37518
llvm-svn: 312648
This matches the checks done at the beginning of isKnownNonEqual that this code is partially emulating.
Without this we can get assertion failures due to the bit widths of the KnownBits not matching.
llvm-svn: 306044
Using various methods, BasicAA tries to determine whether two
GetElementPtr memory locations alias when its base pointers are known
to be equal. When none of its heuristics are applicable, it falls back
to PartialAlias to, according to a comment, protect TBAA making a wrong
decision in case of unions and malloc. PartialAlias is not correct,
because a PartialAlias result implies that some, but not all, bytes
overlap which is not necessarily the case here.
AAResults returns the first analysis result that is not MayAlias.
BasicAA is always the first alias analysis. When it returns
PartialAlias, no other analysis is queried to give a more exact result
(which was the intention of returning PartialAlias instead of MayAlias).
For instance, ScopedAA could return a more accurate result.
The PartialAlias hack was introduced in r131781 (and re-applied in
r132632 after some reverts) to fix llvm.org/PR9971 where TBAA returns a
wrong NoAlias result due to a union. A test case for the malloc case
mentioned in the comment was not provided and I don't think it is
affected since it returns an omnipotent char anyway.
Since r303851 (https://reviews.llvm.org/D33328) clang does emit specific
TBAA for unions anymore (but "omnipotent char" instead). Hence, the
PartialAlias workaround is not required anymore.
This patch passes the test-suite and check-llvm/check-clang of a
self-hoisted build on x64.
Reviewed By: hfinkel
Differential Revision: https://reviews.llvm.org/D34318
llvm-svn: 305938
This is a fix for the test case in PR32314.
Basic Alias Analysis can ask if two nodes are known non-equal after looking through a phi node to find a GEP. isAddOfNonZero saw an add of a constant from the same phi and said that its output couldn't be equal. But Basic Alias Analysis was really asking about the value from the previous loop iteration.
This patch at least makes that case not happen anymore, I'm not sure if there were still other ways this can fail. As was discussed in the bug, it looks like fixing BasicAA would be difficult so this patch seemed like a possible workaround
Differential Revision: https://reviews.llvm.org/D33136
llvm-svn: 305481
Summary:
llvm.invariant.group.barrier returns pointer that mustalias
pointer it takes. It can't be marked with `returned` attribute,
because it would be remove easily. The other reason is that
only Alias Analysis can know about this, because if any other
pass would know it, then the result would be replaced with it's
argument, which would be invalid.
We can think about returned pointer as something that mustalias, but
it doesn't have to be bitwise the same as the argument.
Reviewers: dberlin, chandlerc, hfinkel, sanjoy
Subscribers: reames, nlewycky, rsmith, anna, amharc
Differential Revision: https://reviews.llvm.org/D31585
llvm-svn: 301227
BasicAA wants to know if a function is either a malloc or calloc like function. Currently we have to check both separately. This means both calls check if its an intrinsic, query TLI, check the nobuiltin attribute, scan the AllocationFnData, etc.
This patch adds a isMallocOrCallocLikeFn so we can go through all of the checks once per call.
This also changes the one other location I saw that called both together.
Differential Revision: https://reviews.llvm.org/D32188
llvm-svn: 300608
This avoids the confusing 'CS.paramHasAttr(ArgNo + 1, Foo)' pattern.
Previously we were testing return value attributes with index 0, so I
introduced hasReturnAttr() for that use case.
llvm-svn: 300367
This adds a parameter to @llvm.objectsize that makes it return
conservative values if it's given null.
This fixes PR23277.
Differential Revision: https://reviews.llvm.org/D28494
llvm-svn: 298430
This is fixing pr31761: BasicAA is deducing NoAlias
on the result of the GEP if the base pointer is itself NoAlias.
This is possible only if the NoAlias on the base pointer is
deduced with a non-sized query: this should guarantee that
the pointers are belonging to different memory allocation
and that the GEP can't legally jump from one to another.
Differential Revision: https://reviews.llvm.org/D29216
llvm-svn: 293293
Summary:
The LibFunc::Func enum holds enumerators named for libc functions.
Unfortunately, there are real situations, including libc implementations, where
function names are actually macros (musl uses "#define fopen64 fopen", for
example; any other transitively visible macro would have similar effects).
Strictly speaking, a conforming C++ Standard Library should provide any such
macros as functions instead (via <cstdio>). However, there are some "library"
functions which are not part of the standard, and thus not subject to this
rule (fopen64, for example). So, in order to be both portable and consistent,
the enum should not use the bare function names.
The old enum naming used a namespace LibFunc and an enum Func, with bare
enumerators. This patch changes LibFunc to be an enum with enumerators prefixed
with "LibFFunc_". (Unfortunately, a scoped enum is not sufficient to override
macros.)
There are additional changes required in clang.
Reviewers: rsmith
Subscribers: mehdi_amini, mzolotukhin, nemanjai, llvm-commits
Differential Revision: https://reviews.llvm.org/D28476
llvm-svn: 292848
There is no need to do this within an analysis. That method shouldn't
even be reached if this predicate holds as the actual useful
optimization is in the analysis manager itself.
llvm-svn: 290614
This requires custom handling because BasicAA caches handles to other
analyses and so it needs to trigger indirect invalidation.
This fixes one of the common crashes when using the new PM in real
pipelines. I've also tweaked a regression test to check that we are at
least handling the most immediate case.
I'm going to work at re-structuring this test some to both scale better
(rather than all being in one file) and check more invalidation paths in
a follow-up commit, but I wanted to get the basic bug fix in place.
llvm-svn: 290603
When iterating over data operands in AA, don't make argument-attribute-specific
queries on bundle operands. Trying to fix self hosting...
llvm-svn: 289765
After r289755, the AssumptionCache is no longer needed. Variables affected by
assumptions are now found by using the new operand-bundle-based scheme. This
new scheme is more computationally efficient, and also we need much less
code...
llvm-svn: 289756
Instead, expose whether the current type is an array or a struct, if an array
what the upper bound is, and if a struct the struct type itself. This is
in preparation for a later change which will make PointerType derive from
Type rather than SequentialType.
Differential Revision: https://reviews.llvm.org/D26594
llvm-svn: 288458
analyses to have a common type which is enforced rather than using
a char object and a `void *` type when used as an identifier.
This has a number of advantages. First, it at least helps some of the
confusion raised in Justin Lebar's code review of why `void *` was being
used everywhere by having a stronger type that connects to documentation
about this.
However, perhaps more importantly, it addresses a serious issue where
the alignment of these pointer-like identifiers was unknown. This made
it hard to use them in pointer-like data structures. We were already
dodging this in dangerous ways to create the "all analyses" entry. In
a subsequent patch I attempted to use these with TinyPtrVector and
things fell apart in a very bad way.
And it isn't just a compile time or type system issue. Worse than that,
the actual alignment of these pointer-like opaque identifiers wasn't
guaranteed to be a useful alignment as they were just characters.
This change introduces a type to use as the "key" object whose address
forms the opaque identifier. This both forces the objects to have proper
alignment, and provides type checking that we get it right everywhere.
It also makes the types somewhat less mysterious than `void *`.
We could go one step further and introduce a truly opaque pointer-like
type to return from the `ID()` static function rather than returning
`AnalysisKey *`, but that didn't seem to be a clear win so this is just
the initial change to get to a reliably typed and aligned object serving
is a key for all the analyses.
Thanks to Richard Smith and Justin Lebar for helping pick plausible
names and avoid making this refactoring many times. =] And thanks to
Sean for the super fast review!
While here, I've tried to move away from the "PassID" nomenclature
entirely as it wasn't really helping and is overloaded with old pass
manager constructs. Now we have IDs for analyses, and key objects whose
address can be used as IDs. Where possible and clear I've shortened this
to just "ID". In a few places I kept "AnalysisID" to make it clear what
was being identified.
Differential Revision: https://reviews.llvm.org/D27031
llvm-svn: 287783
Nikita Popov