A non-escaping global should never alias with non-pointer values
and `ptr null`. This should improve disambiguation of global
pointers with relation to Flang runtime calls (given that
`nosync nocallback` attributes are properly set).
It also seems to be an obvious improvement with little overhead.
This improves handling of `threadlocal.address` intrinsic in analyses:
The thread-id cannot change within a function with the exception of
suspend points of pre-split coroutines. This changes
`llvm::getUnderlyingObject` to look through `threadlocal.address` in
these cases.
`GlobalsAAResult::AnalyzeUsesOfPointer` checks whether an address can be
traced to simple loads/stores or escapes to other places. Starting the
analysis from a thread-local `GlobalValue` the `threadlocal.address`
intrinsic is safe to skip here.
This improves issue #87437
Historically, AA implementations chained to a following implementation
to answer recursive queries. This is no longer the case, but the legacy
lives on in a confusing phrasing of the return-a-conservative-value
paths. Let's just return "don't know" directly, where appropriate; the
current two-step way is confusing.
Differential Revision: https://reviews.llvm.org/D149100
Intrinsics have historically been excluded from the call graph with an
exception of 3 special ones added at some point. This meant that passes
depending on the call graph needed to handle intrinsics explicitly as
the underlying assumption, namely that intrinsics can't call or modify
things, doesn't hold. We are slowly moving away from special handling of
intrinsics, or at least towards explicitly checking what intrinsics we
want to handle differently.
This patch:
- Includes most intrinsics in the call graph. Debug intrinsics are
still excluded.
- Removes the special handling of intrinsics in the GlobalsAA pass.
- Removes the `IntrinsicInst::isLeaf` method.
Properly
Fixes: https://github.com/llvm/llvm-project/issues/52706
See also:
https://discourse.llvm.org/t/intrinsics-are-not-special-stop-pretending-i-mean-it/67545
Differential Revision: https://reviews.llvm.org/D14119
All current analyses ignore the context. We make the argument mandatory
for analyses, but optional for the query interface.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D136512
When an internal global is passed to a 'nocallback' call as
a 'nocapture' pointer, it cannot escape through this call and
be indirectly referenced in this module.
So it must not alias with any pointer in the module.
This may provide some remedy for Fortran module-private array descriptors
that are usually passed by address to some runtime functions
(e.g. to allocation/deallocation functions). In general, a good aliasing
information derived from Fortran language rules would solve the same issue,
but I think this change may be beneficial as-is (given that nocapture,
nocallback attributes are properly set).
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D138336
Followup to D135962 to rename remaining uses of
FunctionModRefBehavior to MemoryEffects. Does not touch API names
yet, but also updates variables names FMRB/MRB to ME, to match the
new type name.
Currently, FunctionModRefBehavior tracks whether the function reads
or writes memory (ModRefInfo) and which locations it can access
(argmem, inaccessiblemem and other). This patch changes it to track
ModRef information per-location instead.
To give two examples of why this is useful:
* D117095 highlights a weakness of ModRef modelling in the presence
of operand bundles. For a memcpy call with deopt operand bundle,
we want to say that it can read any memory, but only write argument
memory. This would allow them to be treated like any other calls.
However, we currently can't express this and have to say that it
can read or write any memory.
* D127383 would ideally be modelled as a separate threadid location,
where threadid Refs outside pre-split coroutines can be ignored
(like other accesses to constant memory). The current representation
does not allow modelling this precisely.
The patch as implemented is intended to be NFC, but there are some
obvious opportunities for improvements and simplification. To fully
capitalize on this we would also want to change the way we represent
memory attributes on functions, but that's a larger change, and I
think it makes sense to separate out the FunctionModRefBehavior
refactoring.
Differential Revision: https://reviews.llvm.org/D130896
Mark ModRefInfo as a bitmask enum, which allows using normal
& and | operators on it. This supersedes various functions like
unionModRef() and intersectModRef(). I think this makes the code
cleaner than going through helper functions...
Differential Revision: https://reviews.llvm.org/D130870
getModRefInfo() queries currently track whether the result is a
MustAlias on a best-effort basis. The only user of this functionality
is the optimized memory access type in MemorySSA -- which in turn
has no users. Given that this functionality has not found a user
since it was introduced five years ago (in D38862), I think we
should drop it again.
The context is that I'm working to separate FunctionModRefBehavior
to track mod/ref for different location kinds (like argmem or
inaccessiblemem) separately, and the fact that ModRefInfo also has
an unrelated Must flag makes this quite awkward, especially as this
means that NoModRef is not a zero value. If we want to retain the
functionality, I would probably split getModRefInfo() results into
a part that just contains the ModRef information, and a separate
part containing a (best-effort) AliasResult.
Differential Revision: https://reviews.llvm.org/D130713
We currently assume in a number of places that free-like functions
free their first argument. This is true for all hardcoded free-like
functions, but with the new attribute-based design, the freed
argument is supposed to be indicated by the allocptr attribute.
To make sure we handle this correctly once allockind(free) is
respected, add a getFreedOperand() helper which returns the freed
argument, rather than just indicating whether the call frees *some*
argument.
This migrates most but not all users of isFreeCall() to the new
API. The remaining users are a bit more tricky.
BasicAA will already call getModRefBehavior() on the Function of
the CallBase if there are no operand bundles. This happens through
getBestAAResults(), i.e. it is a recursive call that will query
other AA providers, not just the BasicAA implementation.
As such, there is no need to reimplement the same functionality
in GlobalsModRef, a combination of BasicAA and GlobalsModRef already
handles it. This does mean that this no longer works under
-disable-basic-aa, but that's a testing only option.
As the FIXME already indicates, I don't see why this code would be
necessary. If there's a call to an allocator function, that should
get treated just like any other function call -- usually it will be
a declaration and handled conservatively based on memory attributes
only. There should be no need to explicitly force it to be modref.
No test failures either, so I think this is just dead code.
Differential Revision: https://reviews.llvm.org/D127273
RequireAnalysis<GlobalsAA> doesn't actually recompute GlobalsAA.
GlobalsAA isn't invalidated (unless specifically invalidated) because
it's self-updating via ValueHandles, but can be imprecise during the
self-updates.
Rather than invalidating GlobalsAA, which would invalidate AAManager and
any analyses that use AAManager, create a new pass that recomputes
GlobalsAA.
Fixes#53131.
Differential Revision: https://reviews.llvm.org/D121167
Extend the existing malloc-family specific optimization to all noalias calls. This allows us to handle allocation wrappers, and removes a dependency on a lib-func check in favor of generic attribute usage.
Differential Revision: https://reviews.llvm.org/D116980
This reverts commit fd4808887ee47f3ec8a030e9211169ef4fb094c3.
This patch causes gcc to issue a lot of warnings like:
warning: base class ‘class llvm::MCParsedAsmOperand’ should be
explicitly initialized in the copy constructor [-Wextra]
Main reason is preparation to transform AliasResult to class that contains
offset for PartialAlias case.
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D98027
We can always look through single-argument (LCSSA) phi nodes when
performing alias analysis. getUnderlyingObject() already does this,
but stripPointerCastsAndInvariantGroups() does not. We still look
through these phi nodes with the usual aliasPhi() logic, but
sometimes get sub-optimal results due to the restrictions on value
equivalence when looking through arbitrary phi nodes. I think it's
generally beneficial to keep the underlying object logic and the
pointer cast stripping logic in sync, insofar as it is possible.
With this patch we get marginally better results:
aa.NumMayAlias | 5010069 | 5009861
aa.NumMustAlias | 347518 | 347674
aa.NumNoAlias | 27201336 | 27201528
...
licm.NumPromoted | 1293 | 1296
I've renamed the relevant strip method to stripPointerCastsForAliasAnalysis(),
as we're past the point where we can explicitly spell out everything
that's getting stripped.
Differential Revision: https://reviews.llvm.org/D96668
There are no changes relative to the original commit. However, an issue
this exposed in BasicAA assumption tracking has been fixed in the
previous commit.
-----
An alias query currently works out roughly like this:
* Look up location pair in cache.
* Perform BasicAA logic (including cache lookup and insertion...)
* Perform a recursive query using BestAAResults.
* Look up location pair in cache (and thus do not recurse into BasicAA)
* Query all the other AA providers.
* Query all the other AA providers.
This is a lot of unnecessary work, all ultimately caused by the
BestAAResults query at the end of aliasCheck(). The reason we perform
it, is that aliasCheck() is getting called recursively, and we of
course want those recursive queries to also make use of other AA
providers, not just BasicAA. We can solve this by making the recursive
queries directly use BestAAResults (which will check both BasicAA
and other providers), rather than recursing into aliasCheck().
There are some tradeoffs:
* We can no longer pass through the precomputed underlying object
to aliasCheck(). This is not a major concern, because nowadays
getUnderlyingObject() is quite cheap.
* Results from other AA providers are no longer cached inside
BasicAA. The way this worked was already a bit iffy, in that a
result could be cached, but if it was MayAlias, we'd still end
up re-querying other providers anyway. If we want to cache
non-BasicAA results, we should do that in a more principled manner.
In any case, despite those tradeoffs, this works out to be a decent
compile-time improvment. I think it also simplifies the mental model
of how BasicAA works. It took me quite a while to fully understand
how these things interact.
Differential Revision: https://reviews.llvm.org/D90094
This reverts commit a3904cc77f181cff7355357688edfc392a236f5d.
It causes the compiler to crash while building Harfbuzz for ARM in
Chromium, reduced reproducer forthcoming:
https://crbug.com/1167305
An alias query currently works out roughly like this:
* Look up location pair in cache.
* Perform BasicAA logic (including cache lookup and insertion...)
* Perform a recursive query using BestAAResults.
* Look up location pair in cache (and thus do not recurse into BasicAA)
* Query all the other AA providers.
* Query all the other AA providers.
This is a lot of unnecessary work, all ultimately caused by the
BestAAResults query at the end of aliasCheck(). The reason we perform
it, is that aliasCheck() is getting called recursively, and we of
course want those recursive queries to also make use of other AA
providers, not just BasicAA. We can solve this by making the recursive
queries directly use BestAAResults (which will check both BasicAA
and other providers), rather than recursing into aliasCheck().
There are some tradeoffs:
* We can no longer pass through the precomputed underlying object
to aliasCheck(). This is not a major concern, because nowadays
getUnderlyingObject() is quite cheap.
* Results from other AA providers are no longer cached inside
BasicAA. The way this worked was already a bit iffy, in that a
result could be cached, but if it was MayAlias, we'd still end
up re-querying other providers anyway. If we want to cache
non-BasicAA results, we should do that in a more principled manner.
In any case, despite those tradeoffs, this works out to be a decent
compile-time improvment. I think it also simplifies the mental model
of how BasicAA works. It took me quite a while to fully understand
how these things interact.
Differential Revision: https://reviews.llvm.org/D90094
Currently, we have some confusion in the codebase regarding the
meaning of LocationSize::unknown(): Some parts (including most of
BasicAA) assume that LocationSize::unknown() only allows accesses
after the base pointer. Some parts (various callers of AA) assume
that LocationSize::unknown() allows accesses both before and after
the base pointer (but within the underlying object).
This patch splits up LocationSize::unknown() into
LocationSize::afterPointer() and LocationSize::beforeOrAfterPointer()
to make this completely unambiguous. I tried my best to determine
which one is appropriate for all the existing uses.
The test changes in cs-cs.ll in particular illustrate a previously
clearly incorrect AA result: We were effectively assuming that
argmemonly functions were only allowed to access their arguments
after the passed pointer, but not before it. I'm pretty sure that
this was not intentional, and it's certainly not specified by
LangRef that way.
Differential Revision: https://reviews.llvm.org/D91649
When constructing a MemoryLocation by hand, require that a
LocationSize is explicitly specified. D91649 will split up
LocationSize::unknown() into two different states, and callers
should make an explicit choice regarding the kind of MemoryLocation
they want to have.
This is (more?) usable by GDB pretty printers and seems nicer to write.
There's one tricky caveat that in C++14 (LLVM's codebase today) the
static constexpr member declaration is not a definition - so odr use of
this constant requires an out of line definition, which won't be
provided (that'd make all these trait classes more annoyidng/expensive
to maintain). But the use of this constant in the library implementation
is/should always be in a non-odr context - only two unit tests needed to
be touched to cope with this/avoid odr using these constants.
Based on/expanded from D72590 by Christian Sigg.
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:
If there are any internal methods whose address was taken, conclude there is nothing known in relation of any other internal method and a global.
Reviewers: nlopes, sanjoy.google
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69690
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:
Both the input Value pointer and the returned Value
pointers in GetUnderlyingObjects are now declared as
const.
It turned out that all current (in-tree) uses of
GetUnderlyingObjects were trivial to update, being
satisfied with have those Value pointers declared
as const. Actually, in the past several of the users
had to use const_cast, just because of ValueTracking
not providing a version of GetUnderlyingObjects with
"const" Value pointers. With this patch we get rid
of those const casts.
Reviewers: hfinkel, materi, jkorous
Reviewed By: jkorous
Subscribers: dexonsmith, jkorous, jholewinski, sdardis, eraman, hiraditya, jrtc27, atanasyan, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D61038
llvm-svn: 359072
Create method `optForNone()` testing for the function level equivalent of
`-O0` and refactor appropriately.
Differential revision: https://reviews.llvm.org/D59852
llvm-svn: 357638
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
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
