Remove the special casing for intrinsics in MemoryLocation::getForDest()
and handle them through the general attribute based code. On the DSE
side, this means that isRemovable() now needs to handle more than a
hardcoded list of intrinsics. We consider everything apart from
volatile memory intrinsics and lifetime markers to be removable.
This allows us to perform DSE on intrinsics that DSE has not been
specially taught about, using a matrix store as an example here.
There is an interesting test change for invariant.start, but I
believe that optimization is correct. It only looks a bit odd
because the code is immediate UB anyway.
Differential Revision: https://reviews.llvm.org/D116210
As reames mentioned on related reviews, we don't need the nocapture
requirement here. First of all, from an API perspective, this is
not something that MemoryLocation::getForDest() should be checking
in the first place, because it does not affect which memory this
particular call can access; it's an orthogonal concern that should
be handled by the caller if necessary.
However, for both of the motivating users in DSE and InstCombine,
we don't need the nocapture requirement, because the capture can
either be purely local to the call (a pointer identity check that
is irrelevant to us), be part of the return value (which we check
is unused), or be written in the dest location, which we have
determined to be dead.
This allows us to remove the special handling for libcalls as well.
Differential Revision: https://reviews.llvm.org/D116148
This is a reapply of a8a51fe5, which was reverted in 1ba99e due to a failing compiler-rt test. That test was a false positive because it was checking asan failures not accounting for the fact the call could be validly optimized out. I hopefully managed to stablize that test in 9b955f. (That's a speculative fix due to disk consumption needed to build compiler-rt tests locally being absurd.)
Original commit message follows..
The majority of this change is sinking logic from instcombine into MemoryLocation such that it can be generically reused. If we have a call with a single analyzable write to an argument, we can treat that as-if it were a store of unknown size.
Merging the code in this was unblocks DSE in the store to dead memory code paths. In theory, it should also enable classic DSE of such calls, but the code appears to not know how to use object sizes to refine unknown access bounds (yet).
In addition, this does make the isAllocRemovable path slightly stronger by reusing the libfunc and additional intrinsics bits which are already in getForDest.
Differential Revision: https://reviews.llvm.org/D115904
The majority of this change is sinking logic from instcombine into MemoryLocation such that it can be generically reused. If we have a call with a single analyzable write to an argument, we can treat that as-if it were a store of unknown size.
Merging the code in this was unblocks DSE in the store to dead memory code paths. In theory, it should also enable classic DSE of such calls, but the code appears to not know how to use object sizes to refine unknown access bounds (yet).
In addition, this does make the isAllocRemovable path slightly stronger by reusing the libfunc and additional intrinsics bits which are already in getForDest.
Differential Revision: https://reviews.llvm.org/D115904
This reverts commit ac60263ad1.
It looks like the test fails on certain non-Darwin system, even though
the triple is explicitly set to macos. Revert while I investigate.
memset_pattern{4,8,16} writes to the first argument. Use getForDest
to return the corresponding MemoryLocation.
Reviewed By: ab
Differential Revision: https://reviews.llvm.org/D114906
memset_pattern{4,8} behave as memset_pattern16, with the only difference
being the size of the pattern location.
Reviewed By: ab
Differential Revision: https://reviews.llvm.org/D114905
getForArgument is missing support for atomic memory transfer
intrinsics. In terms of accessed locations they behave like regular
memory transfer intrinsics and we already support them as such in
getForSource/getForDest.
DSE has some extra logic to determine the write location of library
calls like str*cpy and str*cat. This patch moves the logic to a new
MemoryLocation:getForDest variant, which takes a call and TLI.
This patch should be NFC, because no other places take advantage of the
new helper yet.
Suggested by @reames post-commit 7eec832def.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D114872
strcpy/strcat/strncat access memory starting from the passed in
pointers. Construct memory locations for their args using getAfter.
Discussed in D114872.
Reviewed By: reames
Differential Revision: https://reviews.llvm.org/D114969
The size argument of strncpy can be used as bound for the size of
its pointer arguments.
strncpy is guaranteed to write N bytes and reads up to N bytes.
Reviewed By: xbolva00
Differential Revision: https://reviews.llvm.org/D114871
The size argument for memset_chk is an upper bound for the size of the
pointer argument. memset_chk may write less than the specified length,
if it exceeds the specified max size and aborts.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D114870
getMetadata() currently uses a weird API where it populates a
structure passed to it, and optionally merges into it. Instead,
we can return the AAMDNodes and provide a separate merge() API.
This makes usages more compact.
Differential Revision: https://reviews.llvm.org/D109852
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
Use LocationSize::upperBound instead of precise since we only know an upper bound on the number of bytes read/written.
Reviewed By: fhahn
Differential Revision: https://reviews.llvm.org/D89885
This patch adds support for memcmp in MemoryLocation::getForArgument.
memcmp reads from the first 2 arguments up to the number of bytes of the
third argument.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D86725
MemoryLocation.h was changed to only include Instruction.h. However,
cast<> still needs the full definiton, so move MemoryLocation::getOrNone
to the cpp file.
This has two main effects:
- Optimizes debug info size by saving 221.86 MB of obj file size in a
Windows optimized+debug build of 'all'. This is 3.03% of 7,332.7MB of
object file size.
- Incremental step towards decoupling target intrinsics.
The enums are still compact, so adding and removing a single
target-specific intrinsic will trigger a rebuild of all of LLVM.
Assigning distinct target id spaces is potential future work.
Part of PR34259
Reviewers: efriedma, echristo, MaskRay
Reviewed By: echristo, MaskRay
Differential Revision: https://reviews.llvm.org/D71320
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
Trying to keep these patches super small so they're easily post-commit
verifiable, as requested in D44748.
This one sadly isn't *super* small, but all of the changes here are
either to:
- libfuncs that are passed a constant size (memcpy, memset, ...)
- instructions that store/load a constant size
So they have to be precise
llvm-svn: 350017
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 third patch in a series intended to make
https://reviews.llvm.org/D44748 more easily reviewable. Please see that
patch for more context. The second being r344013.
The intent is to make the output of printing a LocationSize more
precise. The main motivation for this is that we plan to add a bit to
distinguish whether a given LocationSize is an upper-bound or is
precise; making that information available in pretty-printing is nice.
llvm-svn: 344108
AliasSetTracker has special case handling for memset, memcpy and memmove which pre-existed argmemonly on functions and readonly and writeonly on arguments. This patch generalizes it using the AA infrastructure to any call correctly annotated.
The motivation here is to cut down on confusion, not performance per se. For most instructions, there is a direct mapping to alias set. However, this is not guaranteed by the interface and was not in fact true for these three intrinsics *and only these three intrinsics*. I kept getting myself confused about this invariant, so I figured it would be good to clearly distinguish between a instructions and alias sets. Calls happened to be an easy target.
The nice side effect is that custom implementations of memset/memcpy/memmove - including wrappers discovered by IPO - can now be optimized the same as builts by LICM.
Note: The actual removal of the memset/memtransfer specific handling will happen in a follow on NFC patch. It was originally part of this one, but separate for ease of review and rebase.
Differential Revision: https://reviews.llvm.org/D50730
llvm-svn: 341713
The fix is fairly simple, but is says something unpleasant about the usage and testing of invariant.start/end scopes that this went undetected. To put this in perspective, *any* invariant.end in a loop flowing through LICM crashed. I haven't bothered to figure out just how far back this goes, but it's not caused by any of the recent changes. We're probably talking months if not years.
llvm-svn: 339936
Summary:
This change teaches DSE that the atomic memory intrinsics are stores
that can be eliminated, and can allow other stores to be eliminated.
This change specifically does not teach DSE that these intrinsics
can be partially eliminated (i.e. length reduced, and dest/src changed);
that will be handled in another change.
Reviewers: mkazantsev, skatkov, apilipenko, efriedma, rsmith
Reviewed By: efriedma
Subscribers: dmgreen, llvm-commits
Differential Revision: https://reviews.llvm.org/D45535
llvm-svn: 330629
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
I tried to be as close as possible to the strongest check that
existed before; cleaning these up properly is left for future work.
Differential Revision: http://reviews.llvm.org/D19469
llvm-svn: 267758
virtual interface on AliasAnalysis only deals with ModRef information.
This interface was both computing memory locations by using TLI and
other tricks to estimate the size of memory referenced by an operand,
and computing ModRef information through similar investigations. This
change narrows the scope of the virtual interface on AliasAnalysis
slightly.
Note that all of this code could live in BasicAA, and be done with
a single investigation of the argument, if it weren't for the fact that
the generic code in AliasAnalysis::getModRefBehavior for a callsite
calls into the virtual aspect of (now) getArgModRefInfo. But this
patch's arrangement seems a not terrible way to go for now.
The other interesting wrinkle is how we could reasonably extend LLVM
with support for custom memory location sizes and mod/ref behavior for
library routines. After discussions with Hal on the review, the
conclusion is that this would be best done by fleshing out the much
desired support for extensions to TLI, and support these types of
queries in that interface where we would likely be doing other library
API recognition and analysis.
Differential Revision: http://reviews.llvm.org/D10259
llvm-svn: 239884
port it to the new pass manager.
All this does is extract the inner "location" class used by AA into its
own full fledged type. This seems *much* cleaner as MemoryDependence and
soon MemorySSA also use this heavily, and it doesn't make much sense
being inside the AA infrastructure.
This will also make it much easier to break apart the AA infrastructure
into something that stands on its own rather than using the analysis
group design.
There are a few places where this makes APIs not make sense -- they were
taking an AliasAnalysis pointer just to build locations. I'll try to
clean those up in follow-up commits.
Differential Revision: http://reviews.llvm.org/D10228
llvm-svn: 239003
Nikita Popov