When we run the CGSCC pass we should only invest time on the SCC. We can
initialize AAs with information from the module slice but we should not
update those AAs. We make an exception for are call site of the SCC as
they are helpful providing information for the SCC.
Minor modifications to pointer privatization allow us to perform it even
in the CGSCC pass, similar to ArgumentPromotion.
When we run the CGSCC pass we should only invest time on the SCC. We can
initialize AAs with information from the module slice but we should not
update those AAs.
The Attributor, as many other parts in LLVM, uses pointer equivalence
for `llvm::Value`s. This only works as long as `llvm::Value`s are
dynamically unique, or, to be exact, we will never end up with the same
`llvm::Value` representing two dynamic instances. We already provided a
helper to check the former, namely `AA::isDynamicallyUnique`, however we
could not check the latter. In this patch we move the logic into a
separate AA which helps with the growing complexity and use cases. We
also extend the interface to answer the second question rather than the
first. So we do not determine dynamically uniqueness but if we might end
up with the `llvm::Value` describing a different dynamic instance. Note
that the latter is very much tied to the Attributor capabilities to look
through memory, recursion, etc. so we need to update the logic as we go.
We look through loads in the "generic value traversal" and we
consequently don't need to look through them again in AAValueSimplify*.
The test changes stem from the fact that we allowed any simplified
value, incl. non-dynamically unique ones, as long as the underlying
memory was an alloca. This doesn't seem to make sense as allocas do not
protect against dynamically non-unique values. We need to make the
unique check better rather than excluding allocas. That in mind, we can
remove a lot of code by simply relying on the generic value traversal
load look through.
To soften the blow some minor adjustments have been made that allow more
simplification through the now used scheme and some tests have been
given a `norecurse` for now.
Prior to this change, CallBase::hasFnAttr checked the called function to
see if it had an attribute if it wasn't set on the CallBase, but
getFnAttr didn't do the same delegation, which led to very confusing
behavior. This patch fixes the issue by making CallBase::getFnAttr also
check the function under the same circumstances.
Test changes look (to me) like they're cleaning up redundant attributes
which no longer get specified both on the callee and call. We also clean
up the one ad-hoc implementation of this getter over in InlineCost.cpp.
Differential Revision: https://reviews.llvm.org/D122821
Most intrinsics, especially "default" ones, will not call back into the
IR module. `nocallback` encodes this nicely. As it was not used before,
this patch also makes use of `nocallback` in the Attributor which
results in many more `norecurse` deductions.
Tablegen part is mechanical, test updates by script.
Differential Revision: https://reviews.llvm.org/D118680
There is potential for endless recursion if we try to determine the
underlying objects of a load, just to end up with the load as underlying
object. A proper solution will require us to pass a visited set around.
This will happen as we cleanup genericValueTraversal soon.
With debug information enabled (-g) Clang will wrap the actual target
region into a new function which is called from the "kernel". The problem
is that the "kernel" is now basically a wrapper without all the things
we expect. More importantly, if we end up asking for an AAKernelInfo
for the "target region function" we might try to turn it into SPMD mode.
That used to cause an assertion as that function doesn't have an
appropriately named `_exec_mode` global. While the global is going away
soon we still need to make sure to properly handle this case, e.g.,
perform optimizations reliably.
Differential Revision: https://reviews.llvm.org/D122043
Hardcode the function type as ParallelTask, which is the guaranteed
pointee type of this runtime function argument (if pointee types
exist). The elimination of the callee bitcast is left for InstCombine.
Differential Revision: https://reviews.llvm.org/D120885
Outside users of the Attributor, e.g., OpenMP-opt, want to seed AAs
themselves. We should not seed all default AAs one an internal function
becomes live. That said, there should be a callback such that they can
do lazy seeding as well.
Differential Revision: https://reviews.llvm.org/D121489
We already look through memory to determine where a value that is stored
might pop up again (potential copies). This patch introduces the other
direction with similar logic. If a value is loaded, we can follow all
the accesses to the pointer (or better object) and try to determine what
value might have been stored.
Both `undef` and `nullptr` are maximally aligned. This is especially
important as we often see `undef` until a proper value has been
identified during simplification.
Heap-2-stack and heap-2-shared can replace an allocation call with
something else. To avoid us deriving information from the allocator
implementation we register a simplification callback now that will
force us to stop at the call site. We probably should create the
replacement memory eagerly and return that instead though.
This is the second step in obviating two columns about allocation
functions in MemoryBuiltins.cpp.
Differential Revision: https://reviews.llvm.org/D119583
The custom state machine had a check for surplus threads that filtered
the main thread if the kernel was executed by a single warp only. We
now first check for the main thread, then for surplus threads, avoiding
to filter the former out.
Fixes#54214.
Reviewed By: jhuber6
Differential Revision: https://reviews.llvm.org/D121011
One of the optimizations performed in OpenMPOpt pushes globalized
variables to static shared memory. This is preferable to keeping the
runtime call in all cases, however if too many variables are pushed to
hared memory the kernel will crash. Since this is an optimization and
not something the user specified explicitly, there should be an option
to limit this optimization in those cases. This path introduces the
`-openmp-opt-shared-limit=` option to limit the amount of bytes that
will be placed in shared memory from HeapToShared.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D120079
This patch adds the '_kmpc_get_hardware_num_threads_in_block'
OpenMP RTL function to the externalization RAII struct. This was getting
optimized out and then being replaced with an undefined value once added
back in, causing bugs for complex reductions.
Fixes#53909.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D120076
When we move an allocation from the heap to the stack we need to
allocate it in the alloca AS and then cast the result. This also
prevents us from inserting the alloca after the allocation call but
rather right before.
Fixes https://github.com/llvm/llvm-project/issues/53858
`UsedAssumedInformation` is a return argument utilized to determine what
information is known. Most APIs used it already but
`genericValueTraversal` did not. This adds it to `genericValueTraversal`
and replaces `AllCallSitesKnown` of `checkForAllCallSites` with the
commonly used `UsedAssumedInformation`.
This was supposed to be a NFC commit, then the test change appeared.
Turns out, we had one user of `AllCallSitesKnown` (AANoReturn) and the
way we set `AllCallSitesKnown` was wrong as we ignored the fact some
call sites were optimistically assumed dead. Included a dedicated test
for this as well now.
Fixes https://github.com/llvm/llvm-project/issues/53884
If we assume `llvm.amdgcn.s.barrier` is aligned we may remove it and
cause OpenMP GPU applications on the AMD GPU to be stuck or wrongly
synchronized.
Reported by Carlo Bertolli.
The oversight caused us to ignore call sites that are effectively dead
when we computed reachability (or more precise the call edges of a
function). The problem is that loads in the readonly callee might depend
on stores prior to the callee. If we do not track the call edge we
mistakenly assumed the store before the call cannot reach the load.
The problem is nicely visible in:
`llvm/test/Transforms/Attributor/ArgumentPromotion/basictest.ll`
Caused by D118673.
Fixes https://github.com/llvm/llvm-project/issues/53726
Changes the remark to emit on the function call that captures the globalized
variable instead of the globalized variable itself. The user should be able to
see which variable it was in the argument list of the function.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D106980
We missed out on AANoRecurse in the module pass because we had no call
graph. With AAFunctionReachability we can simply ask if the function may
reach itself.
Differential Revision: https://reviews.llvm.org/D110099
This fixes a conceptual problem with our AAIsDead usage which conflated
call site liveness with call site return value liveness. Without the
fix tests would obviously miscompile as we make genericValueTraversal
more powerful (in a follow up). The effects on the tests are mixed but
mostly marginal. The most prominent one is the lack of `noreturn` for
functions. The reason is that we make entire blocks live at the same
time (for time reasons). Now that we actually look at the block
liveness, which we need to do, the return instructions are live and
will survive. As an example, `noreturn_async.ll` has been modified
to retain the `noreturn` even with block granularity. We could address
this easily but there is little need in practice.
Patch originally by Giorgis Georgakoudis (@ggeorgakoudis), typos and
bugs introduced later by me.
This patch allows us to remove redundant barriers if they are part
of a "consecutive" pair of barriers in a basic block with no impacted
memory effect (read or write) in-between them. Memory accesses to
local (=thread private) or constant memory are allowed to appear.
Technically we could also allow any other memory that is not used to
share information between threads, e.g., the result of a malloc that
is also not captured. However, it will be easier to do more reasoning
once the code is put into an AA. That will also allow us to look through
phis/selects reasonably. At that point we should also deal with calls,
barriers in different blocks, and other complexities.
Differential Revision: https://reviews.llvm.org/D118002
We used to remove noinline from known OpenMP runtime functions (which
are declared in OMPKinds.td). Now we remove noinline from all functions
with the proper prefixes: __kmpc, _ZN4_OMP (= namespace omp), omp_
Summary:
This patch modifies code generation in OpenMPIRBuilder to pass arguments
to the parallel region outlined function in an aggregate (struct),
besides the global_tid and bound_tid arguments. It depends on the
updated CodeExtractor (see D96854) for support. It mirrors functionality
of Clang codegen (see D102107).
Differential Revision: https://reviews.llvm.org/D110114
Currenly we push some variables to a global constant containing shared
memory as an optimization. This generated constant had internal linkage
and should not have collided with any known identifiers in the
translation unit. However, there have been observed cases of this
optimiztaion unintentionally colliding with undocumented PTX
identifiers. This patch adds a suffix to the created globals to
hopefully bypass this.
Depends on D118059
Reviewed By: tianshilei1992
Differential Revision: https://reviews.llvm.org/D118068
Previously in OpenMPOpt we did not correctly inherit the calling
convention of the callee when creating new OpenMP runtime calls. This
created issues when the calling convention was changed during
`GlobalOpt` but a new call was creating without the correct calling
convention. This lead to the call being replaced with a poison value in
`InstCombine` due to undefined behaviour and causing large portions of
the program to be incorrectly eliminated. This patch correctly inherits
the existing calling convention from the callee.
Reviewed By: tianshilei1992, jdoerfert
Differential Revision: https://reviews.llvm.org/D118059
While we might know the value if an ICV at a getter position it is not
always clear that we can simply use it. Verify the value is valid first
to avoid invalid IR.
Fixes#53300.
Similar to loads, we want to be aggressive when it comes to store
simplification. Not everything in LLVM handles dead stores well when
address space casts are involved, we can simply ask the Attributor to do
it for us though.
Reviewed By: tianshilei1992
Differential Revision: https://reviews.llvm.org/D109998
One of the unused ident_t fields now holds the size of the string
(=const char *) field so we have an easier time dealing with those
in the future.
Differential Revision: https://reviews.llvm.org/D113126
This patch uses the return alignment attribute now present in the
`__kmpc_alloc_shared` runtime call to set the alignment of the shared
memory global created to replace it.
Depends on D115971
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D116319
Before SPMDzation it was sufficient to add an incompatible instruction
to the SPMDCompatibilityTracker. However, now adding instructions means
they need guarding. As calls cannot be guarded in general we need to
explicitly prevent SPMD mode.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D115158
If two reaching kernels disagree on the execution mode we cannot guard a
function right now. Ensure we do not as we otherwise will cause a
deadlock.
Reviewed By: JonChesterfield
Differential Revision: https://reviews.llvm.org/D114866
This patch uses the abstract attributor introduced in D111054 to get the
assumption values instead of the `hasAssumption` function. This also
calls it so assumption information should propagate throug the device
where applicabile.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D111445
If we assume SPMD-mode during the fixpoint iteration we have to execute
the kernel in SPMD-mode. If we change our mind during manifest there is
the chance of a mismatch between the simplification, e.g., of
`__kmpc_is_spmd_exec_mode` calls, and the execution mode. This problem
was introduced in D109438.
This patch is compromise to resolve the problem purely in OpenMP-opt
while trying to keep the benefits of D109438 around. This might not
always work, see `get_hardware_num_threads_in_block_fold` but it often
does. At the same time we do keep value specialization and execution
mode in sync.
Proper solutions to this problem should be considered. I believe a new
execution mode is the easiest way forward (Singleton-SPMD).
Alternatively, SPMD-mode execution can be used with a way to provide a
new thread_limit (here 1) to the runtime. This is more general and could
be useful if we see `num_threads` clauses or workshared loops with small
trip counts in the kernel. In either proposal we need to disable the
guarding for the kernel (which was the motivation for D109438).
Reviewed By: jhuber6
Differential Revision: https://reviews.llvm.org/D112894
Before we had aligned barriers the `__kmpc_barrier_simple_spmd` was
OK to be used in the custom state machine. Now that SPMD barriers are
assumed to be aligned we need to use a "generic" barrier in places
that are not aligned.
Reviewed By: tianshilei1992
Differential Revision: https://reviews.llvm.org/D112893
A lot of NVVM intrinsics can use the default intrinsic attributes (e.g.,
nosync, nofree, ...) as well as `speculatable`. The latter is important
if we want to recompute intrinsics results instead of communicating them
via memory.
I did use default attributes for almost all `readnone` attributes but
speculatable only where I had reasonable confidence they cannot
experience UB. That said, someone should double check.
TODO: There seem to be various intrinsics marked `Commutative` which
should not, e.g., fma and div.
Reviewed By: tra
Differential Revision: https://reviews.llvm.org/D109987
When we strip and accumulate constant offsets we need to pick the right
address space such that the offset APInt has the right bit width.
Reviewed By: JonChesterfield
Differential Revision: https://reviews.llvm.org/D112544
Currently the max alignment representable is 1GB, see D108661.
Setting the align of an object to 4GB is desirable in some cases to make sure the lower 32 bits are clear which can be used for some optimizations, e.g. https://crbug.com/1016945.
This uses an extra bit in instructions that carry an alignment. We can store 15 bits of "free" information, and with this change some instructions (e.g. AtomicCmpXchgInst) use 14 bits.
We can increase the max alignment representable above 4GB (up to 2^62) since we're only using 33 of the 64 values, but I've just limited it to 4GB for now.
The one place we have to update the bitcode format is for the alloca instruction. It stores its alignment into 5 bits of a 32 bit bitfield. I've added another field which is 8 bits and should be future proof for a while. For backward compatibility, we check if the old field has a value and use that, otherwise use the new field.
Updating clang's max allowed alignment will come in a future patch.
Reviewed By: hans
Differential Revision: https://reviews.llvm.org/D110451
Currently the max alignment representable is 1GB, see D108661.
Setting the align of an object to 4GB is desirable in some cases to make sure the lower 32 bits are clear which can be used for some optimizations, e.g. https://crbug.com/1016945.
This uses an extra bit in instructions that carry an alignment. We can store 15 bits of "free" information, and with this change some instructions (e.g. AtomicCmpXchgInst) use 14 bits.
We can increase the max alignment representable above 4GB (up to 2^62) since we're only using 33 of the 64 values, but I've just limited it to 4GB for now.
The one place we have to update the bitcode format is for the alloca instruction. It stores its alignment into 5 bits of a 32 bit bitfield. I've added another field which is 8 bits and should be future proof for a while. For backward compatibility, we check if the old field has a value and use that, otherwise use the new field.
Updating clang's max allowed alignment will come in a future patch.
Reviewed By: hans
Differential Revision: https://reviews.llvm.org/D110451
