When analysis reaches code with UB at runtime, this write needs to be
ignored to avoid corrupting memory with UB at compile time.
Drive-by finding during review of
https://github.com/llvm/llvm-project/pull/178356.
With the advent of intrinsic-less debug-info, we no longer need to
scatter calls to getPrevNonDebugInstruction around the codebase. Remove
most of them -- there are one or two that have the "SkipPseudoOp" flag
turned on, however they don't seem to be in positions where skipping
anything would be reasonable.
These are identified by misc-include-cleaner. I've filtered out those
that break builds. Also, I'm staying away from llvm-config.h,
config.h, and Compiler.h, which likely cause platform- or
compiler-specific build failures.
This patch addresses clang-tidy's readability-const-return-type by
dropping const from the return type while switching to StringRef at
the same time because these functions just return string constants.
Currently BlockAddresses store both the Function and the BasicBlock they
reference, and the BlockAddress is part of the use list of both the
Function and BasicBlock.
This is quite awkward, because this is not really a use of the function
itself (and walks of function uses generally skip block addresses for
that reason). This also has weird implications on function RAUW (as that
will replace the function in block addresses in a way that generally
doesn't make sense), and causes other peculiar issues, like the ability
to have multiple block addresses for one block (with different
functions).
Instead, I believe it makes more sense to specify only the basic block
and let the function be implied by the BB parent. This does mean that we
may have block addresses without a function (if the BB is not inserted),
but this should only happen during IR construction.
DenseSet, SmallPtrSet, SmallSet, SetVector, and StringSet recently
gained C++23-style insert_range. This patch replaces:
Dest.insert(Src.begin(), Src.end());
with:
Dest.insert_range(Src);
This patch does not touch custom begin like succ_begin for now.
Summary:
This code is intended to block transformations if the call isn't
present, however the way it's coded it silently lets it pass if the
definition doesn't exist at all. This previously was always valid since
we included the runtime as one giant blob so everything was always
there, but now that we want to move towards separate ones, it's not
quite correct.
Add initial parsing/sema support for new assumption clause so clause can
be specified. For now, it's ignored, just like the others.
Added support for 'no_openmp_construct' to release notes.
Testing
- Updated appropriate LIT tests.
- Testing: check-all
Add a new AutoUpgrade function to convert some legacy nvvm.annotations
metadata to function level attributes. These attributes are quicker to
look-up so improve compile time and are more idiomatic than using
metadata which should not include required information that changes the
meaning of the program.
Currently supported annotations are:
- !"kernel" -> ptx_kernel calling convention
- !"align" -> alignstack parameter attributes (return not yet supported)
This patch implements an LLVM IR pass, named kernel-info, that reports
various statistics for codes compiled for GPUs. The ultimate goal of
these statistics to help identify bad code patterns and ways to mitigate
them. The pass operates at the LLVM IR level so that it can, in theory,
support any LLVM-based compiler for programming languages supporting
GPUs. It has been tested so far with LLVM IR generated by Clang for
OpenMP offload codes targeting NVIDIA GPUs and AMD GPUs.
By default, the pass runs at the end of LTO, and options like
``-Rpass=kernel-info`` enable its remarks. Example `opt` and `clang`
command lines appear in `llvm/docs/KernelInfo.rst`. Remarks include
summary statistics (e.g., total size of static allocas) and individual
occurrences (e.g., source location of each alloca). Examples of its
output appear in tests in `llvm/test/Analysis/KernelInfo`.
Specifying a kernel with the `ptx_kernel` or `amdgpu_kernel` calling
convention is a more idiomatic and compile-time performant than using
the `nvvm.annoation !"kernel"` metadata.
Transition OMPIRBuilder to use calling conventions for PTX kernels and
no longer emit `nvvm.annoation`. Update OpenMPOpt to work with kernels
specified via calling convention as well as metadata. Update OpenMP
tests to use the calling conventions.
As part of the "RemoveDIs" project, BasicBlock::iterator now carries a
debug-info bit that's needed when getFirstNonPHI and similar feed into
instruction insertion positions. Call-sites where that's necessary were
updated a year ago; but to ensure some type safety however, we'd like to
have all calls to moveBefore use iterators.
This patch adds a (guaranteed dereferenceable) iterator-taking
moveBefore, and changes a bunch of call-sites where it's obviously safe
to change to use it by just calling getIterator() on an instruction
pointer. A follow-up patch will contain less-obviously-safe changes.
We'll eventually deprecate and remove the instruction-pointer
insertBefore, but not before adding concise documentation of what
considerations are needed (very few).
The preprocessor definition used to enable asserts and the one that
`llvm::Error` and `llvm::Expected` use to ensure all created instances are
checked are not the same. By making these checks inside of an `assert` in cases
where errors are not expected, certain build configurations would trigger
runtime failures (e.g. `-DLLVM_ENABLE_ASSERTIONS=OFF
-DLLVM_UNREACHABLE_OPTIMIZE=ON`).
The `llvm::cantFail()` function, which was intended for this use case, is used
by this patch in place of `assert` to prevent these runtime failures. In tests,
new preprocessor definitions based on `ASSERT_THAT_EXPECTED` and
`EXPECT_THAT_EXPECTED` are used instead, to avoid silent failures in release
builds.
Summary:
We currently have an unnecessary level of indirection when initializing
the RPC client. This is a holdover from when the RPC client was not
trivially copyable and simply makes it more complicated. Here we use the
`asm` syntax to give the C++ variable a valid name so that we can just
copy to it directly.
Another advantage to this, is that if users want to piggy-back on the
same RPC interface they need only declare theirs as extern with the same
symbol name, or make it weak to optionally use it if LIBC isn't
avaialb.e
This patch implements an approach to communicate errors between the
OMPIRBuilder and its users. It introduces `llvm::Error` and
`llvm::Expected` objects to replace the values returned by callbacks
passed to `OMPIRBuilder` codegen functions. These functions then check
the result for errors when callbacks are called and forward them back to
the caller, which has the flexibility to recover, exit cleanly or dump a
stack trace.
This prevents a failed callback to leave the IR in an invalid state and
still continue the codegen process, triggering unrelated assertions or
segmentation faults. In the case of MLIR to LLVM IR translation of the
'omp' dialect, this change results in the compiler emitting errors and
exiting early instead of triggering a crash for not-yet-implemented
errors. The behavior in Clang and openmp-opt stays unchanged, since
callbacks will continue always returning 'success'.
This patch ensures the `IsGPU` flag is set by the OpenMPOpt pass, so
that it can be relied upon by `OpenMPIRBuilder` methods when called by
that pass as well.
Since currently there are very limited callers for the
`OpenMPIRBuilder::isGPU()` method, no assertions are being triggered by
the lack of initialization of this flag. However, when more
offloading-related features are implemented, it will eventually start
happening.
If we can't transform the region to SPMD, we should not wait till the
end to decide that. Other AAs might assume SPMD, and we did set the
constant initializer to indicate SPMD, but we did not change the code
properly.
This reverts commit e592c2dcf5b7d2da6c2564f5d9990aa34079bad4.
We can finally reland the PR since the issue that caused the PR to be
reverted has been resolved in
https://github.com/llvm/llvm-project/pull/104051.
We don't have any legacy pass manager CGSCC passes that modify the call
graph (we only use it in the codegen pipeline to run function passes in
call graph order). This is the beginning of removing CallGraphUpdater
and making all the relevant CGSCC passes directly use the new pass
manager APIs.
Since `raw_string_ostream` doesn't own the string buffer, it is
desirable (in terms of memory safety) for users to directly reference
the string buffer rather than use `raw_string_ostream::str()`.
Work towards TODO comment to remove `raw_string_ostream::str()`.
This is a helper to avoid writing `getModule()->getDataLayout()`. I
regularly try to use this method only to remember it doesn't exist...
`getModule()->getDataLayout()` is also a common (the most common?)
reason why code has to include the Module.h header.
Uses the new InsertPosition class (added in #94226) to simplify some of
the IRBuilder interface, and removes the need to pass a BasicBlock
alongside a BasicBlock::iterator, using the fact that we can now get the
parent basic block from the iterator even if it points to the sentinel.
This patch removes the BasicBlock argument from each constructor or call
to setInsertPoint.
This has no functional effect, but later on as we look to remove the
`Instruction *InsertBefore` argument from instruction-creation
(discussed
[here](https://discourse.llvm.org/t/psa-instruction-constructors-changing-to-iterator-only-insertion/77845)),
this will simplify the process by allowing us to deprecate the
InsertPosition constructor directly and catch all the cases where we use
instructions rather than iterators.
This is a followup to #81014 and #84582: Before this patch, Clang
would accept `__attribute__((assume))` and `[[clang::assume]]` as
nonstandard spellings for the `[[omp::assume]]` attribute; this
resulted in a potentially very confusing name clash with C++23’s
`[[assume]]` attribute (and GCC’s `assume` attribute with the same
semantics).
This pr replaces every usage of `__attribute__((assume))` with
`[[omp::assume]]` and makes `__attribute__((assume))` and
`[[clang::assume]]` alternative spellings for C++23’s `[[assume]]`;
this shouldn’t cause any problems due to differences in appertainment
and because almost no-one was using this variant spelling to begin
with (a use in libclc has already been changed to use a different
attribute).
As part of the RemoveDIs project we need LLVM to insert instructions using
iterators wherever possible, so that the iterators can carry a bit of
debug-info. This commit implements some of that by updating the contents of
llvm/lib/Transforms/Utils to always use iterator-versions of instruction
constructors.
There are two general flavours of update:
* Almost all call-sites just call getIterator on an instruction
* Several make use of an existing iterator (scenarios where the code is
actually significant for debug-info)
The underlying logic is that any call to getFirstInsertionPt or similar
APIs that identify the start of a block need to have that iterator passed
directly to the insertion function, without being converted to a bare
Instruction pointer along the way.
Noteworthy changes:
* FindInsertedValue now takes an optional iterator rather than an
instruction pointer, as we need to always insert with iterators,
* I've added a few iterator-taking versions of some value-tracking and
DomTree methods -- they just unwrap the iterator. These are purely
convenience methods to avoid extra syntax in some passes.
* A few calls to getNextNode become std::next instead (to keep in the
theme of using iterators for positions),
* SeparateConstOffsetFromGEP has it's insertion-position field changed.
Noteworthy because it's not a purely localised spelling change.
All this should be NFC.
The deduplication of the calls to `omp_get_thread_limit` used to be
legal when originally added in
<e28936f613 (diff-de101c82aff66b2bda2d1f53fde3dde7b0d370f14f1ff37b7919ce38531230dfR123)>,
as the result (thread_limit) was immutable.
However, now that we have `thread_limit` clause, we no longer have
immutability; therefore `omp_get_thread_limit()` is not a deduplicable
runtime call.
Thus, removing `omp_get_thread_limit` from the
`DeduplicableRuntimeCallIDs` array.
Here's a simple example:
```
#include <omp.h>
#include <stdio.h>
int main()
{
#pragma omp target thread_limit(4)
{
printf("\n1:target thread_limit: %d\n", omp_get_thread_limit());
}
#pragma omp target thread_limit(3)
{
printf("\n2:target thread_limit: %d\n", omp_get_thread_limit());
}
return 0;
}
```
GCC-compiled binary execution: https://gcc.godbolt.org/z/Pjv3TWoTq
```
1:target thread_limit: 4
2:target thread_limit: 3
```
Clang/LLVM-compiled binary execution:
https://clang.godbolt.org/z/zdPbrdMPn
```
1:target thread_limit: 4
2:target thread_limit: 4
```
By my reading of the OpenMP spec GCC does the right thing here; cf.
<https://www.openmp.org/spec-html/5.2/openmpse12.html#x34-330002.4>:
> If a target construct with a thread_limit clause is encountered, the
thread-limit-var ICV from the data environment of the generated initial
task is instead set to an implementation defined value between one and
the value specified in the clause.
The common subexpression elimination (CSE) of the second call to
`omp_get_thread_limit` by LLVM does not seem to be correct, as it's not
an available expression at any program point(s) (in the scope of the
clause in question) after the second target construct with a
`thread_limit` clause is encountered.
Compiling with `-Rpass=openmp-opt -Rpass-analysis=openmp-opt
-Rpass-missed=openmp-opt` we have:
https://clang.godbolt.org/z/G7dfhP7jh
```
<source>:8:42: remark: OpenMP runtime call omp_get_thread_limit deduplicated. [OMP170] [-Rpass=openmp-opt]
8 | printf("\n1:target thread_limit: %d\n",omp_get_thread_limit());
| ^
```
OMP170 has the following explanation:
https://openmp.llvm.org/remarks/OMP170.html
> This optimization remark indicates that a call to an OpenMP runtime
call was replaced with the result of an existing one. This occurs when
the compiler knows that the result of a runtime call is immutable.
Removing duplicate calls is done by replacing all calls to that function
with the result of the first call. This cannot be done automatically by
the compiler because the implementations of the OpenMP runtime calls
live in a separate library the compiler cannot see.
This optimization will trigger for known OpenMP runtime calls whose
return value will not change.
At the same time I do not believe we have an analysis checking whether
this precondition holds here: "This occurs when the compiler knows that
the result of a runtime call is immutable."
AFAICT, such analysis doesn't appear to exist in the original patch
introducing deduplication, either:
-
9548b74a83
- https://reviews.llvm.org/D69930
The fix is to remove it from `DeduplicableRuntimeCallIDs`, effectively
reverting the addition in this commit (noting that `omp_get_max_threads`
is not present in `DeduplicableRuntimeCallIDs`, so it's possible this
addition was incorrect in the first place):
- [OpenMP][Opt] Annotate known runtime functions and deduplicate more,
-
e28936f613 (diff-de101c82aff66b2bda2d1f53fde3dde7b0d370f14f1ff37b7919ce38531230dfR123)
As a result, we're no longer unsoundly deduplicating the OpenMP runtime
call `omp_get_thread_limit` as illustrated by the test case: Note the
(correctly) repeated `call i32 @omp_get_thread_limit()`.
---------
Co-authored-by: Joseph Huber <huberjn@outlook.com>
Using the LoopInfo from OMPInfoCache after the Attributor ran resulted
in a crash due to it being in an invalid state.
---------
Co-authored-by: Ivan Radanov Ivanov <ivanov2@llnl.gov>
The specialisation will not be valid when ConstantInt gains native
support for vector types.
This is largely a mechanical change but with extra attention paid to constant
folding, InstCombineVectorOps.cpp, LoopFlatten.cpp and Verifier.cpp to
remove the need to call `getIntegerType()`.
Co-authored-by: Nikita Popov <github@npopov.com>
* Remove a call to CreatePointerBitCastOrAddrSpaceCast which merely adds
a no-op ptr-to-ptr bitcast.
* Most of the diff is from removing checks for no-op ptr-to-ptr bitcasts
in relevant LIT tests
Added support for LLVM IR code generation which is used for handling omp
target parallel code. The call for __kmpc_parallel_51 is generated and
the parallel region is outlined to separate function.
The proper setup of kmpc_target_init mode is not included in the commit.
It is assumed that the SPMD mode for target initialization is properly
set by other codegen functions.
Summary:
Part of the work done in the `libc` project is to provide host services
for things like `printf` or `malloc`, or generally any syscall-like
behaviour. This scheme works by emitting an externally visible global
called `__llvm_libc_rpc_client` that the host runtime can pick up to get
a handle to the global memory associated with the client. We use the
presence of this symbol to indicate whether or not we need to run an RPC
server. Normally, this symbol is only present if something requiring an
RPC server was linked in, such as `printf`. However, if this call to
`printf` was subsequently optimizated out, the symbol would remain and
cannot be removed (rightfully so) because of its linkage. This patch
adds a special-case optimization to remove this symbol so we can
indicate that an RPC server is no longer needed.
This patch puts this logic in `OpenMPOpt` as the most readily available
place for it. In the future, we should think how to move this somewhere
more generic. Furthermore, we use a hard-coded runtime name (which isn't
uncommon given all the other magic symbol names). But it might be nice
to abstract that part away.
