This PR removes the old `nocapture` attribute, replacing it with the new
`captures` attribute introduced in #116990. This change is
intended to be essentially NFC, replacing existing uses of `nocapture`
with `captures(none)` without adding any new analysis capabilities.
Making use of non-`none` values is left for a followup.
Some notes:
* `nocapture` will be upgraded to `captures(none)` by the bitcode
reader.
* `nocapture` will also be upgraded by the textual IR reader. This is to
make it easier to use old IR files and somewhat reduce the test churn in
this PR.
* Helper APIs like `doesNotCapture()` will check for `captures(none)`.
* MLIR import will convert `captures(none)` into an `llvm.nocapture`
attribute. The representation in the LLVM IR dialect should be updated
separately.
Since byval arguments are passed via a hidden copy of the pointee, they
do not have the same semantics as normal pointer arguments. The callee
cannot capture or write to the pointer and the copy is a read of the
pointer.
This patch fixes a couple of places where memprof-related metadata
(!memprof and !callsite) were being dropped, and one place where PGO
metadata (!prof) was being dropped.
All were due to instances of combineMetadata() being invoked. That
function drops all metadata not in the list provided by the client, and
also drops any not in its switch statement.
Memprof metadata needed a case in the combineMetadata switch statement.
For now we simply keep the metadata of the instruction being kept, which
doesn't retain all the profile information when two calls with
memprof metadata are being combined, but at least retains some.
For the memprof metadata being dropped during call CSE, add memprof and
callsite metadata to the list of known ids in combineMetadataForCSE.
Neither memprof nor regular prof metadata were in the list of known ids
for the callsite in MemCpyOptimizer, which was added to combine AA
metadata after optimization of byval arguments fed by memcpy
instructions, and similar types of optimizations of memcpy uses.
There is one other callsite of combineMetadata, but it is only invoked
on load instructions, which do not carry these types of metadata.
Pass EarliestEscapeInfo to BatchAA in MemCpyOpt. This allows memcpy
elimination in cases where one of the involved pointers is captured
after the relevant memcpy/call.
We currently elide memcpys for readonly nocapture noalias arguments.
noalias is checked to make sure that there are no other ways to write
the memory, e.g. through a different argument or an escaped pointer.
In addition to the current noalias check, also query alias analysis, in
case it can prove that modification is not possible through other means.
This fixes the problem reported in
https://discourse.llvm.org/t/problem-about-memcpy-elimination/81121.
This patch is moving out stepvector intrinsic from the experimental
namespace.
This intrinsic exists in LLVM for several years now, and is widely used.
For the case where the memcpy size is zero, this transform is a complex
no-op. This can lead to an infinite loop when the size is zero in a way
that BasicAA understands, because it can still understand that dst and
dst + src_size are MustAlias.
I've tried to mitigate this before using the isZeroSize() check, but we
can hit cases where InstSimplify doesn't understand that the size is
zero, but BasicAA does.
As such, this bites the bullet and adds an explicit isKnownNonZero()
check to guard against no-op transforms.
Fixes https://github.com/llvm/llvm-project/issues/98610.
This patch makes the final major change of the RemoveDIs project, changing the
default IR output from debug intrinsics to debug records. This is expected to
break a large number of tests: every single one that tests for uses or
declarations of debug intrinsics and does not explicitly disable writing
records.
If this patch has broken your downstream tests (or upstream tests on a
configuration I wasn't able to run):
1. If you need to immediately unblock a build, pass
`--write-experimental-debuginfo=false` to LLVM's option processing for all
failing tests (remember to use `-mllvm` for clang/flang to forward arguments to
LLVM).
2. For most test failures, the changes are trivial and mechanical, enough that
they can be done by script; see the migration guide for a guide on how to do
this: https://llvm.org/docs/RemoveDIsDebugInfo.html#test-updates
3. If any tests fail for reasons other than FileCheck check lines that need
updating, such as assertion failures, that is most likely a real bug with this
patch and should be reported as such.
For more information, see the recent PSA:
https://discourse.llvm.org/t/psa-ir-output-changing-from-debug-intrinsics-to-debug-records/79578
This is mostly NFC but some output does change due to consistently
inserting into poison rather than undef and using i64 as the index
type for inserts.
Without this change, the included test cases crash the compiler. I
believe this is fallout from the homogenous scalable struct work from a
while back; I think we just forgot to update this case.
Likely to fix https://github.com/llvm/llvm-project/issues/80463.
Add the `dead_on_unwind` attribute, which states that the caller will
not read from this argument if the call unwinds. This allows eliding
stores that could otherwise be visible on the unwind path, for example:
```
declare void @may_unwind()
define void @src(ptr noalias dead_on_unwind %out) {
store i32 0, ptr %out
call void @may_unwind()
store i32 1, ptr %out
ret void
}
define void @tgt(ptr noalias dead_on_unwind %out) {
call void @may_unwind()
store i32 1, ptr %out
ret void
}
```
The optimization is not valid without `dead_on_unwind`, because the `i32
0` value might be read if `@may_unwind` unwinds.
This attribute is primarily intended to be used on sret arguments. In
fact, I previously wanted to change the semantics of sret to include
this "no read after unwind" property (see D116998), but based on the
feedback there it is better to keep these attributes orthogonal (sret is
an ABI attribute, dead_on_unwind is an optimization attribute). This is
a reboot of that change with a separate attribute.
Debugify is extremely useful as a testing and debugging tool, and a good
number of LLVM-IR transform tests use it. We need it to support "new"
non-instruction debug-info to get test coverage, but it's not important
enough to completely convert right now (and it'd be a large
undertaking). Thus: convert to/from dbg.value/DPValue mode on entry and
exit of the pass, which gives us the functionality without any further
work. The cost is compile-time, but again this is only happening during
tests.
Tested by: the large set of debugify tests enabled here. Note the
InstCombine test (cast-mul-select.ll) that hasn't been fully enabled:
this is because there's a debug-info sinking piece of code there that
hasn't been instrumented.
Call slot optimization may introduce writes to the destination object
that occur earlier than in the original function. We currently already
check that that the destination is dereferenceable and aligned, but we
do not make sure that it is writable. As such, we might introduce a
write to read-only memory, or introduce a data race.
Fix this by checking that the object is writable. For arguments, this is
indicated by the new writable attribute. Tests using
sret/dereferenceable are updated to use it.
There are many tests that specify a target triple/CPU flags but no
DataLayout which can lead to IR being generated that has unusual
behaviour. This commit attempts to use the default DataLayout based
on the relevant flags if there is no explicit override on the command
line or in the IR file.
One thing that is not currently possible to differentiate from a missing
datalayout `target datalayout = ""` in the IR file since the current
APIs don't allow detecting this case. If it is considered useful to
support this case (instead of passing "-data-layout=" on the command
line), I can change IR parsers to track whether they have seen such a
directive and change the callback type.
Differential Revision: https://reviews.llvm.org/D141060
Relocate the GEP modification to a later stage of the function
performCallSlotOptzn(), ensuring that the code remains unchanged if the
optimization fails.
Co-authored-by: aklkaiyan <aklkaiyan@tencent.com>
…ptzn.
This changes performStackMoveOptzn to take a TypeSize instead of
uint64_t to avoid an implicit conversion when called from
processStoreOfLoad.
performStackMoveOptzn has been updated to allow scalable types in the
rest of its code.
Stack-move optimization, the optimization that merges src and dest
alloca of the full-size copy, replaces all uses of the dest alloca with
src alloca. For safety, we needed to check all uses of the dest alloca
locations are dominated by src alloca, to be replaced. This PR adds the
check for that.
Fixes#65225
This adds an additional transform to drop zero-size memcpys, also in
the case where the size is only zero after instruction simplification.
The motivation is the case from PR54983 where the size is non-trivially
zero, and processMemSetMemCpyDependence() keeps trying to reduce the
memset size by zero bytes.
This fix it's not really principled. It only works on the premise that
if InstSimplify doesn't realize the size is zero, then AA also won't.
The principled approach would be to instead add a isKnownNonZero()
guard to the processMemSetMemCpyDependence() transform, but I
suspect that would render that optimization mostly useless (at least
it breaks all the existing test coverage -- worth noting that the
constant size case is also handled by DSE, so I think this transform
is primarily about the dynamic size case).
Fixes https://github.com/llvm/llvm-project/issues/54983.
Fixes https://github.com/llvm/llvm-project/issues/64886.
Differential Revision: https://reviews.llvm.org/D124078
This reverts commit 3bb32c61b2f1f5d14dd056dd198dc898dce5a44e.
Use InsertionPt for DT to handle non-memory access dominators
Differential Revision: https://reviews.llvm.org/D155406
