I think byval/sret and the others are close to being able to rip out
the code to support the missing type case. A lot of this code is
shared with inalloca, so catch this up to the others so that can
happen.
These intrinsics don't need to be marked as arbitrary writing,
it's sufficient to write inaccessible memory (aka "side effect")
to preserve control dependencies. This means less special-casing
in BasicAA. This is intended as an alternative to D98925.
Differential Revision: https://reviews.llvm.org/D99022
Since D86233 we have `mustprogress` which, in combination with
`readonly`, implies `willreturn`. The idea is that every side-effect
has to be modeled as a "write". Consequently, `readonly` means there
is no side-effect, and `mustprogress` guarantees that we cannot "loop"
forever without side-effect.
Reviewed By: fhahn
Differential Revision: https://reviews.llvm.org/D94125
The update_test_checks script can now check for global symbols and is able
to handle them properly when they differ across prefixes, e.g.,
attribute #0 might be different in different runs.
This patch simply updates all the Attributor tests with the new script.
Reviewed By: sstefan1
Differential Revision: https://reviews.llvm.org/D97906
This patch makes uses of the context bridges introduced in D83299 to make
AAValueConstantRange call site specific.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D83744
We don't need a bool and an enum to express the three options we
currently have. This makes the interface nicer and much easier to
use optional dependencies. Also avoids mistakes where the bool is
false and enum ignored.
This is a follow-up of D95238's LangRef update.
This patch updates `programUndefinedIfUndefOrPoison(V)` to return true if
`V` is used by any memory-accessing instruction.
Interestingly, this affected many tests in Attributors, mainly about adding noundefs.
The tests are updated using llvm/utils/update_test_checks.py. I checked that the diffs
are about updating noundefs.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D96642
This was reported as PR49104. The reproducer uses varargs but the issue
is the same, we know an argument is dead but can't change the signature
for some reason. The PR49104 situation was: We are in an CG-SCC
traversal and we remove all the uses of an argument and proof it thereby
dead. However, if we do not remove the argument, via signature rewrite,
we need to ensure that the `undef` we introduce at the call site doesn't
clash with a `noundef` attribute.
Link: https://lists.llvm.org/pipermail/llvm-dev/2020-October/146162.html "[RFC] FileCheck: (dis)allowing unused prefixes"
If a downstream project using lit needs time for transition,
add the following to `lit.local.cfg`:
```
from lit.llvm.subst import ToolSubst
fc = ToolSubst('FileCheck', unresolved='fatal')
config.substitutions.insert(0, (fc.regex, 'FileCheck --allow-unused-prefixes'))
```
Differential Revision: https://reviews.llvm.org/D95849
This is similar to D94106, but for the
isGuaranteedToTransferExecutionToSuccessor() helper. We should not
assume that readonly functions will return, as this is only true for
mustprogress functions (in which case we already infer willreturn).
As with the DCE change, for now continue assuming that readonly
intrinsics will return, as not all target intrinsics have been
annotated yet.
Differential Revision: https://reviews.llvm.org/D95288
With the addition of the `willreturn` attribute, functions that may
not return (e.g. due to an infinite loop) are well defined, if they are
not marked as `willreturn`.
This patch updates `wouldInstructionBeTriviallyDead` to not consider
calls that may not return as dead.
This patch still provides an escape hatch for intrinsics, which are
still assumed as willreturn unconditionally. It will be removed once
all intrinsics definitions have been reviewed and updated.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D94106
Currently LLVM is relying on ValueTracking's `isKnownNonZero` to attach `nonnull`, which can return true when the value is poison.
To make the semantics of `nonnull` consistent with the behavior of `isKnownNonZero`, this makes the semantics of `nonnull` to accept poison, and return poison if the input pointer isn't null.
This makes many transformations like below legal:
```
%p = gep inbounds %x, 1 ; % p is non-null pointer or poison
call void @f(%p) ; instcombine converts this to call void @f(nonnull %p)
```
Instead, this semantics makes propagation of `nonnull` to caller illegal.
The reason is that, passing poison to `nonnull` does not immediately raise UB anymore, so such program is still well defined, if the callee does not use the argument.
Having `noundef` attribute there re-allows this.
```
define void @f(i8* %p) { ; functionattr cannot mark %p nonnull here anymore
call void @g(i8* nonnull %p) ; .. because @g never raises UB if it never uses %p.
ret void
}
```
Another attribute that needs to be updated is `align`. This patch updates the semantics of align to accept poison as well.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D90529
The dominating condition handling in isKnownNonZero() currently
only takes into account conditions of the form "x != 0" or "x == 0".
However, there are plenty of other conditions that imply non-zero,
a common one being "x s> 0".
Peculiarly, the handling for assumes was already dealing with more
general non-zero-ness conditions, so this just reuses the same
logic for the dominating condition case.
This commit copies existing tests at llvm/Transforms and replaces
'insertelement undef' in those files with 'insertelement poison'.
(see https://reviews.llvm.org/D93586)
Tests listed using this script:
grep -R -E '^[^;]*insertelement <.*> undef,' . | cut -d":" -f1 | uniq |
wc -l
Tests updated:
file_org=llvm/test/Transforms/$1
file=${file_org%.ll}-inseltpoison.ll
cp $file_org $file
sed -i -E 's/^([^;]*)insertelement <(.*)> undef/\1insertelement <\2> poison/g' $file
head -1 $file | grep "Assertions have been autogenerated by utils/update_test_checks.py" -q
if [ "$?" == 1 ]; then
echo "$file : should be manually updated"
# I manually updated the script
exit 1
fi
python3 ./llvm/utils/update_test_checks.py --opt-binary=./build-releaseassert/bin/opt $file
Explicitly opt-out llvm/test/Transforms/Attributor.
Verified by flipping the default value of allow-unused-prefixes and
observing that none of the failures were under llvm/test/Transforms.
Differential Revision: https://reviews.llvm.org/D92404
```
// The legacy PM CGPassManager discovers SCCs this way:
for function in the source order
tarjanSCC(function)
// While the new PM CGSCCPassManager does:
for function in the reversed source order [1]
discover a reference graph SCC
build call graph SCCs inside the reference graph SCC
```
In the common cases, reference graph ~= call graph, the new PM order is
undesired because for `a | b | c` (3 independent functions), the new PM will
process them in the reversed order: c, b, a. If `a <-> b <-> c`, we can see
that `-print-after-all` will report the sole SCC as `scc: (c, b, a)`.
This patch corrects the iteration order. The discovered SCC order will match
the legacy PM in the common cases.
For some tests (`Transforms/Inline/cgscc-*.ll` and
`unittests/Analysis/CGSCCPassManagerTest.cpp`), the behaviors are dependent on
the SCC discovery order and there are too many check lines for the particular
order. This patch simply reverses the function order to avoid changing too many
check lines.
Differential Revision: https://reviews.llvm.org/D90566
When we promote pointer arguments we did compute a wrong offset and use
a wrong type for the array case.
Bug reported and reduced by Whitney Tsang <whitneyt@ca.ibm.com>.
Before we used to only mark unreachable static functions as dead if all
uses were known dead. Now we optimistically assume uses to be dead until
proven otherwise.
If we are looking at a call site argument it might be a load or call
which is in a different context than the call site argument. We cannot
simply use the call site argument range for the call or load.
Bug reported and reduced by Whitney Tsang <whitneyt@ca.ibm.com>.
In the AANoAlias logic we determine if a pointer may have been captured
before a call. We need to look at other uses in the call not uses of the
call.
The new code is not perfect as it does not allow trivial cases where the
call has multiple arguments but it is at least not unsound and a TODO
was added.
D70365 allows us to make attributes default. This is a follow up to
actually make nosync, nofree and willreturn default. The approach we
chose, for now, is to opt-in to default attributes to avoid introducing
problems to target specific intrinsics. Intrinsics with default
attributes can be created using `DefaultAttrsIntrinsic` class.
The old function attribute deduction pass ignores reads of constant
memory and we need to copy this behavior to replace the pass completely.
First step are constant globals. TBAA can also describe constant
accesses and there are other possibilities. We might want to consider
asking the alias analyses that are available but for now this is simpler
and cheaper.
If the function is not assumed `noreturn` we should not wait for an
update to mark the call site as "may-return".
This has two kinds of consequences:
- We have less iterations in many tests.
- We have less deductions based on "known information" (since we ask
earlier, point 1, and therefore assumed information is not "known"
yet).
The latter is an artifact that we might want to tackle properly at some
point but which is not easily fixable right now.
When we assume a return value is dead we might still visit return
instructions via `Attributor::checkForAllReturnedValuesAndReturnInsts(..)`.
When we do so the "returned value" is potentially simplified to `undef`
as it is the assumed "returned value". This is a problem if there was a
preexisting `noundef` attribute that will only be removed as we manifest
the `undef` return value. We should not use this combination to derive
`unreachable` though. Two test cases fixed.
In AAMemoryBehaviorFloating we used to track benign uses in a SetVector.
With this change we look through benign uses eagerly to reduce the
number of elements (=Uses) we look at during an update.
The test does actually not fail prior to this commit but I already wrote
it so I kept it.
This reverts commit 55c4ff91bd.
Issues were introduced as discussed in https://reviews.llvm.org/D88241
where this change made previous bugs in the linker and BitCodeWriter
visible.
Make the corresponding change that was made for byval in
b7141207a4. Like byval, this requires a
bulk update of the test IR tests to include the type before this can
be mandatory.
The langref already states it does, but this wasn't implemented. Also
covers inalloca and preallocated. Also helps fix a dependence on
pointer element types.
This commit cleans up the ::initialize method of various AAs in the
following ways:
- If an associated function is required, give up on declarations.
This was discovered as a real problem when lots of llvm.dbg.XXX
call sites were assumed `noreturn` until proven otherwise. That
does not make any sense and caused huge regressions and missed
deductions.
- Require more associated declarations for function interface AAs.
- Use the IRAttribute::initialize to determine if function interface
AAs can be used in IPO, don't replicate the checks (especially
isFunctionIPOAmendable) all over the place. Arguably the function
declaration check should be moved to some central place to.
As we handle callback calls we need to disambiguate the call site
argument number from the callee argument number. While always equal in
non-callback calls, a callback comes with a partial parameter-argument
mapping so there is no implicit correspondence. Here we split
`IRPosition::getArgNo()` into two public functions, `getCallSiteArgNo()`
and `getCalleeArgNo()`. Usages are adjusted to pick the right one for
their purpose. This fixed some problems that would have been exposed as
we more aggressively optimize callbacks.
This was disabled as we were looking for a weird CGSCC problem. I
think/hope we fixed it as there were a lot of updates recently. I could
never reproduce this locally so I'll use the pre-commit phab builds to
confirm this suspicion and if they seem to be happy I'll assume this is
fixed.
Reviewed By: sstefan1
Differential Revision: https://reviews.llvm.org/D87266
Matt Arsenault