This patch add mayContainUnboundedCycle helper function which checks whether a function has any cycle which we don't know if it is bounded or not.
Loops with maximum trip count are considered bounded, any other cycle not.
It also contains some fixed tests and some added tests contain bounded and
unbounded loops and non-loop cycles.
Reviewed By: jdoerfert, uenoku, baziotis
Differential Revision: https://reviews.llvm.org/D74691
Resolution for below fixme:
(ii) Check whether the value is captured in the scope using AANoCapture.
FIXME: This is conservative though, it is better to look at CFG and
check only uses possibly executed before this callsite.
Propagates caller argument's noalias attribute to callee.
Reviewed by: jdoerfert, uenoku
Reviewers: jdoerfert, sstefan1, uenoku
Subscribers: uenoku, sstefan1, hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D71617
This patch introduces the propagation of known information based on path exploration.
For example,
```
int u(int c, int *p){
if(c) {
return *p;
} else {
return *p + 1;
}
}
```
An argument `p` is dereferenced whatever c's value is.
For an instruction `CtxI`, we accumulate branch instructions in the must-be-executed-context of `CtxI` and then, we take the conjunction of the successors' known state.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D65593
It is possible that an instruction to be changed to unreachable is
in the same block with a terminator that can be constant-folded.
In this case, as of now, the instruction will be changed to
unreachable before the terminator is folded. But, then the
whole BB becomes invalidated and so when we go ahead to fold
the terminator, we trap.
Change the order of these two.
Differential Revision: https://reviews.llvm.org/D75780
We can look through calls with `returned` argument attributes when we
collect subsuming positions. This allows us to get existing attributes
from more places.
We are often interested in an assumed constant and sometimes it has to
be an integer constant. Before we only looked for the latter, now we can
ask for either.
If we propagate function pointers across function boundaries we can
create new call edges. These need to be represented in the CG if we run
as a CGSCC pass. In the new pass manager that is currently not handled
by the CallGraphUpdater so we need to prevent the situation for now.
We usually will ask for liveness of an argument anyway so we ended up
lazily creating the attribute anyway. However, that is not always the
case and even if it is we should go the eager route here. Various tests
show how this can improve the outcome. One test exposed a problem with
type mismatches between argument and call site argument, a fix is
included. For liveness various more tests were added as well.
If a function pointer is casted into a different type the resulting
expression can be a constant. If so, it can be used multiple times which
cannot be handled by the AbstractCallSite constructor alone. Instead, we
follow the cast expression uses now explicitly during the call site
traversal.
In addition to a single bit per memory locations, e.g., globals and
arguments, we now collect more information about the actual accesses,
e.g., what instruction caused it, was it a read/write/read+write, and
what the underlying base pointer was. Follow up patches will make
explicit use of this.
Reviewed By: uenoku
Differential Revision: https://reviews.llvm.org/D73527
While the function return updateImpl did only look at call sites the
manifest method looked at return values. If we don't do this during the
updateImpl we might create new abstract attributes during manifest. This
is a problem when it comes to liveness information.
This caused an error when passes iterated over cached assumptions in the
tracker and assumed them to be `null` or an instruction. I failed to
create a test case so far.
In addition to memory behavior attributes (readonly/writeonly) we now
derive memory location attributes (argmemonly/inaccessiblememonly/...).
The former is part of AAMemoryBehavior and the latter part of
AAMemoryLocation. While they are similar in nature it got messy when
they were put in a single AA. Location attributes for arguments and
floating values will follow later.
Note that both memory attributes kinds can derive readnone. If there are
no accesses AAMemoryBehavior will derive readnone. If there are accesses
but only to stack (=local) locations AAMemoryLocation will derive
readnone.
Reviewed By: uenoku
Differential Revision: https://reviews.llvm.org/D73426
Due to the genericValueTraversal we might visit values for which we did
not create an AAValueConstantRange object, e.g., as they are behind a
PHI or select or call with `returned` argument. As a consequence we need
to validate the types as we are about to query AAValueConstantRange for
operands.
We used coarse-grained liveness before, thus we looked if the
instruction was executed, but we did not use fine-grained liveness,
hence if the instruction was needed or could be deleted even if the
surrounding ones are live. This patches introduces this level of
liveness checks together with other liveness queries, e.g., for uses.
For more control we enforce that all liveness queries go through the
Attributor.
Test have been adjusted to reflect the changes or augmented to prevent
deletion of the parts we want to check.
Reviewed By: sstefan1
Differential Revision: https://reviews.llvm.org/D73313
If we have a replacement for a value, via AAValueSimplify, the original
value will lose all its uses. Thus, as long as a value is simplified we
can skip the uses in checkForAllUses, given that these uses are
transitive uses for the simplified version and will therefore affect the
simplified version as necessary.
Since this allowed us to remove calls without side-effects and a known
return value, we need to make sure not to eliminate `musttail` calls.
Those we keep around, or later remove the entire `musttail` call chain.
We relied on wouldInstructionBeTriviallyDead before but that functions
does not take assumed information, especially for calls, into account.
The replacement, AAIsDead::isAssumeSideEffectFree, does.
This change makes AAIsDeadCallSiteReturn more complex as we can have
a dead call or only dead users.
The test have been modified to include a side effect where there was
none in order to keep the coverage.
Reviewed By: sstefan1
Differential Revision: https://reviews.llvm.org/D73311
As an approximation to a dead edge we can check if the terminator is
dead. If so, the corresponding operand use in a PHI node is dead even if
the PHI node itself is not.
The changeXXXAfterManifest functions are better suited to deal with
changes so we should prefer them. These functions also recursively
delete dead instructions which is why we see test changes.
This is a minimal but important advancement over the existing code. A
cast with an operand that is only used in the cast retains the no-alias
property of the operand.
Traversing PHI nodes is natural with the genericValueTraversal but also
a bit tricky. The problem is similar to the ones we have seen in AAAlign
and AADereferenceable, namely that we continue to increase the range in
each iteration. We use a pessimistic approach here to stop the
iterations. Nevertheless, optimistic information can now be propagated
through a PHI node.
The change is performed as stated by the FIXME and the tests are
adjusted. All changes look fine to me and values can be inferred as
undef without it being an error.
Casts can be handled natively by the ConstantRange class. We do limit it
to extends for now as we assume an integer type in different locations.
A TODO and a test case with a FIXME was added to remove that restriction
in the future.
In addition to the module pass, this patch introduces a CGSCC pass that
runs the Attributor on a strongly connected component of the call graph
(both old and new PM). The Attributor was always design to be used on a
subset of functions which makes this patch mostly mechanical.
The one change is that we give up `norecurse` deduction in the module
pass in favor of doing it during the CGSCC pass. This makes the
interfaces simpler but can be revisited if needed.
Reviewed By: hfinkel
Differential Revision: https://reviews.llvm.org/D70767
If all call sites are in `norecurse` functions we can derive `norecurse`
as the ReversePostOrderFunctionAttrsPass does. This should make
ReversePostOrderFunctionAttrsLegacyPass obsolete once the Attributor is
enabled.
Reviewed By: uenoku
Differential Revision: https://reviews.llvm.org/D72017
If we know that all call sites have been processed we can derive an
early fixpoint. The use in this patch is likely not to trigger right now
but a follow up patch will make use of it.
Reviewed By: uenoku, baziotis
Differential Revision: https://reviews.llvm.org/D72016
Summary:
In a release build this variable becomes unused and may break the build
with `-Werror,-Wunused-variable`.
Reviewers: gribozavr2, jdoerfert, sstefan1
Reviewed By: gribozavr2
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D73683
