When merging scales of `LinearExpression` that have common index
variables, we cannot guarantee the NSW flag still applies to the merged
expression.
Fixes#69096.
This test is checking alias analysis. The attribute tests are
brittle but fortunately unneccesary. Delete them.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D156600
We currently preserve the nsw flag when negating scales, which is
incorrect for INT_MIN.
However, just dropping the NSW flag in this case makes BasicAA
behavior unreliable and asymmetric, because we may or may not
drop the NSW flag depending on which side gets subtracted.
Instead, leave the Scale alone and add an additional IsNegated flag,
which indicates that the whole VarIndex should be interpreted as a
subtraction. This allows us to retain the NSW flag.
When accumulating the offset range, we need to use subtraction
instead of adding for IsNegated indices. Everything else works on
the absolute value of the scale, so the negation does not matter
there.
Fixes https://github.com/llvm/llvm-project/issues/63266.
Differential Revision: https://reviews.llvm.org/D153270
This operand bundle on an assume informs alias analysis that the
arguments point to regions of memory that were allocated separately
(i.e. different heap allocations, different allocas, or different
globals).
As a safety measure, we leave the analysis flag-disabled by default.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D136514
BasicAA currently has an optional dependency on the PhiValues
analysis. However, at least with our current pipeline setup, we
never actually make use of it. It's possible that this used to work
with the legacy pass manager, but I'm not sure of that either.
Given that this analysis has not actually been in use for a long
time, and nobody noticed or complained, I think we should drop
support for it and focus on one code path. It is worth noting that
analysis quality for the non-PhiValues case has significantly
improved in the meantime.
If we really wanted to make use of PhiValues, the right way would
probably be to pass it in via AAQI in places we want to use it,
rather than using an optional pass manager dependency (which are
an unpredictable PITA and should really only ever be used for
analyses that are only preserved and not used).
Differential Revision: https://reviews.llvm.org/D139719
Similar to 9f9e8ba114ce, add support for memcyp_chk to
MemoryLocation::getForArgument.
The size argument for memcpy_chk is an upper bound for the size of the
pointer argument. memcpy_chk may read/write less than the specified length,
if it exceeds the specified max size and aborts.
Reviewed By: xbolva00, jdoerfert
Differential Revision: https://reviews.llvm.org/D138613
This switches everything to use the memory attribute proposed in
https://discourse.llvm.org/t/rfc-unify-memory-effect-attributes/65579.
The old argmemonly, inaccessiblememonly and inaccessiblemem_or_argmemonly
attributes are dropped. The readnone, readonly and writeonly attributes
are restricted to parameters only.
The old attributes are auto-upgraded both in bitcode and IR.
The bitcode upgrade is a policy requirement that has to be retained
indefinitely. The IR upgrade is mainly there so it's not necessary
to update all tests using memory attributes in this patch, which
is already large enough. We could drop that part after migrating
tests, or retain it longer term, to make it easier to import IR
from older LLVM versions.
High-level Function/CallBase APIs like doesNotAccessMemory() or
setDoesNotAccessMemory() are mapped transparently to the memory
attribute. Code that directly manipulates attributes (e.g. via
AttributeList) on the other hand needs to switch to working with
the memory attribute instead.
Differential Revision: https://reviews.llvm.org/D135780
These weren't running anywhere because of bad specifications.
One test has bit-rotted and had to be XFAILed, the rest are okay.
Differential Revision: https://reviews.llvm.org/D136612
We currently only take operand bundle effects into account when
querying the function-level memory attributes. However, I believe
that we also need to do the same for parameter attributes. For
example, a call with deopt bundle to a function with readnone
parameter attribute cannot treat that parameter as readnone,
because the deopt bundle may read it.
Differential Revision: https://reviews.llvm.org/D136834
The pointsToConstantMemory() method returns true only if the memory pointed to
by the memory location is globally invariant. However, the LLVM memory model
also has the semantic notion of *locally-invariant*: memory that is known to be
invariant for the life of the SSA value representing that pointer. The most
common example of this is a pointer argument that is marked readonly noalias,
which the Rust compiler frequently emits.
It'd be desirable for LLVM to treat locally-invariant memory the same way as
globally-invariant memory when it's safe to do so. This patch implements that,
by introducing the concept of a *ModRefInfo mask*. A ModRefInfo mask is a bound
on the Mod/Ref behavior of an instruction that writes to a memory location,
based on the knowledge that the memory is globally-constant memory (in which
case the mask is NoModRef) or locally-constant memory (in which case the mask
is Ref). ModRefInfo values for an instruction can be combined with the
ModRefInfo mask by simply using the & operator. Where appropriate, this patch
has modified uses of pointsToConstantMemory() to instead examine the mask.
The most notable optimization change I noticed with this patch is that now
redundant loads from readonly noalias pointers can be eliminated across calls,
even when the pointer is captured. Internally, before this patch,
AliasAnalysis was assigning Ref to reads from constant memory; now AA can
assign NoModRef, which is a tighter bound.
Differential Revision: https://reviews.llvm.org/D136659
This commit adds some tests in preparation for D136659, which allows alias
analysis to treat locally-invariant memory pointed to by readonly noalias
pointers the same as globally-invariant memory in some cases. The existing
behavior for these tests is marked as expected and will be changed when that
diff lands.
Differential Revision: https://reviews.llvm.org/D136993
In D136659 I found a few tests that write through readonly parameters:
* Analysis/BasicAA/pr18573.ll: @foo1 writes through %arr.ptr, but declares it
readonly. I removed the readonly annotation.
* CodeGen/ARM/ParallelDSP/aliasing.ll: @restrict writes through the readonly
%arg3, @store_alias_arg3_illegal_1 writes through the readonly %arg3, and
@store_alias_arg3_illegal_2 writes through the readonly %arg3. I removed
readonly from all three. Also, I added some CHECK-LABEL directives to make it
harder for FileCheck output to be mixed up.
* Transforms/LoopVectorize/AArch64/sve-gather-scatter.ll:
@gather_nxv4i32_ind64_stride2 writes through the readonly %a. I removed the
readonly attribute.
* Transforms/LoopVectorize/interleaved-accesses.ll: @load_gap_reverse writes
through the readonly %P1 and %P2. Also, the corresponding C code in the comment
didn't match the test. I removed the readonly attribute from both parameters
and corrected the C code.
Differential Revision: https://reviews.llvm.org/D136880
Another step towards getting rid of dependencies to the legacy
pass manager.
Primary change here is to just do -passes=foo instead of -foo in
simple situations (when running a single pass). But also
updated a few test running multiple passes.
When looking for underlying objects, if we encounter one that we
have already seen, then we should skip it (as it has already been
checked) rather than bail out. In particular, this adds support
for the case where we have a loop use of a phi recurrence.
If we have translated across a cycle backedge, the same SSA value
for the condition might be referring to two different loop iterations.
Use the isValueEqualInPotentialCycles() helper to avoid assuming
equality in that case.
getModRefInfo() queries currently track whether the result is a
MustAlias on a best-effort basis. The only user of this functionality
is the optimized memory access type in MemorySSA -- which in turn
has no users. Given that this functionality has not found a user
since it was introduced five years ago (in D38862), I think we
should drop it again.
The context is that I'm working to separate FunctionModRefBehavior
to track mod/ref for different location kinds (like argmem or
inaccessiblemem) separately, and the fact that ModRefInfo also has
an unrelated Must flag makes this quite awkward, especially as this
means that NoModRef is not a zero value. If we want to retain the
functionality, I would probably split getModRefInfo() results into
a part that just contains the ModRef information, and a separate
part containing a (best-effort) AliasResult.
Differential Revision: https://reviews.llvm.org/D130713
Following some recent discussions, this changes the representation
of callbrs in IR. The current blockaddress arguments are replaced
with `!` label constraints that refer directly to callbr indirect
destinations:
; Before:
%res = callbr i8* asm "", "=r,r,i"(i8* %x, i8* blockaddress(@test8, %foo))
to label %asm.fallthrough [label %foo]
; After:
%res = callbr i8* asm "", "=r,r,!i"(i8* %x)
to label %asm.fallthrough [label %foo]
The benefit of this is that we can easily update the successors of
a callbr, without having to worry about also updating blockaddress
references. This should allow us to remove some limitations:
* Allow unrolling/peeling/rotation of callbr, or any other
clone-based optimizations
(https://github.com/llvm/llvm-project/issues/41834)
* Allow duplicate successors
(https://github.com/llvm/llvm-project/issues/45248)
This is just the IR representation change though, I will follow up
with patches to remove limtations in various transformation passes
that are no longer needed.
Differential Revision: https://reviews.llvm.org/D129288
The patch adds an extra check to only set MinAbsVarIndex if
abs(V * Scale) won't wrap. In the absence of IsNSW, try to use the
bitwidths of the original V and Scale to rule out wrapping.
Attempt to model https://alive2.llvm.org/ce/z/HE8ZKj
The code in the else if below probably needs the same treatment, but I
need to come up with a test first.
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D121695
With opaque pointers, we cannot use the pointer element type to
determine the LocationSize for the AA query. Instead, -aa-eval
tests are now required to have an explicit load or store for any
pointer they want to compute alias results for, and the load/store
types are used to determine the location size.
This may affect ordering of results, and sorting within one result,
as the type is not considered part of the sorted string anymore.
To somewhat minimize the churn, printing still uses faux typed
pointer notation.
Currently, basic AA has special support for llvm.memcpy.* intrinsics. This change extends this support for any memory trancsfer opration and in particular llvm.memmove.* intrinsic.
Reviewed By: reames, nikic
Differential Revision: https://reviews.llvm.org/D117095
Presence of operand bundles changes semantics in respect to ModRef. In particular, spec says: "From the compilers perspective, deoptimization operand bundles make the call sites theyre attached to at least readonly. They read through all of their pointer typed operands (even if theyre not otherwise escaped) and the entire visible heap. Deoptimization operand bundles do not capture their operands except during deoptimization, in which case control will not be returned to the compiled frame". Fix handling of llvm.memcpy.* according to the spec.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D118033
New test checks results of BasicAA for llvm.memcpy.*/llvm.memmove.* intrinsics in presence of deopt bundle. By specification expected result for unrelated global memory should be Ref. Currently this is not the case and will be fixed in upcoming patches.
Reviewed By: fhahn
Differential Revision: https://reviews.llvm.org/D118031
