This adds the LLVM IR attribute `mustprogress` as defined in LangRef through D86233. This attribute will be applied to functions with in languages like C++ where forward progress is guaranteed. Functions without this attribute are not required to make progress.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D85393
IRCE has some overhead for runtime checks and in case number of iteration is small
the overhead can kill the benefit from optimizations.
This CL bases on BlockFrequencyInfo of pre-header and header to estimate the
number of loop iterations. If it is less than irce-min-estimated-iters we do not transform the loop.
Probably it is better to make more complex cost model but for simplicity it seems the be enough.
The usage of BFI is added only for new pass manager and tries to use it efficiently.
Reviewers: ebrevnov, dantrushin, asbirlea, mkazantsev
Reviewed By: mkazantsev
Subscribers: llvm-commits, fhahn
Differential Revision: https://reviews.llvm.org/D89541
The main tricky thing here is forward-declaring the enum:
we have to specify it's underlying data type.
In particular, this avoids the danger of switching over the SCEVTypes,
but actually switching over an integer, and not being notified
when some case is not handled.
I have updated most of such switches to be exaustive and not have
a default case, where it's pretty obvious to be the intent,
however not all of them.
If we switch over an enum, compiler can easily issue a diagnostic
if some case is not handled. However with an if cascade that isn't so.
Experimental evidence suggests new behavior to be superior.
Fixes a number of stage2 buildbots that were failing when I generalized the m_ConstantInt() logic - that didn't match for pointer types but m_Zero() does......
Scalar cases were already being handled by foldLogOpOfMaskedICmps (so this was dead code), but refactoring to support non-uniform vectors will take some time, so tweak this fold in the meantime.
This broke Chromium's PGO build, it seems because hot-cold-splitting got turned
on unintentionally. See comment on the code review for repro etc.
> This patch adds -f[no-]split-cold-code CC1 options to clang. This allows
> the splitting pass to be toggled on/off. The current method of passing
> `-mllvm -hot-cold-split=true` to clang isn't ideal as it may not compose
> correctly (say, with `-O0` or `-Oz`).
>
> To implement the -fsplit-cold-code option, an attribute is applied to
> functions to indicate that they may be considered for splitting. This
> removes some complexity from the old/new PM pipeline builders, and
> behaves as expected when LTO is enabled.
>
> Co-authored by: Saleem Abdulrasool <compnerd@compnerd.org>
> Differential Revision: https://reviews.llvm.org/D57265
> Reviewed By: Aditya Kumar, Vedant Kumar
> Reviewers: Teresa Johnson, Aditya Kumar, Fedor Sergeev, Philip Pfaffe, Vedant Kumar
This reverts commit 273c299d5d.
All existing SCEV cast types operate on integers.
D89456 will add SCEVPtrToIntExpr cast expression type.
I believe this is best for consistency.
Reviewed By: mkazantsev
Differential Revision: https://reviews.llvm.org/D89455
isNoopIntrinsic returns true for some intrinsics that are modeled in
MemorySSA but do not actually read or write any memory and do not block
DSE. Such intrinsics should not be considered as read-clobbers.
This patch adds metadata !noundef and makes load instructions can optionally have it.
A load with !noundef always return a well-defined value (has no undef bit or isn't poison).
If the loaded value isn't well defined, the behavior is undefined.
This metadata can be used to encode the assumption from C/C++ that certain reads of variables should have well-defined values.
It is helpful for optimizing freeze instructions away, because freeze can be removed when its operand has well-defined value, and showing that a load from arbitrary location is well-defined is usually hard otherwise.
The same information can be encoded with llvm.assume with operand bundle; using metadata is chosen because I wasn't sure whether code motion can be freely done when llvm.assume is inserted from clang instead.
The existing codebase already is stripping unknown metadata when doing code motion, so using metadata is UB-safe as well.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D89050
We can not bitcast pointers across different address spaces, and VectorCombine
should be careful when it attempts to find the original source of the loaded
data.
Differential Revision: https://reviews.llvm.org/D89577
Logic of widenWithVariantUse is split into check and transform
part, unlike any other transform in IndVars. We want to pass some
extra flags from analysis to transform part and standartize
the code at once, so merging them together.
Variable ExtendOperExpr only exists to check whether it is a SCEV ext.
We create it as SCEV ext right here, so semantically this check is
trivially true. In theory, it may fail if SCEV is smart enough and can
simplify the expression. However, no matter whether it is an ext or not,
we never use this fact for further reasoning. So this code is currently
useless and in theory may become harmful with SCEV's development.
We do not expect any behavior changes with removing it. If it caused
negative changes, the patch should be reverted.
Some facts have already been checked in widenWithVariantUse and then
checked again in widenWithVariantUseCodegen. The latter is redundant,
we can replace it with asserts.
Prep work for PR35155 - renamed narrowRotate to narrowFunnelShift, rewrote some comments and adjusted code to collect separate shift values, although we bail if they don't match (still only rotations are only actually folded).
I'm trying to match matchFunnelShift as much as possible in case we finally get to merge these one day.
After investigation by @asbirlea, the issue that caused the
revert appears to be an issue in the original source, rather
than a problem with the compiler.
This patch enables MemorySSA DSE again.
This reverts commit 915310bf14.
This patch adds -f[no-]split-cold-code CC1 options to clang. This allows
the splitting pass to be toggled on/off. The current method of passing
`-mllvm -hot-cold-split=true` to clang isn't ideal as it may not compose
correctly (say, with `-O0` or `-Oz`).
To implement the -fsplit-cold-code option, an attribute is applied to
functions to indicate that they may be considered for splitting. This
removes some complexity from the old/new PM pipeline builders, and
behaves as expected when LTO is enabled.
Co-authored by: Saleem Abdulrasool <compnerd@compnerd.org>
Differential Revision: https://reviews.llvm.org/D57265
Reviewed By: Aditya Kumar, Vedant Kumar
Reviewers: Teresa Johnson, Aditya Kumar, Fedor Sergeev, Philip Pfaffe, Vedant Kumar
This is an initial cleanup of the way LoopVersioning interacts with LAA.
Currently LoopVersioning has 2 ways of initializing things:
1. Passing LAI and passing UseLAIChecks = true
2. Passing UseLAIChecks = false, followed by calling setSCEVChecks and
setAliasChecks.
Both ways of initializing lead to the same result and the duplication
seems more complicated than necessary.
This patch removes the UseLAIChecks flag from the constructor and the
setSCEVChecks & setAliasChecks helpers and move initialization
exclusively to the constructor.
This simplifies things, by providing a single way to initialize
LoopVersioning and reducing duplication.
Reviewed By: Meinersbur, lebedev.ri
Differential Revision: https://reviews.llvm.org/D84406
Following up D81682 and D83903, remove the code for the old value profiling
buckets, which have been replaced with the new, extended buckets and disabled by
default.
Also syncing InstrProfData.inc between compiler-rt and llvm.
Differential Revision: https://reviews.llvm.org/D88838
Replace m_ConstantInt with m_APInt to support uniform vectors (with no undef elements)
Adding non-undef support would involve some refactoring of the MaskOps struct but this might still be worth it.
This reverts commit 25a97c3a43.
We have other constant folds that fold undef funnel shift amounts to 0 - so we need to be consistent.
If we end up with regressions where we lose a splat shift amount pattern we'll have to investigate other canonicalizations, but matchFunnelShift currently protects us from that.
This was broken by 16295d521e, when
instructions started being handled and not just constant
expressions. This was re-inserting an equivalent bitcast to the
original memcpy operand, which made a non-functional IR change on
every iteration.
This also fixes a secondary problem where it was inserting
addrspacecasts which may not have been legal (i.e. it changed the
source address space). Start visiting all pointer users and fail out
if we can't process them. Also start handling the relevant memory
intrinsic users. These cases can be dealt with by running
InferAddressSpaces separately.
This reverts the revert commit 710aceb645
and includes a fix for a memsan failure.
Original message:
This patch turns VPMemoryInstructionRecipe into a VPValue and uses it
during VPlan construction and codegeneration instead of the plain IR
reference where possible.
m_SpecificInt doesn't accept undef elements in a vector splat value - tweak specific_intval to optionally allow undefs and add the m_SpecificIntAllowUndef variants.
Allows us to remove the m_APIntAllowUndef + comparison hack inside matchFunnelShift
By always performing a modulo on the shift amount constants this was causing undef amounts being replaced with zero, meaning we were losing funnel shift by splat (with undef) patterns.
Tweaked the shift amount bounds check to support (passthrough) undefs, and use Constant::mergeUndefsWith to preserve the undefs after folding.
While we haven't encountered an earth-shattering problem with this yet,
by now it is pretty evident that trying to model the ptr->int cast
implicitly leads to having to update every single place that assumed
no such cast could be needed. That is of course the wrong approach.
Let's back this out, and re-attempt with some another approach,
possibly one originally suggested by Eli Friedman in
https://bugs.llvm.org/show_bug.cgi?id=46786#c20
which should hopefully spare us this pain and more.
This reverts commits 1fb6104293,
7324616660,
aaafe350bb,
e92a8e0c74.
I've kept&improved the tests though.
LV fails with assertion checking that UF > 0. We already set UF to 1 if it is 0 except the case when IC > MaxInterleaveCount. The fix is to set UF to 1 for that case as well.
Reviewed By: fhahn
Differential Revision: https://reviews.llvm.org/D87679
Replace m_SpecificInt with m_APIntAllowUndef to matching splats containing undefs, then use ConstantExpr::mergeUndefsWith to merge the undefs together in the result.
The undef funnel shift amounts are getting replaced with zero later on - I'll address this in a later patch, otherwise we lose potential shift by splat value patterns.
D85703 will need to create shallow wrappers in order to track the spmd icv. We need to make it available.
Differential Revision: https://reviews.llvm.org/D89342
-loop-extract-single is just -loop-extract on one loop.
-loop-extract depended on -break-crit-edges and -loop-simplify in the
legacy PM, but the NPM doesn't allow specifying pass dependencies like
that, so manually add those passes to the RUN lines where necessary.
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D89016
While promotion currently always has an AST available, it is only
relevant for invalidation purposes in LoopPromoter, so we do not
need to have it as a hard dependency.
This adds an -enable-memcpyopt-memoryssa option that currently does
nothing apart from requiring MSSA as a dependency. The tests are
split to run both with the option disabled and enabled. I went with
this rather than the separate directory DSE uses, as I found it
convenient to have a direct side-by-side comparison of differences.
Differential Revision: https://reviews.llvm.org/D89206
moveUp() moves instructions, so we should move the corresponding
memory accesses as well. We should also move the store instruction
itself: Even though we'll end up removing it later, this gives us
a correct MemoryDef to replace.
The implementation is somewhat more complicated than it should be,
because we also handle the case where P does not have a memory
access due to a degnerate AA pipeline. Hopefully, the need for this
will go away in the future, when the rest of the pass is based on
MSSA.
Differential Revision: https://reviews.llvm.org/D88778
If the memcpy operands are the same (which is allowed since D86815)
then the memcpy is effectively a no-op and the partially overlapping
memset is not dead.
Differential Revision: https://reviews.llvm.org/D89192
MemCpyOpt can shorten a memset if it is later partially overwritten
by a memcpy. It checks that the destination is not read in between,
but we also need to make sure that the destination cannot be observed
via unwinding.
Differential Revision: https://reviews.llvm.org/D89190
The previous code added the scope on each iteration, so that the
same scope was represented many times in the same !noalias metadata.
That's legal, and semantically equivalent to only storing the scope
once, but it's also wasteful and may pessimize further optimization
if AATags get intersected naively, as done by the AliasSetTracker.
Based on the recent patches D88475 and D88429 where we are losing undef values due to extension/comparisons.
I've added a Constant::mergeUndefsWith method that merges the undef scalar/elements from another Constant into a specific Constant.
Differential Revision: https://reviews.llvm.org/D88687
This relands commit 1c021c64ca which was
reverted in commit 17cec6a11a because
an assertion was being triggered, since `BuildConstantFromSCEV()`
wasn't updated to handle the case where the constant we want to truncate
is actually a pointer. I was unsuccessful in coming up with a test case
where we'd end there with constant zext/sext of a pointer,
so i didn't handle those cases there until there is a test case.
Original commit message:
While we indeed can't treat them as no-ops, i believe we can/should
do better than just modelling them as `unknown`. `inttoptr` story
is complicated, but for `ptrtoint`, it seems straight-forward
to model it just as a zext-or-trunc of unknown.
This may be important now that we track towards
making inttoptr/ptrtoint casts not no-op,
and towards preventing folding them into loads/etc
(see D88979/D88789/D88788)
Reviewed By: mkazantsev
Differential Revision: https://reviews.llvm.org/D88806
This patch turns VPMemoryInstructionRecipe into a VPValue and uses it
during VPlan construction and codegeneration instead of the plain IR
reference where possible.
Reviewed By: dmgreen
Differential Revision: https://reviews.llvm.org/D84680
> While we indeed can't treat them as no-ops, i believe we can/should
> do better than just modelling them as `unknown`. `inttoptr` story
> is complicated, but for `ptrtoint`, it seems straight-forward
> to model it just as a zext-or-trunc of unknown.
>
> This may be important now that we track towards
> making inttoptr/ptrtoint casts not no-op,
> and towards preventing folding them into loads/etc
> (see D88979/D88789/D88788)
>
> Reviewed By: mkazantsev
>
> Differential Revision: https://reviews.llvm.org/D88806
It caused the following assert during Chromium builds:
llvm/lib/IR/Constants.cpp:1868:
static llvm::Constant *llvm::ConstantExpr::getTrunc(llvm::Constant *, llvm::Type *, bool):
Assertion `C->getType()->isIntOrIntVectorTy() && "Trunc operand must be integer"' failed.
See code review for a link to a reproducer.
This reverts commit 1c021c64ca.
60b852092c introduced SCEV verification to
deleteDeadLoop, but it appears this check is currently a bit over-eager
and some users of deleteDeadLoop appear to only patch up SE after
calling it (e.g. PR47753).
Remove the extra check for now. We can consider adding it back after we
tracked down the source of the inconsistency for PR47753.
If value tracking can confirm that a shift value is less than the type bitwidth then we can more confidently fold general or(shl(a,x),lshr(b,sub(bw,x))) patterns to a funnel/rotate intrinsic pattern without causing bad codegen regressions in the backend (see D89139).
Reapplied after the shift canonicalization in rG02295e6d1a15 which removed the need to flip the shift values.
Differential Revision: https://reviews.llvm.org/D88783
After rG02295e6d1a15 we no longer need to invert the shift values for fshr - this is just hidden at the moment as funnel shifts only ever match for constant values so never use the fshr "Sub on SHL" path.
While we indeed can't treat them as no-ops, i believe we can/should
do better than just modelling them as `unknown`. `inttoptr` story
is complicated, but for `ptrtoint`, it seems straight-forward
to model it just as a zext-or-trunc of unknown.
This may be important now that we track towards
making inttoptr/ptrtoint casts not no-op,
and towards preventing folding them into loads/etc
(see D88979/D88789/D88788)
Reviewed By: mkazantsev
Differential Revision: https://reviews.llvm.org/D88806
I have introduced a new template PolySize class, where the template
parameter determines the type of quantity, i.e. for an element
count this is just an unsigned value. The ElementCount class is
now just a simple derivation of PolySize<unsigned>, whereas TypeSize
is more complicated because it still needs to contain the uint64_t
cast operator, since there are still many places in the code that
rely upon this implicit cast. As such the class also still needs
some of it's own operators.
I've tried to minimise the amount of code in the base PolySize
class, which led to a couple of changes:
1. In some places we were relying on '==' operator comparisons
between ElementCounts and the scalar value 1. I didn't put this
operator in the new PolySize class, and thought it was actually
clearer to use the isScalar() function instead.
2. I removed the isByteSized function and replaced it with calls
to isKnownMultipleOf(8).
I've also renamed NextPowerOf2 to be coefficientNextPowerOf2 so
that it's more consistent with coefficientDivideBy.
Differential Revision: https://reviews.llvm.org/D88409
And another step towards transforms not introducing inttoptr and/or
ptrtoint casts that weren't there already.
As we've been establishing (see D88788/D88789), if there is a int<->ptr cast,
it basically must stay as-is, we can't do much with it.
I've looked, and the most source of new such casts being introduces,
as far as i can tell, is this transform, which, ironically,
tries to reduce count of casts..
On vanilla llvm test-suite + RawSpeed, @ `-O3`, this results in
-33.58% less `IntToPtr`s (19014 -> 12629)
and +76.20% more `PtrToInt`s (18589 -> 32753),
which is an increase of +20.69% in total.
However just on RawSpeed, where i know there are basically
none `IntToPtr` in the original source code,
this results in -99.27% less `IntToPtr`s (2724 -> 20)
and +82.92% more `PtrToInt`s (4513 -> 8255).
which is again an increase of 14.34% in total.
To me this does seem like the step in the right direction,
we end up with strictly less `IntToPtr`, but strictly more `PtrToInt`,
which seems like a reasonable trade-off.
See https://reviews.llvm.org/D88860 / https://reviews.llvm.org/D88995
for some more discussion on the subject.
(Eventually, `CastInst::isNoopCast()`/`CastInst::isEliminableCastPair`
should be taught about this, yes)
Reviewed By: nlopes, nikic
Differential Revision: https://reviews.llvm.org/D88979
This expands upon the inloop reductions added in e9761688e41cb9e976,
allowing them to be inserted into tail folded loops. Reductions are
generates with the form:
x = select(mask, vecop, zero)
v = vecreduce.add(x)
c = add chain, v
Where zero here is chosen as the identity value for add reductions. The
backend is then expected to fold the select and the vecreduce into a
single predicated instruction.
Most of the code is fairly straight forward, except for the creation of
blockmasks which need to ensure they are created in dominance order. The
order they are added is altered to be after any phis, keeping the
requirements for the underlying IR.
Differential Revision: https://reviews.llvm.org/D84451
As shown in the affected test, we could increase instruction
count without this limitation. There's another test with extra
use that shows we still convert directly to a real "sext" if
possible.
If value tracking can confirm that a shift value is less than the type bitwidth then we can more confidently fold general or(shl(a,x),lshr(b,sub(bw,x))) patterns to a funnel/rotate intrinsic pattern without causing bad codegen regressions in the backend (see D89139).
Differential Revision: https://reviews.llvm.org/D88783
This exposes the helper for other power-of-2 instcombine folds that I'm intending to add vector support to.
The helper only operated on power-of-2 constants so getExactLogBase2 is a more accurate name.
This patch is a refactoring of how we process spills and allocas during CoroSplit.
In the previous implementation, everything that needs to go to the heap is put into Spills, including all the values defined by allocas.
And the way to identify a Spill, is to check whether there exists a use-def relationship that crosses suspension points.
This approach is fundamentally confusing, and unfortunately, incorrect.
First of all, allocas are always process differently than spills, hence it's quite confusing to put them together. It's a much cleaner to separate them and process them separately.
Doing so simplify lots of code and makes the logic more clear and easier to reason about.
Secondly, use-def relationship is insufficient to decide whether a value defined by AllocaInst needs to go to the heap.
There are many cases where a value defined by AllocaInst can implicitly be used across suspension points without a direct use-def relationship.
For example, you can store the address of an alloca into the heap, and load that address after suspension. Or you can escape the address into an object through a function call.
Or you can have a PHINode that takes two allocas, and this PHINode is used across suspension point (when this happens, the existing implementation will spill the PHINode, a.k.a a stack adddress to the heap!).
All these issues suggest that we need to separate spill and alloca in order to properly implement this.
This patch does not yet fix these bugs, however it sets up the code in a better shape so that we can start fixing them in the next patch.
The core idea of this patch is to add a new struct called FrameDataInfo, which contains all Spills, all Allocas, and a map from each definition to its layout index in the frame (FieldIndexMap).
Spills and Allocas are identified, stored and processed independently. When they are initially added to the frame, we record their field index through FieldIndexMap. When the frame layout is finalized, we update each index into their final layout index.
In doing so, I also cleaned up a few things and also discovered a few other bugs.
Cleanups:
1. Found out that PromiseFieldId is not used, delete it.
2. Previously, SpillInfo is a vector, which is strange because every def can have multiple users. This patch cleans it up by turning it into a map from def to users.
3. Previously, a frame Field struct contains a list of Spills that field corresponds to. This isn't necessary since we only need the layout index for each given definition. This patch removes that list. Instead, we connect each field and definition using the FieldIndexMap.
4. All the loops that process Spills are simplified now because we use a map instead of a vector.
Bugs:
It seems that we are only keeping llvm.dbg.declare intrinsics in the .resume part of the function. The ramp function will no longer has it. This means we are dropping some debug information in the ramp function.
The next step is to start fixing the bugs where the implementation fails to identify some allocas that should live on the frame.
Differential Revision: https://reviews.llvm.org/D88872
MemCpyOpt can hoist stores while load+store pairs into memcpy.
This hoisting can currently result in stores being executed that
weren't guaranteed to execute in the original problem.
Differential Revision: https://reviews.llvm.org/D89154
Summary:
The current instruction sink pass uses findNearestCommonDominator of all users to find block to sink the instruction to.
However, a user may be in a dead block, which will result in unexpected behavior.
This patch handles such cases by skipping dead blocks. This patch fixes:
https://bugs.llvm.org/show_bug.cgi?id=47415
Reviewers:
MaskRay, arsenm
Differential Revision:
https://reviews.llvm.org/D89166
If a module has many values that need to be resolved by
ResolvedUndefsIn, compilation takes quadratic time overall. Solve should
do a small amount of work, since not much is added to the worklists each
time markOverdefined is called. But ResolvedUndefsIn is linear over the
length of the function/module, so resolving one undef at a time is
quadratic in general.
To solve this, make ResolvedUndefsIn resolve every undef value at once,
instead of resolving them one at a time. This loses a little
optimization power, but can be a lot faster.
We still need a loop around ResolvedUndefsIn because markOverdefined
could change the set of blocks that are live. That should be uncommon,
hopefully. We could optimize it by tracking which blocks transition from
dead to live, instead of iterating over the whole module to find them.
But I'll leave that for later. (The whole function will become a lot
simpler once we start pruning branches on undef.)
The regression test changes seem minor. The specific cases in question
could probably be optimized with a bit more work, but they seem like
edge cases that don't really matter.
Fixes an "infinite" compile issue my team found on an internal workoad.
Differential Revision: https://reviews.llvm.org/D89080
There are cases that generated OpenMP code consists of multiple,
consecutive OpenMP parallel regions, either due to high-level
programming models, such as RAJA, Kokkos, lowering to OpenMP code, or
simply because the programmer parallelized code this way. This
optimization merges consecutive parallel OpenMP regions to: (1) reduce
the runtime overhead of re-activating a team of threads; (2) enlarge the
scope for other OpenMP optimizations, e.g., runtime call deduplication
and synchronization elimination.
This implementation defensively merges parallel regions, only when they
are within the same BB and any in-between instructions are safe to
execute in parallel.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D83635
In the NPM, a pass cannot depend on another non-analysis pass. So pin
the test that tests that -lowerswitch is run automatically to legacy PM.
Reviewed By: sameerds
Differential Revision: https://reviews.llvm.org/D89051
There might be a better way to specify the pre-conditions,
but this is hopefully clearer than the way it was written:
https://rise4fun.com/Alive/Jhk3
Pre: C2 < 0 && isShiftedMask(C2) && (C1 == C1 & C2)
%a = and %x, C2
%r = add %a, C1
=>
%a2 = add %x, C1
%r = and %a2, C2
Atmn Patel