If we have a logical and/or in select form and the true/false operand
is an fcmp with poison generating FMF, we won't be able to fold it
to an and/or instruction. This prevents us from optimizing the case
where it is a logical operation of two fcmps with identical operands.
This patch adds explicit checks for this case that doesn't rely on
converting to and/or to do the optimization. It reuses the existing
foldLogicOfFCmps, but adds a new flag to disable the other combine
that is inside that function.
FMF flags from the two FCmps are intersected using the logic added in
D121243. The FIXME has been updated to indicate that we can only use
a union for the non-select form.
This allows us to optimize cases like this from compare-fp-3.c in the
gcc torture suite with fast math.
void
test1 (float x, float y)
{
if ((x==y) && (x!=y))
link_error0();
}
Reviewed By: spatel
Differential Revision: https://reviews.llvm.org/D121323
Only call it for intrinsic min/max. The moved implementation is
unchanged apart from the one-use check: It is now hardcoded to
one-use, without the two-use special case for SPF.
This is an alternate version of D115914 that handles/tests all binary opcodes.
I suspect that we don't see these patterns too often because -simplifycfg
would convert the minimal cases into selects rather than leave them in phi form
(note: instcombine has logic holes for combining the select patterns too though,
so that's another potential patch).
We only create a new binop in a predecessor that unconditionally branches to
the final block.
https://alive2.llvm.org/ce/z/C57M2Fhttps://alive2.llvm.org/ce/z/WHwAoU (not safe to speculate an sdiv for example)
https://alive2.llvm.org/ce/z/rdVUvW (but it is ok on this path)
Differential Revision: https://reviews.llvm.org/D117110
This change may not be entirely NFC, because a number of early
returns will now only early return from this particular fold,
rather than the whole visitGetElementPtr() implementation. This
is also the reason why I'm doing this change, as I don't think
this was intended.
The transform can require an optional shuffle instruction to be sound,
so we need to use Builder to create all values and then replace the
original instruction with whatever that final value is.
This is a generalization/extension of the existing and/or
folds noted with TODO comments. Those have a one-use
constraint that is not necessary.
Potential follow-ups are noted by the TODO comments in
the new function. We can also call this function from
other binop visit* functions, but we need to add tests
first.
This solves:
https://llvm.org/PR52543https://alive2.llvm.org/ce/z/NWuCR5
We already handle more complicated cases like:
extelt (bitcast (inselt poison, X, 0)) --> trunc (lshr X)
But we missed this simpler pattern:
https://alive2.llvm.org/ce/z/D55h64 / https://alive2.llvm.org/ce/z/GKzzRq
This is part of solving:
https://llvm.org/PR52057
I made the transform depend on legal/desirable int type to avoid creating
a shift of an illegal type (for example i128). I'm not sure if that
restriction is actually necessary, but we can change that as a follow-up
if the backend can deal with integer ops on too-wide illegal types.
The pile of AVX512 test changes are all neutral AFAICT - the x86 backend
seems to know how to turn that into the expected "kmov" instructions.
Differential Revision: https://reviews.llvm.org/D111082
This removes repeated calls to m_Not, so hopefully a little
more efficient.
Also, we may need to enhance some of these blocks to allow
logical and/or (select of bools).
This splits out the logic from shouldChangeType() that
currently allows 8/16/32-bit transforms even if those
types are not listed as legal in the data layout.
This could be useful as a predicate for vector
insert/extract transforms.
Note that this leaves the subsequent checks in
shouldChangeType() unchanged. We may want to merge
the checks for i1 and/or "ToLegal" into "isDesirable",
but that may alter existing transforms.
InstCombine's worklist can be re-used by other passes like
VectorCombine. Move it to llvm/Transform/Utils and rename it to
InstructionWorklist.
Reviewed By: lebedev.ri
Differential Revision: https://reviews.llvm.org/D110181
The motivating case is an infinite loop shown with a reduced test from:
https://llvm.org/PR51762
To solve this, I'm proposing we delete the most obviously broken part of this code.
The bug example shows a fundamental problem: we ask computeKnownBits if a transform
will be profitable, alter the code by creating new instructions, then rely on
computeKnownBits to return the same answer to actually eliminate instructions.
But there's no guarantee that the results will be the same between the 1st and 2nd
calls. In the infinite loop example, we get different answers, so we add
instructions that conflict with some other transform, and we're stuck.
There's at least one other problem visible in the test diff for
`@zext_or_masked_bit_test_uses`: the code doesn't check uses properly, so we can
end up with extra instructions created.
Last, it's not clear if this set of transforms actually improves analysis or
codegen. I spot-checked a few targets and don't see a clear win:
https://godbolt.org/z/x87EWovso
If we do see a regression from this change, codegen seems like the right place to
add a cmp -> bit-hack fold.
If this is too big of a step, we could limit the computeKnownBits calls by not
passing a context instruction and/or limiting the recursion. I checked that those
would stop the infinite loop for PR51762, but that won't guarantee that some other
example does not fall into the same loop.
Differential Revision: https://reviews.llvm.org/D109440
This adds a call to matchSAddSubSat from smin/smax instrinsics, allowing
the same patterns to match if the canonical form of a min/max is an
intrinsics, not a icmp/select.
Differential Revision: https://reviews.llvm.org/D108077
The inttoptr/ptrtoint roundtrip optimization is not always correct.
We are working towards removing this optimization and adding support to specific cases where this optimization works.
In this patch, we focus on phi-node operands with inttoptr casts.
We know that ptrtoint( inttoptr( ptrtoint x) ) is same as ptrtoint (x).
So, we want to remove this roundtrip cast which goes through phi-node.
Reviewed By: aqjune
Differential Revision: https://reviews.llvm.org/D106289
In D106041, a freeze was added before the branch condition to solve the miscompilation problem of SimpleLoopUnswitch.
However, I found that the added freeze disturbed other optimizations in the following situations.
```
arg.fr = freeze(arg)
use(arg.fr)
...
use(arg)
```
It is a problem that occurred when arg and arg.fr were recognized as different values.
Therefore, changing to use arg.fr instead of arg throughout the function eliminates the above problem.
Thus, I add a function that changes all uses of arg to freeze(arg) to visitFreeze of InstCombine.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D106233
The inttoptr/ptrtoint roundtrip optimization is not always correct.
We are working towards removing this optimization and adding support
to specific cases where this optimization works. This patch is the
first one on this line.
Consider the example:
%i = ptrtoint i8* %X to i64
%p = inttoptr i64 %i to i16*
%cmp = icmp eq i8* %load, %p
In this specific case, the inttoptr/ptrtoint optimization is correct
as it only compares the pointer values. In this patch, we fold
inttoptr/ptrtoint to a bitcast (if src and dest types are different).
Differential Revision: https://reviews.llvm.org/D105088
In D104569, Freeze was inserted just before br to solve the `branching on undef` miscompilation problem.
But value analysis was being disturbed by added freeze.
```
v = load ptr
cond = freeze(icmp (and v, const), const')
br cond, ...
```
The case in which value analysis disturbed is as above.
By changing freeze to add immediately after load, value analysis will be successful again.
```
v = load ptr
freeze(icmp (and v, const), const')
=>
v = load ptr
v' = freeze v
icmp (and v', const), const'
```
In this patch, I propose the above optimization.
With this patch, the poison will not spread as the freeze is performed early.
Reviewed By: nikic, lebedev.ri
Differential Revision: https://reviews.llvm.org/D105392
If a logical and/or is used, we need to be careful not to propagate
a potential poison value from the RHS by inserting a freeze
instruction. Otherwise it works the same way as bitwise and/or.
This is intended to address the regression reported at
https://reviews.llvm.org/D101191#2751002.
Differential Revision: https://reviews.llvm.org/D102279
Remove the requirement that the instruction is a BinaryOperator,
make the predicate check more compact and use slightly more
meaningful naming for the and operands.
This reverts commit 13ec913bdf.
This commit introduces new uses of the overflow checking intrinsics that
depend on implementations in compiler-rt, which Windows users generally
do not link against. I filed an issue (somewhere) to make clang
auto-link the builtins library to resolve this situation, but until that
happens, it isn't reasonable for the optimizer to introduce new link
time dependencies.
It used to be that all of our intrinsics were call instructions, but over time, we've added more and more invokable intrinsics. According to the verifier, we're up to 8 right now. As IntrinsicInst is a sub-class of CallInst, this puts us in an awkward spot where the idiomatic means to check for intrinsic has a false negative if the intrinsic is invoked.
This change switches IntrinsicInst from being a sub-class of CallInst to being a subclass of CallBase. This allows invoked intrinsics to be instances of IntrinsicInst, at the cost of requiring a few more casts to CallInst in places where the intrinsic really is known to be a call, not an invoke.
After this lands and has baked for a couple days, planned cleanups:
Make GCStatepointInst a IntrinsicInst subclass.
Merge intrinsic handling in InstCombine and use idiomatic visitIntrinsicInst entry point for InstVisitor.
Do the same in SelectionDAG.
Do the same in FastISEL.
Differential Revision: https://reviews.llvm.org/D99976
This patch improves https://reviews.llvm.org/D76971 (Deduce attributes for aligned_alloc in InstCombine) and implements "TODO" item mentioned in the review of that patch.
> The function aligned_alloc() is the same as memalign(), except for the added restriction that size should be a multiple of alignment.
Currently, we simply bail out if we see a non-constant size - change that.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D100785
recognizeBSwapOrBitReverseIdiom + collectBitParts have pattern matching to bail out early if a bswap/bitreverse pattern isn't possible - we should be able to rely on this instead without any notable change in compile time.
This is part of a cleanup towards letting matchBSwapOrBitReverse /recognizeBSwapOrBitReverseIdiom use 'root' instructions that aren't ORs (FSHL/FSHRs in particular which can be prematurely created).
Differential Revision: https://reviews.llvm.org/D97056
Some utilities used by InstCombine, like SimplifyLibCalls, may add new
instructions and replace the uses of a call, but return nullptr because
the inserted call produces multiple results.
Previously, the replaced library calls would get removed by
InstCombine's deleter, but after
292077072e this may not happen, if the
willreturn attribute is missing.
As a work-around, update replaceInstUsesWith to set MadeIRChange, if it
replaces any uses. This catches the cases where it is used as replacer
by utilities used by InstCombine and seems useful in general; updating
uses will modify the IR.
This fixes an expensive-check failure when replacing
@__sinpif/@__cospifi with @__sincospif_sret.
Iff we know we can get rid of the inversions in the new pattern,
we can thus get rid of the inversion in the old pattern,
this decreasing instruction count.
Note that we could position this transformation as just hoisting
of the `not` (still, iff y is freely negatible), but the test changes
show a number of regressions, so let's not do that.
Iff we know we can get rid of the inversions in the new pattern,
we can thus get rid of the inversion in the old pattern,
this decreasing instruction count.
There are 1-2 potential follow-up NFC commits to reduce
this further on the way to generalizing this for vectors.
The operand replacing path should be dead code because demanded
bits handles that more generally (D91415).
matchBSwapOrBitReverse was hardcoded to just match bswaps - we're going to need to expose the ability to match bitreverse as well, so make this part of the function call.
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.
In some cases, we can negate instruction if only one of it's operands
negates. Previously, we assumed that constants would have been
canonicalized to RHS already, but that isn't guaranteed to happen,
because of InstCombine worklist visitation order,
as the added test (previously-hanging) shows.
So if we only need to negate a single operand,
we should ensure ourselves that we try constant operand first.
Do that by re-doing the complexity sorting ourselves,
when we actually care about it.
Fixes https://bugs.llvm.org/show_bug.cgi?id=47752
When replacing X == Y ? f(X) : Z with X == Y ? f(Y) : Z, make sure
that Y cannot be undef. If it may be undef, we might end up picking
a different value for undef in the comparison and the select
operand.
Normal dead code elimination ignores assume intrinsics, so we fail to
delete assumes that are not meaningful (and potentially worse if they
cause conflicts with other assumptions).
The motivating example in https://llvm.org/PR47416 suggests that we
might have problems upstream from here (difference between C and C++),
but this should be a cheap way to make sure we remove more dead code.
Differential Revision: https://reviews.llvm.org/D87149
While since D86306 we do it's sibling fold for `insertvalue`,
we should also do this for `extractvalue`'s.
And unlike that one, the results here are, quite honestly, shocking,
as it can be observed here on vanilla llvm test-suite + RawSpeed results:
```
| statistic name | baseline | proposed | Δ | % | |%| |
|----------------------------------------------------|-----------|-----------|--------:|--------:|-------:|
| asm-printer.EmittedInsts | 7945095 | 7942507 | -2588 | -0.03% | 0.03% |
| assembler.ObjectBytes | 273209920 | 273069800 | -140120 | -0.05% | 0.05% |
| early-cse.NumCSE | 2183363 | 2183398 | 35 | 0.00% | 0.00% |
| early-cse.NumSimplify | 541847 | 550017 | 8170 | 1.51% | 1.51% |
| instcombine.NumAggregateReconstructionsSimplified | 2139 | 108 | -2031 | -94.95% | 94.95% |
| instcombine.NumCombined | 3601364 | 3635448 | 34084 | 0.95% | 0.95% |
| instcombine.NumConstProp | 27153 | 27157 | 4 | 0.01% | 0.01% |
| instcombine.NumDeadInst | 1694521 | 1765022 | 70501 | 4.16% | 4.16% |
| instcombine.NumPHIsOfExtractValues | 0 | 37546 | 37546 | 0.00% | 0.00% |
| instcombine.NumSunkInst | 63158 | 63686 | 528 | 0.84% | 0.84% |
| instcount.NumBrInst | 874304 | 871857 | -2447 | -0.28% | 0.28% |
| instcount.NumCallInst | 1757657 | 1758402 | 745 | 0.04% | 0.04% |
| instcount.NumExtractValueInst | 45623 | 11483 | -34140 | -74.83% | 74.83% |
| instcount.NumInsertValueInst | 4983 | 580 | -4403 | -88.36% | 88.36% |
| instcount.NumInvokeInst | 61018 | 59478 | -1540 | -2.52% | 2.52% |
| instcount.NumLandingPadInst | 35334 | 34215 | -1119 | -3.17% | 3.17% |
| instcount.NumPHIInst | 344428 | 331116 | -13312 | -3.86% | 3.86% |
| instcount.NumRetInst | 100773 | 100772 | -1 | 0.00% | 0.00% |
| instcount.TotalBlocks | 1081154 | 1077166 | -3988 | -0.37% | 0.37% |
| instcount.TotalFuncs | 101443 | 101442 | -1 | 0.00% | 0.00% |
| instcount.TotalInsts | 8890201 | 8833747 | -56454 | -0.64% | 0.64% |
| instsimplify.NumSimplified | 75822 | 75707 | -115 | -0.15% | 0.15% |
| simplifycfg.NumHoistCommonCode | 24203 | 24197 | -6 | -0.02% | 0.02% |
| simplifycfg.NumHoistCommonInstrs | 48201 | 48195 | -6 | -0.01% | 0.01% |
| simplifycfg.NumInvokes | 2785 | 4298 | 1513 | 54.33% | 54.33% |
| simplifycfg.NumSimpl | 997332 | 1018189 | 20857 | 2.09% | 2.09% |
| simplifycfg.NumSinkCommonCode | 7088 | 6464 | -624 | -8.80% | 8.80% |
| simplifycfg.NumSinkCommonInstrs | 15117 | 14021 | -1096 | -7.25% | 7.25% |
```
... which tells us that this new fold fires whopping 38k times,
increasing the amount of SimplifyCFG's `invoke`->`call` transforms by +54% (+1513) (again, D85787 did that last time),
decreasing total instruction count by -0.64% (-56454),
and sharply decreasing count of `insertvalue`'s (-88.36%, i.e. 9 times less)
and `extractvalue`'s (-74.83%, i.e. four times less).
This causes geomean -0.01% binary size decrease
http://llvm-compile-time-tracker.com/compare.php?from=4d5ca22b8adfb6643466e4e9f48ba14bb48938bc&to=97dacca0111cb2ae678204e52a3cee00e3a69208&stat=size-text
and, ignoring `O0-g`, is a geomean -0.01%..-0.05% compile-time improvement
http://llvm-compile-time-tracker.com/compare.php?from=4d5ca22b8adfb6643466e4e9f48ba14bb48938bc&to=97dacca0111cb2ae678204e52a3cee00e3a69208&stat=instructions
The other thing that tells is, is that while this is a massive win for `invoke`->`call` transform
`InstCombinerImpl::foldAggregateConstructionIntoAggregateReuse()` fold,
which is supposed to be dealing with such aggregate reconstructions,
fires a lot less now. There are two reasons why:
1. After this fold, as it can be seen in tests, we may (will) end up with trivially redundant PHI nodes.
We don't CSE them in InstCombine presently, which means that EarlyCSE needs to run and then InstCombine rerun.
2. But then, EarlyCSE not only manages to fold such redundant PHI's,
it also sees that the extract-insert chain recreates the original aggregate,
and replaces it with the original aggregate.
The take-aways are
1. We maybe should do most trivial, same-BB PHI CSE in InstCombine
2. I need to check if what other patterns remain, and how they can be resolved.
(i.e. i wonder if `foldAggregateConstructionIntoAggregateReuse()` might go away)
This is a reland of the original commit fcb51d8c24,
because originally i forgot to ensure that the base aggregate types match.
Reviewed By: spatel
Differential Revision: https://reviews.llvm.org/D86530
Craig Topper