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
This patch intersects the fast math flags from the two fcmps instead
of dropping them.
I poked at this a bunch with Alive2 for nnan and ninf flags and it seemed
to check out. With the other flags it told me "Couldn't prove the
correctness of the transformation". Not sure if I should just preserve
nnan and ninf?
Reviewed By: spatel, lebedev.ri
Differential Revision: https://reviews.llvm.org/D121243
The similar getICmpCode and getPredForICmpCode are already there.
This moves FP for consistency.
I think InstCombine is currently the only user of both.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D120754
Instead of passing an InstCmpInt * and a bool just pass the predicate
from the caller.
I'm considering moving the similar FCmp functions from InstCombine
over here and this makes the interface consistent with what is used
for FCmp.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D120609
While this might be marginally more precise, we generally don't
bother with this in InstCombine, and let the IRBuilder assign the
debug location. I don't see why this one fold, out of the thousands
done in InstCombine, should be treated specially.
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
~(iN X s>> (N-1)) & Y --> (X s< 0) ? 0 : Y
https://alive2.llvm.org/ce/z/JKlQ9x
This is similar to D111410 / 727e642e97 ,
but it includes a 'not' of the signbit and so it
saves an instruction in the basic pattern.
DAGCombiner or target-specific folds can expand
this back into bit-hacks.
The diffs in the logical-select tests are not true
regressions - running early-cse and another round
of instcombine is expected in a normal opt pipeline,
and that reduces back to a minimal form as shown
in the duplicated PhaseOrdering test.
I have no understanding of the SystemZ diffs, so
I made the minimal edits suggested by FileCheck to
make that test pass again. That whole test file is
wrong though. It is running the entire optimizer (-O2)
to check IR, and then topping that by even running
codegen and checking asm. It needs to be split up.
Fixes#52631
or (mul X, Y), X --> mul X, (add Y, 1) (when the multiply has no common bits with X)
We already have this fold if the pattern ends in 'add', but we can miss it if the
'add' becomes 'or' via another no-common-bits transform.
This is part of fixing:
http://llvm.org/PR49055
...but it won't make a difference on that example yet.
https://alive2.llvm.org/ce/z/Vrmoeb
Differential Revision: https://reviews.llvm.org/D114729
I noticed that adding a seemingly unrelated fold for xor caused
regressions on similar patterns, and this is one of the
underlying causes.
This could also be a variation for code as seen in:
https://llvm.org/PR34047
...although that exact example should be fixed after:
D113035 / c36b7e21bd
The vector test shows that we are actually missing a potential
canonicalization for bitcast-of-sext-of-not or the inverse.
The scalar test shows that even if we had that canonicalization,
it would still be possible to see this pattern due to extra uses.
https://alive2.llvm.org/ce/z/y2BAgi
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
For the scalar/splat case, this fold is subsumed by
foldLogOpOfMaskedICmps(). However, the conjugated fold for "or"
also supports splats with undef. Make both code paths consistent
by using m_ZeroInt() for the "and" implementation as well.
https://alive2.llvm.org/ce/z/tN63cuhttps://alive2.llvm.org/ce/z/ufB_Ue
When folding and/or of icmps, look through add of a constant and
adjust the icmp range instead. Effectively, this decomposes
X + C1 < C2 style range checks back into a normal range. This allows
us to fold comparisons involving two range checks or one range check
and some other condition. We had a fold for a really specific case
of this (or of range check and eq, and only one one side!) while
this handles it in fully generality.
Differential Revision: https://reviews.llvm.org/D113510
Since there is just a single check for LHS in ~(A | B) & C | ...
transforms and multiple RHS checks inside with more coming I am
removing m_OneUse checks for LHS and adding new checks for RHS.
This is non essential as long as there is total benefit.
In addition (~(A | B) & C) | (~(A | C) & B) --> (B ^ C) & ~A
checks were overly restrictive, it should be good without any
additional checks.
Differential Revision: https://reviews.llvm.org/D113141
A problem was noted in the post-commit review for
c36b7e21bd / D113035 :
If the source type is not integer or integer vector,
then we could crash when trying to ComputeNumSignBits().
The implementation for and/or is the same, apart from the choice
of exactIntersectWith() vs exactUnionWith(). Extract a common
function to make future extension easier.
Rather than testing for many specific combinations of predicates
and values, compute the exact icmp regions for both comparisons
and check whether they union/intersect exactly. If they do,
construct the equivalent icmp for the new range. Assuming that the
existing code handled all possible cases, this should be NFC.
Differential Revision: https://reviews.llvm.org/D113367
(Cond & C) | (~bitcast(Cond) & D) --> bitcast (select Cond, (bc C), (bc D))
This is part of fixing:
https://llvm.org/PR34047
That report shows a case where a bitcast is sitting between the select condition
candidate and its 'not' value due to current cast canonicalization rules.
There's a bitcast type restriction that might be violated in existing matching,
but I still need to investigate if that is possible -
Alive2 shows we can only do this transform safely when the bitcast is from
narrow to wide vector elements (otherwise poison could leak into elements
that were safe in the original code):
https://alive2.llvm.org/ce/z/Hf66qh
Differential Revision: https://reviews.llvm.org/D113035
The added test has poison lanes due to the vector shuffle. This can
cause an infinite loop of combines in instcombine where it folds
xor(ashr, -1) -> select (icmp slt 0), -1, 0 -> sext (icmp slt 0) -> xor(ashr, -1).
We usually prevent this by checking that the xor constant is not -1,
but with vectors some of the lanes may be -1, some may be poison. So
this changes the way we detect that from "!C1->isAllOnesValue()" to
"!match(C1, m_AllOnes())", which is more able to detect that some of the
lanes are poison.
Fixes PR52397
The tests diffs are logically equivalent, and so this is
generally NFC, but this makes the code match the code
comment.
It should also be more efficient. If we choose the 'not'
operand (rather than the 'not' instruction) as the select
condition, then we don't have to invert the select
condition/operands as a subsequent transform.
Similar to 54e969cffd (and with cosmetic updates to hopefully
make that easier to read), this fold has been around since early
in LLVM history.
Intermediate folds have been added subsequently, so extra uses
are required to exercise this code.
The test example actually shows an unintended consequence with
extra uses - we end up with an extra instruction compared to what
we started with. But this at least makes scalar/vector consistent.
General proof:
https://alive2.llvm.org/ce/z/tmuBza
This fold was added long ago (part of fixing PR4216),
and it matched scalars only. Intermediate folds have
been added subsequently, so extra uses are required
to exercise this code.
General proof:
https://alive2.llvm.org/ce/z/G6BBhB
One of the specific tests:
https://alive2.llvm.org/ce/z/t0JhEB
The sequence of instructions `xor (ashr X, BW-1), C` (or with a truncation
`xor (trunc (ashr X, BW-1)), C)` takes a value, produces all zeros or all
ones and with it optionally inverts a constant depending on whether the
original input was positive or negative. This is the same as checking if
the value is positive, and selecting between the constant and ~constant.
https://alive2.llvm.org/ce/z/NJ85qY
This is a fairly general version of a fold that helps pull saturating
arithmetic into a canonical form.
Differential Revision: https://reviews.llvm.org/D109151
Fixes non-determinisctic order of XOR instructions created after
5a7a458306. The order of call argument evaluation is not
defined, so create one Value before the call.
This removes an over-specified fold. The more general transform
was added with:
727e642e97
There's a difference on an existing test that shows a potentially
unnecessary use limit on an icmp fold.
That fold is in InstCombinerImpl::foldICmpSubConstant(), and IIRC
there was some back-and-forth on it and similar folds because they
could cause analysis/passes (SCEV, LSR?) to miss optimizations.
Differential Revision: https://reviews.llvm.org/D111410
(iN X s>> (N-1)) & Y --> (X < 0) ? Y : 0
https://alive2.llvm.org/ce/z/qeYhdz
I was looking at a missing abs() transform and found my way to this
generalization of an existing fold that was added with D67799.
As discussed in that review, we want to make sure codegen handles
this difference well, and for all of the targets/types that I
spot-checked, it looks good.
I am leaving the existing fold in place in this commit because
it covers a potentially missing icmp fold, but I plan to remove
that as a follow-up commit as suggested during review.
Differential Revision: https://reviews.llvm.org/D111410
This is NFC-intended for scalar code. There are still unnecessary
m_ConstantInt restrictions in surrounding code, so this is not a
complete fix.
This prevents regressions seen with a planned follow-on to D111410.
Craig Topper