If a ctlz operation is performed on higher datatype and then
downcasted, then this can be optimized by doing a ctlz operation
on a lower datatype and adding the difference bitsize to the result
of ctlz to provide the same output:
https://alive2.llvm.org/ce/z/8uup9M
The original problem is shown in
https://llvm.org/PR50173
Differential Revision: https://reviews.llvm.org/D103788
This adds support for addrspace casts involving opaque pointers to
InstCombine, as well as the isEliminableCastPair() helper
(otherwise the assertion failure would just move there).
Add PointerType::hasSameElementTypeAs() to hide the element type
details.
Differential Revision: https://reviews.llvm.org/D104668
Reapplied without changes -- this was reverted together with an
underlying patch.
-----
Bitcasts having opaque pointer source or result type cannot be
converted into a zero-index GEP, GEP source and result types
always have the same opaque-ness.
Relative to the original patch, an InstCombine test has been
added to show a previously missed pattern, and the Coroutine
test that resulted in the revert has been regenerated.
-----
Move this into a separate function, to make sure that early
returns do not accidentally skip other transforms. This previously
happened for the isSized() check, which skipped folds like
distributing a bitcast over a select.
Bitcasts having opaque pointer source or result type cannot be
converted into a zero-index GEP, GEP source and result types
always have the same opaque-ness.
Move this into a separate function, to make sure that early
returns do not accidentally skip other transforms. There is
already one isSized() check that could run into this issue,
thus this change is not strictly NFC.
It's not possible to bitcast between different address spaces,
and this is ensured by the IR verifier. As such, this bitcast to
addrspacecast canonicalization can never be hit.
This patch updates InstCombine to use poison constant to represent the resulting value of (either semantically or syntactically) unreachable instrs, or a don't-care value of an unreachable store instruction.
This allows more aggressive folding of unused results, as shown in llvm/test/Transforms/InstCombine/getelementptr.ll .
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D104602
This is similar to b865eead76 ( D103617 ) and fixes:
https://llvm.org/PR5057541b71f718b did this and more (noted with TODO
comments in the tests), but it didn't handle the case
where the destination is narrower than the source, so
it got reverted.
This is a simple match-and-replace. If there's evidence
that the TODO cases are useful, we can revisit/extend.
This is a patch that replaces shufflevector and insertelement's placeholder value with poison.
Underlying motivation is to fix the semantics of shufflevector with undef mask to return poison instead
(D93818)
The consensus has been made in the late 2020 via mailing list as well as the thread in https://bugs.llvm.org/show_bug.cgi?id=44185 .
This patch is a simple syntactic change to the existing code, hence directly pushed as a commit.
This does not solve PR17101, but it is one of the
underlying diffs noted here:
https://bugs.llvm.org/show_bug.cgi?id=17101#c8
We could ease the one-use checks for the 'clear'
(no 'not' op) half of the transform, but I do not
know if that asymmetry would make things better
or worse.
Proofs:
https://rise4fun.com/Alive/uVB
Name: masked bit set
%sh1 = shl i32 1, %y
%and = and i32 %sh1, %x
%cmp = icmp ne i32 %and, 0
%r = zext i1 %cmp to i32
=>
%s = lshr i32 %x, %y
%r = and i32 %s, 1
Name: masked bit clear
%sh1 = shl i32 1, %y
%and = and i32 %sh1, %x
%cmp = icmp eq i32 %and, 0
%r = zext i1 %cmp to i32
=>
%xn = xor i32 %x, -1
%s = lshr i32 %xn, %y
%r = and i32 %s, 1
Note: this is a re-post of a patch that I committed at:
rGa041c4ec6f7a
The commit was reverted because it exposed another bug:
rGb212eb7159b40
But that has since been corrected with:
rG8a156d1c2795189 ( D101191 )
Differential Revision: https://reviews.llvm.org/D72396
We could go either direction on this transform. VectorCombine already goes this
way for bitcasts (and handles more complicated cases using the cost model), so
let's try cast-first.
Deferring completely to VectorCombine is another possibility. But the backend
should be able to invert this easily when the vectors have the same shape, so
it doesn't seem like a transform that we need to avoid.
The motivating example from https://llvm.org/PR49081 has an int-to-float
sandwiched between 2 shuffles, and the backend currently does not reduce that,
so on x86, we get something like:
pshufd $249, %xmm0, %xmm0]
cvtdq2ps %xmm0, %xmm0
shufps $144, %xmm0, %xmm0
...instead of just a single conversion instruction.
Differential Revision: https://reviews.llvm.org/D103038
This is a more convoluted form of the same pattern "sext of NSW trunc",
but in this case the operand of trunc was a right-shift,
and the truncation chops off just the zero bits that were shifted-in.
This patch is related to https://reviews.llvm.org/D100032 which define
some illegal types or operations for x86_amx. There are no arguments,
arrays, pointers, vectors or constants of x86_amx.
Reviewed By: pengfei
Differential Revision: https://reviews.llvm.org/D100472
A bug was found within InstCombineCasts where a function call
is only implemented to work with FixedVectors. This caused a
crash when a ScalableVector was passed to this function.
This commit introduces a regression test which recreates the
failure and a bug fix.
Differential Revision: https://reviews.llvm.org/D98351
Sometimes you want to get a type with same vector element count
as the current type, but different element type,
but there's no QOL wrapper to do that. Add one.
This patch is plumbing to support work towards the goal outlined in the recent llvm-dev post "[llvm-dev] RFC: Decomposing deref(N) into deref(N) + nofree".
The point of this change is purely to simplify iteration on other pieces on way to making the switch. Rebuilding with a change to Value.h is slow and painful, so I want to get the API change landed. Once that's done, I plan to more closely audit each caller, add the inference rules in their own patch, then post a patch with the langref changes and test diffs. The value of the command line flag is that we can exercise the inference logic in standalone patches without needing the whole switch ready to go just yet.
Differential Revision: https://reviews.llvm.org/D98908
The load/store instruction will be transformed to amx intrinsics
in the pass of AMX type lowering. Prohibiting the pointer cast
make that pass happy.
Differential Revision: https://reviews.llvm.org/D98247
The structure of this fold is suspect vs. most of instcombine
because it creates instructions and tries to delete them
immediately after.
If we don't have the operand types for the icmps, then we are
not behaving as assumed. And as shown in PR49475, we can inf-loop.
Currently make_early_inc_range cannot be used with iterators with
operator* implementations that do not return a reference.
Most notably in the LLVM codebase, this means the User iterator ranges
cannot be used with make_early_inc_range, which slightly simplifies
iterating over ranges while elements are removed.
Instead of directly using BaseT::reference as return type of operator*,
this patch uses decltype to get the actual return type of the operator*
implementation in WrappedIteratorT.
This patch also updates a few places to use make use of
make_early_inc_range.
Reviewed By: dblaikie
Differential Revision: https://reviews.llvm.org/D93992
If the shift amount was undef for some lane, the shift amount in opposite
shift is irrelevant for that lane, and the new shift amount for that lane
can be undef.
If the shift amount was undef for some lane, the shift amount in opposite
shift is irrelevant for that lane, and the new shift amount for that lane
can be undef.
As discussed on PR35155, this extends narrowFunnelShift (recently renamed from narrowRotate) to support basic funnel shift patterns.
Unlike matchFunnelShift we don't include the computeKnownBits limitation as extracting the pattern from the zext/trunc layers should be a indicator of reasonable funnel shift codegen, in D89139 we demonstrated how to efficiently promote funnel shifts to wider types.
Differential Revision: https://reviews.llvm.org/D89542
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.
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
Annoyingly vectors aren't supported by shouldChangeType(), but we have precedents for always performing this on vector types (e.g. narrowBinOp).
Differential Revision: https://reviews.llvm.org/D89067
Attempt to fold trunc (*shr (trunc A), C) --> trunc(*shr A, C) iff the shift amount if small enough that all zero/sign bits created by the shift are removed by the last trunc.
Helps fix the regressions encountered in D88316.
I've tweaked a couple of shift values as suggested by @lebedev.ri to ensure we have coverage of shift values close (above/below) to the max limit.
Differential Revision: https://reviews.llvm.org/D88429
This came from @lebedev.ri's suggestion to use m_SpecificInt_ICMP for D88429 - since I was going to change the m_APInt to m_Constant for that patch I thought I would do it for the only other user of the APInt first.
I've added a ConstantExpr::getUMin helper - its trivial to add UMAX/SMIN/SMAX but thought I'd wait until we have use cases.
Differential Revision: https://reviews.llvm.org/D88475
Dylan Fleming