InstCombine canonicalizes `add` to `or` when possible, but this makes
some optimizations applicable to `add` to be missed because they don't
realize that the `or` is equivalent to `add`.
In this patch we generalize `foldICmpBinOp` to handle such cases.
When the sub arguments are ptr2int it is not possible to determine
computeKnownBits() of its arguments.
For scalar case generally sub of 2 ptr2int are converted to sub of
indexes.
However a loop with recursive GEP/PHI where the arguments to sub is of
type ptr2int, if it is possible to determine that a sub of this GEP and
another pointer with the same base is KnownNonZero we can return this.
This helps subsequent passes to optimize the loop further.
Return poison instead of undef for non-demanded lanes in the AMDGPU
demanded element simplification hook.
Also bail out of dmask is 0, as this case has special semantics:
> If DMASK==0, the TA overrides DMASK=1 and puts zeros in VGPR followed by
> LWE status if exists. TFE status is not generated since the fetch is dropped.
Otherwise we may replace undef with poison.
Note that a lot of tests regressing here already have variants
that use poison instead of undef (often in a separate
inseltpoison file), which is why I'm not adjusting them to the
new pattern.
Do not poison `undef` demanded elements in `SimplifyDemandedVectorElts`.
A miscompilation issue has been addressed with refined checking.
Proofs: https://alive2.llvm.org/ce/z/WA5oD5.
This patch tries to canonicalize the pattern `Overflow | icmp pred Res,
C2` into `Overflow | icmp pred X, C2 +/- C1`, where `Overflow` and `Res`
are return values of `xxx.with.overflow X, C1`.
Alive2: https://alive2.llvm.org/ce/z/PhR_3SFixes#75360.
We are able to fold
or (mul X, Y), X --> mul X, (add Y, 1) (when the multiply has no common bits with X)
but we miss it if the mul operands are commuted.
This is an experimental address space for strided buffers. These buffers
can have structs as elements and
a stride > 1.
These pointers allow the indexed access in units of stride, i.e., they
point at `buffer[index * stride]`.
Thus, we can use the `idxen` modifier for buffer loads.
We assign address space 9 to 192-bit buffer pointers which contain a
128-bit descriptor, a 32-bit offset and a 32-bit index. Essentially,
they are fat buffer pointers with an additional 32-bit index.
Change (add x, c) to (xor x, c) iff c is constant and c equals the top bit of the demanded bits.
Alive2: https://alive2.llvm.org/ce/z/DKmkwF
---------
Signed-off-by: Peter Han <fujun.han@iluvatar.com>
Co-authored-by: Peter Han <fujun.han@iluvatar.com>
Instead of checking whether the GEP as a whole is constant, only
check whether it has constant incides. This matches what we do in
other places in this code.
This has little practical impact, because it is mostly already
handled through other cases anyway. We see a difference for
non-inbounds equality comparisons.
We have a bunch of folds that basically perform X pred Y to ~Y pred ~X
for various special cases where this saves an instruction.
Generalize these folds to use isFreeToInvert(). We have to make sure
that we consume an instruction in either of the inversions, otherwise
we're just going to swap the icmp back and forth.
Fixes https://github.com/llvm/llvm-project/issues/74302.
When I originally added this fold, it did not actually fix my
motivation case, where the add was represented as an or. Now that
we have the disjoint flag this can finally be cleanly supported.
This adds support for using dominating conditions in computeKnownBits()
when called from InstCombine. The implementation uses a
DomConditionCache, which stores which branches may provide information
that is relevant for a given value.
DomConditionCache is similar to AssumptionCache, but does not try to do
any kind of automatic tracking. Relevant branches have to be explicitly
registered and invalidated values explicitly removed. The necessary
tracking is done inside InstCombine.
The reason why this doesn't just do exactly the same thing as
AssumptionCache is that a lot more transforms touch branches and branch
conditions than assumptions. AssumptionCache is an immutable analysis
and mostly gets away with this because only a handful of places have to
register additional assumptions (mostly as a result of cloning). This is
very much not the case for branches.
This change regresses compile-time by about ~0.2%. It also improves
stage2-O0-g builds by about ~0.2%, which indicates that this change results
in additional optimizations inside clang itself.
Fixes https://github.com/llvm/llvm-project/issues/74242.
It's not safe for InstCombine to add disjoint metadata when converting
Add to Or otherwise.
I've added noundef attribute to preserve existing test behavior.
Use disjoint instead of haveNoCommonBitsSet(), which is slightly
stronger in case the information used to infer disjoint has been
lost.
Introduce the m_DisjointOr() matcher to make handling cases like
this cleaner.
