[LLVM][IR] Use splat syntax when printing ConstantExpr based splats. (#116856)

This brings the printing of scalable vector constant splats inline with
their fixed length counterparts.

[LLVM][IR] Use splat syntax when printing Constant[Data]Vector. (#112548)

[IR][PatternMatch] Only accept poison in getSplatValue() (#89159)

In #88217 a large set of matchers was changed to only accept poison
values in splats, but not undef values. This is because we now

[IR][PatternMatch] Only accept poison in getSplatValue() (#89159)

In #88217 a large set of matchers was changed to only accept poison
values in splats, but not undef values. This is because we now use
poison for non-demanded vector elements, and allowing undef can cause
correctness issues.

This patch covers the remaining matchers by changing the AllowUndef
parameter of getSplatValue() to AllowPoison instead. We also carry out
corresponding renames in matchers.

As a followup, we may want to change the default for things like m_APInt
to m_APIntAllowPoison (as this is much less risky when only allowing
poison), but this change doesn't do that.

There is one caveat here: We have a single place
(X86FixupVectorConstants) which does require handling of vector splats
with undefs. This is because this works on backend constant pool
entries, which currently still use undef instead of poison for
non-demanded elements (because SDAG as a whole does not have an explicit
poison representation). As it's just the single use, I've open-coded a
getSplatValueAllowUndef() helper there, to discourage use in any other
places.

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[LLVM][tests/Transforms/InstCombine] Convert instances of ConstantExpr based splats to use splat().

This is mostly NFC but some output does change due to consistently
inserting into poison rather th

[LLVM][tests/Transforms/InstCombine] Convert instances of ConstantExpr based splats to use splat().

This is mostly NFC but some output does change due to consistently
inserting into poison rather than undef and using i64 as the index
type for inserts.

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[InstCombine] Replace non-demanded undef vector with poison

If an operand (esp to shufflevector or insertelement) is not
demanded, canonicalize it from undef to poison.

[InstCombine] Canonicalize splat shuffles to use poison operand

If the splat shuffle is represented using an undef RHS, replace it
with poison.

[InstCombine] Remove bitcast handling from SimplifyDemandedBits

The complex set of type checks in this code reduces down to
"always return nullptr". Drop the code to use the default
implementation i

[InstCombine] Remove bitcast handling from SimplifyDemandedBits

The complex set of type checks in this code reduces down to
"always return nullptr". Drop the code to use the default
implementation instead, which will just compute the KnownBits
for the bitcast.

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[test][InstCombine] Update some test cases to use opaque pointers

These tests cases were converted using the script at
https://gist.github.com/nikic/98357b71fd67756b0f064c9517b62a34

Differential Re

[test][InstCombine] Update some test cases to use opaque pointers

These tests cases were converted using the script at
https://gist.github.com/nikic/98357b71fd67756b0f064c9517b62a34

Differential Revision: https://reviews.llvm.org/D135094

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[test] Use -passes=instcombine instead of -instcombine in lots of tests. NFC

Another step moving away from the deprecated syntax of specifying
pass pipeline in opt.

Differential Revision: https://r

[test] Use -passes=instcombine instead of -instcombine in lots of tests. NFC

Another step moving away from the deprecated syntax of specifying
pass pipeline in opt.

Differential Revision: https://reviews.llvm.org/D119081

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[InstCombine] Generalize and-reduce pattern to handle `ne` case as well as `eq`

Following Sanjay's proposal from discussion in D118317, this patch
generalizes and-reduce handling to fold the followi

[InstCombine] Generalize and-reduce pattern to handle `ne` case as well as `eq`

Following Sanjay's proposal from discussion in D118317, this patch
generalizes and-reduce handling to fold the following pattern
```
icmp ne (bitcast(icmp ne (lhs, rhs)), 0)
```
into
```
icmp ne (bitcast(lhs), bitcast(rhs))
```

https://alive2.llvm.org/ce/z/WDcuJ_

Differential Revision: https://reviews.llvm.org/D118431
Reviewed By: lebedev.ri

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Recommit "[InstCombine] Fold and-reduce idiom"

Checks of original vector types made more thorough.

Differential Revision: https://reviews.llvm.org/D118317

[Test] Add pointer comparison test that crashed with D118317

Revert "[InstCombine] Fold and-reduce idiom"

It causes builds to fail with

llvm/include/llvm/Support/Casting.h:269:
typename llvm::cast_retty<X, Y*>::ret_type llvm::cast(Y*)
[with X = llvm::Integer

Revert "[InstCombine] Fold and-reduce idiom"

It causes builds to fail with

llvm/include/llvm/Support/Casting.h:269:
typename llvm::cast_retty<X, Y*>::ret_type llvm::cast(Y*)
[with X = llvm::IntegerType; Y = const llvm::Type; typename llvm::cast_retty<X, Y*>::ret_type = const llvm::IntegerType*]:
Assertion `isa<X>(Val) && "cast<Ty>() argument of incompatible type!"' failed.

See the code review for link to a reproducer.

> This patch introduces folding of and-reduce idiom and generates code
> that is easier to read and which is lest costly in terms of icmp operations.
> The folding is
> ```
> icmp eq (bitcast(icmp ne (lhs, rhs)), 0)
> ```
> into
> ```
> icmp eq(bitcast(lhs), bitcast(rhs))
> ```
>
> See PR53419.
>
> Differential Revision: https://reviews.llvm.org/D118317
> Reviewed By: lebedev.ri, spatel

This reverts commit 8599bb0f26738ed88aae62aba57d82f7cf326cf9.

This also revertes the dependent change:

"[Test] Add 'ne' tests for and-reduce pattern folding"

This reverts commit a4aaa5995308ac2ba1bf180c9ce9c321cdb9f28a.

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[Test] One more test for 'ne' and-reduce pattern

[InstCombine] Fold and-reduce idiom

This patch introduces folding of and-reduce idiom and generates code
that is easier to read and which is lest costly in terms of icmp operations.
The folding is
`

[InstCombine] Fold and-reduce idiom

This patch introduces folding of and-reduce idiom and generates code
that is easier to read and which is lest costly in terms of icmp operations.
The folding is
```
icmp eq (bitcast(icmp ne (lhs, rhs)), 0)
```
into
```
icmp eq(bitcast(lhs), bitcast(rhs))
```

See PR53419.

Differential Revision: https://reviews.llvm.org/D118317
Reviewed By: lebedev.ri, spatel

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[Test] Add data layout to relevant tests + some wide-typed tests

[InstCombine] Update InstCombine to use poison instead of undef for shufflevector's placeholder (2/3)

This patch is for fixing potential shufflevector-related bugs like D93818.
As D93818, this patch

[InstCombine] Update InstCombine to use poison instead of undef for shufflevector's placeholder (2/3)

This patch is for fixing potential shufflevector-related bugs like D93818.
As D93818, this patch change shufflevector's default placeholder to poison.
To reduce risk, it was divided into several patches, and this patch is for InstCombineCompares and InstructionCombining.

Reviewed By: spatel

Differential Revision: https://reviews.llvm.org/D110227

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[InstCombine] reduce vector casting before icmp

There may be some generalizations (see test comments) of these patterns,
but this should handle the cases motivated by:
https://llvm.org/PR51315
https

[InstCombine] reduce vector casting before icmp

There may be some generalizations (see test comments) of these patterns,
but this should handle the cases motivated by:
https://llvm.org/PR51315
https://llvm.org/PR51259

The backend may want to transform differently, but at least for
the x86 examples that I looked at, there does not appear to be
any significant perf diff either way.

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[InstCombine] add tests for icmp of casted vector; NFC

https://llvm.org/PR51315

Fix the default alignment of i1 vectors.

Currently, the default alignment is much larger than the actual size of
the vector in memory. Fix this to use a sane default.

For SVE, temporarily remove l

Fix the default alignment of i1 vectors.

Currently, the default alignment is much larger than the actual size of
the vector in memory. Fix this to use a sane default.

For SVE, temporarily remove lowering of load/store operations for
predicates with less than 16 elements. The layout the backend was
assuming for SVE predicates with less than 16 elements doesn't agree
with the frontend. More work probably needs to be done here.

This change is, strictly speaking, not backwards-compatible at the
bitcode level. But probably nobody is actually depending on that; i1
vectors in memory are rare, and the code that does use them probably
ends up forcing the alignment to something sane anyway. If we think
this is a concern, I can restrict this to scalable vectors for now
(where it's actually causing issues for me at the moment).

Differential Revision: https://reviews.llvm.org/D88994

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[InstCombine] canonicalize cmp-of-bitcast-of-vector-cmp to use zero constant

We can invert a compare constant and preserve the logic
as shown in this sampling:
https://alive2.llvm.org/ce/z/YAXbfs
(I

[InstCombine] canonicalize cmp-of-bitcast-of-vector-cmp to use zero constant

We can invert a compare constant and preserve the logic
as shown in this sampling:
https://alive2.llvm.org/ce/z/YAXbfs
(In theory, we could deal with non-all-ones/zero as well,
but it doesn't seem worthwhile.)

I noticed this as a part of the x86 codegen difference in
https://llvm.org/PR51259 - it ends up using "test"
instead of "not + cmp" in that example.

This pattern also shows up in https://llvm.org/PR41312
and https://llvm.org/PR50798 .

Differential Revision: https://reviews.llvm.org/D107170

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[InstCombine] add more tests for vector cmp-bitcast; NFC

D107170

[InstCombine] add more tests for vector-cmp bitcast; NFC

[InstCombine] add tests for vector cmp-bitcast; NFC

[Constants] Extend support for scalable-vector splats

This patch extends the various "isXXX" functions of the `Constant` class
to include scalable-vector splats.

In several "isXXX" functions, code

[Constants] Extend support for scalable-vector splats

This patch extends the various "isXXX" functions of the `Constant` class
to include scalable-vector splats.

In several "isXXX" functions, code that was separately inspecting
`ConstantVector` and `ConstantDataVector` was unified to use
`getSplatValue`, which already includes support for said splats.

In the varous "isNotXXX" functions, code was added to check whether the
scalar splat value -- if any -- satisfies the predicate.

An extra fix for `isNotMinSignedValue` was included, as it previously
crashed when passed a scalable-vector type because it unconditionally
cast to `FixedVectorType`

These changes address numerous missed optimizations, a compiler crash
mentioned above and -- perhaps most egregiously -- an infinite loop in
InstCombine due to the compiler breaking canonical form when it failed
to pick up on a splat in a select instruction.

Test cases have been added to cover as many of these functions as
possible, though existing coverage is slim; it doesn't appear that there
are any in-tree uses of `Constant::isNegativeZeroValue`, for example.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D103421

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