[InstCombine] Drop nsw in negation of select (#112893)

Closes https://github.com/llvm/llvm-project/issues/112666 and
https://github.com/llvm/llvm-project/issues/114181.

[InstCombine] Remove unused includes (NFC) (#114709)

Identified with misc-include-cleaner.

[InstCombine] Avoid infinite loop when negating phi nodes (#104581)

Closes https://github.com/llvm/llvm-project/issues/96012

---------

Co-authored-by: Nikita Popov <github@npopov.com>

[NFC] Eliminate top-level "using namespace" from some headers. (#102751)

- Eliminate top-level "using namespace" from some headers.

[InstCombine] Fold negation of calls to `ucmp/scmp` by swapping its operands (#98360)

Proofs: https://alive2.llvm.org/ce/z/cp_a36

[InstCombine] Avoid use of ConstantExpr::getShl()

Use IRBuilder instead, as we don't care about the return type
here. Use ImmConstant to ensure that constant folding will
succeed.

[InstCombine] Fix miscompile in negation of select (#89698)

Swapping the operands of a select is not valid if one hand is more
poisonous that the other, because the negation zero contains poison
e

[InstCombine] Fix miscompile in negation of select (#89698)

Swapping the operands of a select is not valid if one hand is more
poisonous that the other, because the negation zero contains poison
elements.

Fix this by adding an extra parameter to isKnownNegation() to forbid
poison elements.

I've implemented this using manual checks to avoid needing four variants
for the NeedsNSW/AllowPoison combinations. Maybe there is a better way
to do this...

Fixes https://github.com/llvm/llvm-project/issues/89669.

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[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] Remove nuw neg (#86295)

This patch removes APIs that creating NUW neg. It is a trivial case
because `sub nuw 0, X` always gets simplified into zero.
I believe there is no optimization oppor

[LLVM] Remove nuw neg (#86295)

This patch removes APIs that creating NUW neg. It is a trivial case
because `sub nuw 0, X` always gets simplified into zero.
I believe there is no optimization opportunities in the real-world
applications that we can take advantage of the nuw flag.

Motivated by
https://github.com/llvm/llvm-project/pull/84792#discussion_r1524891134.

Compile-time improvement:
https://llvm-compile-time-tracker.com/compare.php?from=d1f182c895728d89c5c3d198b133e212a5d9d4a3&to=da7b7478b7cbb32c09d760f6b8d0e67901e0d533&stat=instructions:u

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[InstSimplify][InstCombine] Remove unnecessary `m_c_*` matchers. (#81712)

This patch removes unnecessary `m_c_*` matchers since we always
canonicalize `commutive_op Cst, X` into `commutive_op X, Cs

[InstSimplify][InstCombine] Remove unnecessary `m_c_*` matchers. (#81712)

This patch removes unnecessary `m_c_*` matchers since we always
canonicalize `commutive_op Cst, X` into `commutive_op X, Cst`.

Compile-time impact:
https://llvm-compile-time-tracker.com/compare.php?from=bfc0b7c6891896ee8e9818f22800472510093864&to=d27b058bb9acaa43d3cadbf3cd889e8f79e5c634&stat=instructions:u

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[Transforms] Remove unused forward declarations (NFC)

[Transforms] Remove unnecessary includes (NFC)

[InstCombine] Use disjoint flag instead of haveNoCommonBitsSet()

Slightly stronger, if disjoint was inferred earlier with information
that is no longer available.

[InstCombine] Don't transform `sub X, ~Y` -> `add X, -Y` unless `Y` is actually negatable

This combine was previously adding instruction in some cases (see the
tests).

Closes #72767

[llvm] Stop including llvm/ADT/iterator_range.h (NFC)

Identified with misc-include-cleaner.

[ValueTracking] Use SimplifyQuery in haveNoCommonBitsSet() (NFC)

Pass SimplifyQuery instead of unpacked list of arguments.

[InstCombine] Propagate nsw flag when negating

When pushing a sub nsw 0, %x negation into an expression, try to
preserve the nsw flag for the cases where this is possible. Do this
by passing the fla

[InstCombine] Propagate nsw flag when negating

When pushing a sub nsw 0, %x negation into an expression, try to
preserve the nsw flag for the cases where this is possible. Do this
by passing the flag through recursive Negator::negate() calls.

Proofs: https://alive2.llvm.org/ce/z/oRPNcY

Differential Revision: https://reviews.llvm.org/D158510

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Don't include Optional.h

These files no longer use llvm::Optional.

[Transforms/InstCombine] llvm::Optional => std::optional

[ADT] Don't including None.h (NFC)

These source files no longer use None, so they do not need to include
None.h.

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://

[ADT] Don't including None.h (NFC)

These source files no longer use None, so they do not need to include
None.h.

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

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[Transforms] Use std::nullopt instead of None (NFC)

This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated. The intent is to reduce
the amount

[Transforms] Use std::nullopt instead of None (NFC)

This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated. The intent is to reduce
the amount of manual work required in migrating from Optional to
std::optional.

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

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[InstCombine] don't canonicalize shl+sub to mul+add

This stops Negator from transforming:
`C1 - shl X, C2 --> mul X, (1<<C2) + C1`
...in the general case. There does not seem to be any analysis
bene

[InstCombine] don't canonicalize shl+sub to mul+add

This stops Negator from transforming:
`C1 - shl X, C2 --> mul X, (1<<C2) + C1`
...in the general case. There does not seem to be any analysis
benefit to using mul in IR, and there's definitely downside in
codegen (particularly when the multiply has to be expanded).

If `C1` is 0, then there's a stronger argument that the single
mul is a better canonicalization than negate-of-shl, but we may
want to remove that too.

This was noted as a potential conflict for D133667.

Differential Revision: https://reviews.llvm.org/D134310

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[InstCombine] fold signbit splat pattern that uses negate

0 - (zext (i8 X u>> 7) to iN) --> sext (i8 X s>> 7) to iN

https://alive2.llvm.org/ce/z/jzv4Ud

This is part of solving issue #57381.

[llvm] LLVM_FALLTHROUGH => [[fallthrough]]. NFC

With C++17 there is no Clang pedantic warning or MSVC C5051.

[llvm] LLVM_NODISCARD => [[nodiscard]]. NFC

With C++17 there is no Clang pedantic warning.