Changes

[X86] Simplify patterns for avx512 vpcmp. NFC

This removes the commuted PatFrags that only existed to carry
an SDNodeXForm in its OperandTransform field. We know all the places
that need to use the commuted SDNodeXForm and there is one transform
shared by signed and unsigned compares. So just hardcode the
the SDNodeXForm where it is needed and use the non commuted PatFrag
in the pattern.

I think when I wrote this I thought the SDNodeXForm name had to
match what is in the PatFrag that is being used. But that's not
true. The OperandTransform is only used when the PatFrag is used
in an instruction pattern and not a separate Pat pattern. All
the commuted cases are Pat patterns.

[GCOV] Drop unnecessary const from return types (NFC)

Identified with readability-const-return-type.

[TableGen] Use ListSeparator (NFC)

[AsmPrinter] Use range-based for loops (NFC)

[Polly] Hide Simplify implementation from header. NFC.

Move SimplifiyVisitor from Simplify.h to Simplify.cpp. It is not
relevant for applying the pass in either the NewPM or the legacyPM.
Rename it to SimplifyImpl to account for that.

This is possible due its state not being necessary to be preserved
between runs and thefore SimplifyImpl not needed to be held in the
pass object. Instead, SimplifyImpl is only instatiated for the
current Scop. In the NewPM as a function-local variable, and in the
legacy PM inside a llvm::Optional object because the state must be
preserved between the printScop (invoked by opt -analyze) and the most
recent runOnScop calls.

[AMDGPU] Refactor MIMG tables to better handle hardware variants

Add mimgopc object to represent the opcode allowing different
opcodes for different hardware variants.
This enables image_atomic_fcmpswap, image_atomic_fmin, and
image_atomic_fmax on GFX10

Reviewed By: foad, rampitec

Differential Revision: https://reviews.llvm.org/D96309

[clang][cli] Fix gcc warning (NFC)

GCC warning:
```
/llvm-project/clang/lib/Frontend/TestModuleFileExtension.cpp:131:20: warning: ‘llvm::raw_ostream& clang::operator<<(llvm::raw_ostream&, const clang::TestModuleFileExtension&)’ has not been declared within ‘clang’
  131 | llvm::raw_ostream &clang::operator<<(llvm::raw_ostream &OS,
      |                    ^~~~~
In file included from /llvm-project/clang/lib/Frontend/TestModuleFileExtension.cpp:8:
/llvm-project/clang/lib/Frontend/TestModuleFileExtension.h:75:3: note: only here as a ‘friend’
   75 |   operator<<(llvm::raw_ostream &OS, const TestModuleFileExtension &Extension);
      |   ^~~~~~~~
```

[Test] Add negative tests where usub optimization should not apply

[Codegenprepare][X86] Use usub with overflow opt for IV increment

Function `replaceMathCmpWithIntrinsic` artificially limits the scope
of the optimization, setting a requirement of two instructions be in
the same block, due to two reasons:
- usage of DT for more general check is costly in terms of compile time;
- risk of creating a new value that lives through multiple blocks.

Because of this, two semantically equivalent tests may be or not be the
subject of this opt depending on where the binary operation is located.
See `test/CodeGen/X86/usub_inc_iv.ll` for motivation

There is one important particular case where this limitation is  too strict:
it is when the binary operation is the increment of the induction variable.
As result, the application of this opt becomes fragile and highly reliant on
where other passes decide to place IV increment. In most cases, they place
it in the end of the latch block, killing the opt opportunity (when in fact it
does not matter where to insert the actual instruction).

This patch handles this particular case separately.
- The detector does not use dom tree and has constant cost;
- The value of IV or IV.next lives through all loop in any case, so this should not
  create a new unexpected long-living value.

As result, the transform becomes more robust. It also seems to lead to
better code generation in some cases (see `test/CodeGen/X86/lsr-loop-exit-cond.ll`).

Differential Revision: https://reviews.llvm.org/D96119
Reviewed By: spatel, reames

NFC comment-only cleanups

 - Remove leftover comment from de2568aab819f
 - Fix a typo in a comment

NFC; fix typo in comment

This should have gone in with a76761cf0deeb223ca1c0b0e5ee68cfcd436e0c4.

[NFC] Don't pass redundant arguments

Some parameters were already part of the Config passed in.